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Full text of "A text-book of mycology and plant pathology"



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A TEXT-BOOK 

OF 

MYCOLOGY AND PLANT 
PATHOLOGY 



HARSHBERGER 



A TEXT-BOOK 

OF 

MYCOLOGY AND PLANT 
PATHOLOGY 



BY 

JOHN W. HARSHBERGER, Ph.D. 

PROFESSOR OF BOTANY, UNIVERSITY' OF PENNSYLVANIA; MEMBER OF 

THE BOTANICAL SOCIETY OF AMERICA; VICE-PRESIDENT OF THE 

ECOLOGICAL SOCIETY OF AMERICA, ETC. 



WITH 271 ILLUSTRATIONS 



PHILADELPHIA 

P. BLAKISTON'S SON & CO. 

1012 WALNUT STREET 



Copyright, 191 7, by P. Blakiston's Son & Co. 



THE MAPLE PRESS YORK PA 



PREFACE 

This book is the outcome of twenty-seven years' experience, as a 
teacher of botany, during which fifteen years have been given to a 
graduate course on the morphology, classification and physiology of the 
fungi, and five years to a course which combined with this considera- 
tion a parallel study of the most important cultural and inoculation 
methods used by the practical bacteriologist and mycologist at the 
present day. The English and Germans have led in the production 
of text-books on mycology and pathology; Berkeley, Smith, Cooke 
and Massee in England, Frank, Sorauer, von Tubeuf and Kiister in 
Germany. Americans have been behind in this important field, 
notwithstanding, that American plants harbor some of the most 
destructive fungi, which, through our careless methods of agriculture 
and horticulture up to the present, are annually destructive to the 
extent of millions of dollars. This lack is being rapidly remedied and 
the appearance of text-books by Duggar, Stevens, Hall and' Stevens, 
Mel T. Cook and general monographs by Erwin T. Smith, and others, 
augurs well for the future of this line of literary and scientific labor. 
The bacteriologists have led and mycologists should follow. 

The following pages represent in a much extended form the lectures 
and laboratory exercises given by the author before his botanic classes 
at the University of Pennsylvania, and before public audiences else- 
where, especially, Farmers' Institutes with which he has had three 
years' experience as a lecturer in Pennsylvania. The arrangement of 
the text has been suggested by the needs of the classroom and from an 
acquaintance with similar work in other colleges and universities in 
America. It is hoped that the book and the suggestions, as to teaching 
which it contains, will appeal to those responsible for similar courses. 
The keys are given with the anticipation that they will prove useful 
to the student and teacher who desire exercises in the classification of 
the fungi: The illustrations have been chosen with care, and credit is 
given in all cases for those borrowed from other books and monographs. 
The author hopes that the book is reasonably free from misleading 



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A(ii^ US'? 00 



statements, and that it will prove useful to the teaching and student 
body. The exercises, which are given in detailed form are designed to 
acquaint the student with the methods that are used in the cultural 
investigation of the bacteria and fungi. It is also designed to introduce 
the student to the highly important subject of Technical Mycology. 

The modern demands for investigators trained in technical my- 
cology are many. The health bureaus of our large cities need men and 
women, who can make a study of the milk, water and food supplies. 
The men, who are engaged in the fermentation industries, frequently 
demand expert information on the bacterial and fungal organisms, that 
are either useful, or harmful, in the fermentation process. The bread 
baker should have someone to whom questions relative to his, one of the 
oldest, arts could be referred. The canner also needs such expert 
advice. The farmer depends upon the fertility of his soil for the growth 
of crops, and the character of that fertility determines whether his 
crop shall be a large or a small one. It is conceded on all sides at 
present that fertility is due not alone to the chemical character of the 
soil, but also to other conditions which are quite as influential, such as, 
the physical state, the bacterial and fungous flora and the presence or 
absence of toxic substances. A study of the mycologic flora of the soil 
can only be pursued satisfactorily by those who have been trained in 
cultural methods. 

Then too the study of plant diseases and animal diseases rests funda- 
mentally upon technical mycologic laboratory methods. The alarm- 
ing increase of plant diseases has attracted a larger and ever growing 
number of young men into the study of bacteriology and fungology. 
There seem to be unlimited opportunities for such carefully trained men 
and women to get profitable employment in health bureaus, manufac- 
turing plants, agricultural experiment stations, and as plant doctors 
stationed in our larger towns and cities, ready, as a medical doctor is 
ready, to give for a monetary consideration expert advice and treatment. 
Lastly, there are chances for men and women trained in technical 
mycology to become professors, or teachers, of the subject in our col- 
leges and agricultural high schools. Such trained specialists can help 
to increase the crop-producing capacity of our farms by eliminating 
the prevalent diseases, which reduce seriously the farmers' profits. 
Such specialists are conservationists in the truest sense of the term. 



PREFACE Vll 

The author, with great pleasure, thanks the following persons for 
suggestive help in the preparation of the text-book: Professor J. C. 
Arthur read the proof of the chapter on the rust fungi; Prof. D. H. 
Bergey of the University of Pennsylvania the pages dealing with 
laboratory methods. Prof. Mel T. Cook and his associates J. C. 
Helyar and C. A. Schwarze of the New Jersey Agricultural Experiment 
Station, New Brunswick, read the galley proofs throughout and made 
valuable suggestions. Dr. J. S. Hepburn read the pages dealing with 
bio-chemistry, Messrs. H. R. Fulton and Donald Reddick also made 
valuable suggestions as to the arrangement of the contents of the book, 
while Prof. L. R. Jones and Dr. C. L. Shear furnished illustrations for 
reproduction in the text. Prof. A. H. Reginald Buller of the University 
of Manitoba gave permission to use five illustrations in his book, 
Researches on Fungi. ' ' The au thor desires to express his thanks for the 
uniform courtesy of members of the firm of P. Blakiston's Son & Co., 
especially to Mr. C. V. Brownlow, whose unfailing interest has done 
so much to forward the publication of the work. 

J. W. H. 



CONTENTS 
PART I. MYCOLOGY 

Page 

CHAPTER I. — General Statement and Classification i 

CHAPTER II.— Slime Moulds (Myxomycetes) 7 

CHAPTER III.— The Bacteria in General 21 

Name; Size; Locomotion; Cell Division and Reproduction; Photogens; 

Chromogens; Thermogens; Aerobism and Anaerobism. 

CHAPTER IV.— Classification of Bacteria • 28 

According to Nutrition; Prototrophic Bacteria; Metatrophic Bacteria; 

Paratrophic Bacteria; Systematic Account of the Bacteria; Bibliography. 

CHAPTER V. — Characteristics of the True Fungi 42 

CHAPTER VI. — Histology and Chemistry of Fungi 52 

Histology; Cell Contents; Colors; Physiology; Enzymes; Classification of 

Enzymes in Fungi; Chemotaxis. 
CHAPTER VII.— General Physiology of Fungi 61 

Influence of Light; Luminosity; Liberation of Spores. 
CHAPTER VIII.— Ecology of Fungi 69 

Saprophytes and Parasites; Sclerotia; Galls; Habitats; Xerophytism; 

lachen Fungi. 
CHAPTER IX.— Fossil Fungi and Geographic Distribution 82 

Fossil Fungi; Geographic Distribution; Habitats of Lichens; Distribution of 

Chestnut Blight; Laboulbeniaceae; Family Clathraceae. 
CHAPTER X. — Phylogeny of Fungi ^9 

CHAPTER XL— Mould Fungi ' ' ^^ 

Order Zygomycetales; Sexual Reproduction; Spores and Sporangia; Fer- 
mentation; Key to Families of the Order Zygomycetales; Mucoracese; 
I^Iortierellacea;; Choanephoracea;; Chaetocladiacea;; Piptocephalidaceae; 
Entomophthoraceae; Bibliography. 

CHAPTER XII.— Oospore-producing Algal Fungi 107 

Sexual Reproduction; Haploid and Diploid State; Key to Families; Mono- 
blepharidaces; Saprolegniaceae; Peronosporaceae; Generic Key to Family 
Peronosporaceee. 

ix' 



X CONTENTS 

Page 

CHAPTER XIII.— OoMYCETALES (Continued) ii6 

Chytridiaceae; Ancyclistaceae; Bibliography. 

CHAPTER XIV.— Higher Fungi 120 

Ascomycetales; Sexuality, Claussen and Harper; Life Cycle; Bibliography. 

CHAPTER XV. — Sac Fungi in Particular (Yeasts, etc.) 131 

Endomycetaceae, Exoascaceae; Saccharomycetaceas; Yeasts, cells and fer- 
mentation, etc.; Systematic Position. 

CHAPTER XVI.— Sac Fungi (Continued) 143 

Gymnoascaceae; Aspergillaceae; Elaphomycetaceae; Terfeziaceae; Tuberaceae 
(TruflBes) ; Myriangiaceae. 

CHAPTER XVIL— Mildews and Related Fungi 154 

Erysiphaceae (Mildews); Perisporiaceae; Microthyriaces; Hypocreaceae; 
Dothideaceae; Sordariaceae; Chaetomiaceae; Sphaeriaceae; Valsaceae; Melo- 
grammataceae; Xylariaceae; Hysteriaceae; Phacidiaceae; Pyronemaceae; 
Ascobolaceae; Pezizaceae; Helotiaceae; Mollisiaceae; Geoglossaceae; Helvel- 
laceae; Cyttariaceae; Rhizinaceae; Phylogeny of Ascomycetales; General 
Bibliography. 

CHAPTER XVIII.— Basidia-bearing Fungi (Smuts) 177 

Key to Suborders; Ustilaginaceae (Smuts); Bibliography of Smuts. 

CHAPTER XIX.— Rust Fungi 187 

General Structure; Forms; Life Cycles; Cytology; Phylogeny; Endophyl- 
lacese; Coleosporiaceae; Pucciniacese; Bibliography of Rusts; Auriculariaceae; 
Tremellaceae (Trembling Fungi). 

CHAPTER XX.— Fleshy and Woody Fungi 218 

Cytology; Dacryomycetaceae; Exobasidiaceae; Hypochnaceae; Thele- 
phoraceae; Clavariaceae; Hydnaceae; Polyporaceae; Manuals. 

CHAPTER XXI.— Mushrooms and Toadstools 231 

Agaricaceae; Development of Fruit Bodies; Cultivation of Mushrooms; 
Chemistry and Toxicology of Mushrooms; Gasteromycetes; Hymeno- 
gastraceae; Tylostomaceae; Lycoperdaceae; Nidulariaceae; Key to; Sclero- 
dermacese; Sphserobolaceae; Phallomycetes; Development of Carrion Fungi; 
Clathraceae; Phallaceae; Bibliography of Eubasidii. 

CHAPTER XXII. — Fungi Imperfecti (Deuteromycetes) 258 

General Characters; Systematic Position; Sphaeropsidales ; Melanconiales; 
Hyphomycetales. 



PART II. GENERAL PLANT PATHOLOGY 



CHAPTER XXIII. — General Consideration of Plant Diseases . . .271 
Etiology; Predisposing Causes; Determining Causes; Physical Character of 
Soil; Climatic and Meteorologic Factors, Effect of Smoke, etc.; Trauma- 
tism; Animate Agents of Disease; Insects. 



CONTENTS XI 

Page 

CHAPTER XXIV. — Plants as Disease Producers, Epiphytotism, Prophy- 
laxis 298 

Vegetal Agents of Disease; Parasitic Flowering Plants; Fungous Organisms 
as the Cause of Disease; Mechanic Injuries; Injuries Due to Meteorologic 
Causes; Infection; Incubation; Duration of Disease; Dissemination of 
Fungi; Epiphytotisms (Epidemics); Prophylaxis. 

CHAPTER XXV.— Practical Tree Surgery 319 

Preventive Measures; Character of Work; Cavity Treatment; Mixing and 
Placing the Cement; Metal-covered Cavities; Guying. 

CHAPTER XXVI.— Internal Causes of Disease .^26 

Enzymes; Panaschiering; Calico; Nutritive Disturbances; Mutations; Mal- 
formations and Monstrosities; Graft Hybrids; Chimaeras. 

CHAPTER XXVII. — Classification of Abnormalities 331 

CHAPTER XXVIII. — Symptoms of Disease (Symptomatology) 341 

Symptoms of Disease; Discolorations; Shot-holes; Wilting; Necrosis, 
Dwarfing; Hypertrophy; Replacement; Mummification; Alteration of 
Position; Destruction of Organs; Excrescences and Malformations; 
Exudations; Rotting; Bibliography of Diseases in General. 

CHAPTER XXIX.— Pathologic Plant Anatomy 354 

Restitution; Hypoplasia; Metaplasia. 

CHAPTER XXX. — Pathologic Plant Anatomy (Continued) 364 

Hypertrophy; Excrescences; Intumescences; Callous Hypertrophy; Ty- 
loses; Gall Hypertrophies; Hyperplasia; Homooplasia; Heteroplasia; 
Callus; Conditions of Callous Formation; Wound Wood; Wound Cork. 

CHAPTER XXL— Galls 384 

Kinds of Galls; Cataplasms; Histology of Cataplasms; Histology of Galls. 
Cecidial Tissue Forms; Bibliography of Galls. 

CHAPTER XXXII.^ — Mechanic Development of Pathologic Tissues . . 403 
General Consideration; Bibliography of Developmental Mechanice, Sug- 
gestions to Teachers and Students. 



PART III. SPECIAL PLANT PATHOLOGY 



CHAPTER XXXIIL— Specific Diseases OF Plants 411 

General Statement; Principal Publications; List of Common and Important 
Diseases of Economic Plants in "the United States and Canada Arranged 
according to Host Plants. 

CHAPTER XXXIV. — Detailed Account of Specific Diseases of Plants . 475 
Alfalfa to Grape. 

CHAPTER XXXV.— Detailed Account of Specific Plant Diseases 

(Continued) 517 

Hemlock to Wheat. 



Xll CONTENTS 

Page 
CHAPTER XXXVI. — Non-parasitic, or Physiologic Plant Diseases.. . 564 
Classification; Stag-head; Root Asphyxiation; Desiccation; Water-logging; 
Oidema; Frost Necrosis; Apple Fruit Spots; Water-core of Apple; Die- 
back, or Exanthema; Mottle-leaf; Curly-top of Sugar Beets; Peach Yel- 
lows; Tip-burn of Potato; Leaf -casting; Curly-dwarf of Potato; Bean 
Mosaic; Mosaic of Tobacco; Bibliography. 



PART IV. LABORATORY EXERCISES IN THE 
CULTURAL STUDY OF FUNGI 

CHAPTER XXXVIL— Laboratory and Teaching Methods 581 

Introductory Remarks; Lesson i, Micrometry; Lesson 2, Plugging Test- 
tubes, etc.; Lesson 3, Microscopic Study of Culture Material; Stains; 
Lesson 4, Liquid Nutrient Solutions; Lesson 5, Potatoes as Medium; Lesson 
6, Solid Vegetable Substances; Lesson 7, Plant Juices; Lesson 8, Milk, Beer- 
wort; Lesson 9, Bouillon; Lesson 10, Eggs; Lesson 11, Nutrient Gelatin; 
Lesson 12, Agar-Agar; Lesson 13, Various Nutrient Agars; Lesson 14, 
General Directions for Making Plant Agars; Lesson 15, Potato Juice Agar; 
Lesson 16, Starch Agar; Lesson 17, Culture Media for Nitric Organisms; 
Lesson 18, Standardization of Culture Media; Lesson 19, Germination 
Studies; Lesson 20, Counting of Yeasts and Bacteria; Lesson 21, Cultiva- 
tion of Yeasts on Gypsum Blocks, Method of Pouring Plates, Streak 
Method; Lesson 22, Isolation of Fungi; Lesson 23, Water Analysis; Lesson 
24, Methods of Identification; Lesson 25, Plate Counter; Lesson 26, Sys- 
tematic Bacteriology; Lesson 27; Scheme for the Study of Bacteria; Lesson 
. 2.8, Detailed Study of Bacteria; Lesson 29, Directions for the Study of 
Pathogenic Fungi. 

CHAPTER XXXVIII. — Laboratory and Teaching Methods (Continued) 643 
Lesson 30, Inoculation Experiments; Lesson 31, Do.; Lesson 32, Do.; 
Lesson ^^, Do.; Lesson 34, Do.; Lesson 35, Experiments with Artificial 
Wounding of Plants; Lesson 36, Gas Injuries; Lesson 37, Enzyme Diseases; 
Lesson 38, Study of Mistletoe; Lesson 39, Wire Worms in Plants; Lesson 40, 
Relation of Light to Pathogenic Conditions; Lesson 41, Withering, or Wilt- 
ing of Plants; Lesson 42, Methods of Sectioning, Celloidin, Paraffin; 
Lesson 43, Freezing and Cutting of Material; Lesson 44, Use of Drawing 
and Projection Apparatus, Drawing Methods; Lesson 45, Suggestions to 
Teachers and Students; Lesson 46, Content of Field Trips and Excursions. 

APPENDIX I.— Fungicides 669 

Bordeaux Mixture, etc. 

APPENDIX II.— Spray Calendar 680 

APPENDIX III. — Antisepsis and Disinfection ............ 692 

Preservation of Woods. 



CONTENTS Xlll 

Page 

APPENDIX IV. — Culture of Mushrooms 693 

APPENDIX V. — Synopsis of Families and Principal Genera of Myxo- 

GASTRALES 693 

APPENDIX VI. — Key for the Determination of Species of Mucor . . . 695 
APPENDIX VII. — Keys for the Determination of Species of Asper- 
gillus and Penicillium 702 

APPENDIX VIII. — Keys to the Genera of the Erysiphace^ 721 

APPENDIX IX.— Collection and Preservation of Fleshy Fungi . . .726 
APPENDIX X. — List of Keys to Fleshy Fungi and Selected Keys of 

Fleshy Fungi 729 

APPENDIX XI.— Key to Agaricace^ 732 

Index 753 



PART I 
MYCOLOGY 

CHAPTER I 
GENERAL STATEMENT AND CLASSIFICATION 

The lower plant organisms which concern the mycologist, or the 
student of the fungi, may be considered in a general sense, or in a 
narrow way. A general definition would include all those thallo- 
phytes, or lower cellular plants (lacking archegonia), which are 
destitute of chlorophyll and in its absence become dependent, with 
the exception of the prototrophic bacteria, upon extraneous supplies 
of organic food, either Hving or dead. This broad definition compels 
the mycologist to study the slime moulds, the bacteria and the true 
fungi, both as to their morphology and their physiology. He finds on 
such study, that broadly speaking, there are similarities of structure 
and function in both groups of dependent plants, in fact, he finds that 
the function of these plants is connected with cell organization and 
structure and vice versa. With this clearly in view, the mycologist 
finds that he has to deal with three distinct classes of chlorophylless 
plants, namely: 

Class Myxomycetes (slime moulds). 

Class Schizomycetes (bacteria). 

Class Eumycetes (true fungi). 

The classification of these colorless (chlorophylless) lower plants 
has been elaborated in recent years with considerable detail by various 
authors, 30 that the broad fundamental facts both of taxonomy and 
phylogeny are known fairly well, but much remains to be done along 
the classificatory fines, especially, since the life histories of many 
of the bacteria and fungi are incompletely known. It may be 
many years before a generally acceptable nomenclature and classifi- 
cation win be an accompHshed fact. The choice of a classification by 
any worker in mycology depends largely on his training and bias and 
on his detailed study of the various groups. No two men would 
entirely agree as to which was the best sequence to adopt in a system- 
atic treatment of the different forms. The classification adopted in this 

fHOPERTf^UBRARY 
N. C. State College 



2 MYCOLOGY 

treatise is based on that of Engler and Gilg, as published in the seventh 
illustrated edition of "Syllabus der PflanzenfamiUen," Berlin, 1912, and 
on that of Wettstein in his "Handbuch der Systematischen Botanik," 
Leipzig and Vienna, 191 1. Where consistent, the classificatory sys- 
tems of these two books are harmonized and any departures which the 
student will find from the taxonomic arrangements of Engler and 
Wettstein have been made to simplify them by the omission of cer- 
tain group names, or to bring the two systems into line with the facts 
as at present known. The author has not hesitated to make changes, 
where from his experience as a teacher, he has found it best to make 
such alterations, especially where, for example, Wettstein uses Ordnung 
and Engler Reihe for the same classificatory group, and where in 
American usage order and family are used. Then, too, the author has 
found it convenient to replace the name of a family, or order, as given 
by Engler for one used by Wettstein, or some other author, where such 
replacement is recommended by American usage, or where etymolog- 
ically the name is more suggestive of the character of the group, and, 
therefore, best for the use of students who do not expect to follow out 
the intricacies of any system of classification. As the statements and 
views of Engler and Wettstein are generally dependable and as their 
classification is founded on long experience, as systematic botanists, 
it will be found that with respect to the larger subdivisions of the 
fungi their classifications are remarkably harmonious. The attempt 
has been made in the pages that follow to simphfy for student use 
the facts of classificatory importance and while the groups are ar- 
ranged in lineal sequence, it should be explained that true relationship 
is expressed better by a family tree with main trunk, larger and smaller 
branches. It will be noted that the arrangement of the famiUes, as 
given in the two systematic works above mentioned, are sometimes 
reversed. The simple groups are given first place, followed by the 
more complex. 

CLASS I. MYXOMYCETES. 
ORDER I. ACRASIALES. 

Family i. Guttulinaceae. 
Family 2. Dictyosteliaceae. 

ORDER II. PHYTOMYXALES. 

Family i. Plasmodiophoraceae. 



GENERAL STATEMENT AND CLASSIFICATION 

ORDER III. MYXOGASTRALES. 

Suborder. Exospore^. 

Family i. Ceratiomyxacese. 
Suborder. ENDOspoREiE. 

Family 2. Physaraceae. 

Family 3. Didymiaceag. 

Family 4. Stemonitaceae. 

Family 5. Brefeldiaceae. 

Family 6. Cribrariaceae. 

Family 7. Liceacese. 

Family 8. Tubiferaceae. 

Family 9. Reticulariaceae. 

Family 10. Trichiaceae. 

CLASS II. SCHIZOMYCETES. 
ORDER I. EUBACTERIALES. 

Family i. Coccaceae. 

Family 2. Bacteriaceae. 

Family 3. Spirillaceae. 

Family 4. Phycobacteriaceae (Chlamydobacteriaceae). 

Family 5. Thiobacteriaceae (Beggiatoaceae). 

Family 6. Actinomycetaceje (position doubtful). 

ORDER II. MYXOBACTERIALES. 
Family i. Myxobacteriaceae. 

CLASS III. EUMYCETES. 

Subclass. Phycomycetes. 

ORDER I. ZYGOMYCETALES. 

Family i. Mucoraceae. 

Family 2. Mortierellaceae. 

Family 3. Choanephoraceae. 

Family 4. Chaetocladiaceae. 

Family 5. Piptocephalidaceae. 

Family 6. Entomophthoraceae. 



MYCOLOGY 

ORDER II. OOMYCETALES. 

Family i. Monoblepharidacejr. 
Family 2. Saprolegniaceae. 
Family 3. Peronosporaceae, 
Family 4. Chytridiaceae. 
Family 5. Ancyclistaceas. 

Subclass. Mycomycetes. 

ORDER III. ASCOMYCETALES. 
Suborder A. Protoasciine^. 
Family i. Endomycetaceae. 
Family 2. Exoascaceae. 

Suborder B. Saccharomycetiine;1': 
Family i. Saccharomycetaceas. 



Suborder C. Plectasciine^. 


Family i. 
Family 2. 
Family 3. 
Family 4. 
Family 5. 


Gymnoascaceae. 

Aspergillaceje. 

Elaphomycetaceae. 

Terfeziaceae. 

Tuberaceae. 


Suborder D. Perisporiine^. 


Family i. 
Family 2. 
Family 3. 


Erysiphaceae. 

Perisporiaceae. 

Microthyriaceae. 



Suborder E. Pyrenomycetiine^. 
Family i. Hypocreaceae. 
Family 2. Dothideaceae. 
Family 3. Sordariaceae. 
Family 4. Chaetomiaceae. 
Family 5. Sph^eriacea?. 
Family 6. Valsaceae. 
Family 7. Melogrammataceae. 
Family 8. Xylariaceae. 



GEN-ERAL STATEMENT AND CLASSIFICATION 

Suborder F. Discomycetiine^, 
Family i. Hysteriaceae. 
Family 2. Phacidiaceae. 
Family 3. Pyronemaceae. 
Family 4. Ascobolaceae. 
Family 5. Pezizaceae. 
Family 6. Helotiaceae. 
Family 7. Mollisiaceae. 
Family 8. Celidiaceae. 
Family 9. Patellariaceas. 
Family 10. Cenangiaceas. 

Suborder G. HELVELLiiNEiE. 
Family i. Geoglossaceae. 
Family 2. Helvellaceae. 
Family 3. Cyttariaceae. 
Family 4. Rhizinaceae. 

Suborder H. Laboulbeniine^. 
Family i. Peyritschiellaceae. 
Family 2. Laboulbeniaceae. 
Family 3. Zodiomycetaceae. 

ORDER IV. BASIDIOMYCETALES. 
Suborder. Hemibasidiine^. 
Family i. Ustilaginaceas. 
Family 2. Tilletiaceas. 

Suborder. Uredine^. (Usually Order Uredinales). 
Family i. Endophyllaceae. 
Family 2. Melamsporaceae. 
Family 3. Pucciniaceae. 
Family 4. Coleosporaccce. 

Suborder. Auricularin^. 
Family i. Auriculariaceae. 
Family 2. Pilacraceae. 

Suborder. Tremellin^. 
Family i. Tremellaceae. 



6 MYCOLOGY 

Suborder. Eubasidiine^. 

A. Hymenomycetes. 
Family i. Dacryomycetaceae. 
Family 2. Exobasidiaceae. 
Family 3. Hypochnaceae. 
Family 4. Thelephoraceae. 
Family 5. Clavariaceas. 
Family 6. Hydnaceae. 
Family 7. Polyporaceae. 
Family 8. Agaricacese. 

