B3ULLETIN NO. 27, OF THE MAY, 1891m AGRICULTURAL EXPERIMENT STATION, Agricultural and Mechanical College, AUBURN. 0 ALA. BLACK "Jc-lJST" of COTTON. lThe Bulletins of this Station will be sent Free to any citizen on application to t he' Director. of' the S' ate Ri. J. Rice, Job IPrinter and Stationer. Auburn, Alat. Board of Visitors. COMMITTEE OF TRUSTEES ON EXPERIMENT HON. J. G. GILOHRIST, STATION: B. MITOHELL. HON. R. F. LIGON, How. J. Board of Direction. W. L. BROU ............................................. J. S. NEWMAN .................. T. LUPTON .......... H. MELL .................. N. P. President. Director and Agriculturist. [ice-Director and Chemist. Botanist and Meteorologist . ............................ ASSISTANTS : GEO. F. ATKINSON ................................................ Biologist . First Assistant Agriculturist, charge Live Stock and Dairy. ISAAC Ross .... Second Assistant Agriculturist. JAS. CLAYTON .................. First Assistant Chemist. ........ J. T. ANDERSON, PH . D.................... L. W. WILKINsON, M. Sc ............. econd Assistant Chemist. J. F. WILKINSON, B. Sc............................. ............ R. E. NOBLE, B. Sc :.................. A. M. LLOYD, B. Sc .................................... W. B. FEAZer ......................................... Third Assistant Chemist. Fourth Assistant Chemist. Assistant Botanist. Clerk and Accountant. *Deceased.' Black "Rust" of Cotton.* BY GEO. F. ATKINSON, Biologist. Early in the past year I began the study of the fungus diseases of the cotton plant with the special object to determine the disease called 'black rust." The first of August, 1890, one hundred circular letters were sent to different farmers of Alabama requesting specimens of cotton affected with the disease variously termed "rust," "red rust," "black rust," "frenching," etc. From tiAventy-five to thirty replies were received including specimens marked rot." t The disease has been very prevalent and destructive during the season and excellent opportunities were offered for studying it in the vicinity of Auburn, not only upon the Station farm, but on field, I found the neighboring plantations. July 22d, on one of my visits to the cotton disease had made its appearance remainder being opment in full force in several spots, "black rust, ' "red rust," "frenching" and "root where fully one-half of the leaves of the plants had fallen off, the curled, dried, and blackened by a profuse develand spores of several fungi, so that by the smut of dark hyphae jarring a leaf the spores would float off in clouds like *The substance of this article read in a paper by the author before the was Botanical section of the American Association of Agricultural Colleges and Experiment Stations,Champaign,Ill., Nov. 1889. Later published in the Botanical Gazette, Vol. XVI., 3, Mar. 1891, pp. 61-65. t An account of this disease was Published in Bulletin No. 24. Dec. 1889. New Root-rot Disease of Cotton." "A 165 spores of some of the Ustilaginece. Some of the plants showed still the earlier stages of the disease, and in other parts of the field were numerous opportunities to study the earlier stages. For two months my time was occupied in noting the external character, collecting material, examining the different fungi found and noting the relation of each species to the variety of exterpal characters presented in the progress of the disease. A Complex Disease,-The disease is a complex one, that is, it is not due to one organism, but to the combined effect of several nicroscopic plants called fungi, which grow within the leaves of the cotton plant, absorbing the living parts. Organisms that grow or in plants or animals obtaining their own nourishment from their hosts are called parasites. So the microscopic plants causing diseases of other plants are called parasitic fungi. It is of great importance in speaking of them to apply some term defining this prominent character of parasitism for there are vast numbers of species of fungi, many which are not parasites growing also in plants, that is,.they cannot grow on or in a living plant, but only on dead plants or dead parts of plants. Such fungi are called saprophytic fungi to distinguish them from the parasitic forms. A number of persons prior to my own investigations have exmined with the microscope the leaves of cotton affected with the "black rust" and have reported that fungi were present, some attributing to these fungi the cause of the disease. So far as I have been able to learn none of these persons have recorded what these fungi were which were seen, and it is quite probable that no determination was made. The fact alone that fungi are found on the leaves of diseased cotton plants affected with black "rust" is no argument in favor of their being the cause of the disease. The nature of these fungi must first be ascertained before one can predicate anything respecting their causal relation to the disease. There are several ways in which their nature can be ascertained but even then it can be done only by one who is familiar with the accepted methods of research upon similar subjects, and has at his command the apparatus and literature required for accuracy; just as a trained chemist is the only person who can ,on 166 accurately determine the chemical constitutents of substances capable of analysis. Confusion of Names for the Disease.