B. Gasteromycetes. 
Family i. Hymenogastraceae 
Family 2. Tylostomaceae. 
Family 3. Lycoperdaceae. 
Family 4. Nidulariaceae. 
Family 5. Sclerodermacese. 
Family 6. Sphaerobolacese. - 

C. Phallomycetes. 
Family i. Clathraceae. 
Family 2. Phallaceae. 

Fungi Imperfecti (Deuteromycetes). 
ORDER I. SPH^ROPSIDALES, with 4 families. 
ORDER II. MELANCONIALES, with i family. 
ORDER III. HYPHOMYCETALES, with 4 families. 

The above classification has been given in outline with the object 
of presenting to students the information which is requested frequently 
of the professor in the class room. A detailed presentation of the spe- 
cial morphology, histology, embryology and taxonomy of each group 
will be given in the pages which follow, omitting matters concerning 
pathology and practice. A separate section of this treatise will be 
devoted to the consideration of fungous diseases of plants and their 
treatment. 



CHAPTER II 

SLIME MOULDS (MYXOMYCETES) 

CLASS I. MYXOMYCETES 

Considerable attention has been given in recent years to the sHme 
moulds on account of their biologic interest, taxonomic relationship 
and disease-producing forms. As organisms, they have been bandied 
about. They have been claimed by zoologists and botanists alike, 
for in certain stages of their life cycle they strongly suggest the protozoa, 
such as the amoeba. Perhaps on account of this uncertainty one would 
be justified in placing the slime moulds in the class Protista of Haeckel, 
which group was intended to include all such primitive organisms 
which naturalists have been unable to put satisfactorily either in the 
animal, or the vegetable kingdoms, but which partake of the nature of 
both the animal and the plant phylae. Hence we would have as a 
tentative arrangement 

Protista 
/ \ 

/ \ 

Protozoa Protophyta 

where the Protista represent the primitive stock of organisms which 
have given rise to simple animals on the one hand, or primitive plants 
on the other. 

Fries and some of his predecessors considered that the slime moulds 
were puffballs (Gasteromycetes) and the expression of this view is 
suggested in the name Myxogastres given them by Fries in 1833. 
Wallroth in 1836 viewing them as related to the fungi termed them 
MYXOMYCETES. De Bary, the German botanist, in 1858, impressed 
by their closer relationship with the animal world, called them Myce- 
TOZOA. Zo'pi in 1885 describes them as Die Pilzthiere and Rostafinski, 
a pupil of De Bary, working under his supervision in an elaboration 
of a monograph of these organisms, calls them Mycetozoa. We, there- 
fore, are limited by strict priority to adopt the name Myxogastres 
for them; but there are valid reasons why the name Myxomycetes 

7 



8 MYCOLOGY 

should be used. One of the strongest arguments is thai if we consider 
them as plants they belong to the phylum of the fungi and hence this 
name Myxomycetes aligns itself with Schizomycetes and Eumycetes 
generally adopted for the other groups of fungi. It conduces to clarity 
and simplification of classification to adopt the name of Wallroth for 
the class of organisms incapable of an independent existence, being 
destitute of chlorophyll and mainly saprophytic. The older name is 
retained, however, as the name of the third order of Myxomycetes, 
hence there should be little criticism of the view taken above. The 
Myxomycetes (Mycetozoa, Schleimpilze, Pilztiere, Slime Moulds) are 
chlorophylless organisms. Their vegetative condition is known as a 
Plasmodium which is a naked streaming mass of protoplasm. Repro- 
duction is by means of spores produced as exospores, or endospores, 
the latter in sporangia, gethalia, or plasmodiocarps. The spores give 
rise to amceboid cells or flagellate swarmers which unite later to form 
the Plasmodium, or develop directly into the plasmodium. 

ORDER I. ACRASIALES.—The members of this order live on 
the excrements of animals and on the decaying parts of plants. They 
commence their development with the escape of an amoeboid body 
from the walls of the spore and then move about by creeping move- 
ments, never assuming ciHa for locomotion. The amoeboid cells pile 
up on one another without coalescing to form what has been called an 
aggregate plasmodium, and they remain distinct, and artificially sepa- 
rable, though closely packed together until the fructification forms, 
when they rise above the substratum and form bodies of definite 
shape. Every one, or the majority of these definitely arranged amoe- 
boid bodies, becomes a spore covered by a dehcate membrane and of an 
average size of 5 to 10 m- These heaps of spores resemble the sporangia 
of the true shme moulds, but there is no distinct sporangial wall, 
the spores being held together by a structureless enveloping substance. 
The plants of this group are saprophytes. Gutkdina rosea lives on 
decaying wood in Europe. Dictyosteliuni mucoroides is frequent on 
old dung, while Acrasis granulata is found on old yeast cakes. Poly- 
sphondylium violacewn occurs in southern Europe on manure. 

ORDER II. PHYTOMYXALES.— The shme moulds of this order 
are parasites which live in the cells of higher plants. The plasmodium 
is limited by the cell walls of the host plants, and has its origin in 
amoeboid cells which enter and infest the host cells, resulting in a 



SLIME MOULDS (mYXOMYCETES) 9 

stimulation of the host to form gall-hke swelUngs. The whole Plas- 
modium is later transformed by division into a greater or less number 
of parts, which become surrounded by membranes to form spores. 
The spores are free in the cells of Plasmodiophora, while in SorosphcBra 
and in Tetramyxa they are clumped, and surrounded by a delicate 
membrane. The order includes a single family: 

Family i. Plasmodiophorace^. — ^The characters of this family are 
coincident with those of the class as given above. The family includes 
four genera distinguished as follows: 

A. Spores distinct from each other, irregularly aggregated and fiUing 
the host cells. 

{a) Spores regular in shape, spheric, (i) Plasmodiophora. 

(b) Spores irregularly shaped, rod-like, or angular. (2) Phytomyxa. 

B. Spores united into clumps inclosed by a delicate membrane. 
{a) Spores united in groups of four each. (3) Tetramyxa. 

(b) Spores in greater number, united into hollow spheres. (4) 
Sorosphcera. 

The genus Plasmodiophora comprises possibly three species found 
in Europe and America. They are parasites in the parenchyma cells 
of the cortex of the roots of the higher plants, where they produce 
gall-like swellings. The plasmodium fills some of the living cells of 
the host. The spores formed subsequently are spheric and lie free 
within the host cells. The best known species is P. brassicce which 
is the cause of a serious disease known as club foot, or finger and toes 
(Fig. i). The symptoms of the disease, the relationship of host and 
parasite, will be described in a subsequent section of this book. Two 
other species have been described, viz., P. alni in the roots of the alder; 
and P. eleagni in the roots of Eleagnus, the silverberry. Considerable 
more study will have to be made of the organisms in the roots of the 
alder and silverberry before we can definitely place the causal organ- 
isms. Tentatively, we may adopt the generally accepted view of the 
systematic relationship of the two responsible organisms until later 
investigation either proves or disproves the nature of the parasites 
attacking Alnus and Eleagnus. 

The genus Phytomyxa is represented by two species which live as 
parasites in the roots of Hving plants and cause tuber-like enlargements. 
The Plasmodia fills the host cells, and later, the irregularly shaped 



MYCOLUGY 




Pig. I. — Club-root of cabbage, Plasniodiophora brassicce. i, Turnip with club- 
root; 2, section of cabbage root with parenchyma cells filled with slime mould; 3, 
isolated parenchyma cell, (v) vacuole, (0 oil-drops in Plasmodium, (/>) Plasmodium; 
4, lower cell with Plasmodium, upper cell with spores developing; 5, parenchyma 
cell with ripe spores; 6, isolated ripe spores; 7, germinating spores; 8, myxamoeba. 
{Figs. 2-8, after Woronin in Soraucr, Handbuch der PJlanzenkrankheiten, 1886, p. 72.) 



SLIME MOULDS (mYXOMYCETES) . II 

spores fill the infested host cells. Two species have been described. 
The nature of Ph. leguminosanim is doubtful, as it may have been 
•confused with one of the stages of the nodule-producing bacteria, 
which are found in the roots of leguminous plants. 

The parasitic slime mould, Tetramyxa, occurs as one described 
species Tetramyxa parasitica, which lives in the stems and flower stalks 
of water plants, as Ruppia rostellata, where it causes tubercles 0.5 to 
I mm. in diameter. Each host cell contains numerous colorless spores 
united into tetrads. 

SorosphcBra is represented in Germany by S. veronica; found in the 
stems and petioles of Veronica hederifolia, V. triphylla and V. chamce- 
drys. The cells of the galls are swollen and filled with numerous 
spheric or ellipsoidal brown balls, 15 to 22 /x in diameter, formed of a 
single layer of spores united into a hollow sphere and covered externally 
by their pellicle. 

ORDER III. MYXOGASTRALES.— This order includes the true 
slime moulds which are non-parasitic, but live on decaying organic 
material, such as old logs, leaf mould in the forest, compost heaps, 
spent tan bark and other organic debris in the fields, woods, and 
along the roadsides. One form grows over the grass of lawns and 
smothers the grass with its plasmodium and later by its sporangia and 
spores. The plasmodium is a naked mass of protoplasm usually of a 
reticulate structure and multinucleate. It arises by the union of the 
myxamoeba which are developed from the flagellate myxomonads by 
the loss of the vibratile flagella. Such a plasmodium is known as a 
fusion Plasmodium.^ It usually assumes a reticulate, or net-like, 
structure and currents of protoplasm are seen flowing along the strands 
of greater or less thickness of which the plasmodium is composed. The 
central portion of each current is denser and moves more rapidly than 
the marginal clearer protoplasm. Perhaps we are justified in stating 
that the outer protoplasm is the ectoplasm and the inner granular 
cytoplasm containing food substances and other included substances 
is the endoplasm. For some time the plasmodium may flow in a given 
direction and later it may reverse its course, moving in an entirely 
opposite direction. The color of the plasmodium difi"ers in different 
species, as the following table will show. White or yellow seem to be 
the more usual colors. 

1 In Lahyrinlhiila Cicnkowskii parasitic in Vauchcria the plasmodium is filamen- 
ous. 



12 . MYCOLOGY 

Yellow Fiiligo seplica. 

Orange TricJiia scabra. 

White Pliysai'um. cUipsoidcum. 

Lead-colored Crihraria argillacea. 

Pink Enteridiv.m splendens. 

Ruby-red , Hemitrichia vesparum. 

Red Tubifera ferruglnea. 

Scarlet Cribrarla purpurea. 

Brown Tubifera Casparyi. 

Violet Cribraria violacea. 

The movement of the plasmodium is associated with the incorpora- 
tion of food. The yellow plasmodium of Badhamia utricularis has 
been most carefully studied in its relation to a food supply. It can be 
cultivated on such woody fungi as Stereum hirsutum, over which it 
extends, devouring by enzyme action the more delicate hyphae. 
Thus nourished, it will spread over the moist filter paper inside of the 
covering bell jar until I have seen the plasmodium hanging down 
like stalactites from the inner top of the bell jar. Such a captive 
Plasmodium has been fed by the writer pieces of mushroom 
Agaricus campestris. Shaggymane, Coprinus comatus and beefsteak 
have been placed on the surface of the protoplasm and in a few hours 
these substances have been found in advanced stages of digestion. 
Cheese is reluctantly invaded and is more refractory. The plas- 
modium is responsive to changes in the moisture surroundings. It 
moves toward a more abundant water supply. It is hydrotropic. 
It moves against a current of water and is, therefore, rheotropic. 
When highly illuminated, the plasmodium moves away from the 
lighted surface. It is negatively heliotropic. If there is a sudden 
change in the watery environment, the plasmodium will become 
massed into a cake-like lump in which form it remains as a sclerotium, 
macrocyst, or phlebomorph, if the substratum loses its water supply. 
In the sclerotial condition, the writer has kept a plasmodium for 
nine months on a plate of glass placed inside of a laboratory case 
in an absolutely dry condition. It was started into activity at the 
end of this period of rest on restoring free water to it again, and 
by feeding it mushrooms, it was kept in its restored activity for 
several weeks beneath a bell jar. The plasmodial stage may be pro- 
longed for an indefinite period, if the environmental conditions of 
temperature, Hght, moisture and food, are favorable. The writer has 



SLIME MOULDS (m\^OMYCETES) 1 3 

kept a Plasmodium in a streaming condition for over a month be- 
neath a bell jar. Physarum psitiacinuni, which inhabits the rotten 
stumps of old trees, appears to pass a year as a plasmodium. 

The early stages in the formation of the sporangium have been de- 
scribed in Comatricha oUusata. When the fruiting period is reaclifd, 
the watery- white plasmodium issues from the wood crannies and spreads 
over an area perhaps half an inch across. The plasmodium is seen to 
concentrate in thirty or forty centers and in an hour or two each 
center has by rhythmic pulsation of the protoplasm risen into, a pear- 
shaped body with a slender base and an enlarged upper portion. The 
black hair-Uke stalk has grown to its full length in six hours and on 
its summit is borne the young sporangium, which is a white viscid 
globule of protoplasm. A pink flush now begins to appear in the 
sporangium. The included nuclei are like those of the plasmodium 
at first, but later as spore formation proceeds they divide mitotically. 
The sporangia of the different slime moulds take various forms which 
will be described in general in the systematic generic keys which 
follow. They may be either symmetric or irregular in shape, sessile or 
stalked. The irregular sessile forms, which simulate the net-like 
appearance of the streaming protoplasm, are called plasmodiocarps. 
When the fruit body is fiat and cake-like with separating walls imper- 
fectly developed it forms an cethalium. The protoplasm which is 
left on the substratum and dries down as a film-like residuum is known 
as the hypothallus (Figs. 2 and 3). 

The changes which take place in the formation of spores and 
capilhtium have been minutely studied in a number of sUme moulds. 
We owe much to R. A. Harper, E. W. Olive and B. O. Dodge in America 
and to E. Jahn in Germany for our knowledge of these processes. The 
process in Didymium melanospermum, according to Harper,^ is as 
follows: The spore plasm condenses so that it is finely granular in the 
peripheral region and central region near the columella and foamy 
vacuolar in the middle zone. The capillitium is already formed before 
the condensation of the protoplasm has been accomplished. It con- 
sists of smooth threads which pass radially outward from the central 
dome-shaped columellar cavity to the sporangial wall. The threads 
of the capillitium are attached at their ends. The protoplasm is in 
contact with these threads and at this stage the nuclei are scattered 

1 Harper, R. A.: Amcr. Journ. Rot., i: 127-144, March, 1914. 



14 



MYCOLOGY 



rather uniformly through the spore plasm and are of unequal size. 
Vacuoles are formed in a still further condensation of the sporangial 
-protoplasm and each of these apparent vacuoles is pierced by a capilli- 
tial thread which runs through its central axis. Droplets of water are 
formed along the capillitial thread as a still further evidence of water 
extrusion. Cleavage planes now appear at the periphery of the mass 
of sporangial protoplasm and progress inwardly toward the center. 
The process of cleavage parallels the extrusion of water and the for- 
mation of the blocks of protoplasm by these cleavage lines is assisted 




Fig. 2. — -A, B, Comatricha nigra. A, Sporangium, natural size; B, capillitium, 
20/1; C, E, Stemonitis fusca; C, sporangium, natural size; D and E, capillitia, 5/1, 
20/1; F, H, Enerthema papillatum, F, unripe; G, mature sporangium, lo/i; H, capil- 
litium, 20/1. (C, D, after nature. A, F, G, H, after Rostafinski; B, E, after de Bary 
in Die natiirlichen Pflatizenfamilien I. i, p. 26.) 



by the presence of the vacuoles. The splitting up of the irregular blocks 
of protoplasm, which have the nuclei irregularly distributed through 
them, proceeds until the protoplasmic blocks arebinucleated,and before 
this the nuclei are seen in various stages of division which proceeds 
irregularly in Didymium, while in Fuligo the division of the nuclei is 
simultaneous in a particular spore sack. The plasma membranes of 
the capillitial openings are the source of cleavage furrows to even a 
greater degree than the original surface plasma membrane of the spore 
sack as a whole. In Fuligo in the final stages of spore formation the 
spore plasm is condensed about the nuclei, but in Didymium, the ultimate 



SLIME MOULDS (mYXOMYCETES) 1$ 

result of the progressive cleavage in f urrowin,^ is the formation of uninu- 
cleated rounded spores. They he packed between the capillitial 
threads. 

Most genera of slime moulds have a capiUitium (Figs. 2 and 3) 
consisting of a system of threads, and as we have seen, it appears be- 
fore the spores are formed. When the capiUitium extends from the 
base of the sporangium, it is associated with a columella (Fig. 2). It 
differs widely in the dififerent genera of the groups. In some genera, as 
Trichia and Arcyria, the capiUitium consists of free threads, or elaters. 
In those genera in which calcium carbonate is present in the sporangia, 
it is found in the capiUitium usually when several threads meet forming 
then the so-caUed hme knots. In Dictydimn, purplish-red granules 
are imbedded in the threads of the false capiUitium and are known 
as dictydin granules. The formation of the capiUitium in certain 
myxomycetes has been investigated by Harper and Dodge.^ They 
find that the capiUitium is formed by the deposit of materials in the 
vacuoles from which the capiUitial thread is formed and that radiating 
threads run out from the larger granules which are deposited by the 
process of intraprotoplasmic secretion. These radiating fibrUs sug- 
gest rather strongly that they are cytoplasmic streams which are 
bringing materials for the formation of the capillitial wall and its thick- 
enings which are laid down sometimes as spirals, suggesting that the 
process is comparable to the ordinary processes of cell-waU formation, 
but along internal plasma membranes, rather than external. The 
relation of the fibrils to the capillitial granules is best seen where a 
capiUitial vacuole runs longitudinally. Strasburger's earher observa- 
tions are confirmed by the recent work on capiUitial formation, when 
he described the capiUitium of Trichia fallax as originating in vacuolar 
spaces in the cytoplasm which elongate and take on the tubular form 
of young capillitial threads, while the formation of the wall and spiral 
thickenings are due to the deposition of granules as intraprotoplasmic 
secretions consisting of microsomes of the membranogenous type. 
Where the capiUitial threads are solid they may be called stereone- 
mata; where hollow, coelonemata. 

The spores are discharged from the sporangia, and if they find a 
suitable medium in which to grow,- such as free water, they give rise to 
swarm cells, as amoeboid bodies, or myxamoebse. These soon acquire a 

^Annals of Botany, xxviii: 1-18, January, rQi4. 



I 6 MYCOLOGY 

.flagellum at the anterior end and creep in a linear form with the flagellum 
extended in advance, or swim about in the water with a dancing move- 
ment occasioned by the lashing of the flagellum. They have a single 
nucleus and a contractile vacuole. To a large extent they feed on 
bacteria which are swallowed by pseudopodia which project from the 
posterior end of the cell. The swarm cells increase rapidly by biparti- 
tion. When this takes place, the flagellum is first withdrawn and the 
main cell assumes a globular form; it then elongates and a constriction 
occurs at right angles to the long axis. The nucleus divides by karyo- 
kinesis and in the course of a few minutes the halves of the nuclear 
plate separate and retreat to the opposite ends of the constricted cell 
which now divides into two, each new cell acquiring a flagellum. 
Sometimes the swarm cells become encysted to form the so-called 
microcysts, or zoocysts. 

The spores of Ceratiomyxa, which are borne on the outside of 
column-like sporophores, are white in color. The surface of the 
sporophore is divided into lozenge-shaped areas each with a projecting 
stalk bearing a single spore. The nucleus. of these spores, according 
to Jahn, twice divide by karyokinesis, and finally, when the spore 
germinates, eight amoeboid bodies are liberated, each of which develops 
a flagellum and the cluster swims away by the lashing of the flagella. 
Finally, these cells separate. All other myxomycetes have spores 
which in germination produce only one myxamoeba. 

Spores of Reticularia which had been dry for eight months germi- 
nated in thirty-five minutes at a temperature of 21°. Spores exposed 
to a temperature of 37° for only five minutes germinated in eleven 
minutes. The spores of Stemonitis flaccida germinated in one hour, 
those of AmauroclKBte in two and one-half hours, those of Didymium in 
four to five hours, while it took the spores of Stemonitis ferruginea in 
wood decoction three to five days to germinate. 

Some remarkable discoveries have been made with regard to an 
alternation of generations in the slime moulds connected with a so- 
called sexual act. Jahn, Kranzlin and Olive have worked upon this 
problem. The generation in all the Myxomycetes, including Ceratio- 
myxa, with the double chromosome number (8)' (diploid condition) in 
the nuclei is of short duration. The nuclei of the swarm bodies, amoe- 
boid bodies and the plasmodium have the single number (4) of chromo- 
somes. Union of the nuclei to form fusion nuclei with double 



SLIME MOULDS (mYXOMYCETES) 



17 



the number (8) of chromosomes immediately precedes the formation 
of the sporangia. The reduction division, which results in the forma- 
tion of spores, is preceded by synapsis, cUakinesis and heterotypic 
nuclear division. Small nuclei and large nuclei are seen. The large 
nuclei are probably fusion nuclei. The small nuclei probably 
disintegrate. 

To the order Myxogastrales belong the majority of the Myxo- 
MYCETES (Figs. 2 and 3). Many are found on decaying wood as Dic- 
tydium cernumn with black spore contents, Arcyria nutans and A. 




Fig. 3. — A, B, Leocarpus fragilis. A, Sporangium, natural size; B, capillitium 
200/1; C. Craterium leucocephalum sporangia, 6/1; D, Physarum sinuosum spor- 
angium, 6/1; E, F, Tilmadoche miitabilis; E, sporangia, 20/1; F, capillitium, 200/1. 
(.4, C, D, after nature; B, E, F, after Rostafinski in Die natiirlichen Pflanzenfamilien 
I. I, p. 32.) 



punicea have net-like capilHtia, the former with yellow, the latter 
with a red one. Lycogala epidendrum has a cinnabar-red plasmodium 
and a brownish-gray aethalium. Trichia varia, T. chrysosperma, He- 
miarcyria clavata have yellow sporangia and golden-yellow spirally 
sculptured elaters, Reticularia lycoperdon has a large brown cake-like 
aethalium. The yellow plasmodium of Fuligo septica sometimes covers 
spent tan bark and is known as "flowers of tan. " It is one of the most 
generally distributed of slime moulds and the writer has found its 
sethaha on the bark of street trees and even on the bricks of the street 
pavements, as yellow-brown, cake-like fructifications crumbling readily 



1 8 MYCOLOGY 

into a powder. The Plasmodium of a species of Chondriodcrma lives at 
the edge of melting snow fields, or even on the snow itself. The organ- 
ism of malaria frequently called Plasmodium malaria; is not a slime 
mould, but rightly belongs to the group of HdmosporidicB, a division 
of the Protozoa. 

The sHme moulds are cosmopolitan. Many of the same forms have 
been found in North and South America, the West Indies, Europe, 
Cape of Good Hope, AustraHa, New Zealand and Japan. The writer 
has used a manual of the Myxomycetes of Buitenzorg, Java, in the 
identification of species found near Philadelphia. About 214 species are 
represented in the British Museum collection. 

Laboratory Exercise. — The wjiter has found in his experience as a 
teacher that time may be profitably spent by a class in mycology in the 
identification of the common slime moulds. The sporangia, aethalia 
and plasmodiocarps of the different kinds can be kept separately in 
different small pasteboard boxes and material out of these boxes can 
be distributed to the members of the class. The dried material is first 
treated with 70 per cent, alcohol to remove the air, and then the treated 
material is mounted for permanent preservation in glycerine jelly. 
The absorption of water by the glycerine jelly is prevented by a ring 
of asphalt. The "Guide to the British Mycetozoa exhibited in the 
Department of Botany, British Museum Natural History," ist 
Edition, 1895, 2d Edition, 1905, 3d Edition, 1909, has been used in 
classes at the University of Pennsylvania with much success. After 
the generic name has been determined. Lister's "British Mycetozoa" 
or MacBride's "North American Slime Moulds" can be used to find 
the name of the species. 

BIBLIOGRAPHY 

CoNARD, H. S.: Spore Formation in Lycogala exigiium Morg. Iowa Acad. Sci., 

17: 83, 1910. 
Cooke, M. C: The Myxomycetes of Great Britain Arranged According to the 

Method of Rostafinski, 96 pp., 24 pis., London, Williams & Norgate, 1877. 
Cooke, M. C: The Myxomycetes of the United States Arranged According to the 

Method of Rostafinski. Annals Lyceum, Nat. Hist., New York, 11: 378-409, 

1877. 
Cook, O. F.: Methods of Collecting and Preserving Myxomycetes. Botanical 

Gazette, 16: 263, 1891. 
DE Bary, Anton: Comparative Morphology and Biology of the Fungi, Mycetozoa 

and Bacteria. Oxford at the Clarendon Press, 1887, especially pp. 420-453. 



SLIME MOULDS (mYXOMYCETES) 1 9 

Harper, R. A.: Cell and Nuclear Division in Fiiligo varians. Botanical Gazette, 

30: 217, 1900. 
Harper, R. A.: IVogressive Cleavage in Didymium. Science, new ser. 27: 341, 

1908. 
Harper, R. A.: Cleavage in Didymium melanospermum (Pers.) Macbr. Amer. 

Journ. Bot., i: 127-143, March, 1914, with 2 plates. 
Harper, R. A. and Dodge, B. O. : The Formation of the Capillitium in Certain 

Myxomycetes. Annals of Botany, xxviii: 1-18, January, 1914, with 2 plates. 
Harshberger, J. W.: Observations upon the Feeding Plasmodia of Fuligo septica. 

Botanical Gazette, 31: 198-203, 1901. 
— ■ — ■ — Distribution of Nuclei in the Feeding Plasmodia of Fuligo septica. Journ. of 

Mycology, 8: 158-160, 1902. 
• — ■ — ■ — A Grass-killing Slime Mould (Physarum cinereum). Proc. Amer. Philos. 

Soc, 45: 271-273, 1906. 
Jahn, E.: Myxomyceten Studien. Ber. Deutsch. Bot. Gesellsch. I. Dictydium 

umbilicatum, 19: 97-115, 1901; II. Arten aus Blumenau, 20: 268-280, 1902; 

III. Kernteilung und Geisselbildung bei den Schwarmen von Stemonitis flaccida, 

22: 84-92, 1904; IV. Die Keimung der Sporen, 23: 489-497, 1905; V. Listerella 

paradoxa, 24: 538-541, 1906; VT. Kernverschmelzungen und Reduktionsteilun- 

gen, 25: 23-26, 1907; VII. Ceratiomyxa, 26": 342-352, 1908; VIII. Der Sexualakt, 

29: 231-247, 1911. 
Kranzlin, H.: Zur Entwicklungsgeschicte der Sporangien bei den Trichlen und 

Arcyrien. Archiv Protistenkunde, ix: 170-194, 1907. 
Lister, A: Notes on the Plasmodium of Badhamia utricularisand Brefeldia maxima. 

Annals of Botanj^, 2: 1-24, 1888. 
Lister, A.: On the Division of Nuclei in the Mycetozoa. Linn. Soc. Journ., xxxix: 

529, 1893. 
Lister, A.: A Monograph of the Mycetozoa, 224 pp., 78 pis., p. 894. 
Lister, A: Guide to the British Mycetozoa Exhibited in the Department of Botany, 

British Museum of Natural History, ist Edition, 1895; 2d Edition, 1905; 

3d Edition, 1909. 
MacBride, T. H.: The North American Slime Moulds, being a list of all Species 

hitherto described from North America including Central America, pp. xvii + 

269: 16 pis., MacmiUan Co., 1899. 
MacBride, T. H. : On Studying Slime Moulds. Journ. Applied Microscopy, 2: 

585-587, 1899. ^ 

MacBride, T. H.: The Slime Moulds. Rhodora, 2: 75-81, 1900. 
Masses, G.: A Monograph of the Myxogastres, 336 pp., 12 pis., London, Methuen 

& Co., 1892. 
Olive, Edgar W.: Cytological Studies on Ceratiomyxa. Trans. Wise. Acad. Sci. 

Arts and Letters, XV : 753-773. 

Monograph of the Acrasieae. Proc. Boston. Soc. Nat. Hist., xxx: 451, 1902. 

Evidences of Sexual Reproduction in the Slime Moulds. Science, new ser. 

xxv: 266, 1907. 
Penzig, O: Die Myxomyceten der Flora von Buitenzorg, Leiden, 1898. 



20 MYCOLOGY 

Rex, G. a.: The Myxomycetes, Their Collection and Preservation. Botanical 

Gazette, lo: 290, 188';. 
ScHROETER, J.: Myxogasteres in Engler and Prantl; Die naturlichen Pflanzenfam- 

ilien, i: Abth. i, pp. 1-35, 1889-92. 
Schwartz, E. J. : The Plasmodiophoraccce and Their Relationship to the Mycetozoa 

and the Chytrideae. Annals of Botany, xxviii: 227, 1914. 
Strasburger, E.: Zur Ent\vickelungegeschichte der Sporangien von Trichia fallax. 

Bot. Zeitung, xliii: 305-16; 321-3, May 16, 1884 and May 23, 1884. 
Sturgis, W. C: The Myxomycetes of Colorado, No. i. Science, ser. xii. No. I, 

pp. 1-43; general ser. No. 30, September, 1907; No. II. Science, ser. xii, No. 

12, pp. 435-454, April, 1913; Colorado College Publications. 
Sturgis, W. C: A Guide to the Botanical Literature of the Myxomycetes from 

1875 to 1912. Science, ser. xii. No. 11, pp. 385-434. June-September, 1912, 

Colorado College Publication. 
ZoPF, W.: Die Pilzthiere oder Schleimpilze, i-vi -f 1-174 pp.. Figs. 1-51, Breslau. 



CHAPTER III 

THE BACTERIA IN GENERAL 

CLASS II. SCHIZpMYCETES 

The name Schizomycetes comes from two Greek roots (ax'i-^oi, 
I split + ijLVKr]s, a fungus) which combined are equivalent to the term 
splitting fungi, or fission fungi in allusion to the manner in which the 
bacterial cells divide. The Germans call them Spaltpilze, which is 
the German way of expressing the same thing. The name bacteria 
is in American science used in a general sense to include all of the 
Schizomycetes without reference in particular to the genus Bacterium. 
In popular use, such as newspaper articles, these lowly plants are 
described as germs, microbes, or microorganisms. These English 
synonyms are, however, inexact, having different shades of meaning 
and are used in different ways in common speech, as consultation with 
any large dictionary of our language will show. There is no ambiguity, 
if we speak of all the Schizomycetes as bacteria, or bacterial organisms. 
These plants are generally unicellular, or the single cells are united 
into a coenobium. These coenobia are filamentous, sheet-Uke, or in 
groups, seldom arranged in fructification-like masses of definite form, 
as is the case with the Myxobaderia. All cells of the coenobium are 
alike and only in the highest developed forms do we find a differentiation 
into basal cells and filament cells. The heterocyst, found in the blue- 
green algae, is totally absent. The cells of bacteria are the smallest 
of plant cells; for example: Micrococcus progrediens has a diameter 
of o.i5ju and Spirillum parvum has a thickness of o.i to 0.3^1, but yet 
smaller are the ultramicroscopic organisms, which have come into 
prominence recently as the cause of certain diseases. The smallest 
bacteria stand at the borderline o,f what is with the best lenses and 
optimum illumination the practical limit of microscopic vision. On 
the other hand, with the application of the ultraviolet light of short 
wave length in microphotography, it has been possible to obtain an 
image of small objects whose enlargement has been 4000-fold. It 
has been possible with the ultramicroscope of Siedentopf and Zsig- 



MYCOLOGY 



mondy to demonstrate small particles whose size is only many million 
times that of a miUimeter. The accompanying figure (Fig. 4) adopted 
from Fuhrmann' represents the relative size of the spheric bacteria 
and the rod-shaped organisms, while the breadth of the largest known 
bacterial cell, that of Beggiatoa mirabilis, which approaches that of a 
human hair in thickness, is represented in the larger area where the 
width of the cell is twice its length. 




4. — Diagram representing the relative sizes of spheric and rod-shaped bacteria 
{After Fuhrmann.) 









Diameter in m 




I. 


Micrococcus progredictis 


0. 


s 


Spheric 
Bacteria 


2. 


Micrococcus urece 


I to 


i-S 


3- 


Sarcina maxima 


4- 







. 4- 


Thiophysa volutans 


7 to 

Length in /i 


18 

Breadth in ^ 




5- 


Pscudomonas indigojcra 


0.18 


0.06 




6. 


Bacillus influenza; 


4.2 


0.4 






Methane bacillus 


50 


0.4 


Rod-shaped 


s'. 


Urobacillus Duclaiixii 


2 to ID 


. 6 to 0. 8 


Bacteria 


9. 


Bacillus nitri 


3 to 8 


2 to 3 




10. 


Beggiatoa alba 


2 . 9 to s . 8 


2.8 to 2.Q 


. 


II. 


Chromatium Okeni 


10 to 15 


5° 




12. 


Beggiatoa mirabilis 


ID to 20 ■ 


1.5 to 2.0 



The cells exhibit a definite cell wall which differs from that of the 
higher plants in not containing cellulose. The chemical character of 
the cell membrane indicates its close relationship to the living proto- 
plasm of the cell. Chitin has been found in the cell wall of some 
bacteria. Frequently the cell membrane undergoes a mucilaginous 
modification, so that the filamentous forms are surrounded by a sheath 

1 Fuhrmann, F.: Vorlesungen iiber Technische Mykologie, Fig. 7, page 17. 




THE BACTERIA IN GENERAL 23 

and the numerous individual forms are united into slimy, skin-like 
or lumpy masses known as zoogloea. 

The interior of the cell shows no differentiation into nucleus and 
cytoplasm, but the nuclein in certain forms seems to be scattered in 
the plasma (Fig. 5). Considerable diversity of opinion exists as to the 
nature of the cell substance of bacteria. The uniform staining of the 
cell by ordinary methods suggests that the cell substance is all cyto- 
plasm without nucleus. An opposite opinion is that the cell substance 
is composed almost entirely of nuclear matter (chromatin) with perhaps 
a thin layer of ectoplasm. Another view is that 
of Zettnow (Zeitschr. f. Hyg., 1899: 18), who regards 
the cell body of bacteria as composed largely or 
almost wholly of chromatin mingled with varying 
amounts of cytoplasm. This, however, can be said, 
that it is fairly certain that bacteria contain both 
chromatin and cytoplasm which vary in amount and 
position in different cells (Fig. 5). The cell mem- Fig. 5.— i,c/!)'o- 
brane is mostly colorless; seldom does it appear BTg^glai'oT"aibl' 
greenish or rose-red, as in the purple bacteria. Bacteria with a cen- 
When colonies of bacteria are colored, the coloring ch^'romatln °g'rtTns 

matter is an excretion product. which are considered 

Locomotion. — The movement of many bacteria is equiv^rienTof^a 
a true movement from place to place, not merely a nucleus. (From 
Brownian movement. It is accomplished in nearly f^l"'sfLTE7uion, 
all cases by the presence of cilia, or.flagella, which p. 91- After 
by some are considered to arise directly from the ^"^^'^''^^■^ 
cell membrane," by other investigators to arise from the ectoplasm 
within; its origin in some way associated with a blepharoplast. Which- 
ever view is the correct one, the motile filaments can in some large 
spirilla be seen in the living unstained organism, but generally it re- 
quires special methods of treatment and staining to make them out. 
Great differences exist as to their distribution. Some forms, as the 
cholera bacillus, have a single flagellum at one pole {monotrichous) ; 
others, as many spirilla, have a flagellum at each pole {amphitrichous) ; 
others, as certain large spirilla, have a tuft at one pole {lophotrichous) ; 
while others have cilia covering the whole cell, as the typhoid organism 
{peritrichous) . Many organisms are without cilia, or flagella {atrichous) , 
and hence are non-motile. 



24 MYCOLOGY 

Cell Division mid Reproduction. — As with other plant cells in general 
it may be said that growth is not conditioned on cell division. Growth 
is the enlargement of the cell, not merely a swollen condition, and this 
increase in size is within definite limits for each species, which can be 
determined by statistic study. As long as division is not preceded 
by nuclear division, the term fission is applicable. Certain students 
of the group claim that there is a division of the nuclear substance 
(Fig. 6), and Fuhrmaftn actually figures division of the nuclear mate- 
rial in such forms as Bacillus nitri, 
''^- ^ Micrococcus butyricus, Spirillum 

i_^ / ® ^ W volutans and the potato bacillus. 

^ L ^' Possibly then division of the 

nuclear substance precedes that 
of cell division, and if that phenom- 
enon is found general, the term 
fission is no longer apphcable. 



^. 



-O 









Fig. 6. Fig. 7. 

Fig. 6. — Bacterium gammari. a, b, c. Cells with typical nucleus of nucleoplasm, 
surrounded by a nuclear membrane and by one or two karyosomes also showing 
karyokinesis; d, a filamentous bacterium from intestine of an annelid worm, Bryo- 
drilus chlorii, each cell with a nucleus. {From Marshall. Microbiology, Second Edi- 
tion, p. 89, after Vejdowsky.) 

Fig. 7. — Cells of Bacillus megatherimn. i. Polar granules as nuclei; 2, increase 
in size of nucleus at time of sporulation; 3, same; 4, change in size of nucleus which 
is surrounded by a membrane and becomes a spore. (Fro?n Marshall, Microbiology, 
Second edition, p. 90, after Penan) 

Cell division may take place quite rapidly under favorable conditions. 
Bacillus siihtilis divides in thirty minutes; Vibrio cholera, every twenty 
minutes. The young cells attain full size in a short space of time. 
Bacteriologists have estimated, that if bacterial multiplication was 
unchecked and the division of each cell was accomplished inside of an 
hour that in two days the descendants of a single cell would number 
281,500,000,000, and that in three days the offspring of a single cell 
would weigh 148,356 hundredweights. Lack of food, accumulation of 
bacterial products injurious to the organisms that formed them explain 
why their rapid multiplication is kept in check. 

fformr library 

Ml r Qtnt0 Cnllpift 



THE BACTERIA IN GENERAL 25 

The spores formed by the bacteria are of two kinds, arthrospores 
and endospores. Arthrospores are whole vegetative cells which by a 
thickening of their walls become resting spores. Some bacteriologists 
would not include arthrospores as true spores. The true spores are 
formed in the cells and differ from the cells in resisting greater heat 
and by other definite structural and physiologic quaUties. (Fig. 7.) 
The shape of the cell may be altered with the formation of one or two 
spores within (endospores). In the hav bacillus, the spore occupies the 
center of the cell and is smaller than the original mother cell, hence the 
shape of the parent cell is not altered. Bacterium pants and Bacillus 
amylobacter become swollen in the middle when the spore forms so that 
the mother cell becomes spindle-shaped. The bacillus of lockjaw de- 
velops a spore at one end of the cell, which becomes drumstick-shaped, 
hence the German name trommelschlagel for such forms and the generic 
name Plectridium now given to cells that produce terminal spores. 

Bacillus amylobacter may develop one terminal spore, or two spores, 
one at each end of the cell, so that the mother cell becomes dumbbell- 
shaped. Bacillus inflatus may develop two spores also. 

Spores may germinate at the poles, as in Bacillus BiitscJili and B. 
amylobacter ; at the equator, as in Bacillus subtilis and B. loxosporus, or 
obliquely, as in Bacillus loxosus. In germination resting spores absorb 
water, and become more or less swollen, when the spore membrane 
is dissolved and the germ tube protrudes. 

The classification of bacteria according to their special activities, 
or the products formed by these activities, is useful in presenting 
another phase of the subject to the mycologic student. The fact is 
noteworthy that we can group the various organisms into the photo- 
genic (light-producing), chromogenic (color-producing), thiogenic 
(sulphur-producing), zymogenic (ferment-producing), pathogenic (dis- 
ease-producing), saprogenic (decay-producing) and thermogenic (heat- 
producing) without reference to their morphology, or genetic rela- 
tionship. It is useful to be able to discuss the light, heat, color, etc., 
produced by these organisms as distinct phenomena worthy of experi- 
mental treatment. 

Photogenic Bacteria. — The phosphorescence associated with decaying 
haddocks, mackerel and other sea fishes, the faint glow seen on badly 
preserved meats (beef, mutton, veal) and sausages are produced by 
photogenic bacteria. Most success is obtained by using sea fishes in 



26 MYCOLOGY 

experimenting with the phosphorescent bacteria, for these organisms 
require in their culture media from 2 to 3 per cent, of sodium chloride, 
besides the usual salts and peptone, the medium should contain some 
other source of carbon, such as sugar, glycerine, etc. The number of 
known photogenic bacteria is considerable. Migula names twenty- 
five species and Molisch twenty-six. A few need only be mentioned 
here, viz.: Bacterium phosphor escens Fischer; Bacillus photogenus 
Molisch; B. luminescens Molisch; Microspira glutinosa (Fischer) 
Migula; M. luminosa (Beijerinck) Migula; Pseudomonas javanica 
(Eijkmann) Migula. The results of numerous experiments are that 
the production of light by bacteria is an exclusively aerobic phenome- 
non, for in the absence of oxygen, they are non-luminous. The light 
is sometimes strong enough that jars containing luminous bacteria can 
be photographed by the light emitted by the organisms within the jar. 

Chromogenic Bacteria. — Most bacteria are colorless and even in such 
forms in which color is associated with their growth on culture media, 
the organisms are colorless. The bacillus which causes the "bleeding 
host," Bacillus prodigiosus, is colorless with the pigment in the form of 
granules scattered about between the bacterial cells. In other cases, 
the pigments and fluorescent substances are diffused in the culture 
medium outside the living cells. Hence, we may call such bacteria as 
chromoparous. The chromophorous species are those in which the 
protoplasm is actually colored. Such are some sulphur bacteria 
Chromatium and Thiocystis, and finally, there are some forms as Bacillus 
violaceus in which pigment is lodged in the cell wall, when we may call 
them parachromatophorous. Practically all of the colors of the spectrum 
are represented in the color productions of bacteria: violet {Bacillus 
violaceus), indigo {B. janthinus), blue {B. pyocyaneus), green {B. 
fluor escens), yellow {Sarcina lutea), orange {Sarcina aurantiaca) and red 
{B. prodigiosus). The erythrobacteria, or colored sulphur bacteria, 
are unique in the power of assimilating carbon dioxide in the presence 
of sunlight by the activity of bacteriopurpurin (a red coloring matter) 
which behaves Hke the chlorophyll of green plants. 

Thermogenic Bacteria. — Such substances as hay, silage, manure and 
cotton waste frequently become heated, the temperature inside the 
mass being raised to 60° or 7o°C. This spontaneous heating is due to 
the respiratory activity of the thermogenic bacteria of Cohn (aerobic), 
which set up fermentation and putrefaction. The horticulturist uses 



THE BACTERIA IN GENERAL 27 

manure, especially horse manure, in the construction of hot l)eds for 
the cultivation and forcing of young plants. In silos, the highest 
temperature recorded during the fermentation of the ensiled material 
was 7o°C. but the best silage is secured by keeping the temperature 
below 5o°C. Sometimes this spontaneous heating increases to the point 
of actual ignition (spontaneous combustion) and it may occasionally 
happen that such substances, as baled cotton, may be set on fire in this 
way, for Cohn found in damp cotton waste a Micrococcus which, when 
furnished with a plentiful supply of air, raised the temperature of the 
decaying mass to 67°C. 

Aerobic and Anaerobic Organisms. — Another useful division of 
bacteria is into those which are aerobic, requiring oxygen for their 
growth, and anaerobic, those which are indifferent to the presence of 
oxygen. The process of respiration in the aerobes is the same as in 
all ordinary organisms. Contrasted with the obligatory aerobes, we 
have those which thrive only in the absence of oxygen (obligatory 
anaerobes). The growth of some of the latter is inhibited by small 
traces of oxygen (Bacillus tetani and some butyric organisms). One 
of the classic experiments in biology was devised by Engelmann 
(Botanische Zeitung, 1881 and 1882) to detect minute traces of free 
oxygen. It is a well-known fact that in the process of photosynthesis, 
or carbon fixation, by green plants that free oxygen is formed. Experi- 
ments have shown that not all the rays of the spectrum are equally 
effective in causing this chemic change. The red rays between Fraun- 
hofer's lines B and C are most effective and after them those just 
beyond the F line. It is these rays that are most active in the evolution 
of oxygen. Engelmann reasoned, that if a green alga was placed under 
the microscope and illuminated from below by a spectrum, so that the 
algal filament paralleled the band of spectrum colors, that if aerobic 
organisms were introduced into water beneath the cover glass, these 
aerobic organisms would congregate in greatest numbers along the 
green alga at those points illuminated by the rays most effective in 
oxygen evolution by the plant. His anticipations were realized for 
he found a grouping of the aerobic bacteria in the neighborhood of the 
B and C Fraunhofer lines and beyond the F line, where theory told him 
to expect the greatest photosynthetic activity. Such minute quan- 
tities of oxygen must be formed by a filamentous green alga, that this 
experiment becomes a microchemic test for the gas. 



CHAPTER IV 
CLASSIFICATION OF BACTERIA 

Classification According to Nutrition. — An illuminating classification 
of bacteria has been based on their mode of life, where three biologic 
groups may be recognized: the prototrophic, the metatrophic and the 
paratrophic bacteria. The prototrophic bacteria, which include the 
nitrifying bacteria, bacteria of root nodules, sulphur and iron bacteria 
and erythrobacteria, are those which either require no organic com- 
pounds for their nutrition, or which given a small amount of organic 
carbon can derive all of their nitrogen from the atmosphere, or which 
with a minimum of organic matter can derive energy by breaking up 
inorganic bodies. 

The sulphur bacteria live in sulphur springs where hydrogen sul- 
phide (HoS) is formed by putrefaction of dead animals and plants. 
The sulphur bacteria in such places form a white furry growth on the 
rotting vegetation. Here the H2S is attacked and water and sulphur 
are formed, H2S + O = H2O -\- S. The sulphur is deposited in the 
living cells of the bacteria as yellow amorphous granules, which impart 
to the organism a yellow color. To explain the facts observed, we need 
assume only that the protoplasm increases the oxidizing power of the 
atmospheric oxygen and renders it active. The conversion of H2S 
into water and S gives 71 calories and the further oxidation of the freed 
sulphur into sulphuric acid 2109 calories. The fact that the sulphur 
bacteria can live without organic compounds together with their inability 
to live without sulphur indicates that it is the oxidation of the sulphur 
alone which takes the place of respiration in other organisms. 

The ferrobacteria live in stagnant pools in marshy places. On 
such pools of water, we find a greasy scum of ferric hydroxide Fe(0H)3 
together with organic matter and some phosphate of iron. The ferric 
compounds are reduced by the action of reducing substances formed by 
putrefaction to the ferrous state which are dissolved by carbon dioxide 
CO2 and unite also with it to form ferrous carbonate. The atmospheric 
oxygen can convert this carbonate back to ferric hydroxide, but Wino- 



CLASSIFICATION OF BACTERIA 29 

gradsky has shown that the process is assisted by the iron bacteria 
and the ferric hydroxide is deposited as a tube about such organisms 
as Leptothrix ochracea. These tubes, or sheaths, are deposited later 
as bog iron ore. 

The nitrifying bacteria are found in the soils of our gardens, fields 
and meadows and in virgin soil derived from places the world over. 
Winogradsky has discovered that the conversion of ammonia into 
nitric acid takes place in two steps and that bacteria are effective in 
both of these operations. One set of bacteria belonging to the genera 
Nitrosococcus and Nitrosomonas oxidize the 
ammonia to nitrous acid, or its nitrite, and the 
conversion of this nitrous acid (nitrite) to nitric 
acid, or its nitrate, is accomplished by Nitro- 
bader. Nitrosococcus is a non-motile spheric 
cell, 3^t in diameter, found in soil from South 
America and Australia, while Nitrosomonas 
europcea found in all soils from Europe, Africa 
and Japan is a short ellipsoidal motile iorm 0.9 
to iju wide and 1.2 to i.8/x long with a short 
cilium. Nitrosomonas javanensis from Java is 
almost spheric, 0.5 to 0.6/^, with a cilium 30/x 
long, which is the longest known among bac- 
teria. Nitrobacter are minute non-motile rods 

/ . , \ rr.1 • r ii. Fig. 8. — Roots of soy 

(o.5M X 0.25M). These organisms are of the i,ean. Glycine his pida, with 
greatest importance in putting the nitrogen of tubercles. (After Conn, 

,1 •!•- r !•! uuuji Agricultural Bacteriology, 

the sou mto a form which can be absorbed by p g^ ) 
the roots of the cultivated plants. 

The bacteria which produce the nodules (Fig. 8) on the roots of 
leguminous plants are probably the same the world over and to them 
Beyerinck has given the name of Bacillus radicicola, while Frank called 
them Rhizobium leguminosarum (Fig. 10). When the seeds of clover, or 
some other leguminous species are planted, and soon after the primary 
root appears with its root hairs. Bacillus radicicola, attracted chemo- 
tactically to the fine root hairs, penetrates the walls of these root hairs 
by ferment action. So many bacilli enter the root hair cells that they 
form slimy cords, almost hyphae-like, as they move into the middle 
cortex cells of the root. Here in the cortex cells, the microorganisms 
form nests or pockets, that are filled with the nodule-producing bacteria 




30 



MYCOLOGY 



(Fig. 9). The presence of these bacteria causes the formation of swell- 
ings, tubercles, or nodules on the roots of the leguminous plants. Here 
Bacillus radicicola remains, utilizing free atmospheric nitrogen until 
about the time of flowering of the host, when it begins to assume in- 
volution forms, enlarging considerably and assuming S-shaped or 
Y-shaped forms (Fig. i o) . Then they are gradually absorbed by the 



""*>§»**' 











Fig. 9. — Cells of root tubercle of Lupinus angustifolius magnified to show the 
bacteria; four cells with nuclei. {After Moore, Geo. T., Yearbook U. S. Dept. Agric, 
1902, 'pi. xxxix.) 



green leguminous plants and their substance is transformed into a 
form of nitrogenous substance, which is utilized by the leguminous 
host, either as food, or stored as nitrogenous reserve supplies. The 
nodule becomes emptied of its contents and remains as a hollow sac, 
enough of the organisms being returned to the soil to seed it and provide 
for infection of other leguminous crops that may follow. The growth 



CLASSIFICATION OF BACTERIA 3 1 

of these useful organisms in the soil is stimulated by aeration, by some 
organic material, by proper soil drainage, by the application of lime 
which overcomes soil acidity. The farmer becomes independent of 
the ordinary nitrogenous fertilizers, which are expensive, by plowing 
under the leguminous crops, which on decay yield up to the soil the 
nitrogenous substance largely accumulated by bacterial action where 
it is available to that large class of nitrogen-consuming plants such as 
the grasses, weeds, root crops, fruit crops and the like, which are de- 
pendent on the soil nitrates for their nitrogen. The leguminous plants 
as nitrogen-storing plants should, in an up-to-date rotation, be 
alternated with the nitrogen-consuming crops. 






C' '"b-^y 



Fig. io. — Left, branching forms of bacteria from clover tubercle (X2000); 
right, rod forms from fenugreek tubercle ( X 2000). {After Moore, Geo. T., Yearbook 
U. S. Dept. Agric, 1902, pi. xxxix.) 

Metatrophic Bacteria. — The metatrophic bacteria include the zymo- 
genic, saprogenic and saprophile bacteria, which cannot live unless 
they have organic substances at their disposal, both nitrogenous and 
carbonaceous. They flourish where organic substances and foodstuffs 
are exposed to decay in impure water and in the waste from animal 
bodies. Many of them produce profound fermentative changes 
(zymogenic bacteria) in bodies. Others cause putrefaction and decay 
(saprogenic bacteria), while others develop in media which have been 
decomposed by saprogenic species and as saprophile organisms break 
these substances up into simpler chemical form. 



32 MYCOLOGY 

P'ermentation is well exemplified in an old and well-known process, 
the conversion of alcohol into acetic acid by a number of organisms 
morphologically very similar. Hansen considers that there are three 
different species concerned in the acetic fermentation, namely, Bacterium 
aceticum, B. Pasteurianus and B. KiUzingianus, which are non-motile, 
medium-sized rods often in chains and forming pellicles which appear 
on the surface of the liquid, afterward sinking to form in the liquid a 
deposit known as mother of vinegar. The changes which take place 
in the conversion of alcohol to acetic acid may be expressed as follows: 

CH3.CH2.OH + O = CH3.CHO -f H2O 

Alcohol Aldehyde 

CH3.CHO + O = CH3.COOH 

[Aldehyde Acetic Acid 

This is conducted in barrels with wood shavings, where the alcoholic 
fluid trickling over the shavings coated with the bacteria, and in contact 
with the air, is changed to acetic acid. 