-It must be understood that ' in writing now of black "rust" of cotton, I refer only to the cases which have come under my own observation, either through personal inspection of diseased fields, or through specimens received from farmers. It may be possible that there are other diseases of cotton which are termed also "black rust" which I have not seen. It is unfortunate that the name "rust" was ever applied to any disease of cotton since the fungi commonly known as rusts, like wheat rust, oat rust, fig rust, etc., all belong to a group of plants called U'redinece. No members of this group have ever plant so far as recorded, so in that It would be been found on the cotton respect there is no true rust of cotton yet known. very difficult, however, to bring any other name into popular use, and even if it were possible it would not be appropriate to introduce a new name until all the term black "rust." ed stage of black "rust." In some cases when a cotton grower speaks of "red rust" he refers to the reddening of the leaves which is so common in worn out lands. While in North and South Carolina my attention was called to this disease which was chiefly characterized by a reddening of the leaves not produced nor accompanied by any fungous gro-vth. most cases this seemed to be due to some condition ment of erythrophyl in the cell sap of the leaves. of the In soil the important complications of the disease shall have been studied. Therefore I shall at present use I include in this term also what many farmers in Alabama call "red rust," whichis but an early or arrest- which induces a hastened maturity of the plant and the developIn some cases, especially in North and South infection experiments. of this was Ag: icultural Carolina, the development of ery- throphyl is induced by the irritation of mites as I have proved by From several places in both States cotton quite severely injured by mites has been sent me. An account published in Bulletin No. 4 of the South Carolina Experiment Station, January, 1889. These mites a great variety of weeds (Tetrasychus telarius, Linn.) feed on 167 6 and other plants including clover. It would not be surprising if there would be found in this an explanation of the statement originating in North Carolina that carrying an armful of wilted clover across a cotton field, later the "red rust" could be traced spreading from the same course. Other cotton growers do not speak of the peculiar reddening of the leaf which I have described as a rust of any kind, rightly saying it is due to some condition of the soil. When they speak of "red rust" they refer to leaves that do not have a heal hy green color, there being a tinge of yellow, or even in some cases a tinge of red, accompanied also by dark circular spots on the leaves that are dead, the edges of the leaves usually being dead also. the Such a leaf is represented in Plate I., upper leaf in the figure, and the one at the left below. These are from photographs of diseased leaves. Again by "black rust" the planter refers to the blackened condition of a whole or large part of the leaf, which ultimately falls off. This continues until the plant is entirely stripped of its leaves. This is only a more advanced or serious stage of the preceding kind of "rust." A leaf with black "rust" is represented at the right hand in the lower figure of Plate I. A Fungus Disease.-The fungi commonly present and which play an important part in the disease are Cercospora gossypina C.Coke,Colletotrichm Gossypii E. A. Southworth, Macrosporium nigrica"ntium Atkinson, a species of Alternaria and a bacterial organism which sometimes produces a characteristic disease of the leaves. The vegetive, or growing portion of the fungi concerned, consists of very minute thread-like bodies which grow on the inside of the leaf. At first the only external sign is the dead spots on the leaf. A little later fruiting threads (fertile hyphe) grow through the epidermis of the leaf to the outside, and bear on their ends the germs, or spores, of the fungus. These fertile hyphe and some of the spores are dark colored. Therefore when they appear on the leaf in great numbers they give it a more or less black color. Difference Between Cotton-leaf Blight and Black " Bust."