Lactic acid fermentation is important to man, because upon the 
changes in milk by the lactic acid organisms depends the manufacture 
of a considerable number of valuable products of the dairy, such as 
buttermilk and cheese. This fermentation is an aerobic process whose 
optimum is found between 30° and 3S°C. There is a considerable 
number of bacteria capable of converting milk sugar into lactic acid, 
such as Vibrio cholera, Bacillus prodigiosus and others, but the true lactic 
acid bacteria are those which are the cause of the souring of milk. 
Formerly, they were all classed as Bacterium acidi lactici, but recent 
investigations have shown that not one species but a considerable 
number are at work, sometimes one form; sometimes another being 
active. A common kind is a short non-motile rod, o.^^xX. i to 2/^, 
facultatively anaerobic, known by such names as Bacterium acidi lactici, 
B. aerogenes, and probably comprising several races of one species. 
The true lactic acid fermentation is the change of lactose, or milk 
sugar, into lactic acid. As lactose is not directly fermentable it must 
"be converted into such simple sugars as glucose and galactose. The 
following equation approximately represents the chemic change 
involved. 

C12H02O11 + H2O = CeHi.Ofi -f CeHisOe 

Lactose Water Glucose Galactose 

C6Hi20r. = 2C3Hfi03 

Lactic Acid 



CLASSIFICATION (W BACTERIA ^t^ 

Several other important fermentations are due to bacteria, as the 
causal organisms, namely, the butyric, cellulose, and mucilaginous 
fermentations. The retting of vegetable fibers, the manufacture of 
indigo, the curing of tobacco are all dependent on bacterial fermentations. 

The saprogenic organisms are concerned with decay, or putrefac- 
tion. The decomposition of dead animal and plant bodies is far from 
being a simple putrefactive process. Nitrogenous and non-nitrogenous 
bodies are both concerned in the putrefactive changes and they are 
broken down into simpler nitrogenous and non-nitrogenous compounds, 
or even elements. Proteins are spUt up into albumoses and peptones, 
aromatic compounds (indol and- skatol), amino compounds (leucin, 
tyrosin, glycocol), fatty and aromatic acids and inorganic end products 
(nitrogen, ammonia, hydrogen, methane, carbon dioxide and hydrogen 
sulphide). Ptomaines and, 'other poisonous bodies are formed known 
as toxins, a name applied indiscriminately to all bacterial poisons.^ 

The activity of all these organisms in causing decomposition of 
animal and plant products is important in preserving the circulation 
of carbon and nitrogen in nature. Without such destructive changes, 
the elements carbon and nitrogen would be combined in such a form 
as to be forever lost to animals, and plants. In the dissolution of these 
complex bodies, the simpler chemic compounds are released and can 
be used over again by living animals and plants. Much should be 
made of the circulation of the elements in nature and the two chief 
cycles are the carbon cycle and the nitrogen cycle with a sulphur and 
phosphorus cycle as well. There are two main processes in organic 
life: the constructive processes (anabolism), and the destructive 
processes (katabolism) . Construction is accomplished mainly by green 
plants and the prototrophic bacteria. Destruction is the work of 
animals, metatrophic and paratrophic organisms; which have to break 
down organic matter to Uve. Thus the elements of the organic world 
are kept in perpetual circulation. 

Paratrophic Bacteria. — -These organisms occur only in the tissues 
and vessels of living organisms and are, therefore, true parasites. Many 
of them are responsible for animal and plant diseases and the special 
types, as far, as they concern this book, namely, those which induce 

^Consult Lathrop, Elbert C: The Organic Nitrogen Compounds of Soils and 
Fertilizers. Journ. Franklin Inst. 1S3 : 169-206, Feb.; 303-321, Mch.; 465- 
498, Apr., 191 7. 



34 MYCOLOGY 

diseases in plants will be considered at length in another section. 
Most attention has been paid to diseases of animals and man due to 
bacteria and the number of special works dealing with the subjects of 
bacteriology, pathology, immunity and disease would form a library. 
Nearly every phase of the relationship of bacteria to animals and man 
has been cultivated, and microbiology has been placed on a firm founda- 
tion, as a subject of human inquiry. The field is too vast for one man 
to cultivate it, and hence, we find a narrow specialism perhaps more 
than in any of the other departments of biologic investigation. 

An interesting phase of the relationship of parasite and host has 
come recently into the scientific limelight. Dr. Erwin F. Smith in 
the study of the organism which produces the crown gall of woody 
plants, Pseudomonas tumefaciens (Fig. 143), finds that the growth and 
formation of the tumors suggests the development of cancer in man. 
He thinks the formation of tumors in plants away from the point of 
infection suggests a similarity (Fig. 158). 

SYSTEMATIC ACCOUNT OF THE BACTERIA 

For the use of students who may not have access to larger works 
on bacteria and who would like a short systematic account of the 
bacteria the following synopsis is given. 

ORDER I. EUBACTERIALES.— The organisms of this order 
are unicellular, or in plate-like, spheric, or filamentous coenobia, if 
imbedded in a slimy matrix, then not of a definite form. 

Family i. Coccace^. — Single spheric cells. Division in one, 
two or three directions. 

Streptococcus.- — Division always in one direction, coenobia, there- 
fore, chain-like, cells without flagella. Pathogenic: 6'. erysipelatos, 
specific germ of erysipelas to be distinguished with difficulty from S. 
pyogenes. Not pathogenic: S. mesenterioides {Leuconostoc mesen- 
terioides), occurring in mucilaginous masses in the molasses waste of 
sugar factories, and its presence disastrous to the industry. 

Micrococcus. — Division in two directions, coenobia, sheet-like, 
without flagella. Pathogenic: Micrococcus pyogenes aureus ( = 
Staphylococcus pyogenes aureus), the cause of pus formation and 
purulent discharge from wounds, M. gonorrhxce (= Gonococcus gonor- 
rhcece) specific germ of gonorrhoea. Not pathogenic: M. aurantiacus, 
luteus, cinnabareus producing pigments. 



CLASSIFICATION OF BACTERIA 35 

Sarcina. — Division in three planes, coenobia in bales, or pockets, 
no flagella. S. ventriculi, frequent in the stomach of men, but non- 
pathogenic. S. aiirantiaca, flava, luiea are chromogenic. .S'. rosea 
with red cell contents occurs in swamps, or colors the soil a rose-red 
color. 

Planococcus. — Division and coenobic formation as in Micrococcus, 
flagellate. P. citreus produces a yellow color. 

Planosarcina. — Division and coenobic formation as in Sarcina, 
flagellate. 

Family 2. Bacteriace.e. — Cells longer or shorter cylindric, 
straight, or at least never spirally twisted. Division always at right 
angles to the long axis, and only after a preliminary elongation of the 
cell. The rods may separate early in some species, in others they 
remain united for a considerable time as longer or shorter filaments. 
Endospores are frequent, rare, or wanting. Flagella may or may not 
be present. 

Bacterium (Ehrenberg char, emend.). — Cells as longer or shorter 
cylindric rods, often forming filaments of considerable length. With- 
out flagella. Endospore formation in many species, absent in others. 
Erwin F. Smith ("Bacteria in Relation to Plant Diseases": 168 to 
171) believes that bacteriologists should substitute Bacterium for 
Pseudomonas as the older generic name, and he would establish a new 
generic name Aplanobacter for the non-motile forms generally referred 
to Bacterium. This distinction is not adopted in this text-book. 
Pathogenic: Bacterium (Aplanobacter) Rathayi the cause of Rathay's 
disease of the orchard grass; B. michiganense the cause of the Grand 
Rapids (Mich.) tomato disease; B. anthracis the first organism deter- 
mined to be the cause of disease, causing anthrax or splenic fever; 
B. mallei specific in glanders in men and horses; 5. pneumonice, the cause 
of pneumonia; B. tuberculosis responsible for tuberculosis (consumption, 
phthisis) in man and animals. It can be distinguished by its staining 
reactions. If stained with carbol fuchsin and then treated with dilute 
nitric acid (1:5), the stain remains fast, while with other organisms, 
the stain will be washed out. After this treatment the tissues can be 
treated with methylene blue for differential staining. B. leprcB, the 
organism of leprosy; B. influenza, the cause of influenza, or grippe; B. 
diptheritidis, the causal bacterium of diphtheria; B. pestis, specific in 
the disease known as the plague, which as the Black Death devastated 



36 MYCOLOGY 

London in 1665 in which 70,000 persons perished. It is carried by 
infested rats. 

N on- pathogenic: B. acelicum sets up in alcohoHc sokition the acetic 
acid fermentation and its films later form mother of vinegar. B. 
acidi lactici ferments sweet milk transforming it into sour milk where 
the acidity is due to lactic acid. B. phosphoreiim is a phosphorescent 
fresh- water organism. 

Bacillus (Cohn char, emend.). — Cells straight, rod-shaped to ovoid, 
long or short, sometimes united into filaments. Motile by wavy, 
bent flagella scattered over the whole surface of the cell. Formation 
of endospores frequent. Motility may be active for a time, and then 
is lost. Pathogenic: B. muscB causes the Trinidad banana disease; 
B. tracheiphilus is responsible for the wilt of cucurbitaceous plants; 
B. amylovorus, the pear-blight organism; B. carotovorus, specific in 
soft rot of carrot; B. aroidew, an organism which causes soft rot of the 
calla; B. tetani, the causal microbe in tetanus, or lockjaw, is found in 
the soil and may enter the skin or superficial muscles of man through a 
pin prick, or rusty nail point; B. typhi, the typhoid bacillus. Non- 
pathogenic: Bacillus subtilis, the hay bacillus found in hay infusion, and 
is the cause of decay. B. coli in the alimentary canal of animals and 
men and in the water polluted by sewage. B. butyricus produces 
butyric acid fermentation and the coagulation of casein. B. radicicola 
(= Rhizobium leguminosarum) lives in the roots of leguminous plants 
and forms the root tubercles or nodules (Figs. 8, 9, 10). B. amylobacter 
(= Clostridium butyricum) ferments cellulose, dissolves casein and is 
useful in the retting of plants for fiber production. B. prodigiosus 
is found on many food substances imparting to them a dark red color. 
B. calfactor appears in hay infusions, where it produces a rise of tem- 
perature. B. putrificus, a widely distributed organism. Many bacilli 
that occur in the ocean are luminous. 

Pseudomonas. — Cylindric bacteria, sometimes long, sometimes short, 
occasionally in threads. Locomotion accomplished by polar flagella, 
the number of which may vary from one to ten, most frequently 
one flagellum is present, or three to six. Endospores are formed, but 
are rare. The following are the causes of diseases in cultivated plants: 
Pseudomonas campestris is responsible for the black rot of cabbage and 
other cruciferous plants. Ps. hyacinthi causes the yellow disease of 
hyacinths. Ps. vascularum is associated as the causal bacterium in 



CLASSIFICATION OF BACTERIA 37 

Cobb's disease of sugar cane. Ps. pyocyanea causes blue pus. Ps. 
putida occurs in water, where it develops a green fluorescent pigment. 
Ps. syncyanea produces in milk a blue coloring matter (blue milk). 
Ps. etiropcea belongs to the group of organisms which cause nitrification. 

Family 3. Spirillace^.^ — Spirally wound or bent cells with occa- 
sional endospore formation, usually motile. Cell division transverse 
to the long axis of the cell. 

Spirosoma. — -Spirally bent, rigid cells usually rather large and with- 
out flagella. Unicellular free or enveloped in a gelatinous capsule. 
Only a few species are known. 

Microspira. — -Comma-shaped, or sausage-shaped, single, or united 
cells, motile by means of a single, wavy, polar flagellum (rarely two or 
three flagella), rarely longer tha*n the cell. Endospores unknown. 
Usually united with the next genus. 

Spirillum. — Rigid rod-shaped cells of varying thicknesses, lengths 
and pitch of spiral turns, hence, either as long screws, or loosely wound. 
Flagella occur at one or both ends of the cells as polar tufts varying in 
number from five to twenty. In some species, endospore formation 
has been observed. Sp. comma is the cause of asiatic cholera and is 
found in cultures often in long spirally wound filaments. There are 
nmny non-pathogenic spirilla in water from rivers and ponds as S. 
danubicum in the Danube, Sp. berolinense in Spree water, Sp. ruftim 
in stagnant water. Sp. rufum forms blood-red slimy masses between 
decaying algae. 

SpirochcBta. — Thin, flexible, snake-like, motile cells usually quite 
long without observed flagella and endospores, and unsegmented. 
Spirochceta Obermeieri is the cause of relapsing fever (f ebris recurrans) . 
S. {Treponema) pallida is the organism of syphilis. S. dentium is found 
associated with the teeth in man. 

Family 4. Phycobacteriace^ (Chlamydobacteriace^). — Cylin- 
dric cells united into sheath-surrounded threads and reproducing by 
motile or non-motile conidia, which arise from the vegetative cells 
without a resting stage. 

Streptothrix (== Chlamydothrix, Leptothrix, Gallionella). — Non-motile 
cylindric cells in unbranched threads possessing a sheath of varying 
thickness. Septa vague. Reproduction is accomplished by roundish, 
non-motile conidia arising from the vegetative cells. S. fluitans in 
water. 



38 MYCOLOGY 

Crenothrix. — The cells are arranged in unbranched threads attached 
at one end and enlarging toward the distal extremity. Filaments 
covered by a rather thick sheath. The reproductive cells are non- 
motile conidia, which on discharge immediately germinate. Crenothrix 
polyspora in springs and water pipes, where it forms attached slimy 
growths. The sheaths in iron waters are impregnated with iron 
oxidhydrate. 

Phragniidiothrix. — Cylindric cells with delicate, scarcely visible 
sheath. The cells of the filament are at first in one plane which later 
divide in three directions to form clumps or packets of cells. Later 
the single cells round off and become free. Ph. nrnltiseptata with fila- 
ments 3 to 12/X broad and looyu long attached to the bodies of crustaceae. 

Cladothrix {SphceroHlus in part). — The fixed and often tufted 
filaments form delicate sheaths. The cells are cylindric and by inter- 
calary growth may break laterally through the sheath to form false 
dichotomous branches. Reproduction is accomplished by motile 
swarm spores (gonidia) which bear a tuft of flagella a little to one side 
of a pole. Cladothrix dichotoma occurs frequently in stagnant water, 
attached and forming furry growths. The following species occur in 
the soil: C. rufula, C. profundus, C. intestinalis, C. fungiformis, while 
C. intrica has been isolated from sea water and sea mud. 

Family 5. Thiobacteriace^ (Beggiatoace.e). — Cells with sul- 
phur inclusions, unpigmented, or colored rose, red or violet by bacterio- 
purpurin; never green. The plants are generally filamentous with 
division transverse to the long axis. 

Thiothrix. — Unequally thick attached filaments encased in a 
delicate, scarcely visible sheath. Rod-shaped conidia are formed at 
the ends of the threads. Th. nivea is found in sulphur springs and in 
stagnant water. 

Beggiatoa. — Sheathless, free-filamentous bacteria, motile by means 
of an undulating membrane. Cells with included sulphur granules. 
Spore formation unknown. B. alba is found in dirty water, drain 
water from sugar factories and attached to decayed plants in sulphur 
springs. B. mirabilis forms white growths on dead marine algae. 

The colored sulphur bacteria, sometimes placed in the family 
Rhodobacteriace^, belong here. They have rose, red or violet cell 
contents due to the presence of bacteriopurpurin (see ante). The im- 



CLASSIFICATION OF BACTERIA 39 

portaut genera according to Erwin F. Smith (''Bacteria in Relation to 
Plant Diseases," I: 163) are Thiocystis, Thiocapsa, Thiosarcina, 
Lamprocystis, Thiopedia, Amosbobader, Thiothece, Thiodictyon, Thiopoly- 
coccus, as well, as the three genera Chromatium, Rhabdochromatium, 
Thiospir ilium. 

Family 6. Actinomycetace.'E (Position doubtful). — Radially ar- 
ranged branched filaments in colonies, non-motile. Filaments divid- 
ing into oidia-like reproductive cells. 

Actinomyces chromogenes occurs in soil. A. bovis is the cause of 
lumpjaw in cattle and occasionally in man. The plant occurs in 
rosettes usually 30 to 40/i in diameter. The filaments which are often 
curved sometimes spirally exhibit true branching and are interlaced 
in a network. Recently Youngken (Amer. Jour. Pharm., September, 
1 91 5) has described the foundation of the large swellings (mycodomatia) 
on the roots of the waxberry, Myrica carolinensis, and other species, as 
due to a species of ray fungus, Actinomyces myricarum, that abun- 
dantly fills infested cells in the cortex of the tubercular swellings. A. 
thermophilus is found on hay and manure. 

ORDER II. MYXOBACTERIALES.— Individual plants en- 
closed in slimy masses which assume more or less regular fructifica- 
tion-Hke shapes. 

Family i. Myxobacteriace^.^ — Erwin Baur and Roland Thaxter 
have studied these forms most intimately. The plants of this family 
consist of motile, rod-like microorganisms, with a gelatinous base and 
forming false plasmodioid aggregations preceding a cyst-producing, 
quiescent state in which the rods may be encysted in groups or con- 
verted into spore-masses. The slightly reddish rods in the vegetative 
stage are elongate, sometimes 15// long and vary httle in size in the 
different genera and species. Cell division is by fission and the active 
rods show a slow sliding movement without organs of locomotion. The 
vegetative phase in artificial cultures usually lasts about a week, or 
even two weeks, and the formation of cysts which follows must be more 
rapid in nature. These organisms are found in moist places on decay- 
ing wood, dung, funguses and lichens, growing best, according to Baur, 
at 3o°C. Three genera are included in this family. 

Chondromyces. — Rods producing free cysts within which they 
remain unchanged. The cysts are various, sessile or developed on a 
stalk (cystophore). 



40 



MYCOLOGY 



Folvangiiim {= Myxobacter, Cyslobacter). — The rods form large 
rounded cysts one or more of which are free inside a gelatinous stalked 
matrix. 

Myxococcus. — Slender rods which swarm together, after a vegetative 
phase, to form well-defined, more or less sessile or stalked encysted 
masses of coccus-like spores. 

BIBLIOGRAPHY 

Abbott, A. C: The Principles of Bacteriology, 9th Edition: Lea & Febiger, 1915. 
DE Bary, a.: Comparative Morphology and Biology of the Fungi, Mycetozoa and 

Bacteria. Oxford at the Clarendon Press, 1887. 
Baur, Erwin: Myxobakterien Studien. Archiv fur Protistenkunde, v Bd., Heft I, 

92-121, 1904. 
Buchanan, Estelle D. and Robert Earle: Household Bacteriology. The 

Macmillan Co., New York, 1914. 
Chester, Frederick D.: A Manual of Determinative Bacteriology. The Mac- 
millan Co., 1914. 
Conn, H. W.: Bacteria, Yeasts, and Molds in the Home. Ginn & Co., Boston, 1903. 
DuGGAR, Benjamin M.: Fungous Diseases of Plants. Ginn & Co., Boston, 1909. 
Ellis, David: Outhnes of Bacteriology (Technical and Agricultural), Longmans, 

Green & Co., 1909. 
Engler, Adolf and Gilg, Ernest: Syllabus der Pflanzenfamilien. Berlin, 191 2, 

Siebente Auflage, pp. 1-5. 
Eyre, J. W. H.: The Elements of Bacteriological Technique. Philadelphia, W. 

B. Saunders & Co., 1902. 
Fischer, Alfred, transl. by Jones, A. Coppen: The Structure and Functions of 

Bacteria. Oxford at the Clarendon Press, 1900. 
Fuhrmann, Dr. Franz: Vorlesungen iiber technische Mykologie. Jena, Gustav 

Fischer, 19 13. 
Hiss, Philip H. and Zinsser, Hans: A Text-book of Bacteriology. D. Apple ton 

& Co., 1915. 
Jordan, Edwin O.: A Text-book of General Bacteriology, 3d Edition. Phila- 
delphia, W. B. Saunders & Co., 191 3. 
KisSKALT, K.: Bakteriologie Zweite Auilage. Erster Teil von Prakticum der 

Bakteriologie und Protozoologie. Jena, Gustav Fischer, 1909. 
KtJSTER, Dr. Ernst: Anleitung zur Kultur der Mikroorganismen. Zweite Auflage, 

Leipzig und Berlin, 191 3. 
Lafar, Dr. Franz: Technical Mycology. The Utilization of Microorganisms in 

the Arts and Manufactures. London, Charles Griffin & Co., vol. i, 1898. 
Lipman, Jacob G.: Bacteria in Relation to Country Life. The Macmillan Co., 

New York, 1908. 
Marshall, Charles E. and Others: Microbiology for Agricultural and Domestic 

Science Students. Philadelphia, P. Blakiston's Son & Co., 1911. 



CLASSIFICATION OF BACTERIA 



41 



Meyer, Dr. Arthur: Practicum der botanischen Bakterienkunde. Jena, Gustav 

Fischer, 1903. 
MuiR, Robert and Ritchie, James: Manual of Bacteriology. The Macmillaii 

Co., 1913. 
Newman, George: Bacteria. Especially As They Are Related to the Economy 

of Nature to Industrial Processes and to Public Health. G. P. Putnam's Sons, 

New York, 1899. 
Park, William H. and Williams, Anna W.: Pathogenic Microorganisms. 

Lea & Febiger, Philadelphia, 1914. 
Perch^al, John: Agricultural Bacteriology Theoretical and Practical. Duck- 
worth & Co., London, 1910. 
Prescott, Samuel C. and Winslow, Charles Edward A.: Elements of Water 

Bacteriology, 3d Edition. John Wiley & Sons, New York, 1913. 
QuEHL, A.: Untersuchung liber Myxobakterien. Zentralblatt fur Bakteriologie, 

II Abt., xvi Bd., 1906. 
Smith, Erw7N F.: Bacteria in Relation to Plant Diseases, vol. i, 1905; vol. ii, 1911; 

vol. iii, 1914. Publication No. 27, Carnegie Institution of Washington. 
Th.^xter, Roland: On the Myxobacteriaceae, a New Order of Schizomycetes. 

Bot. Gaz., xvii, 1892; Further Observations on the Myxobacteriacese. Loc. 

cit., xxiii, 1897; Notes on the Myxobacteriaceae. Loc. cit., xxxvii, 1904. 
Wettstein, Richard R. von: Handbuch der Systematischen Botanik Zweite 

Auflage, 191 1 : 69-83. 



CHAPTER V 

CHARACTERISTICS OF THE TRUE FUNGI 

CLASS III. EUMYCETES 

The true fungi or hyphomycetes {v(t)ri, a web + hvktjs, a mushroom) 
are thallophytes in which the thallus, as the Greek derivation implies, 
consists of a system of threads {hypha) which form a cobwebby struc- 
ture known as the mycelium (Fig. 1 1). A single thread of the mycelium 
is an hypha (plural hyphae) and a hypha may be unicellular, or multi- 
cellular. All true fungi are colorless, that is they are chlorophylless; 
and although they may have other pigments present, yet in the absence of 
chlorophyll, they are dependent plants. 
As dependent plants, they must get 
their organic food from extraneous 
sources, and as all organic matter is 
either dead, or living, a natural classi- 
fication of fungi into saprophytes and 
parasites can be made. A saprophyte 
{aairpos, rotten + 4>^t6v, a plant) is any 

Fig. II. — Gray mould, Miicoy, . i • i j • •. i • r r j 

showing mycelium and the sporan- Organism which dcrives its chief food 
gia on upright sporangiophores. supply from dead, or dead and decaying 
^^.^^^ ^^ plant organic material, while 
a parasite {irapaaiTos, one who lives at another's expense) is an 
organism, which exists at the expense of living animals, or plants 
(Fig. 12). But some saprophytes may change their mode of nutri- 
tion and become parasitic; such saprophytes are called facultative 
parasites, while those which retain their saprophytism under all condi- 
tions are obligate saprophytes. Again some parasites can adjust their 
methods of nutrition, so that they can become saprophytes. Such 
parasites are called facultative saprophytes, while those organisms 
which are always parasitic are obligate parasites. These distinctions 
are useful, but it should be emphasized that there is no absolute border- 
line between one condition and the other. There are imperceptible 

42 




CHARACTERISTICS 07 THE TRUE FUNGI 



43 



gradations which preclude an absolute pronouncement as to whether 
a plant is a saprophyte, or a parasite.^ Botanists generally concede 
that the true fungi have been derived from filamentous algal ancestors 
and the groups of algae from which the principal forms of fungi have 




Fig. 12. — Russula nigricans parasitized by Nyctalis aslerophora. {After Brefeld.) 



been derived are fairly well known. For example, it is believed that 
such fungi as belong to the order OOMYCETALES have been derived 

1 Massee, George: On the Origin of Parasitism in Fungi. Annals of Botany, 
xviii: 319. 

Ward, H. M.: Recent Researches on the Parasitism of Fungi. Annals of Bot- 
any, xix: I. 

Bancroft, C. K.: Researches on the Life History of Parasitic Fungi. Annals 
of Botany, xxiv: 359, 1910. 



44 



MYCOLOGY 



from a green alga like Vaucheria. With our present knowledge, it is 
impossible to name any one existing alga as the progenitor of a definite 
fungous form, but we are safe in assuming in a general way that certain 
phyla of fungi have been derived from certain phyla of algae, by the 
loss of chlorophyll and in the loss of an independent existence. Another 
view, which is open to argument, is that certain of the prototrophic 




Fig. 13. — Development of Mucor miicedo. a, b, c, d, Stages in the formation of 
zygospore; /, sporangium; g, mature sporangiospores; h, one germinating. {After 
Schneider, Pharmaceutical Bacteriology, p. 142.) 



filamentous bacteria to which attention has been previously called 
have been the direct progenitors of certain of the filamentous fungi, 
but on account of the character of the reproductive organs in the lower 
true fungi their derivation from green algae is the more probable, and 
mycologists even speak of the algal fungi referring especially to aquatic 
genera, such as Saprolegnia, which like their algal ancestors not only 
retain the general morphologic features of the algae, but also live in an 



CHARACTERISTICS OF THE TRUE FUNGI 45 

aquatic medium, and the success of the process of fertilization depends 
on the presence of free water. Such fungi form a subclass of EUMY- 
CETES, the PHYCOMYCETES. 

The vegetative organs of fungi are concerned with the absorption 
of food, the assimilation of the food and in the nutrition of the organs 
of fructification which together form the reproductive system. That 
the student may appreciate the morphology of the vegetative organs of 
the fungi, three examples from widely divergent orders will be chosen 
by way of illustration. A common mould is Mucor mucedo which 
appears on horse manure. If a spore of this fungus is placed in a nutri- 
tive medium, its wall breaks and there protrudes a germ tube rich in 
protoplasmic contents (Fig. 13, h). This germ tube grows in length 
into an hypha without the development of partition walls dividing it 
into shorter cells. This hypha branches and rebranches in its growth 
over the nutrient substratum spreading in all directions, if unimpeded 
by other organisms growing on the same food substance. The ultimate 
branches of this mycelium, which is throughout unicellular, are much 
attenuated, fine hyphse representing the end ramifications of larger and 
coarser hyphae nearer the point of origin of the whole mycelium (Fig. 
13). The finest hyphae usually enter the substratum, while the coarser, 
stronger hyphae form a cobwebby mass over its surface. We can 
distinguish therefore the feeding hyphae, which are rhizoidal hyphae, 
and the aerial hyphae in which probably the metabolic changes are 
most active where the mycelium is in open contact with the air. Later, 
when the mycelium is well established on the nutrient substratum, 
erect vertical hyphae appear at indefinite points on the larger aerial 
hyphae. These are the fruiting hyphae, or sporangiophores, which 
ultimately cut off a terminal cell which becomes the sporangium, or case, 
in which the reproductive cells or spores are formed, while the end of 
the sporangiophore projects into the interior of the sporangium as a 
columella (Fig. 13, /). 

The common green mould, Penicillium glaucum, may be taken as the 
second illustration (Fig. 14). If we sow a spore on nutrient agar in a 
Petri dish after a few hours the spore swells and there emerges a germ 
tube which at first is undivided by a partition wall. Later, as the older 
hyphae branch to form new ramifications, cross-partitions are formed 
which divide the mycelium into short cells, so that in that respect the 
mycelium of PeniciUhim differs from that of Mucor. The hyphal 



46 MYCOLOGY 

branches are coarser in Penicillium and do not form the fine-pointed 
ends found in Mucor. The presence of transverse walls in the fungi is 
thought of sufficient importance to make a subclass known as the 
MYCOMYCETES to contain all of the true fungi EUMYCETES 
which have a mycelium which is multicellular in contradistinction 
to those which have unicellular mycelia and that form the subclass 
PHYCOMYCETES. From this spreading myceHum of transversely 
septated hyphae in Penicillium arise hyphae which branch at the 
extremity into a number of erect branches from the ends of which 
are cut off in sequence a series of small round cells, the spores, which if 
undisturbed remain connected in a chain, so that the 
fructification roughly resembles a small broom, or 
whisk. The large vertical hypha is a conidiophore, 
and as the spores are pinched, or abstricted off from 
the secondary branches as single cells, they are 
known as conidiospores {kovls, dust + airopa a seed) 
(Fig. 14 and Figs. 243 to 263 inclusive). 

The third example, which we will use to describe 
in general terms the vegetative organs of the fungi, 
is the honey-colored toadstool, Armillaria mellea 
(Fig. 15). The toadstools, or fruit bodies, often form 
Fig. 14. — Con- dense clumps around the base of some dead or dving 
mo°n ""Te'en-mouS; tree, or almost cover an old stump on which ihey 
Penicillium glau- grow. The Cap is of a houcy-colored brown, about 
llZnr'^oi ^coSSo- two inches across, and the stem may be six inches 
spores. (After Conn, long and paler than the cap. Microscopic sections 

that are closely bound together to form the stem and 
cap. If we examine the base of the stalk, we find that it arises from 
a dark-colored cord-like strand which has been termed a rhizomorph 
because of its resemblance to a root (Fig. 15, II and IV). These 
rhizomorphs constitute the mycelium and they either ramify through 
the soil, or else are found beneath the bark of the dead tree, where 
they unite to form open-meshed nets of a dark brown color. These 
rhizomorphs are strands of hyphae that run longitudinally. The 
hyphal cells are bound together in a cord-like cable which is peculiar 
in that it shows apical growth, constantly elongating at its extremity, 
as it grows beneath the bark, or penetrates the soil (Fig. 15) 




CHARACTERISTICS OF THE TRUE FUNGI 



47 




Fig. 15. — Details of the mycelium of Armillaria niellea. I, Piece of mycelium 
on slide; II, piece of old mycelium {Rhizomorpha sublerranea); III, rhizomorph pro- 
ducing fruit bodies; IV, apex of rhizomorph capable of growth; (a) peripheral hyphs; 
{b) pseudo-epidermis; (c) growing point; {d, e, h) pith; (/?) hollow center. (7 and 
IV after Brefeld; III, after Hartig in Zopf, Die Pilse, 1890, p. 25.) 



48 MYCOLOGY 

its extremity, as it grows beneath the bark, or penetrates the soil (Fig. 
15). Such a compound thallus differs strikingly from the filamentous 
thalluses of the two previously described fungi. The union of the 
hyphal cells in some of these fleshy fungi may be so intimate as to con- 
stitute a pseudoparenchyma, and this close union of the cells may be 
made still more intimate by clamp connections where two adjoining cells 
are bound together endwise by a clamp-like protuberance of one of the 
cells attached to the end of the other adjoining cell. When the pseudo- 
parenchyma is external, it rnay serve for the protection of the internally 
disposed hyphae, and be looked upon as protective tissue. Mechanic 
tissues for the support of fungi are not unknown in some of the groups, 
as in some of the polypori; where there are clamp connections, trans- 
verse septa and thickened cell walls. A few of the higher fleshy fungi 
have conducting hyphae, which are larger and more tubular than the 
surrounding hyphae, and which conduct later, oil and other substances. 
Those which conduct a milky juice, as in some species of Russula and 
Lactarius, may be termed laticiferous hyphs. There are some fungi in 
which the hyphal form of thallus is not present. The yeasts are either 
single ellipsoidal cells, or these cells are loosely connected together in 
a chain of bed-like cells. These chains are due to the budding or 
sprouting method of cell multiplication where a bud, gemma, or sprout, 
grows out from the mother cell as a daughter cell. It in turn buds 
producing a granddaughter cell and so forth. Such a method of 
reproduction is known as gemmation. 

In the parasitic fungi, the hyphae run either into the cells, through 
the cells (intracellular), or between the cells (intercellular). Where 
the hyphae are intercellular, short branches may be formed which 
penetrate the host cells. These short branches take various forms and 
are known as haustoria; a single one as an haustorium (Figs. 36 and 67). 
Occasionally in the mildews, the mycelium may be superficial and 
hence epiphytic, while the mycelia which are internal are endophytic. 
These are useful terms when describing the parasitic habits of fungi. 
Some of the groups of fungi have mycelia that form resting bodies 
of hyphae. These are the most compact of all forms of mycelia and 
are known as sclerotes {sclerotium — ia), which in many cases assume 
tuberous forms. They are resting states of the mycelia and act as 
stores of reserve material. These are some of the principal forms of 
the vegetative thallus of the fungi. Further details will be given in 
he discussion which follows. Some sudden epidemics of rust fungi 



CHARACTERISTICS OF THE TRUE FUNGI 49 

have been ascribed by Eriksson to the presence of the protoplasm of 
the rust mixed with the protophism of the host. To this included 
fungous protoplasm he gave the name mycoplasm. 

Some fungi are symbiotic, that is, they are found in intimate re- 
lation with chlorophyll-containing plants and obtain from them food 
of a carbonaceous character, but without apparently injuring the 
green symbiont. When they live with algae, they commonly form 
lichens; or if in connection with the roots of trees, orchids; and in 
prothallia they form what is known as mycorhiza (Fig. 16). 

The spores or reproductive cells of fungi may be of two kinds: 
non-sexual spores and sexual spores. The non-sexual spores are cells 
which are formed vegetatively. They are cells which take special 




Fig. 16. — Ectotrophic mycorhizas. At left hyphal mantle on root of hickory 
Carya ovata in cross section; at right root tip of an oak, Quercus, with fungous mantle. 
{From Gager, after W. B. McDougall.) 

forms in the different groups of fungi and are produced as special cells 
in a purely vegetative manner. They represent a special part of the 
thallus given over to reproduction. Upon the formation of these 
spores, which may germinate at once or live for some time as resting 
spores, the rapid multiplication of the fungi depends. It is the innu- 
merable quantity of these non-sexual spores upon which an epidemic 
of some particular fungous disease may depend. Only the most general 
characters of the various kinds of spores can be discussed in an intro- 
duction of this kind. The special kinds will receive due attention as 
we proceed. Spores which are cut off, or pinched off, in concatenation 
from the end of a vertical hypha, are known as conidios pores. In the 
rusts such conidiospores become nredospores, and in the mushrooms 
basidiospores. Where the non-sexual spores are formed in a spore case, 
4 



50 MYCOLOGY 

or sporangium, they may be termed sporangiospores (Fig. 13,/). Fre- 
quently spores are formed by a modification of certain cells of the hy])lial 
branch. These spores are usually thick-walled, as in the smuts, and 
become known as chlamydos pores. Where the whole hypha is divided 
up into a chain of spores one after the other in close order, such spores 
are called oidiospores. Special receptacles are associated with the 
formation of the non-sexual spores. These are found in the sac fungi, 
ASCOMYCETALES, where the depressed conceptacle becomes a pycnidium, 
or conidial fruit, and the spores which it contains are pycnidiospores, 
pycnospores, pycnoconidia or the stylospores of Tulasne. This form of 
conidial fruit is surrounded by a firm wall or peridium. The pycnidia 
may be depressed in the tissues of a host plant or elevated above its 
surface, as the case may be. In some fungi the conidiophores, in- 
stead of being separate, are arranged in parallel order, side by side, 
at an early stage, and thus are united into a fascicle to which the name 
coremium has been applied. 

The principal sexually produced spores in the fungi are zygospores, 
oospores and ascospores. The first two forms are found. in the sub- 
class PHYCOMYCETES. 

Their formation proceeds in such a manner that the zygospores are 
produced isogamously, that is, by the union of two similar cells, while 
the oospores are heterogamous, that is, they are produced by a union of 
an egg cell and a sperm cell. Hence, we distinguish two orders of 
the PHYCOMYCETES, namely, the ZYGOMYCETALES and the 
OOMYCETALES, the first showing isogamy and the latter heterogamy. 
Details will be given when these orders are considered in detail. Until 
recently, it was believed that sexuality did not exist in the sac fungi, 
ASCOMYCETALES, but recent research has shown that the nuclei 
of two adjoining cells unite and this is followed by the formation of a 
spore sac, or ascus, containing sac spores, or ascospores. The formation 
of the asci is usually associated with the production of definite fruit 
bodies. It is doubtful whether sexuality is found in any of the other 
groups of fungi. Curious nuclear fusions in the rusts have been sug- 
gested as a sexual union, but it is safer to await future discoveries 
before adopting such a position. However, there are fungi in which 
sexual organs seem to be lost entirely and many of these belong to the 
most highly developed forms where the thallus and fructifications are 
of a complex type. The whole trend of evolution in the fungi is for 



CHARACTERISTICS OF THE TRUE FUNGI 5 1 

the reduction in size and importance of the sexual organs, until they 
have disappeared completely. This may be a result of the perfect 
manner in which the dififerent specific types are reproduced and multi- 
plied by the various kinds of non-sexual spores found in the different 
fungous groups. 



CHAPTER VI 
HISTOLOGY AND CHEMISTRY OF FUNGI 

Histology. — Naked cells which are destitute of a cell wall and con- 
sist of naked protoplasm occur as motile cells in only two unimportant 
groups of the OOMYCETALES. The cell wall of fungi does not 
appear from the results of numerous workers upon its chemistry 
to be of the same nature in the different groups of them. A general 
term which has been in current use and which was first suggested 
by A. de Bary is that of fungous cellulose, but that term, as far 
as indicating the chemic character of the membrane is concerned, is 
a misnomer. It has its correct application, if we employ the term in 
the sense of fungous membrane substance. We owe to C. van Wis- 
selingh (1898) the examination of about a hundred species from nearly 
all of the orders and most of the families of EUMYCETES. Wissehngh 
could detect the presence of cellulose with certainty only in two families, 
the Saprolegniace^ and the Peronosporace^. This carbohydrate 
could not be detected either in the ZYGOMYCETALES or in any 
of the MYCOMYCETES examined, and especially was it found to be 
absent in the yeast Saccharomyces cerevisia. The researches of 
Winterstein, Gilson and Wisselingh proved that chitin formerly sup- 
posed to be of animal origin was found in the membranes of fungi. 
With the exception of the two families mentioned above, the bacteria 
and the yeasts, chitin has been detected in all other species of fungi 
examined, e.g., Mucor mucedo, M. racemosus, Rhizopus nigricans, 
Penicillinm glaucum, Trichothecium roseum, in the sclerotia of Botrytis 
cinerea and Claviceps purpurea. We do not know at present of the 
simultaneous occurrence of cellulose and chitin in the same cell wall. 
E. Winterstein has found true hemicellulose in certain fungi and other 
chemic substances have been reported such as carbohydrates of the 
pentosan group, pectose, callose, etc. 

The outer layers of the wall, in some fungi (Tremellace^) may be 
mucilaginous, so that it is resolved into a soft gelatinous mass. Lignifi- 
cation has been reported in the large pileated fungi though whether 

52 



HISTOLOGY AND CHEMISTRY OF FUNGI 53 

the presence of lignin is proved thereby must remain an open ques- 
tion. Deposits and incrustations of calcium oxalate crystals are found 
in the membranes of fungi, as the spicules in the sporangial wall of 
Mucor mucedo. 

The cell contents, or protoplasm, of fungi may be divided into 
cytoplasm with its inclusions and nucleoplasm. The cells contain 
either a single nucleus (Erysiphe), two, as in Exoascus, or several, 
as in the mycelial cells of Penicillium glaticum and Peziza convexula. 
The hyphae of many contain numerous, sometimes over hundreds 
of nuclei (PHYCOMYCETES). The structure of the nucleus in 
basidia as described by Wager agrees with that of the higher flowering 
plants. It has a nuclear membrane, nucleolus and nuclear network of 
threads coiled in a loose knot. Chromatin granules occur. The nucleus 
undergoes division either by fission, or by karyokinesis, as first observed 
by Sadebeck. Chromosomes are formed from the chromatin bodies 
when the nucleus begins to divide. A reduction of chromosomes has 
been observed by Stevens. Fats and oils are present in fungous cells 
and are found in the form of drops or globules. Glycogen has been de- 
tected in the spore sacs of the ASCOMYCETALES. Volutin is a 
name given by Meyer to a reserve substance which contained C, H, O, N 
and P atoms. Mannite, trehalose and glucose have been found in 
many fungi by Bourquelot. Special substances of a poisonous nature 
such as ergotin, muscarin, phalhn are of special significance in cer- 
tain fungi. 

Colors. — Full details regarding the coloring matters in fungi will 
be found in Zopf's "Die Pilze in morphologischer, physiologischer, 
biologischer und systematischer Beziehung," 1890. Clear bright 
colors are present in such species as Peziza aurantia, P. coccinea. 
Russula virescens, has a cap with shade of green lighter, or darker, in 
individual specimens. Russula emetica is red. Blue is the predominat- 
ing color in the genus Leptonia. Armillaria mellea has a honey- 
brown, or yellow color. The violet color of Cortinarius violaceus is 
well known. The color in a number of fleshy fungi changes when the 
fruit bodies are broken, injured or exposed to the air. This change of 
color is due to an oxidizing enzyme. The flesh of a number of species 
of Boletus changes from white or yellow to a deep indigo-blue when 
broken, or abraded. The deliquescence of species of the genus 
Coprhius, when the color changes from white to black with the melting 



54 MYCOLOGY 

down of Lhe whole fruit body has been proved to be a process of auto- 
dig^estion. When the hyphae are colored, the color is confined generally 
to the cell wall, although Biffen states that in some hyphae the color 
is located in the contents, the wall remaining colorless. Spores are 
colored frequently as in Ascobolus which grows on manure. The spores 
at first colorless change through pale lilac to clear deep amethyst. The 
coloring matter is confined to the spore walls, but in some cases the 
contents are colored, while the wall is colorless, as in many a^ciospores. 

Physiology or Fungi 

The research of recent years in the nutrition of fungi has shown 
that nine chemic elements are necessary for the structure and complete 
development of the true fungi. These elements are carbon, hydrogen, 
oxygen, nitrogen, sulphur, phosphorus, potassium (or rubidium), 
magnesium and iron. Analysis of the ash. constituents of fungi shows 
that phosphoric acid and potassium are the chief ones, the latter form- 
ing seldom less than one-quarter and sometimes one-half of the total. 
Phosphorus is present in the ash to the extent of 15 to 60 per cent, 
and is eagerly absorbed by growing fungi, as is shown by Dcedalea 
quercina, which in its growth completely extracted the phosphoric 
acid from decayed wood. Winogradsky, Meyer, H. Molisch and W. 
Benecke have shown that magnesium is indispensable to fungi. Be- 
necke has demonstrated a considerable difference in development shown 
by two, otherwise equal, specimens, the one grown without magnesium 
and the other in a medium containing 0.0025 mg- of crystallized magnes- 
ium sulphate per 25 c.c. and Guenther has proved that 0.005 "^g- of 
magnesium sulphate was necessary to induce a sowing of Rhizopus 
nigricans to grow at all. 

As to iron, as an indispensable element before the matter was put 
to the test, it was thought that fungi being chlorophylless did not 
require iron like the green plants in which iron was concerned in the 
formation of chlorophyll. The experiments of Hans Molisch tend to 
prove the essential importance of iron in the nutrition of the true fungi 
for in presumably iron-free cultures, the spores of Aspergillus niger 
did not develop beyond the formation of a sickly mycelium. Similar 
results were obtained with sowings of pressed yeast cells, spores of 
Mucor racemosus and a species of Penicillum. Iron in addition to 



HISTOLOGY AND CHEMISTKY OF FUNGI 55 

being a nutritive material also acts as a stimulant. The position of 
sulphur, as an important nutritive element, is doubtful. It is inferred 
that because this element forms an important constituent of the albu- 
minoids, that it is, therefore, essential to fungi, but there are no re- 
liable experiments which prove that to be so. Awaiting more detailed 
investigations, sulphur has been included in the above list of nutri- 
tive elements. The source of the C, H, and O which form such an 
important part of the food of fungi is the dead or Hving bodies of other 
plants and animals, principally plants in which are found sugars, 
starch, cellulose, mannite, citric acid, and other bodies of organic origin. 
The source of nitrogen is similarly from soluble nitrogenous bodies, 
peptones, propylamin, asparagin and others, but few if any of the 
higher fungi can utihze free atmospheric nitrogen, as can the bacteria 
which form the nodules on the roots of leguminous plants, described in 
a former section of this book. The various culture media on which 
bacteriologists and mycologists cultivate successfully a large series of 
bacteria and fungi will be considered in a subsequent chapter. Modern 
research along the lines of technique has demonstrated many im- 
portant points about the growth and nutrition of the higher fungi 
and these will be discussed, as we proceed to the end of the book. 

The chemic investigation of the fungi began with the refinements 
in the technique of modern organic chemistry and much has been pub- 
lished on the subject, so that there is a bibliography too voluminous to 
give. Much of the most important chemic work on fungi published 
prior to 1890 will be found in Zopf's "Handbook." No general work 
of this kind has recently appeared, so that we must depend on recent 
original papers on the chemistry of fungi, and in part on the statements 
of Zopf's great book. The following inorganic elements have been 
found in fungi: chlorine, sulphur, phosphorus, sihcon, potassium, 
sodium, lithium, calcium, magnesium, aluminium, manganese and 
iron. Manganese has been found in the cap of Lactarius piperatus. 
Aluminium has been reported as occurring in the ash of lichens. The 
mean of a number of analyses^ of mushroom {Agaricus campestris), 
truffle (Tuber), Morchella esculenta, two other species of MorcheUa, 
species of Boletus, a,nd Polyporus officinalis is as follows: potassium 45 
per cent., phosphoric acid 40 per cent., magnesia 2 per cent., sodium 
1.4 per cent., calcium 1.5 per cent., iron oxide i per cent., silicic acid 

'ZoPF, Wilhelm: Die Pilze: ii8. 



56 MYCOLOGY 

I per cent., sul])huric acid 8 per cent., chlorine i per cent. The organic 
compounds of the carbohydrate group found in fungi are cellulose, 
grape sugar, glycogen and kinds of gums, mannit, inosit, and several 
other less important ones. The organic acids include oxalic, malic, 
acetic, citric, formic, lactic, helvelhc, and propionic acid, as well as other 
less well-known acids. 

Fats and oils are often present as reserve substance in many repro- 
ductive spores, as in oospores, zygospores, ascospores, and the like. 
Large quantities are also often present in the mycelium, as in Lactarius 
deliciosus, which contain 6 per cent. (5.86 per cent.). Fat is, as a rule, 
not entirely absent from any species of fungus. Fliickiger gives the 
fat content of the sclerotium of Clavkeps purpurea as 35 per cent. The 
mushroom Agariciis campestris has 0,18 per cent, and Helvella esculent a 
1.65 per cent. 

Resin occurs in fungi in the form of excretions, partly as infiltra- 
tion of the cell walls, partly as contents of the living cells. The intense 
orange-yellow color of the caps and stipe of the Agaricus (Pholiota) 
spectabilis, according to Zopf, as also the pale yellow of the gills and 
the flesh of cap and stipe together with the ochre-yellow color of 
the masses of spores is due to the presence of a resin acid which is 
present as a hyphal cell content. Pigments of various kinds classified 
by Zopf are also found. Besides the important substances mentioned 
above, chemists have found coniferin, muscarin, trimethylamin (spores of 
Tilletia caries), ergotin, cholin, phallin, cholesterin. Several of these 
will be discussed in connection with the poisonous or non-poisonous 
character of certain of the fleshy fungi. 

Enzymes {Jev^vjjios, leavened, from €u, in and ^vp-v, leaven, a term 
first suggested by Kiihne for an unorganized ferment). — The study of 
the ferments, or enzymes, of the fungi and higher plants has thrown a 
flood of light upon their metabolic activity, for enzyme action is the 
strategic center of vital activity. Pasteur emphasized the role of micro- 
organisms as ferment producers, and that led to the classification of 
ferments into organized and unorganized. Since Buchner discovered 
zymase, ferments have been divided into endocellular and extracellular. 
Endocellular enzymes as those which cannot diffuse out of the cell, 
such as zymase, while extracellular enzymes are those which are capable 
of diffusion out of the cell, such as invertase. Hepburn defines an 
enzyme as a soluble organic compound of biologic origin functioning 



HISTOLOGY AND CHEMISTRY OF FUNGI 5 7 

as a thermolabile catalyst in solution. In connection with this defini- 
tion, it is important to know that a catalytic agent is one which alters 
the rate of a reaction without itself entering into the final product 
(Ostwald, 1902), or which does not appear to take any immediate part 
in the reaction, remains unaltered at the end of the reaction and can 
be recovered again from the reaction product unaltered in quantity 
and quality. 

Enzymes differ from ordinary inorganic catalysts in their sensitive- 
ness to heat and light. They are destroyed at 100° C, and most of 
them cannot be heated safely above 60° C.^ The velocity of the 
reaction increases with a rise of temperature up to an optimum and 
as the temperature is increased above the optimum the enzyme is 
permanently inactivated. Enzymes retain activity even after ex- 
posure to action of liquid air. Light in its ordinary form in the pres- 
ence of oxygen and ultraviolet light independent of oxygen are de- 
structive to enzymes. Again, enzymes possess most of the important 
properties of colloidal solutions, such as their non-diffusibility. They 
are soluble in water, in dilute salt solutions, or in glycerin. They 
exhibit the phenomenon of adsorption. 

An important discovery has recently been made which has thrown 
considerable light on the activity of enzymes, and that has been the 
stimulation exercised by certain substances which have been called 
activators and the inhibition exercised by other substances, which have 
been called paralyzers. The activators are in some cases simple chem- 
ical substances, such as acids, alkalis and salts, or they are complex 
bodies of unknown chemic character, but they have this in common that 
they can be separated from the enzyme by dialysis, and are not de- 
stroyed by heating. An enzyme may be rendered inactive by the 
removal of its activator, but it can be restored to activity by mixing 
again with this substance. In the case of some enzymes, the inactive 
substance, as it is formed in a cell may be called a zymogen, or profer- 
ment, but when associated with the activator the active enzyme is 
developed. An activator is inorganic. A kinase is a more or less 
complex organic body which activates a proferment. 

Substances which reduce, or destroy, the activity of enzymes are 
called paralyzers, which may be formed as products of enzymatic 

'Haas, Paul, and Hill, T. G.: An Introduction to the Chemistry of Plant 
Products. 1913: 340-341. 



58 MYCOLOGY 

aclivity or be foreign substances. Acetic and lactic acids formed by 
enzyme activity will destroy the ferments producing them unless 
neutralized. Among foreign substances which act as paralyzers 
may be mentioned formaldehyde, mercuric chloride, alcohol, chloro- 
form and hydrocyanic acid. Anti-enzymes are a class of substances, 
which are antagonistic to the action of enzymes. The distribution of 
the enzymes in the various groups of fungi including the slime moulds, 
bacteria and true fungi have been investigated by a number of zymolo- 
gists. For example, Monilia sitophila may form maltase, trehalase, 
raffinase, invertase, cytase, diastase, lipase, tyrosinase and trypsin. 
Dox^ has demonstrated in moulds, the following: protease, nuclease, 
amidase, lipase, emulsin, amylase, inulase, raffinase, sucrase, maltase, 
lactase, histozyme, catalase and phytase, and he has found that these 
enzymes are formed regardless of the chemic character of the substratum. 
Without going into all the details of the occurrence of enzymes in the 
fungi, the following classification of the principal enzymes found in the 
various groups may prove useful to the student. 

Classification or Enzymes in Fungi 
I. HYDROLYTIC ENZYMES. 