-Cer168 cospora gossypina is a fungus that has been long known as a parasite of the cotton plant. The first description of it was published by Cooke in Grevillea* from specimens distributed from South Carolina by Ravenel in Ray. Amer. Fungi, No. 593. A fuller description was published by Scribner in the report of the section of Vegetable Pathology. t The disease which it produces when alone is called "cotton-leaf blight." Professor Scribner rust. In says (1. c.) that it is quite distinct from the dreaded "cotton rust," and also that it is occasionally confounded with cotton view of the confusion existing in reference to the name cotton rust it is impossible to tell whether the disease referred to by Professor Scribner as cotton rust is the same as the disease I am writiug of. However, some of the planters confuse the cotton leaf "rust," "red rust" and in one case "black blight with the black "rust" as it is known to me for some of the specimens labelled rust,".were affected with nothing of a parasitic nature except Cercospora gossypina. This, however, is not so serious after all since all the specimens of black "rust" I have examined show evidences of the Cercospora. a dark or purple color. green color. Cotton-leaf blight is characterized by irregular light brown or dirty white spots, often bordered by Many times the leaf is of a yellowish Sometimes the spots have a blistered appearance, and are so close together as to give this appearance to a large part of the leaf, when it has often a rusty brown appearance. When, however, it is complicated with other fungi, the appearance of the leaf is totally changed. Botanical Charactersof the Fungi.-If the reader will turn to Plate II. and refer to figures 1, 2, and 3, there will be seen the clusters of fertile hyphe of Cercospora as they appear when magnified under the microscope, the leaf. projecting from the surface of or both in figures 3, They are dark brown in color, toothed, geniculate, They are produced abundantly on nearly straight or curved in outline, as represented 2, and 1 respectively. sides of the leaf. gles, or "teeth," The scars represented on the hyphte at the anrepresent places where spores were formerly plate I. *Vol. XII., 1883, September, p. 31. pp. tlDepartment Agriculture, 1887, 355 and 356. 169 8 attached, Also the scars on the ends of the hypha are the same. All the spores are borne at the ends of the hyphe, but as one The spore is formed the hypha grows out from the side of the end, elongates and produces another spore at its new end and so on. different lenghts of the fertile hyph shown in the figures represent proportionately some of the variations which they are subject to dependent upon conditions of the weather, When the atmosphere is very humid and warm with frequent ains they grow very, rapidly and are then quite long.The spores are colorless, or hyaline, only their outline and the transverse partitionsand the finiely granular protoplasm can be seen. The spores are subject to the same variations in length that the hyphie They are represented in 2a, 3a, etc. They-are curved, or flexuous, and very slender, tapering, toward the distal end. In figure 1 some are shown still attached to thehyphte.* The measurements are as follows: Hyphe .07- .45 mm x .007 mm. Spores. .07-,4 nm>>m .003-.0035 mm, 5-50 septate. x oletot7ichaura Gossypii sometimes produces a distinct disease of the cotton plant and is then called "Anthracnose of cotton,"t As this is quite an important disease a separate bulletin is being prepared on it which I hope will be issued shortly after the appeaxance of this one. For that reason the fungus will not be described nor illustrated here. That it is an aggressive parasite has been proven by myself through inoculations of healthy.plants. 1 irosporium nigric antiumt is illustrated in Plate II., figure 4, a, b, and c. b and c represent the fertile hyphie,° c has a spore still attached to it. The other spores are free. At the place where the hyphie arise from the mycelium in the leaf they are en- are. the perfect (ascosporons) stage of Cercospora gossypina Cke. has not been discovered. I have found on dead leaves a sphwriaceous fungus which probably is the perfect stage. As studies on it are still iu progress I reserve it for future publication.-G. F. A. -During the past year E. A. Southworth,. asst. Mycologist at Washington, D. C., and myself have each studied this disease independently. Specimens were by Miss Southworth only on the bolls. Her account of the fungus was published in the Journal of Mycology. Vol. VI. , No. 3, Jan. 1891, I have found it not only on the bolls but on the leaves and stalks and have been able to make interesting observations in the A paper on this subject was read by myself before the Amer. Asso. Ag. Colleges and Experiment Stations Champaign, Ii..,N ov. 1890. $First described by the author in Bot. Gaz., Vol. XVI., Mar. 1891, p. 62. *Hitherto received seine field. 