(a) Carbohydrate-splitting enzymes (carbohydrases) : 

Amylase, or Diastase, which hydrolyzes starch to dextrin and 
maltose. The Koji fungus, Aspergillus oryzece (Taka-diastase). 
Cytase, which hydrolyzes hemicellulose to galactose and mannose 
in Botrytis. 

Inulase, which hydrolyzes inuhn to levulose. 
Invertase, which hydrolyzes cane sugar to dextrose and levulose. 
Saccharomyces, Fusarium, Aspergillus niger. 
Lactase, which hydrolyzes lactose (milk sugar) to dextrose and 
galactose. Kephir organism. 

Maltase, which hydrolyzes maltose (malt sugar) to dextrose. 
Saccharomyces octosporus. 

Raffinase, which hydrolyzes raffinose to levulose and melitiose. 
Aspergillus niger. 

Trehalase, decomposing trehalose into a reducing sugar. Poly- 
porus sulphiireus. 
1 Dox, A. W.: Enzyme Studies of Lower Fungi. Plant World, 15: 40, February 
1912. 



HISTOLOGY AND CIIEMISTKY OF FUNGI 59 

(b) Protein-splitting enzymes (proteases): 

Pepsin, which hydrolyzes proteins to albumoses and peptones. 
Trypsin, which hydrolyzes proteins to peptides and amino- 
acids in A maniia muscaria and Boletus edulis. 

(c) Urea-splitting enzymes (ureases): 

Urease obtained from Micrococcus urcce, which hydrolyzes urea 
into ammonia and carbon dioxide. 

(d) Nuclease, which spHts nucleic acid. 

(e) Fat-splitting enzymes (esterases and lipases): 

Lipase in Penicillium glaucum and Aspergillus niger, also 
Empusa. Phycomyces, which break up fatty oils. 

(/) Glucoside-splitting enzymes: 

Emulsin, which hydrolyzes amygdalin to glucose, hydrocyanic 
acid and benzaldehyde. Also such other glucosides as saUcin, 
populin, coniferin which fungi are able to utilize. 

2. FERMENTING ENZYMES. 

(a) Alcoholic fermentation of glucose, levulose, mannose, etc., by 

zymase in yeasts. 
{b) Lactic acid fermentation of lactose by lactic acid bacteria, 
(c) Butyric fermentation of lactose by the butyric acid bacteria. 

3. Clotting Enzymes (Coagulation, CurdUng). 

Rennin (Chymosin), which curdles milk. Bacillus mesentericus 
vulgatus. 

4. OXIDIZING ENZYMES. 

(a) Oxidases, which oxidize alcohols to acids, e.g., the action of 

Mycoderma aceti, etc. 
{b) Tyrosinase. Russula nigricans and species of Boletus, Lacta- 

rius, etc. 
(c) Peroxidases, which set free oxygen from hydrogen peroxide, 

causing this substance to blue guaiacum resin. 
{d) Catalase, which decomposes hydrogen peroxide with the 

evolution of molecular oxygen. 

In concluding this brief study of the enzymes it may be stated that 
they can be detected by chemic, bacteriologic, serologic and histologic 



6o MYCOLOGY 

means. Details of the occurrence of the above enzymes will be found 
in the books noted in the footnote below.' 

CHEMOTAXIS 

The attraction or repulsion of motile microorganisms by chemical 
stimulants known as chemotaxis is found in the activity of the zoospores 
of the OOMYCETALES and in the growth of the hyphae of fungi in gen- 
eral toward or away from the stimulus. To these phenomena the names 
of positive and negative chemotropism have been given. The thorough 
investigations of M. Miyoshi with Aspergillus niger, Mucor mucedo, 
Penicillium glaucum, Phycomyces nitens, Rhizopus nigricans have shown 
that the following substances act as powerful stimulants: ammonium 
phosphate, asparagin, dextrin, saccharose and glucose. The threshold 
value (marginal limit) or minimum quantity capable of producing a 
chemotactic effect was ascertained by Miyoshi as o.oi per cent, in 
the case of glucose acting on Mucor mucedo. On gradually increasing 
the dose, a second limit is reached where repulsion occurs. The 
entrance of fungi into leaves and the growth of hyphae along certain 
lines inside of the host tissue and the formation of haustoria are per- 
haps all indications of chemotropic response. 

iRayliss, W. M.: The Nature of Enzyme Action (Monograph on Biochem- 
istry). Longmans, Green & Co., 1914. 

Green, J. Reynolds: The Soluble Ferments and Fermentation. Cambridge 
at the University Press, 1899. 

Haas, Paul and Hill, T. G. : An Introduction to the Chemistry of Plant Prod- 
ucts. London, Longmans, Green & Co., 1913. 

Harden, Arthur: Alcoholic Fermentation (Monograph on Biochemistry). 
London, Longmans, Green & Co., 1914. 

Lafar, Franz, transl. by Salter, Charles, T. C: Technical Mycology, ii, 
Pt. I : 61-65. 

Marshall, Charles E. and others: Microbiology. Philadelphia, P. Blakiston's 
Son & Co., 1911 

Oppenheimer, Carl: Die Fermente und ihre Wirkungen. Leipzig, 1903. 

Vernon, H. M. Intracellular Enzymes. London, John Murray, 1908. 



CHAPTER VII 
GENERAL PHYSIOLOGY OF FUNGI 

The influence of light on the development of the EUMYCETES 
has been investigated by a number of workers. The influence of light 
on the direction of growth is known as phototropism. On account of 
the contradictory evidence of earlier investigations, Friedr. Oltmanns 
experimented with Phycomyces nitens using a powerful electric arc light. 
He found that Phycomyces behaved positively phototropic under weak 
illumination, but negatively so under a powerful light. It remained 
aphototropic with an intermediate illumination, and in young sporangial 
hyphse with gray sporangia, a given degree of illumination caused 
attraction, while with older sporangiophores with blackened sporangia 
repulsion was noticed. The germination of the spores of such fungi, as 
Penicilliwn glaucum, Trichothecium roseum, Fusariiim heterosporium, 
Rhizopus nigricans, does not seem to be affected by light; while 
von Wettstein found that light retarded the germination of the spores 
of Rhodomyces Kochii. The evidence as to the influence of light on 
the vegetative development seems to be contradictory. J. Schmitz 
found that Spharia carpophila grew better in the dark than in daylight. 
G. Winter found Peziza Fuckeliana to cease growth in the dark and the 
fungus perishes if light be long excluded. Mac DougaP experimented 
with Coprinus stercorarius. He found that it developed a much greater 
length than the normal in darkness, but the fruit bodies remained in 
a rudimentary or incomplete stage. After growth had proceeded in 
this manner for some time the illumination of the body was followed 
by the production of fruit bodies in a manner demonstrating most 
conclusively that the action in question was due to a purely stimula- 
tive action of light, since the rays did not participate in any synthesis 
of material. 

The rate of cell reproduction does not seem to be influenced by the 
presence or absence of light. In many fungi, the formation of a 

1 Mac Dougal, D. T. : The Influence of Light and Darkness upon Growth and 
Development. Memoirs of the New York Botanical Garden, ii (1903: 279). 

61 



62 MYCOLOGY 

fructification does not seem to be affected by the light conditions, 
but here the evidence is contradictory, some fructifications being 
formed better in light than in the dark and vice versa. Kolkwitz after 
eliminating various sources of error of earlier experimenters found 
that in his cultures of Aspergillus niger and Oidium ladis that con- 
siderable acceleration of respiration is experienced with a brief illumina- 
tion by a powerful electric arc. Koernicke^ finds that Roentgen rays 
inhibit the growth of fungi with prolonged action. 

Luminosity of Fungi. — The luminosity of wood and decaying logs 
in the forest is associated with the mycelia of certain fungi. The 
phenomenon is connected frequently with gill-bearing fungi, such 
as Agaricus, Armillaria mellea, Pleurotus olearius, and as determined by 
Molisch with the two ascomycetous fungi. Xylaria hypoxylon and A^. 
Cookei. In order to prevent any error arising in the experiments 
through the presence of luminous bacteria, Molisch^ grew Armillaria 
mellea, Xylaria hypoxylon, X. Cookei, Mycelium X. in pure cultures, 
the latter succeeding well on bread. He found that under such con- 
ditions the plants became phosphorescent. Such phosphorescence 
is connected with a supply of oxygen and is not due to the separation 
of some luminous substances, but is intracellular in its origin. 

Liberation of Spores.— The spores of the gill fungi (HYMENOMY- 
CETES) are very adhesive, when freshly set free. As a result of 
this, special arrangements are found for the liberation of the spores 
from the surfaces of the gills and the hymenial tubes. Paraphyses 
between the special conidiophores known as basidia serve to increase 
the spaces between the spores, preventing contact and allowing a 
freer fall of the spores. The arrangement of the gills is such as to 
economically increase the spore-bearing surface, and, therefore, the 
total number of spores that a fruit body can produce. By various 
growth movements of the cap and fruit stalk, the spore-bearing sur- 
face is placed in the best possible position for the liberation of spores. 
The spores liberated from the gills on the under surface of a pileus 
placed over a horizontal sheet of paper fall vertically downward and 
form a spore print, which consists of radiating lines corresponding to 
the inter-lamellar spaces. The number of spores set free by large 
fruit bodies is prodigious. A specimen of the mushroom Agaricus 

1 KoERNiCKE, Max: Ber. d. deutsch. Bot. Ges., 1904: 22, 14H. 

2 Molisch, Hans: Leuchtende Pflanze, 1904: 25-46. 



GENERAL PHYSIOLOGY OF FUNGI 



63 



{PsalUota) campestris with a diameter of 8 cm. produced 1,800,000,000 
spores, one of Coprimis annatus 5,000,000,000 and one of Polyporiis 
sqnamosus 11,000,000,000 spores. Buller has estimated that a large 
fruit body of the giant puffball Lycopcrdon bovisla (40 X 28 X 20 cm.) 




Fig. 17. — Diagram of the discharge of spores from a fruit-body of Polyslictus 
versicolor as seen by a beam of light. A stream of spores is carried round within 
the beaker very slowly by convection currents and recorded. Reduced about 2/3. 
{After Buller: Researches on Fungi, 1909: 97.) 

contained 7,000,000,000,000 spores, or as many as 4000 mushrooms 
of the size above mentioned. 

Spores dropping from any fruit body which is suspended in a 
closed glass chamber can be seen in clouds, or individually, without the 



64 MYCOLOGY 

microscope by concentrating a beam of light upon them (Fig. 17). 
This is a simple method of examining the discharge of spores from the 
mushroom. It can be used conveniently with the xerophytic fruit 
bodies of Lcnzitcs betuUna, Polystictus versicolor, Schizophyllum com- 
mune at any time in the laboratory by keeping them dry for months 
and reviving them by placing them in a jar with wet cotton. They 
quickly revive and begin to shed their spores in six hours and this 
discharge continues for some days. 

Ordinarily, spore discharge from any fruit body is a continuous 
process, but if placed in hydrogen, or carbon dioxide, the liberation of 
spores ceases quickly, demonstrating that oxygen is necessary. Ether 
and chloroform act similarly to the gases above mentioned. The 



X A B 





"•• 







Fig. 18. — The successive and violent discharge of the four spores from the basid- 
ium of a mushroom Agaricus (Psalliola) campeslris. X, The basidium with four 
ripe spores; A, B, C, D, successive stages of the discharge of spores i, 2, 3, 4 respec- 
tively. (After Buller, Researches on Fungi, 1909: 144.) 

special conidiophore, or basidium, usually bears four spores which are 
discharged successively, each spore being shot out violently by the 
pressure of the cell sap upon the wall of the basidium and perhaps also 
on the spore wall within a few seconds or minutes of one another 
(Fig. 18). The rate of the fall was observed by Buller, who used a 
horizontal microscope and a revolving drum to record accurately the 
rate of their fall. The rate of fall of the spores of gill fungi ranges from 
0.3 to 6.0 mm. per second. It varies with the size, specific gravity 
and the progress of desiccation of the spores. Buller found the relatively 
small spores of Collybia dryophila in dry air to fall at an average rate 
of 0.37 mm. per second while the relatively large spores of Amanitopsis 
vaginata in a saturated chamber attained a speed of 6.08 mm. per 



GENERAL PHYSIOLOGY OF FUNGI 



65 



second and the spores of the common mushroom shortly after leaving 
the cap fall at the rate of i mm. per second approximately. 

The violent discharge of the spores prevents the adhesive spores 
from massing together and from sticking fast to the gill surface. At 
first the spore is shot out horizontally, then under the influence of 
gravity, it describes a sharp curve and then falls vertically. The 
path described by the falling spore has been appropriately called a 




Fig. 19. — Amanitopsis vagineta. Relations of spores to the fruit-body. A, 
Transverse section through two gills, h, basidia projecting, the arrows show spore 
parts (sporabola), Magn. 15; B, vertical section of hymenium and subhymenium, c, 
paraphyses, a-c, basidia stages, Magn. 370; C, isolated basidium with two basidios- 
pores; D, discharged spore; E, basidium, Mayer, mo. (After B idler, 1909: 165. )j 

sporabola (Fig. 19). There are two distinct types of fruit bodies as to 
spore production and spore liberation. These are the Coprinus comatus 
and the mushroom types. The deliquescence, or melting of the fruit 
bodies of the Coprini is a process of auto-digestion and it assists mechan- 
ically in the discharge of the spores. Spore discharge precedes deliques- 
cence. The spores are set free from below upward and by auto-diges- 
tion those parts of the gills are removed from which the spores have 
5 



66 



MYCOLOGY 



been shed, thus permitting the opening out of the cap and the freer 
discharge of the remaining spores. The discharged spores are conveyed 
by the wind (Fig. 20). The mushroom type is the usual kind where 
the spores are discharged without deliquescence. 

The spores of Bulgaria, Gyromilra, Peziza and others of the 
AscoMYCETALES are scattered by the wind, but those of Ascpbolus 
immersus and Saccobolus are dispersed by herbivores. The spores of 
Peziza repanda, according to Buller, are shot up into the air to a 
height of 2 to 3 cm. and leave the spore sac (ascus) together, but 




Fig. 20. — Semidiagrammatic sketch in a field with horse mushroom, Agaricus 

{Psalliola ) arvensis, showing Hberation and discharge of spores horizontally 

and from velum. Reduced to y<i. {After Buller, Researches on Fungi, 1909: 218.) 



separate as they leave the ascus mouth. Puffing is due probably to a 
stimulus given'j to the* protoplasm in contact with the ascus Hd, and 
it is observed when poisonous substances are applied such as iodine 
mercuric chloride, silver nitrate, copper sulphate, sulphuric and acetic 
acids are used. With^some of these forms the ascus may be considered 
as a squirting apparatus by which a jet of spores leaves its mouth. 
The writer^ noted the puffing of the spores in Peziza hadia when the 
large saucer-shaped fruit bodies were held in the hand. At intervals 
of several minutes the puffing took place. 

Ascobolus immersus as a coprophilous (dung-inhabiting) fungus has 
1 Harshberger, J. W.: Journ. of Mycol., 8: 158, October, 1902. 



GENERAL PHYSIOLOGY OF FUNGI 67 

special adaptations: (i) the protrusion of the ripe asci beyond the general 
surface of the fruit body; (2) the diurnal periodicity in the ripening of 
successive groups of asci; (3) the positive heliotropism of the asci; (4) 
the considerable distance to which the spores are ejected (sometimes 
30 cm.) with which is associated; (5) the large size of the asci and spores; 
and (6) the clinging of the eight spores together, while describing their 
trajectory through the air. The forcible explosion of the sporangio- 
phore of Pilobolus crystallimis by which the whole sporangium is dis- 
charged a considerable distance into the air is due to the tension exerted 
by gases and water vapor within the swollen sporangiophore. 

The escape of biciliate zoospores (swarm spores) in such genera of 
aquatic fungi as Achlya and Saprolegnia is through a terminal pore in 
the zoosporangium. It appears that the discharge is associated with 
the motility of the cilia. In the moulds (Mucorace^), the sporangial 
wall which is coated with minute particles of calcium oxalate becomes 
soluble in water at maturity and the intersporal substance swells up 
assisting in the liberation of the spores. The entire inner peridium 
about the size of a pin's head is forcibly ejected in the gasteromycetous 
fungus, S phcBrobolus stellatus, and this is due to the unequal tension of 
the different peridial layers. 

The disposal of spores and conidia is facilitated by water in the 
case of the motile zoospores of such fungi as Achlya prolifera, Phytoph- 
thora injestans and Saprolegnia ferax, where cilia come into play. 
Many spores are no doubt carried passively by water currents. Wind 
is, however, one of the chief agents in the distribution of fungous spores, 
such as those of the puffballs, the rusts and the moulds, although the 
distance that such spores are carried is probably exaggerated. Flies, 
which feed upon the strong-smeUing slime in which the minute spores 
of such fleshy fungi as Mutinus caniniis, Icthyphallus impudicus are 
imbedded, assist in the carriage of such spores and those of ergot 
{Claviceps purpurea) in the Sphacelia stage, where viscid drops exude 
that are attractive to flies, and although some flies arekilled by it, yet 
sufficient escape to carry the spores. Slugs and snails by crawling 
alternately over diseased and healthy plants, probably disseminate 
spores. That birds serve as distributors of spores is indicated by the 
studies of Heald with the chestnut blight fungus, Endothia parasitica, 
in which he found that a single downy woodpecker carried as many as 
657,000 pycnospores. Certain subterranean fungi such as truffles are 



68 MYCOLOGY 

eaten by rodents attracted by the strong smell that they possess and 
probably the mammal is instrumental in the spread of the spores. 

Many of the coprophilous fungi have spores which pass through the 
alimentary canals of different animals without being destroyed and 
germinating in the dung, or manure from such animals, they propagate 
the species. Pilobolns crystallinus is one of them. The sporangia, which 
are shot off from the sporangiophore, adhere to blades of grass, which 
are eaten by horses, and later the fungus makes its appearance on horse 
manure. The spores have passed through the horse apparently unaf- 
fected and more readily germinable. Man with his agricultural imple- 
ments is concerned with the spread of fungous spores. Giissow states 
that a threshing machine, which has been used for threshing smutted 
wheat, is infested so fully with spores that any grain subsequently 
threshed, unless the machine is sterilized properly after use, will 
become liable to infection. 



CHAPTER VIII 
ECOLOGY OF FUNGI 

As fungi are either saprophytes or parasites, their Kfe history is 
bound up with the substratum on which the saprophytes are found and 
with the host plant upon which the parasite hves, yet there are many 
diverse forms of saprophytic fungi and the greatest variety of fungous 
parasites. Of special interest in connection with the ecology of fungi 
are the organs by which various fungi are tided over periods of drought, 
inclement seasons, or during the winter's cold. These organs are 
compacted masses of hyphse of a rounded, globular, or ellipsoidal form 
ranging in size from those that are almost microscopic to those which 
are the size of a small canteloupe. These tuber-like masses of hyphae 
in a resting state are known as sclerotia (Gr. ayXupos, hard). They 
are found in a great many fungi, as commonly in the ergot, Claviceps pur- 
purea, a.nd the lettuce drop, Sclerotinia libertiana, which forms sclerotia 
that may reach a length of 3 cm. in exceptional cases. These sclerotia 
are obtained readily in culture tubes with beerwort agar, or glucose agar, 
as culture media. From the sclerotium later arises the stalked fruit 
body, or apothecium. Cordyceps militaris is a fungus which attacks 
the larva of insects. Its mycelium penetrates the insect's body and 
later in the Isaria form produces aerial hyphas which cut off conidio- 
spores. The growth of the mycelium is such as to penetrate to all parts 
of the larva filUng it up as if it were stuffed with cotton. 

The mass of hyphae is converted into asclerotiumand the larval body 
is mummified, but still retaining its original external form. Later, the 
next spring, a stiff-stalked stroma arises with an enlarged extremity in 
which the perithecia with their asci- and ascospores are formed. Later 
the needle-shaped ascospores are set free and by cutting off conidio- 
spores reproduce the disease. Cordyceps (Torrubia) ophioglossoides is 
parasitic upon an underground truffle, Elaphomyces muricatus, Fig. 
21). The stroma is erect, yellow and club-shaped at the extremity. 
Perithecia, asci- and ascospores are borne in the swollen part of the 
stroma. The fungus which discharges its spores above ground finds the 

69 



70 



MYCOLOGY 




Fig. 21. — A Cordyceps tnilitaris; B, Cordyceps Hugelii on a caterpillar; D, Cordy- 
ceps spharocephala on a wasp; E, Cordyceps cinerea on a beetle; F-K, Cordyceps 
ophioglossoides, F on a deer truffle; G, ascus; H, conidiophore; J, conidiospores; K, 
germinating spore. See Die naliirlichcn Pflanzenfamilicn I. i, p. 368. 



ECOLOGY OF FUNGI 7 1 

underground truffle in Llie following manner. When the spores germi- 
nate, they give rise to hyphai which grow over a densely cespitose, com- 
mon moss, Mniiim horniim, which develops a large number of feeding 
rhizoids, that penetrate the soil to the depth at which Elaphomyces 
grows. The mycelium of Cordyceps not only covers the aerial portions 
of the moss, but follows the rhizoids underground until they reach the 
underground truffle over which the moss may happen to grow. Bot- 
anists searching for Elaphomyces always know where to look for it by 
the presence of the Cordyceps hyphae, on the moss Mnium hornum. 
There is a black beetle, a native of France^ with a pale, velvety abdo- 
men, known as Bulboceras gallicus, about as large as a cherry stone. By 
rubbing the end of the abdomen against the edge of the wing cases it 
produces a gentle chirping sound. The male has a horn on his head. 
This insect burrows in the soil among the trees of the pine forests and is 
nocturnal in its habits. It descends vertically into the soil in search 
of the underground truffle-like fungus, Hydnocystis arenaria, upon 
which the insect rabassier feeds. The fungous fruit body is about the 
size of a cherry with a reddish exterior covered with shagreen-like warts. 
The beetle, which feeds upon Hydnocystis arenaria and Tuher Requenii 
one of the truffles, locates the fungi by a subtle sense of smell. The 
human truffle hunter finds these underground by the burrows which 
the beetles make in digging for their chief source of food and he usually 
finds groups of these fleshy funguses directly beneath the openings of 
the beetle holes. 

Rozites gongylophora is a gill fungus which is raised as a fodder by 
leaf-cutting ants in their subterranean passageways in the tropics of 
South Brazil. 

On a visit to the Berlin Botanical Garden in 1898, the writer noted 
the following remarkable examples of sclerotia-bearing fungi: Poly- 
porus sapurema A. Moller (Fig. 92, Teil I, Abt. i**, Die naturlichen 
Pflanzenfamilien, p. 171). The sclerotium is over 30 cm. in diameter 
and weighs at least 20 kg. It is furrowed and roughened and leather 
colored. A specimen from Blumenau, Brazil, developed in the Victoria 
house of the Berlin Garden four large pilei in August and September, 
1897. Polyporus mylittce found in Australia produces a sclerotium 
{Mylitta australis Fr.), which as "native bread" is used as food 
by the natives. Polyporus tuhcraster, which grows in the mountains 

1 Fabre, F. H.: Social Life in the Insect World, 1912 217-237. 



72 MYCOLOGY 

of Italy, develops a large edible sclerotium called by the natives 
pietra fungosa. The sclerotium of Polystictus socer (Fig. 94 A, Teil I, 
Abt. I**, Die naturUchen Pflanzenfamilien, p. 177), known as 
Pachyma malacense, is of variable shape, 8 to 10 cm. long, brownish red 
externally with a white interior. It is found in the Malay Archipelago. 
These are a few of the true sclerotia which probably includes the 
"tuckahoe" of the North American Indian, Pachyma cocos. 

Living on limbs, twigs and the leaves of the beech in the deep 
shade of the forest is found a scale insect {Schizonema imbricator) ,^ 
which is covered by a woolly coat consisting largely of a waxy secretion 
from the body. This woolly material is quite abundant and where the 
insects live in masses together the entire limb, or leaf surface has a 
downy white appearance. The abdomen of the insect moves con- 
stantly with a jerky motion and the cottony material is, therefore, 
constantly agitated. The insects secrete a honey dew so copiously 
that it runs down to the leaves beneath and to the ground. Upon this 
honey dew and the dead bodies of the scale insect, a pyrenomycetous 
fungus, Scorias spongiosa, lives. It grows as a spongy mycelium con- 
sisting of much-branched, rigid, septate hyphge with the strands glued 
together by a mucilage. Pyriform perithecia, long-necked spermogonia 
and pycnidia are formed from the mycelium, which is saprophytic 
on the products of the insect's body. 

The anther smut of the caryophyllaceous flowers occurs in America 
and Europe on Cerastium viscosum, Saponaria officinalis and Silene 
inflaia, and on species of Dianthus, Lychnis, Melandrium, Stellaria, 
etc. The spores of this smut replace the pollen grains in the anthers 
of these plants and when the flowers open a violet smut dust is dis- 
charged from the anthers instead of the pollen. Female flowers of 
Melandrium attacked by the fungus show a marked morphologic 
differentiation in the development of mature stamens out of staminal 
rudiments. These anthers are invaded by the fungus and in them the 
parasite fructifies. 

The formation of galls is a marked feature of the ecology of fungi. 
One form of these malformations is seen in the witches' broom (hexen 
besen) which are due to the attack of a number of species of Exoascus 
on different forest trees; The branchlets are clustered into broom-like 
masses with leaves that are somewhat altered in shape and fall earlier 

^Harshberger, J. W.: Joum. of Mycol., 8: 160, October, 1902. 



ECOLOGY or FUNGI 73 

than those on normal twigs. Witches' brooms are found on such conif- 
erous trees as the white cedar in New Jersey and are due to Gymno- 




FiG. 22. — Black knot of plum, Plowrighlia morbosa, on beach plum, Priinus marilima 
Nantucket, August 17, 1915. 

Sporangium Ellisii, a rust fungus. These malformations occur on the 
hackberry, but on this tree they are due to the attack of a mite Phy- 
toptus followed by a fungus. Plum pockets are a form of gall in which 



74 MYCOLOGY 

the fruit is enlarged by the attack of the fungus at the expense of the 
stone which fails to develop. The hollow galls on the plum are due to 
Exoascus pruni. The so-called cedar apples on our red cedar trees in 
the spring are caused by the attack of an annual rust fungus, Gym- 
nosporangium juniper i-virgini ana, and from the surface of these 
apples two-celled spores arise. The white rust of cruciferous plants, 
Cystopus candidus, produces blisters on the leaves and stems of shep- 
herd's purse. The black knot of the plum is a tumor-like swelling of 
the branches of plum trees due to the attack of an ascomycetous fungus, 
Plowrightia morbosa (Fig. 22). Large swellings on oak trees the size of 
a man's head and over are caused by a fungus, Diachana strumosa, and 
some of these swellings may be the size of a large pumpkin. Galls due 
to insects are frequent on plants, but a discussion of them is extralimital. 

According to conditions of environment, we may briefly treat of 
fungi as hygrophytic, mesophytic and xerophytic forms. The hygro- 
phytic forms include the aquatic fungi, such as Achlya^ Mono- 
ble pilaris, Saprolegnia and other genera which live and carry on 
their reproduction in water. Perhaps to this group would belong 
a fungus of the genus Cyttaria, which was found by Darwin in the 
beech (Nothofagus) forests of southern Patagonia. The beech trees 
grow in cold, wet valleys completely barricaded by great moulder- 
ing trunks of former beech trees on which the globular, bright yellow 
fructification occurs and which is eaten by the Fuegians. 

The mesophytic forms include many of the common fleshy gill 
fungi that live in our woods and forests, appearing in surprisingly great 
numbers after a spell of wet weather. Here we might include species 
of Amanita, Boletus, Russula, and Clavaria and others which are not 
infrequent, while in our meadows occur mushroom and coprini. Three 
conditions seem favorable to their growth: abundant leaf mould, 
warmth and abundant moisture. 

The habitats of the fleshy fungi are of general interest. Collybia 
platyphylla develops its fruit bodies on the shaded side of decaying 
logs. The fairy-ring fungus, Marasmius oreades (Fig. 23) produces its 
sporophores in lawns in the form of rings long known as fairy rings. 
Frequently grassy spots are enclosed by the circle of toadstools which 
are several feet in diameter. The fruit bodies of Pholiota adiposa 
(Fig. 24) grow from wounds in living trees. 

In forest operations the slash, when scattered, rots more rapidly 
than when piled. This is due to the fact that two types of fungi 



ECOLOGY OF FUNGI 75 

are active in rotting the brush, one set entering the Hmbs and branches 
above the ground and the other gaining access to the brush actually 
in contact with the soil. Brush is rotted at the top when piled 
with one group of fungi and at the bottom by another group, while 
the middle of the pile, not in contact with the soil and yet protected 
from the sunlight, apparently will not rot to any extent until the 




Fig. 23.— Fairy ring formed by Marasmius oreades, an edible toadstool. (From 
Wiley, Foods and Their Adulteration. After Coville, Circular 13, Division of 
Botany.' 

pile disintegrates suflSiciently to expose these central layers to the 
soil moisture on the one hand, or to the sunlight on the other. 
Four fungi cause rotting of oak slash in Arkansas, viz., Stereum 
rameale, S. umbrinum, S. versiforme and S. fasciatum. Two fungi are 
responsible for the decay of short-leaf pine slash. They are Lenzites 
sepiaria and Polyslictus abiet'mus.^ 

The xerophytic forms are those which have corky or leathery fruit 

^Lona, W II.: Investigation of the Rotting of Slash in Arkansas. U. S. Dept. 

Agric. Bull. 496, Feb. 16, 191 7; also Humphrey, C. J.: Timber Storage Conditions in 

the Eastern and Southern States with Reference to Decay Problems Bull, 510, U. 

S. Dept. Agric, May 17, 1917. 



76 



MYCOLOGY 



bodies growing on sticks and logs where they can dry up without any 
loss of vitaHty. They revive after a rainfall and resume the function 
of discharging spores and the discharged spores are capable of germina- 



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Fig. 24. — Pholiola aJiposa growing from a wound in a living tree (edible). 
(After Patterson, Floraw and Charles, Vera K., Bzill. 175, U. S, Dept. Agric, Apr.[2S, 
1915-) 

tion. DcBdalea (Fig. 202), Polystictus and Stereum are typical genera of 
the xerophy tic log flora. Buller ^ describes the fruit bodies of Schizophyl- 
lum commune as possessing special adaptations for a xerophytic mode of 
1 BuLLER A. H. Reginald: Researches on Fungi, 1909: ^64. 



ECOLOGY OF FUNGI 



77 




Fig. 25. — Schizophyllum commune, a xerophyte. A and B, fruit-bodies seen 
from above growing on wood, natural size. C and D, two fruit-bodies seen from 
below and in section; about twice magnified; £, section through pileus in wet weather 
showing gills split down their median planes; F, section of a dry pileus; E and F 
about 12 times natural size, (after Buller, Researches on Fungi, 1909: 114.) 



78 MYCOLOGY 

existence (Fig. 25). "The gills are partially or completely divided 
down their median planes into two vertical plates. While desiccation 
is proceeding, the two plates of each of the longer and deeper gills bend 
apart and spread themselves over the shorter and shallower gills. 
When desiccation is complete, the whole hymenium is hidden from 
external view and the fruit body is covered both above and below with a 
layer of hairs (Fig. 25). The closing up of the fruit bodies at the 
beginning of a period of drought serves to protect the hymenium. A 
fruit body which retains its vitality even when dry for two years will 
revive again in a few hours and spores are discharged" (Fig. 25). 

As it is not the purpose of this book to consider the so-called Hchens 
in the classification which follows as distinct entities in which the 
lichen fungus and the lichen alga are in symbiosis forming a 
lichen thallus, it is important to describe the ecology of the actual 
relationship of the two plants to each other, as a matter of botanic 
interest. Danilov, Elenkin, Peirce and Fink have shown that the dual 
hypothesis, or that of mutuahstic symbiosis, is untenable. A lichen 
is a fungus belonging to the orders ASCOMYCETALES, or BASIDIO- 
MYCETALES, which lives during all or part of its life in parasitic 
relation with an algal host and also sustains a relation with an organic 
or an inorganic substratum. Having squarely assumed this position 
as to the true nature of what currently passes for a lichen, it is interest- 
ing to note that there are ten algae known as Hchen hosts: Chlorococcum 
(Cystococcus) humkola, Pahnella botryoides, Trentepohlia (Chroolepus) 
umbrina, Pleurococcus vulgaris, Dactylococcus infusionmn, Nostoc lichen- 
oides (?), Rivularia nitida, Polycoccus pimctijormis, Gleocapsa polyderma- 
tica and Sirosiphon pulvinatus. It is important to note, that although 
the larger number of the above are blue-green algae, yet the two species 
of green algae. Chlorococcum humicola and Trentepohlia umbrina form 
the hosts of many more lichens than all the others combined. Hence 
the student of these plants can study the algicolous fungi, mainly 
ASCOMYCETELES, a few BASIDIOMYCETALES, those parasitic 
upon algje, as the lichens, while the non-algicolous fungi can be over- 
looked by the lichenologists. We can do no better than quote Bruce 
Fink,^ who sums up the main arguments against mutualism and the 

1 Fink, Bruce: The Nature and Classification of Lichens. I. Views and Argu- 
ments, Mycologia, iii: 231-269, September, 1911; II. The Lichen and its Algal Host, 
Mycologia, iv: 97-166, May, 1913. 



ECOLOGY OF FUNGI 79 

advocation of the fungal nature of lichens, as follows: "Lichens com- 
monly grow where there are free algae of the same species as those 
parasitized by these Uchens. The spores of the lichens germinate and 
attack the free alga; as other fungi attack their hosts. Lichens perform 
like other fungi on culture media and may be made to produce their 
reproductive organs on these media. Lichen spores also attack the 
algal hosts, when the spores and the algae are introduced into cultures 
together; and the resulting lichen is normal and sometimes fructifies 
in the cultures. Algal hosts extracted from lichen thalli grow in cul- 
tures like free algae of the same species grown on similar culture 
media. The researches of Elenkin and Danilov prove that lichen 
hyphae absorb food from the algal host cells, which are killed by 
severe parasitism, or more probably by parasitism and saprophytism 
combined. The relation of the lichen to its substratum proves that 
higher lichens can take comparatively little food from it and must 
depend more than lower lichens upon the algal hosts; and this shows 
that the parasitism of the lichen upon the algal host has become more 
severe in the evolution of the higher lichens. Finally, the algae para- 
sitized by lichens are in a disadvantageous position with reference to 
carbon assimilation. 

"Lichens are like other fungi with respect to vegetative structure 
and fruiting bodies. The bridges which connect lichens with other fungi 
are not few, but many. Since it is thoroughly demonstrated that the 
lichen is parasitic, or partly parasitic and partly saprophytic on the 
alga, there is no longer even a poor excuse for a 'consortium' or an 
'individualism' hypothesis. 

"The parasitism of lichens on algae is peculiar in that the unicellular 
or the filamentous hosts are enclosed usually by the parasite, which 
carry more or less food to the host. The host inside of the parasite is 
placed in a disadvantageous position with reference to carbon assimila- 
tion and may depend, for its carbon supply, more or less upon material 
brought from the substratum by the parasite. Some algal individuals, 
not yet parasitized, may be found in most lichen thalli." 

Lichen thalli are of three kinds: crustaceous, foliose and fruticose. 
The arrangement of the layers of the lichen fungus and its algal host 
varies in different lichens, but in Stkta the following are met in a ver- 
tical section of the thallus (Fig. 26) : 

(a) Tegumentary layer. 



8o 



MYCOLOGY 




Fig. 26. — A foHaceous lichen, Parmelia perlata. i, Plant slightly reduced in 
size; a, apothecia; b, lobe of thallus; c, patches of soredia; 2, longitudinal section of 
apothecium and cross-section of thallus; a, ascus; b, c, hypothecium; d, upper gonidial 
(upper algal) layer; e, medullary layer;/, lower gonidial layer; g, lower cortical layer; 
I, 3, cross-section of vegetative thallus. (From Gager. After Schneider.) 



ECOLOGY OF FUNGI 8l 

(b) Upper cortical layer. 

(c) Algal layer (gonidial layer). 

(d) Medullary layer. 

(e) Lower cortical layer. 

The tegumentary layer consists of several rows of flattened hyphal 
cells extending at right angles to the underlying cortical cells which 
consisting of hyphal cells are pseudoparenchymatous, resembling the 
parenchyma tissue of higher plants. The algal layer contains the 
gonidia, or green plants, which act as hosts to the fungous hyphge. The 
medullary layer which is thicker than the others consists of much 
elongated hyphae forming a loosely interwoven tissue with large air 
spaces. The lower cortical layer is pseudoparenchymatous and from its 
lower surface rhizoids are developed. The apothecia and perithecia 
are the fruit bodies of the ascomycetous fungi which form the lichens. 
A vertical section through an apothecium of Sticta shows the following 
layers: (a) the epithecium, (b) the thecium consisting of the spore 
sacs (asci) and paraphyses, (c) the hypothecium or hyphal structure 
immediately below the thecium, (d) upper algal layer, (e) medullary 
layer, (/) .lower algal layer, (g) cortical layer (Fig. 26). 

Some of the fruticose lichens have a central core-like strand of hyphae 
running through the medullary region which serves as supporting 
mechanic tissue as in Usnea barbata. The soredia are vegetative repro- 
ductive bodies consisting of from one to many algae surrounded by 
continuous hyphal tissue and are common upon the upper surface and 
margins of most of the higher lichen thalli. Among the Basidio- 
LiCHENES basidia are formed with basidiospores on sterigmata as in 
Cora, Dictyonema, Laudatea. 



CHAPTER IX 
FOSSIL FUNGI AND GEOGRAPHIC DISTRIBUTION 

Fungi in the Fossil State.^ — All the known fossil fungi numbering 
over 400 species have been figured and described by Meschinelli in his 
"Fungorum fossilium omnium Iconographia " published in 1898. 
Zeiller in discussing the chronologic sequence of the groups of fungi 
states that representatives of the families Chytrideace^, Mucora- 
CE^ and Peronosporace^ have been found in the tissues of the 
higher plants preserved in rocks of lower Carboniferous and Permian 
ages. Many different plants extending from the Carboniferous period 
upward show various forms of the ASCOMYCETALES on leaves and 
in the tissues especially those of the stems. The fleshy fungi of the 
famines Agaricace^ and Polyporace^ have been found in deposits 
of tertiary age. Weiss has announced the discovery of a mycorrhiza 
in the root of a probable Lycopodiaceous plant of the lower Carbonif- 
erous strata. Where Polyporus and Lenzites occur, as in the brown 
coals, silicified woods occur which have been half destroyed by their 
mycelia. 

GEOGRAPHIC DISTRIBUTION OF FUNGI 

This important and interesting subject can be presented in the barest 
outline. The modern teaching of geography emphasizes home geog- 
raphy as a fundamental study. In following this suggestion in the 
investigation of the local fungi, it will be found that we must deal 
with distinct habitats, such as leaf mold, sandy soil, wet soil, decayed 
logs, tree stumps, living trees, living herbs and the like. The black 
mould, Rhizopus nigricans, is one of the commonest of fungi. It occurs 
on bread and other organic substrata, such as sweet potatoes, whenever 
the conditions are suitable for its growth. If horse manure is covered 
with a bell jar with wet paper inside, there develops first the gray 
mould, Mucor mucedo. This is accompanied or followed by Pilobolus 

^Seward, A. C: Fossil Plants, 1898: 207-222. 

Weiss, F. E.: A Mycorrhiza from the Lower Coal Measures. Annals of Botany, 
xviii: 255 with 2 plates. 

82 



FOSSIL FUNGI AND GEOGRAPHIC DISTRIBUTION 83 

crystalliniis, and this in turn by the white flecks of Oospora scabies. 
Coprinus stcrcoraritis usually completes this series of coprophilous 
fungi generally found on horse dung. Sometimes the Mucor is para- 
sitized by Piplocepkalis and sometimes by Chatocladium. Peziza 
coccinea is attached to dead twigs buried in the forest leaf mould, and 
as it rises to the surface, it develops a long stipe with a crimson-red 
saucer-shaped apothecium at its extremity. Russula emetica, R. 
virescens, species of Clavaria and Boletus are regularly found beneath 
deciduous trees growing out of the forest litter. The pufifball, Sclero- 
derma vulgare, is found on the tops of old stumps in gregarious clusters. 
Polyporus sulphur ens grows out of partly dead chestnut and oak trunks; 
while the hymenophores of Armillaria mellea are found clustered about 
the bases of trees beneath the bark of which the rhizomorphs will be 
found growing. A species of Hydnmn was found a few feet above the 
ground on a beech tree and Fistulina hepalica attached to tree trunks, 
where the swollen base gradually blends with the straighter hole above. 
Amanita muscaria and A. phalloides grow in solitary splendor at the 
edges of woods and copses, while the habitat of the mushroom in open 
fields is quite distinctive. 

The earth-star, Geaster hygrometricus, grows more frequently in 
sandy soil, where it spreads out its peridial segments. 

The habitat of the local species of the lichen fungi is of interest. 
The brown-fruited cup cladonia, Cladonia pyxidata, grows on stumps 
and on the earth, while the scarlet-crested cladonia, Cladonia cristatella, 
is found on dead wood. The Iceland moss, Cetraria islandica, grows 
on the ground as also the reindeer-lichen, Cladonia rangiferina, in ex- 
tensive masses. Another earth-inhabiting form is Peltigera canina. 
The trunks of trees are marked by the presence of Parmelia perlata 
and the fruticose bearded lichen, Usnea barhata. Smooth bark appears 
covered with runic character traced by the fruit bodies of Graphis 
scripta. The rock-dwelling lichens include Physcia parietina and the 
rock tripe (tripe de roche), Umbilicaria which grows on the outcrops 
of Octorara schists at the Gulph. 

The distribution of the chestnut blight fungus, Endothia parasitica, 
is of more than local interest, although the agitation to control it 
started near Philadelphia. Apparently the fungus was introduced from 
China, where it has been found recently, with nursery stock into Long 
Island. From the neighborhood of New York City, it spread northeast, 



84 



MYCOLOGY 



northwest, west and southwest.^ Now it is found in Connecticut, 
New York, throughout New Jersey, and as far west as the Alleghany 
mountains in Pennsylvania. In isolated areas, it occurs in Virginia 
and West Virginia, endangering the future of the chestnut tree in 
America (Fig. 27). 

Wherever the cultivation of the higher plants extends, the fungi 
pecuUar to these plants will be found, as the wheat rust, Puccinia 




Fig. 27. — Map of the eastern United States showing distribution of chestnut 
blight disease in ipii. Horizontal lines indicate area with approximately all the 
trees dead; vertical lines approximate area where infection is complete; dots indicate 
advanced points of infection. {From Gager, after Metcalf, U. S. Farmers' Bull. 467.) 



graminis, in Europe, America and Australia. The damping-off fungus^ 
Pythium de Baryanum, which is death to seedlings, has been studied by 
German, English and American botanists, as a reference to the litera- 
ture will show. The downy mildew, of the grape, Plasmopara viticola, 
apparently of eastern American origin, is found now in, Europe and 
Cahfornia, where it has become a serious pest. 

The black knot, Plowrightia morbosa, was apparently at one time 
confined largely to the Atlantic seaboard and was particularly abundant 
in New England and New York. It has now spread across the northern 

' Cf. Stevens, Neil E.: Some Factors influencing the Prevalence of Endothia 
gyrosa. Bull. Torr. Bot. flub, 44 : 127-144. March, 191 7. 



FOSSIL FUNGI AND GEOGKAPHIC DISTRIBUTION 85 

United States to the Pacific coast. Such diseases as the sooty mold of 
orange, Meliola camellicB, and the brown rot of the lemon, Pythiacystis 
citriophthora, arc confined to these last plants and to the regions where 
the citrus fruits grow. The anthracnose of the sycamore, Gnomonia 
veneta, is parasitic upon the leaves and shoots of the sycamore or plane 
tree, Platanus occidentalism causing its leaves to dry up, as if bitten by 
early frosts. It seems to be more prevalent in the bottom of valleys, 
where the plane tree grows along streams, as here we find cold-air 
drainage. Sometimes after the first crop of leaves is lost, a second 
crop appears. Wherever the sycamore grows, Gnomonia may be ex- 
pected. The so-called fly-cholera fungus, Empusa muscce, is parasitic 
in flies and is present on these insects in Europe, even in the far north, 
in North America and South America (Argentina). The coprophilous 
fungus, Basidioboliis ranarum occurs on the dung of frogs in Europe 
and America. Taphrina ccsrulescens does not seem to be choice about 
its hosts, occurring as spots on the leaves of Quercus cerris, puhescens, 
sessiliflora in middle and southern Europe and on Quercus alba, aquatica, 
coccinea, laurifolia, rubra, velutina in North America. The hairy 
earth-tongue, Geoglossmn hirsutum, is truly cosmopoHtan, as it has been 
reported from all over Europd, North America, Java, Mauritius and 
Australia. The genus Cyttaria with eight ascospores in each ascus in- 
cludes six species. C. Darwinii and C. Berterii were discovered by 
Darwin in Patagonia. C. Gunnii occurs in Tasmania and C. Harioti in 
Terra del Fuego. None of the species, therefore, are found outside of 
the southern hemisphere (Fig. 28). The genus Hypomyces includes 
species which live parasitically, or saprophytically, on other fleshy 
fungi. H. ochraceus lives on species of Russula in Germany, England 
and North America; H. chrysospermus occurs on species of Boletus in 
Europe; H. aurantius on Polyporace^ and Thelephorace^ in 
Europe; H. lateritius on Lactarius in Europe and North America; H. 
vlolaceus with its tender small stroma and violet-colored fruit body lives 
on a slime mould Fuligo septica in northern Europe; H. viridis is found 
on species of Lactarius and Russula in northern Europe and North 
America; //. cervinus grows on Helvellace^ and large Pezizace^ in 
Europe; H. fulgens appears on the bark of pine trees in Finland and 
Sweden; H. Stuhlmanni is confined to Poly poms bukabensis in Central 
Africa; H. chrysostomiis is reported from Ceylon and H. flavescens on 
a Polyporus in North America. Hypomyces lactijluorum planes down 



86 MYCOLOGY 

the gill surfaces of the Lactarius sp. on which it grows, converting an 
otherwise grayish-white fruit body into a cinnabar-red one. It is 
found in the woods about Philadelphia, Pa. The fungi belonging to 
the family Laboulbeniace^ are included in 28 genera and approxi- 
mately 152 species, and have been made known largely through the 
studies of Prof. Roland Thaxter of Harvard University. A few species 
are found in Europe, in the tropics of Africa, America and Asia, but 
North America is extraordinarily rich in specific forms. They occur 
on dipterous, neuropterous and coleopterous insects, especially those 
which live in damp places or in the water. The corn-smut Ustilago 
maydis is a parasite confined exclusively to the maize plant, Zea mays, 
and to the closely related if not identically the same grass the teosinte; 
EuchlcBna mexicana as pointed out some years ago by the writer^ as 
proof of the common origin of these two grasses. Wherever maize is 
cultivated the smut is found associated with it. 

The rusts (Uredine^) are arnong the most specialized of fungi in 
their parasitic habits, some species being confined to one or two hosts. 
They ascend with their host plants above the snow line on high moun- 
tains and toward the poles wherever flowering plants and ferns grow. 
Whole genera are confined, however, to certain regions. Thus the 
genus Ravenelia which lives on mimosaceous and caesalpinaceous plants 
extends north to the 40° north latitude. Many rust fungi are iden- 
tically the same in North America, north and middle Europe, and of 
the 500 species known from North America and 400 European rusts 
approximately 150 species are common to both countries. Only a few 
Mediterranean species are found in North America, as Uromyces gly- 
cyrrhizcB and Puccinia Mesneriana. A less number of species are com- 
mon to North and South America. It is noteworthy that Puccinia 
malvacearum introduced into Spain from Chile in 1869 has in the forty- 
six years which have elapsed since its introduction into Europe spread 
over the world. 

The genus Exohasidium includes 18 species of fungi which cause the 
formation of fleshy galls chiefly on plants of the family Ericace^. 
Tabulated the principal species are: 

Exobasidkim laccinii on Vaccinium; Europe, Siberia, America. 
Exohasidium rhododendri on Rhododendron, Europe, America. 
1 Harshberger J. W.: Cont. Bot. Lab. Univ. of Pa., 1901: 234. 



FOSSIL FLTNGI AND GEOGRAPHIC DISTRIBUTION 87 

Exohasidiiivi Icdi on Ledum, Finland. 

Exobasidium andromcdcc on Andromeda, Europe, North America. 

Exobasidimn azalew on Azalea, North America. 

Exobasidium anlarclicum on Lcbetanlhus, Patagonia. 

Exobasidium gaylussacice on Gaylussaeia, Brazil. 

Exobasidium leucothoes on Leucolho'e, Brazil. 

Exobasidium lauri on Laurus, Italy, Portugal, Canaries. 

Exobasidium Warmingii on Saxifraga aizoon, Greenland, Tyrol, North Italy. 

In closing this consideration of the geographic distribution of the 
fungi, the interest which attaches to it as a study may be best empha- 
sized by giving in tabular form the distribution of the species belonging 
to a single family. The family Clathrace^e includes eleven genera of 
highly specialized morphology. 

Family Clathrace^. 

1. Clathrus cancellatiis , Mediterranean Region, South England, 
North America. 

Clathrus columnatus, North and South America. 

2. Blunienavia rhacodes, Brazil. 

3. Ileodidyon cibarium, Australia, New Zealand, South America. 

4. Clathrella chrysomycelina, Tropic South America. 
Clathrella pusilla, Australia, New Caledonia. 
Clathrella kamerunensis , Cameroon. 
Clathrella Preiissii, Cameroon. 

Clathrella crispa, Central and Tropic South America. 

5. Simhliim periphragmoides, Tonkin, Java, Ceylon, East Indies, 
Mauritius. 

Simblum sphcerocephalum, North and South America. 

6. Colus Miilleri, Australia. 

Colus hirudinosus, Mediterranean Region. 
Colus GarcicB, Tropic South America. 
Colus Gardncri, Ceylon. 

7. Lysurus mokusin, China. 

8. Anthurus borealis, North America. 
Anthurus Clarazianus, Argentina. 
Anthurus Woodii, Natal. 
Anthurus Mullerianus, Australia. 
Anthurus cruciatus, Tropic South America. 



88 MYCOLOGY 

9. Aseroe rubra, New Zealand, Australia, Java, Ceylon, Tonkin, 

South America. 
10. Calathiscus sepia, East Indies. 

Calathiscus Puiggarii, South Brazil. 
II Kalchbrennera corallocephala, Africa, Cape, Natal, Angola, 

Cameroon, Zambezi Region. 



CHAPTER X 
PHYLOGENY OF THE FUNGI 

One of the most consistent attempts at representing the phylogeny 
of the fungi has been made by Dr. O. Brefeld through his researches 
which were pubHshed in collected form in " Untersuchungen aus dem 
Gesammtgebiet der Mykologie. " As these volumes are bulky ones, a 
student of Brefeld, Dr. F. von Tavel, has given a useful summary of 
the chief points in his teacher's system in a book pubhshed in 1892, 
entitled " Vergleichende Morphologie der Pilze." The phylogeny of the 
higher fungi, according to Brefeld, is based on the assumption, that 
there is an entire absence of sexual organs in all of those groups above 
the PHYCOMYCETES, but this view has been rendered untenable 
owing to the discovery of undoubted sexual organs among the ASCOMY- 
CETALES and the discovery of nuclear fusions in some of the rusts, 
suggesting a sexual condition. However this may be, Brefeld and von 
Tavel hold that the PHYCOMYCETES are algal-like fungi and prob- 
ably derived from algal ancestors. 

The OOMYCETALES are not linked directly with any of the higher 
fungi, but the ZYGOMYCETALES through the former with sporangia 
and conidia have probably given rise to the HEMIASCI and directly 
through them to the ASCOMYCETALES. The forms of ZYGOMY- 
CETALES with conidia above are phylogenetically connected in the 
Brefeldian system though the HEMIBASIDII with the BASIDIO- 
MYCETALES. This in brief is an outline of the phylogenetic views 
of Brefeld, as expressed in a useful ground plan of the natural system 
of hyphal fungi by von Tavel. 