170 larged as shown at the lower end in the figure. directly below it. When a spore is being produced, as at c, the hypha becomes somewhat enlarged When the spore falls away the hypha elongates at the end, the new growth arising from inside the enlargement, its contour being the same size as that of the hypha just below the enlargement. through it. growth. When the new growth first takes place it apenlargement but projecting into the new from two to pears to be not connected with the As the hypha ages this appearance usually is not present and the enlargement seems to taper above may bear a new spore, and so in favorable weather The new growth thus formed at the end of the hypha eight or more spores may be borne on a single hypha, the point where the successive spores were borne being just at the upper end of the successive enlargements. The hyphae are dark or olive At the enlargements brown and borne on both sides of the leaf. there is usually a darker band around the center. The hyphe thus have a nodulose appearance, as in such species as Macrosporium parasiticum Thiin. The spores are olive brown,oblong, constricted in the middle,and stoutly rostrate at one side of the apex. As the young spore develops it is constricted in the middle before the first transverse partition is formed. This is formed in the constricted l:ortion. Later other transverse, longitudinal and oblique septa are produced. The spore represented at a is a little larger proportionately than it should be, from the fact that the drawing was made after the spore had been sown in a cell culture and just prior to germination (when the drawing was made) it was considerably larger from imbibition of water. Measurements. mm in diameter. made leaf. Hyphfe The fertile hyphte .006-.007 are usually scattered, rarely in clusters of two or three. are .050-.140 mm long x Conidia .018-.022 mm x .036-.050 mm. culture under the microscope, the spore a are shown on the under- The Alternaria is illustrated in Plate II. figure 5. The drawing is from a water having been taken from among a number of others on a cotton Parts of several vegetive hyphae These are side and at the left, the parts of the fungus which The fertile hyphae are seen to proThese spores as 171I grow on the inside of the leaf. duce in a concatenate manner the spores b. 10 well as the fertile hyphw are dark brown in color, and in numbers serve to blacken the leaf. The bacterial disease is often very widespread even when no evidences of the other fungi are to be found,but is mentioned here because frequently it is an accompaniment of the black "rust" and contributes materially to the aggravation of the disease. manifested by a watery appearance in which are bounded by the veinlets of the sometimes very numerous and frequently disease leaf. It is first spots definite areolate conjoined; The spots are often the follows one or more of the main ribs of the leaf being As the dis- bounded on each side by an irregularly zigzag line. ease ages the spots become blackish and quently then bordered sometimes break out extended somewhat centrifugally. then light brown, fre- by a blackish color where the disease has The dead spots in the leaves in the leaves blight. leaving many perforations with ragged edges, somewhat as results in cotton-leaf The disease hastens the falling off of the leaves. F.xternal Charactersand Progressof the Disease.-During the entire season, from July to the close of October, of the thousands of leaves old and young that I examined, Cercosporagossypina has been an almost universal accompaniment, and has not been second in point of attack, except perhaps in rare cases. parallel or immediately succeeding attacks In many cases were made by the Colletotriclhum. The Macrosporium as a rule follows closely the attack of the Cercospora, indeed sometimes seeming to be first to attack. veloped. In such cases possibly it attacked the spots diseased by of the latter were deBy its clusters of The Alternaria usually succeeds the Macrosporium, Cercospora before the hyphe and conidia though often seeming to be parallel with it. hyphte and profusely developed concatenate spores in favorable wcather the leaf is soon covered with a mass of spores giving a blackened appearance to the leaves. My correspondents in Alabama generally use the term "black rust" when the disease progresses very rapidly and the development of the hypha of Cercospora and sete of Colletotrichum, or When the disease progresses more 172 the Macrosporium and Alternaria spores, is very profuse causing the leaves to appear black. 11 slowly, being checked by unfavorable weather, or is in the first stages the term "red rust" is generally used. In such cases the Macrosporium or Alternaria has extended centrifugally the spots attacked by the Cercospora, increasing their size, causing them to become more nearly circular, and marking the spots with concentric lines. Also the edges of the leaf are usually dead and dried, and curled either below.or upward, being favorite places for the attack of either the Cercospora or Colletotrichum. The body of the leaf is still green, paled yellow or dull purple. In some cases in the early stages of the disease the Colletotrichum severely attacks the upper part of the stem of the plant and petioles of the leaves, giving the stems a dark color from internal changes,to the leaves a scalded appearance and to shrivel up and dry, much as if frost bitten. Sometimes the development of the Cercospora may be so great and the attack of the other fungi so tardy as to give the appearance of black "rust" produced by it alone. Specimens of this kind were received from one of my correspondents at Eutaw, Ala. The conditions for the development of the Cercospora were so favorable that from one fourth to three fourths of the leaf surface was covered with a dense mass of the dark brown hyphie, the remaining portion of the leaf being yellowish-with numerous small points of attack. The hyphe and conidia in such cases are very long. Where other fungi, as Colletotrichum, Macrosporium and Alternaria are abundant, it is often very difficult to find the Cercospora on the leaf. By placing the leaves, freshly gathered, in moist chambers for ten to twelve hours I have never failed to get an abundance of Cercospora, even on the smallest, uppermost leaves of the plant. Sometimes the Macrosporium is the predominating fungus in the last stage of the disease, giving a black appearance to the entire leaf. Cercospora and Colletotrichum are both active parasites, and I am convinced from a year's study of Cercospora gossypina that it is a more active and destructive parasite than has been formerly regarded. A diseased condition once started by such a fungus causing them by different shades of a dull 173 12 opens the way for the rapid growth and great injury produced It is possible by such forms as Macrosporium and Alternaria. that the Macrosporium may infect the leaves unaided by other fungi. Inoculations of plants free from other forms must be made to determine this. Cercospora gossypina sometimes produces a serious spot disease of the cotyledons. mental purposes. I first observed this on some young plants for experistarted on the horticultural grounds, in September, I am told that sometimes in cold seasons in May this spot disease is quite injurious along with "sore-shin." * CURRENT THEORIES AS TO CAUSE. Much speculation in agricultural papers has been indulged in the cause of black "rust" of cotton. It would be almost impossible to collect and critically examine all that has been written upon the subject from a purely empirical, or as has regarding been too often the case, from a subjective, stanapoint. Some of the current theories, however, are worthy of consideration. Physical Condition of Soil, Lack of Fertilizers.-Many hold that it is due to the physical condition of the soil, or to a lack of proper fertilization. It is quite likely that there are certain physical conditions of soil which are not so favorable to the healthy growth of the plant as others, and also that there are soils which lack proper and sufficient nutriment for a healthy growth. It is to be hoped that, since progress is being made by experimentation with fertilizers best adapted for the production of cotton on different soils, similar experiments will be made to test the of fungous parasites. efficacy of certain fertilizers in producing a plant able to resist the attacks vent the "rust" that will be better Many of the statements currently made that certain fertilizers will surely preare either without foundation in fact, or the "rust" referred to is not a diseased condition of the plant induced by fungous parasite s. For example, the reddening of the leaves so commonly seen on worn out lands is usually nothing else than a *A pycnidial form of some spheriaceous fungus is also frequently an accompaniment of black "rust." It is probably Phyllosticta gossypina E. and M. Recent cultures in agar agar peptone broth seem to show that it is the pycnidial stage of an undescribed Pleospora which I have found on fallen leaves. -G. F. A. 174 13 physiological condition of the plant, which proper fertilizing will, to a great extent, remedy. It is usually in reference to such lands that we hear of the "fence-row" cotton which escapes the "rust." I have seen several cases during the past year where the "fence-row" cotton was affected with the black "rust" and injured just so severely as the cotton by its side in the field. In this case, however, the soil was all fertile. As yet we are far from knowing just what fertilizer to apply to prevent black "rust." Many cases have Come under my immediate observation wnere good land was well fertilized and yet some of the cotton was very badly diseased. Some of my correspondents who formerly attributed the disease to the peculiar conditons of the soil, lack of fertilizers, etc., say that sometimes in the best soils and with careful fertilizing the disease appears in a very destructive form. The subject has not been inquired into in a satisfactory manner. It should be carefully tested by systematic experiments conducted as thoroughly as is done in determininngthe fertilizer best adapted to the growth and fruiting of the plant.* Conditions.-Anothertheory very commonly held and frequently expressed is that black "rust" is due to "atmospheric conditions." It is an erroneous view, though arising from inofault of those who hold it, but from the fact that these fungous parasites are so small that no one can see them with the natural powers of vision,and so little known that but few people, comparatively how it is that an unseen within a plant and kill it. It is true that, while the cause is not due directly to atmospheric conditions, certain conditions of the atmosphere favor the growth of the parasites. The fact is, there are certain temperature and other organism can grow all org anisms, even cotton conditions of the atmosphere that are favorable to the growth of itself. In the case of many plants speaking, understand Altmospheric these conditions vary, so that what is favorable for one plant is unfavorable for another, Long continued wet weather with a relatively high temperature is unfavorable to the growth and fruiting of cotton, but it is favorable to the growth of the parasites which produce black "rust." "The rust frequently is much worse in spots so that large areas of an acre or more for experiment plats are not so reliable as narrow areas of about 4 row plats across an acre. 175 14 is very reasonable to suppose that, if we had a physical condition of the soil perfectly suited to cotton culture, a fertilizer perfectly adapted to supply the plant with just the proper nutriment, and a climate perfectly regulated to run throughout the season in a n:anner most favorable to cotton, there would be very little damage from black "rust." But while we are approaching the day when we may know the best fertilizer to be applied to certain soils, and may possibly be able to change to some extent the physical conditions of unfavorable soils, we probably will never be able to control atmospheric conditions which are unfaIt vorable to the growth of cotton and favorable to the growth of its parasites. Fruiting Cotton More Subject to Disease.-Another theory which may contain a great deal of truth is, that diseased. only while cotton is fruiting is it subject to the disease, that barren stalks are never It is hardly necessary to call attention to tl e fact that Since the if we avoid the fruiting of cotton, in order to prevent the black 'rut ; ," the main object of cotton culture is defeated, above was written I have been informed by Mr. W. H. Lawson that frequently otherwise vigorous plants have been produced on parts of his farm which bore no fruit but were badly diseased by black rust. The Power of the Plant to Resist Fungous Parasites.-Thepower which some of the lower organisms have, under favorable circumstances, microscope. of successiully resisting the attacks of fungous parasites has been demonstrated by direct observation under the In some of the higher animals observations of the that alsc under resist the favorable From blood taken from subjects inoculated by injection of the germs into the blood vessels demonstrates circumstances they may successfully attack. these direct proofs in a few organisms we are enabled to draw the inference that all animals and plants under favorable circumstances can resist the growth of many parasites inimical to their existence. Perhaps the most remarkable of the earlier experianimals over fungous Beitrag zur Lehre fiber den Virch. Archyiv. Bd. 96, 1884, ments which demonstrate this power of diseases is the work of Metschnikoff,* Kampf der Phagocyten gegen Krankheitserreger. The spores of one of the *Ueber eine Sprosspilzkrankheit der Daphnien. pp. 177-195, 2 Taf. See Zopf; Die Pilze in morphologischer, physiologischer, biologischer und systematischer Beziehung, 1890, pp. 241 and 261-262. 176 15 sprouting fungi (yeast plants) first fed to crustaceans made their way through the alimentary canal into the blood. Certain of the blood corpuscles attack and completely surround a cell of the fungus, and excrete a fluid of the nature of an enzyme which acting upon the fungus cell first deforms and then destroys it. If only a few cells of the fungus entered the blood the action of the peculiar blood corpuscles was sufficient to prevent the growth of the fungus and resist the disease. If, however, numerous germs of the fungus were injected the blood corpuscles were incapable of destroying them all, so that the peculiar blood cells themselves were finally overpowered by the great number of fungus cells, which also excrete an enzyme to act on the corpuscles. Now the fungus was permitted to grow and to develop the disease. While the higher plants do not have free amoeboid cells which can act as the phagocytes, as they are called, in animals do, yet the protoplasm in a healthy condition and under favorable circumstances probably offers resistance to the growth of many fungous parasites. But where the germs of the fungns are very numerous and the plant is under unfavorable conditions of temperature, and thebe very conditions being favorable to the development of the parasites; the plant may not be able to resist the disease. This in fact is what experiments as well as observations prove in plants as well as in animals. Unfavorable changes in the weather alone sometimes render healthy animals and plants temporarily susceptible to parasitic diseases. Over such unfavorable conditions man has no control except in circumscribed areas. Therefore it has been found necessary in many cases to apply to perfectly healthy plants preventives of infectious diseases to tide them over unfavorable periods. Already in the case of the grape, apple,potatoesthe grains and other plants; substantial success has been met with in the treatment of diseases which every care given to soils and fertilizers cannot prevent. Experiments.-Duringthis season experiments will be conducted at the Experiment Station with a view to discover some preventive of the disease. Not only will direct applications be made to the plant of substances to check the growth of the spores, but certain fertilizers will be used in parallel experiments, and alternate areas or rows be left untreated as checks, so that some comparisons can be drawn. The farmers themselves could do valuable work if they could make some careful tests with fertilizers on the cooperative plan. But if undertaken it should be systematically carried out. 177 16 Several alternations of treated and untreated rows should be arranged so as to avoid error. If this year should not be a favorable one for the disease experiments should be continued another year. Object of the Bulletin.-The object of this bulletin is to present some tangible information in regard to the disease called black "rust," to describe it briefly and to give such illustrations of the leaves as will enable farmers to detect the disease and so prevent to a certain extent the confusion which now exists with cottonleaf blight and some conditions of the leaf which are purely physiological or due to mites. It is hoped that farmers will read the bulletin carefully and preserve it to aid them in observing the diseases of cotton during the present year. I would consider it a great favor if the farmers would observe carefully to distinguish this disease from others and send me specimens of all the different diseased conditions of cotton leaves and bolls which they find. A half dozen or more leaves of each kind should be sent. They should be laid separately between sheets of paper and be supported on one side by stiff paper of some kind, so as to keep them from spoiling while they are in the mails. A great deal of aid can thus be given by farmers themselves in this important investigation. The leaves should be sent to meat Auburn, Ala. I wish to express my thanks to the farmers who so kindly aided me the past year in sending specimens and notes on the disease. Their names are given below, Hon. G. R. Banks, Tallassee; W. C. Barkin, Coats Bend; R. E. Browning, Pleasant Hill; S. M. Cathcart, Alberta; C. C. L. Dill, Dillborough; S. A. Driver, Augustin; J, W. Edmunds, Faunsdale; J. W. Eubank, Pine Level G. T. Green, Fayetteville; F. M. Kirksey, Eutaw; R. E. Mobley, West Greene; J. C. Mathews, Crittenden Mills; Rev. J. L. Moultrie, Union Springs; Prof. C. L. Newman, Athens; G. W. Rhodes, Saville; W. M. Trimble, Sandy Creek; J. V. Tutt, Belmont; A. Y. Smith, Prattville; O. D. Smith, Smith's Station; T. J. Waller, Auburn;Mr. Wright, Wright's Mills. Specimens were received twice from some of the gentlemen Figures 1, 2, 3, Cercospora gossypina Explanation of Plate II. Cooke, clusters of hyphe, and few conidia; in figure 1 two conidia are still attached to the hyphae. Fig. 4 Macrosporium nigricantium Atkinson. b and c hyphae. c bears a conidium Fig. 5 Alternaria, a spore grown in water a culture, b chains of conidia. All drawn with aid of camera lucida to same scale. Zeiss microscope, ocular 4, objective D used. 178 55 I i H\ ft ! 1 11 t''!( PI4' F 9\ ATISN \N \F FU F BAK RS"O OT N