The question is asked naturally, whether the origin of the fungi has 
been monophyletic, that is from a single ancestral form, or polyphyletic, 
from a number of distinct ancestors? This question can be answered 
only after an examination of the evidence. There are two orders of the 
PHYCOMYCETES, or algal fungi, namely, ZYGOMYCETALES and 
OOMYCETALES. As to the origin of these forms, the monophyletic 
view would have us derive the ZYGOMYCETALES from the OOMY- 



go MYCOLOGY 

CETALES, which have been derived in all probabiUty from an alga 
like Vaucheria with oogonia and antheridia, where the male sexual 
organs are smaller than the female. To derive the ZYGOMYCE- 
TALES from such a group would necessitate that the sexual organs 
become of equal size. 

Entomophthora is a connecting form where the sexual organs ap- 
proach each other in size. This genus is then connected by insensible 
differences with the heterogamic hermaphroditic moulds where there is 
an appreciable difference in the size of the two cells that conjugate, the 
larger being the female, the smaller the male, as in Absidia spinosa and 
Zygorhynchus heterogamus. These are directly connected with the 
homogamic hermophrodite moulds and these with the homogamic 
heterothallic forms. The polyphyletic -view necessitates the deriva- 
tion of the OOMYCETALES from a Vaucheria-like ancestor, and the 
ZYGOMYCETALES from a Zygnema-like ancestor, where conjugation 
of similar cells (gametes) is found. The polyphyletic origin of the 
fungi is emphasized by the adherents to the doctrine of the origin of the 
AscoMYCETALES from red alg£e, as there are three points of contact: 
first, sac fungi with highly developed trichogyne (sterilized archicarp) of 
the Collema type with red algae-like certain existing forms; second, sac 
fungi with highly developed trichogyne of the Poly stigma type; third, 
sac fungi with simple generalized copulating gametes of the Gymnoascus 
type. We are, however, not in the position to name any known red 
alga as the progenitor of the sac fungi, and it is far more reasonable to 
search for one in another fungous line, where, in the hght of present-day 
knowledge, there are known forms with sexual organs very much like the 
sexual organs of simple, known forms of the Ascomycetales. We are 
not now in a position to name any known phycomycete as a probable 
ancestor, though the likehhood is that the original stock possessed phy- 
comycetous characters, thus attributing a monophyletic origin to them. 
One of the most instructive forms suggesting a mode of transition from 
the PHYCOMYCETES to the ASCOMYCETALES, is Dipodascus. 
Its sexual organs are strikingly like those of certain MucorAce^ or 
Peronosporace^ in their young stages. The sexual organs can be 
recognized as antheridium and oogonium either from tlie same thread 
(homothaUic) or from different threads (heterothallic). After absorption 
of the wall between the gametes, the fertilized oogonium (or zygote) 
grows out into an elongate stout ascus, or zygogametangium with the 



PHYLOGENY OF THE FUNGI 91 

production of numerous spores.^ Eremascus also represents such a con- 
necting form. From Eremascus by reduction forms like Endomyces 
arose which in two diverging series connects various ascomycetous 
fungal forms. One series shows sprout conidia, the other oidia. The 
yeast series, the Exoascus series are thus connected. Some would have 
us derive the Laboulbeniace^ from red algal ancestors, but another 
opposing view is that these unusual fungi have had a Monascus-like 
ancestor. The other branch leads to the Basidiomycetales where the most 
primitive forms have not typical basidia, as in the Hemibasidii, and 
which are connected with such primitive types as are included in the 
family. Entomophthorace^.^ The differentiation of types within 
these large phyla will be dealt with as we proceed with a discussion of 
the various groups of PHYCOMYCETES and MYCOMYCETES. 

1 Atkinson, Geo. F.: Phylogeny and Relationships in the Ascomycetes. Annals 
Missouri Botanical Garden, II: 315-376. 

2 C/. Engler und Peantl; Die natiirlichen Pflanzenfamilien, I Teil Abt.: 
60-63. 

Masses, George: A Text-book of Fungi, 1906: 182-195. 



CHAPTER XI 

MOULD FUNGI 

SUBCLASS PHYCOMYCETES 

The fungi of this subclass are distinguished by their siphon-like 
hyphge, because these hyphae are unicellular and multinucleate and sug- 
gest the algae of the family Siphonace^ to which Vaucheria belongs. 
Hence the fungi of the subclass PHYCOMYCETES {4>vkos, seaweed + 
livKTis, a fungus) are usually designated as algal fungi. Although the 
absence of transverse septa in the hyphae is used as a fundamental char- 
acteristic, yet in the formation of the reproductive organs transverse 
walls or septa cut these organs off from the rest of the vegetative 
mycelium. Transverse septa are found regularly in some of the genera, 
such as Dimargaris, Dispira, Protomyces and Mucor, so that the general 
statement above is modified by such exceptions. A fungus, Leptomitus 
lacteus, found in ditches and rivers shows a characteristic segmentation 
of the hyphae, where through the deposit of a substance known as cellu- 
lin the lumen of the hyphae is nearly closed, but at the point of constric- 
tion, a small pore remains through which the protoplasm passes.^ 

There are genera of the family Chytridiace^, such as Reessia and 
Rozella in which the protoplasm during the vegetative state is not sur- 
rounded by a cell wall, but is naked, and amoeboid in the host cells. 
The fungi of this subclass are saprophytic or parasitic, aquatic, or 
aerial, living endophytically as a rule. A few are parasitic on insects 
and fishes. Two orders are distinguished, viz., the ZYGOMYCET- 
ALES and the OOMYCETALES. 

ORDER ZYGOMYCETALES 

The fungi of this order show a strongly developed mycelium con- 
sisting usually of unicellular, sometimes pluricellular, multinucleate 
hyphas. These hyphae are distinguished in the typic forms as the rhiz- 
oidal hyphae, aerial hyphae and reproductive hyphae. Vegetative re- 

1 Massee, George: Text-book of Fungi, 1906: 242. 
92 



MOULD FUNGI 93 

production is never through motile zoospores, but through immotile 
spores produced in sporangia borne at the tips of the reproductive 
hyphae known as sporangiophores, or by means of conidiospores, 
chlamydospores (Mucor racemosus), oidiospores, or gemmae. Sexual 
reproduction is by the conjugation of two similar or sHghtly dissimilar 
gametes, and the formation of a resting cell, or sexually produced spore, 
known as the zygote, or zygospore. Brefeld beheved that this group 
gave rise to the higher groups of fungi and he showed an interesting 
series of transition forms from those like Mucor with a typic terminal 
sporangium (Fig. 13) with numerous sporangiospores (endospores) 
through Thamnidium elegans with a large terminal sporangium (mega- 
sporangium) and secondary lateral smaller sporangia (sporangioles, 
microsporangia) and Thamnidium chcetocladioides (Fig. 32), where the 
absent terminal megasporangium is represented by a spine-like sporangi- 
phore, to Chcetodadium, where the number of endospores in the spor- 
angioles is reduced to one inclosed within the sporangium, which be- 
haves as a conidiospore; thence to Piptocephalis, where the monosporous 
sporangiole has become virtually a conidium, or conidiospore. He re- 
garded the ascus as potentially a sporangium, but recent discoveries 
have shown this hypothetic view to be untenable, so that his views as 
to the origin of the ASCOMYCETALES and the BASIDIOMYCE- 
TALES from the ZYGOMYCETALES must be considered as not satis- 
factorily proved. 

Blakeslee, who has studied the sexual reproduction in the moulds, 
finds that they may be divided into two groups, the homothallic (mon- 
oecious) and the heterothallic (dioecious) forms. The homothallic 
moulds are those in which the sexual gametes, which conjugate, arise 
from the same mycelium, while the heterothallic forms are those in 
which two distinct mycelia contribute the gametes which ultimately 
unite sexually. The homothallic (hermaphroditic) moulds he divides 
into the heterogamic hermaphrodites in which there is an inequahty in 
the size of the gametes (the large one being female and the small one 
male), and the homogamic hermaphrodites in which the gametes are of 
equal size. The heterogamic hermaphrodites include the following 
fungi : Syncephalis, Dicranophora fulva, A bsidia spinosa, Zygorhynchus 
heterogamiis, Z. Mcelleri, Z. Vuillemini. The homogamic hermaph- 
rodites comprise: Mortierella polycephala, Mucor genevensis, Spinel! us 
fusiger and Sporodinia grandis (Fig. 28). The dioecious, or hetero- 



94 



MYCOLOGY 



thallic species are all homogamic, that is, there is no difference in the 
size of the two gametes which conjugate. This group includes such 




Fig. 28. — Zygospore formation in Sporodinia grandis from material growing on toad- 
stool. {Slide prepared by H. H. York, Cold Spring Harbor, July 29, 1915.) 




)H=*^/ 




\=9c>i 



^^ij=f /' 



Fig. 29. — Conjugation and development of zygospores between + and — races of 
black mould, Rhizopus nigricans. 



fungi as Absidia ccerulea, Mucor mucedo, and five other forms of Mucor, 
Phycomyces nitens and Rhizopus nigricans (Fig. 29). Taking the con- 



MOULD FUNGI 95 

jugation in Mucor mucedo as an illustration of the method, we find that 
the hyphae of two distinct mycelia, which may be designated as the 
+ and — strains, give rise to lateral club-shaped branches. The tips 
of these two branches (progametes) come into contact and a terminal 
cell (gamete) is cut oflF from each branch respectively by a transverse 
wall. The double partition wall is dissolved away by an enzyme, and 
the two cells coalesce, their nuclei uniting in pairs. A zygospore, is 
formed, as a resting spore (Figs. 28, 30 and 2,i)- It becomes covered 
with a thick, warty brown coat. The zygote (zygospore) germinates 
after a period of rest producing at once, because of the concentrated 
foods it contains, a sporangiophore bearing a terminal sporangium with 
sporangiospores. Sometimes the gametes fail to unite through some 
check to the normal conjugation and the two gametes may then round 
off and form thick- walled azygospores, and the size of these azygospores 
depends upon the size of the gametes from which they develop. Blakes- 
lee has discovered that for the production of zygospores in heterothallic 
moulds the contact of the hyphae of two distinct mycelia designated 
+ and — are essential. If two — races or two -|- races meet, there 
is no result. In the homothallic moulds, the two conjugating gametes 
may arise from the same mycelium. Where the -f- race of one species 
of mould meets the — race of another species imperfect "hybrids" are 
formed. The testing out, maleness or femaleness, of the different races 
is made possible by growing in proximity different kinds of moulds, 
where a reaction occurs and imperfect hybrids are formed one race 
must be plus and the other minus. Where the hermaphrodite forms are 
grown, it is noticed that one gamete is larger and the other smaller, and 
it is assumed, that the larger gamete is female and the smaller one male. 
The race of dioecious Mucors, designated tentatively (+), shows a 
sexual reaction with the smaller or male gamete, while the ( — ) or 
vegetatively less vigorous race shows a reaction with the larger or 
female gamete. It is inferred that the -f race of dioecious mucors is 
female and the — race, male. 

The immediate stimulus to the formation of the progametes prob- 
ably lies in the contact of hyphae from different strains through the 
osmotic activity of the hyphal contents. For this reason progametes 
fail to form in relatively dry air. By suspending two small bags filled 
with bread soaked in dilute orange juice and inoculated with mould 
spores, any influence which the substratum might show is eliminated. 



96 MYCOLOGY 

Zygospores were formed in one week where the aerial radiating hyphae 
had come into contact. By this experiment all influences exerted 
through the solid culture media, or which were due to contact of vege- 
tative mycelia, were eliminated. 

The sporangia of Mucor mucedo are raised upon the ends of sporangio- 
phores. When fully formed the sporangium consists of a wall beset 
with spicules of calcium oxalate, the spores separated from each other 
by a slimy intersporal substance (zwischensubstanz), and a columella 
which projects into the interior of the sporangium. The formation of 
spores in Rhizopus nigricans and Phycomyces nitens has been studied by 
Swingle,^ who finds that the columella is formed by the cutting upward 
of a circular surface furrow or cleft, thus cleaving out the columella over 
the end of which a plasma membrane is formed. The spore plasm of 
Rhizopus divides into spores by furrows pushing progressively inward 
from the surface and outward from the columella cleft both systems 
branching, curving and intersecting to form multinucleated bits of pro- 
toplasm (the spores) surrounded only by plasma membranes, which 
become the spore walls and separated by spaces filled with the inter- 
sporal substance (zwischen substanz). The endospores, or sporangio- 
spores, of Rhizopus nigricans and Sporodinia grandis are multinucleate, 
while those of Pilobolus are binucleate, according to Harper. The es- 
cape of the mature sporangiospores takes place when a portion of the 
sporangial wall is dissolved. The spores escape imbedded in the inter- 
sporal slime, which dries up liberating the spores. Certain species of 
Mucor are capable of fermenting grape juice, the power of fermentation 
depending on the species. The following species produce alcoholic fer- 
mentation (Lindner) : 

Quantity of alcohol 
Species by volume, 

per cent. 

Mucor Jansscni 3.41 

Mucor lamprosporus 3.71 

Mucor javanicus 2 . 83 

Mucor phimbeus 4.62 

Mucor pirelloides i • 06 

Mucor racemosus 462 

Mucor Rotixianus 5.25 

Mucor griseo-cyanus 4 . 00 

Mucor genevcnsis 5-2i 

'Swingle, DeanB.: Formation of the Spores in the Sporangia of Rhizopus 

nigricans and of Phycomyces nitens. Bull, jy, Bureau of Plant Industry, 1903. 



MOULD FUNGI 97 

Key to Families or the Order Zygomycetales 
Non-sexual spores in sporangia, which in some genera are reduced 
to conidioid bodies. 

A. Non-sexual spores formed in sporangia in many cases accom- 
panied by conidiospores. 

(a) Sporangia (at least the main sporangia) with columella. 
Conidiospores absent, or only sparingly found. Zygospores 
naked, or only covered by curled outgrowths of the sus- 
pensors. I. Mucorace^. 

(b) Sporangia without columella; zygospore surrounded by a 
thick covering of hyphae. II. Mortierellace^. 

B. Non-sexual spores as conidiospores. Sporangia exceptionally 
present. 

(a) Conidiospores single. Zygospores formed directly by the 
united gametes. 

1. Sporangia present transitional to conidia; sporangia 
monosporic and polysporic. III. Choanephorace^. 

2. Sporangia never present; parasitic on other MUCOR- 
ALES. IV. Ch^tocladiace^. 

{b) Conidia in chains zygospore formed where the bent ends 
of the gametes unite. V. Piptocephalidace^. 

Non-sexual spores as true conidiospores borne singly at the end of 
conidiophores. VI. Entomophorace^. 

Family i. Mucorace^. — The mycelium of the true moulds is 
homogeneous, or it becomes heterogeneous through differentiation into 
aerial and nutritive hyphae. Non-sexual reproduction by the forma- 
tion of endospores in sporangia. The sporangia here may be simple or 
branched. The sporangia are all alike, or there are as in Thamnidium 
two different types known as megasporangia and microsporangia. The 
larger sporangia have a columella, while the smaller ones are mostly 
without a columella, but occasionally a columella is present. The 
formation of conidiospores is unknown in the family. The zygospore 
may arise by the fusion of two similar gametes formed from the same 
mycelium (homogamic hermaphrodites) or by the union of two slightly 
dissimilar gametes the product of the same myceUum (heterogamic her- 
mophrodites), or it arises by the conjugation of similar gametes (+ and 
— races) from two distinct mycelia (heterothallic and homogamic). 



98 



MYCOLOGY 



The important genera of the family are Miicor, Rhizopus, Phycomy- 
ces, Ahsidia, Sporodinia, Thamnidium, Dicranophora, Filaira and Pilo- 
boliis. The genus Mucor, a key for the identification of the species will 
be given at the end of the book, was estabhshed in 1729 by Micheli. 
The genus may be divided into three groups of species. The first 
division includes those species with unbranched sporangiophores, such 
as Mucor mucedo. The second group comprises the moulds with clus- 
tered branches of the sporangiophores, as Mucor cor ymbifer, M. erectus, 
M. fragilis, M. pusillus, M. racemosus, and M. tenuis. The third sec- 
tion is made up of species the sporangiophores of which show sympodial 




Fig. 30. — Details of Chlamydomucor racemosus showing oidia, sporangia and zygo- 
spore formation. 



branching. Such are Mucor alternans, M. circinelloides, M. javanicus, 
M. Rouxii and M. spinosus. (Also consult pages 695-702.) 

The oldest known species, Mucor mucedo, was described fully for the 
first time by O. Brefeld in 1872. Stiff sporangiophores, 30 to 401J, 
thick, arise from the mycelium and are 2 to 15 cm. in height. Each 
bears a single globular sporangium 100 to 200/i in diameter and the 
sporangial wall is beset with fine needles of calcium oxalate. The spores 
are ellipsoidal 3 to 6/i by 6 to 12/i with faint yellowish cell contents. As 
previously described, conjugation is between two similar gametes from 
+ and — mycelia. Mucor racemosus, also known as Chlamydomucor 



MOULD FUNGI 99 

racemosus (Fig. 30), shows the clustered branching of the sporangio- 
phore and in addition the hyphae are marked by the intercalary forma- 
tion of chlamydospores. This mould produces sporangiophores 8 to 20/^ 
thick by 5 to 40 mm. in height, bearing brownish sporangia 20 to 70/x in 
diameter. The globular colorless spores are 5 to ?>^x broad by 6 to lo/x 
in length. This mould which grows on bread and decaying vegetable 
matter, and if cultivated submerged in beer-wort, the hyphae swell ir- 
regularly and a large number of transverse septa appear, which divide 
the hyphae into barrel-shaped portions. These cells or gemmae can be 
separated readily, and when free, they become spheric and multiply by 
budding, as in the true yeasts, and the submerged spores hiso bud and 
constitute the so-called Mucor-yeast. At the surface of the liquid, they 
develop the typic mould form. Miicor racemosus, according to Hansen, 
is the only mould capable of inverting cane-sugar solution. It produces 
in beer- wort as much as 7 per cent, by volume of alcohol. Mucor erectus, 
which grows on decaying potatoes, produces azygospores as well as zygo- 
spores. It has the same appearance as the preceding and possesses an 
active power of fermentation. In beer-wort of ordinary concentration, 
it yields up to 8 per cent, by volume of alcohol, and in dextrin solutions 
it induces alcoholic fermentation. Mucor spinescens, which grows on 
Brazil nuts, has spiny projections on the rounded upper surface of the 
columella. Mucor (Amylomyces) Rouxii occurs in the so-called 
" Chinese yeast," which is in the form of small whitish cakes, consisting 
of rice grains kneaded together with assorted spices. These cakes are 
powdered and mixed with boiled rice upon which the mycelium grows, 
converting the rice by slow degrees into a yellowish liquid which con- 
tains glucose produced by the diastatic ferment of the fungus. 

The black mould Rhizopus nigricans {Mucor stolonifer) grows on 
bread and other organic substrata (Fig. 31). Several sporangiophores 
arise from a single point of origin, namely, at the top of a mass of rooting 
(rhizoidal) hyphae which constitute an adhesive organ or oppressorium. 
Each erect stalk bears oblate spheroidal sporangia with distinct colu- 
mella and sporangiospores, 6 to 17/i long. Arising from the base of the 
clustered sporangiophore is a horizontal hyphae, which often attains a 
length of 3 cm. and is known as the stolon, or stoloniferous hypha. 
When the tip of this stolon comes into contact with the substratum a 
new appressorium is formed from which arises a number of sporangio- 
phores bearing sporangia (Fig. 31). This method of growth enables the 



MYCOLOGY 



black mould to spread rapidly and it sometimes chokes out other moulds 
growing in competition with it on the same nutritive medium. In 1818, 
on account of this method of growth, it was named by Ehrenberg 
Mucor stolonifer. Related to this fungus is one named Rhizopus ory- 
zecB which grows in Ragi. The fungus Phycomyces nitens is found in 
empty oil casks, on oil cakes and in concentrated fodder. It puts forth 
stifif sporangiophores 7 to 30 cm. long and 50 to 150/i in diameter which 
bear at the summit black globular sporangia 0.25 to i.o mm. in diame- 
ter, filled with yellow-brown, thick- walled endospores, 16 to 30/i 
long and 8 to 15/x broad. Its zygospores are 300/x broad and their 




Fig. 31. — Black Mould, Rhizopus nigricans. A, Mature plant showing rhizoidal 
hyphse {myc)\ stoloniferous hypha {st); sporangiophores (sph); sporangia (sp). B, 
Younger cluster of sporangiophores and sporangia. (After Gager.) 

borders are covered with many forked projecting hyphae known as 
suspensoria. Recently H. Burgeff^ has studied the variability, sex- 
uality and heredity of Phycomyces nitens and has brought his cultural 
investigations into line with the recent developments of cytology and 
genetics. His paper should be read by all students, who may be 
interested in the extension of the methods of genetics into an 
investigation of the lower plants. 

The genus Absidia includes five species. In these fungi the suspen*- 
sors are borne at the base of the two gamete cells which fuse to form the 
zygospore, which when mature is covered by a basket-like covering of 

1 BuRGEFF, H.: Untersuchungen liber Variabilitat,. Sexualitat und Erblichkeit 
h&i Phycomyces nitens Kuntze. Flora, Band 108: 353-448; review by G. V. Ubisch 
(Dahlem) in Botanisches Centralblatt, Band 128, Nr. 23: 630-632, 1915. 



MOULD FUNGI 



Straight appressoria, which hook together by their curved extremities, 
thus giving additional protection to the zygospore. Sporodinia grandis, 
the single species of another genus, lives on large fleshy fungi of the 




Fig. 32. 



-Sporangia of i, Thamnidium elegans; 2, 3, 4, Thamnidium chcelodadioides ; 
5, Chalocladium Jonesii. (After Brefeld.) 



families (Fig. 28) Agaricace^, Boletace^, Clavariace^ and Hy- 
DNACE^. Its sporangiophores i to 3 cm. high are finally brown in color 
and dichotomously branched. The .sporangia are spheric with a deli- 



MYCOLOGY 



cate sporangial wall, which soon disappears leaving the spores on a 
hemispheric columella. These spores are ii to 70/x broad. The 300/x 
broad zygospores are produced from similar branches of a dichotomously 
branched zygosphore. The mycelium of the species of Thamnidium 
enters the nutritive substratum. The large sporangia are terminal 
while the smaller secondary sporangia are borne on lateral branches in 
whorls below the terminal sporangium. This is typically seen in Th. 




Fig. ^^. — Details of sporangia and sporangiophores of Pilobulus. i, P. tnicro- 
sporus; 2, P. roridus; 3, 4, 5, P. anomalus; 6, zygospore of P. anomalus. {After 
Brefeld.) 

elegans (Fig. 32). A related species Th. Fresenii has an upright termi- 
nal sporangiophore, which is either sterile, or ends in a large terminal 
sporangium, while the smaller sporangia are as in Th. elegans. In 
Th. amoenum, the lateral smaller sporangia are borne at the end of 
coiled secondary sporangiophores. The secondary sporangia suffer 
reduction in Th. ch(etocladioides (Fig. 32) which in addition to having a 
straight terminal spine-like hypha in place of the terminal sporangia has 
some of the lateral microsporangia replaced by sterile branches. The 



MOULD FUNGI IO3 

commonest species oi Pilobolus (Fig. 33) is P. cryslaUinns which appears 
on horse dung. It has a few short feeding hyphae and an upright spor- 
angiophore swollen at the extremity by gas and water vapor and, there- 
fore, under tension. It bears at its extremity a flat rounded sporan- 
gium filled with sporangiospores. An explosion of the sporangiophore 
causes the whole sporangicum to be shot off a considerable distance. 

Family 2. Mortierellace^. — This family consists of two genera 
Mortierella and Herpocladiella. The genus Mortierella, which is repre- 
sented by a coprophilous species, M. Rostafinski, has a sporangium 
borne on a sporangiophore which arises in a definite way from a snare of 
hyphae that are knotted into a rounded mass at its base. In M. cande- 
labrum, the sporangiophore is branched candelabra-like. Brefeld men- 
tions Mortierella and Rhizopiis as examples of the carposporangiate 
ZYGOMYCETALES, where the sporangiophores appear always at 
predetermined places on the mycelium, and not at indefinite points, as 
in the majority of other moulds. 

Family 3. Choanephorace^. — Represented by a single genus 
Choanephora and a single species infundibulifer on flowers of Hibiscus 
in East Indies. 

Family 4. Chcetocladiace^. — This is a small family of one 
genus {Chcetocladium) and two species, {Ch. Jonesii and Ch. Brefeldii) 
(Fig. 32) which live parasitically on Mucor mucedo and Rhizopus nigri- 
cans. The terminal sporangia of Thamnidium are never formed and 
secondary sporangia are reduced to the unisporous condition suggesting 
conidiospores with pointed branches between them. 

Family 5. Piptocephalidac§.«. — Three genera Piptocephalis, 
Syncephalis -and Syncephalastrum are recognized in Die Natiirlichen 
PflanzenfamiHen. The eight species of Piptocephalis are parasitic 
on the mycelia of Mucor, Pilobolus and Chcetocladium species (Fig. 37). 
The haustorial hypha flattens itself disc-like on the outer surface of 
the host's hyphge and sends five rhizoida'l branches into the host cells. 
An erect dichotomously branched conidiophore bears conidiospores 
in globular clusters at the ends of its principal branches. Some 
species of Syncephalis are parasitic on other fungi; but S. cordata 
grows on manure, presumably as a saprophyte. 

Family 6. Entomophthorace.e. — The mycehum of the fungi of this 
family is more or less richly developed and fives endozoically in animals, 
such as flies, mosquitoes, aphids, and seldom saprophytically as 



I04 



MYCOLOGY 



Basidioboliis on the feces of frogs. Non-sexual reproductions is mainly 
by means of unicellular conidiospores which are discharged forcibly 
from the ends of tubular conidiophores. Sexual reproduction is by the 
conjugation of two gametes dissimilar in size, heterogamic and thus these 
fungi connect the ZYGOMYCETALES with the OOMYCETALES 
where oogamous reproduction is displayed. The zygospores formed 
in conjugation are spheric, while the azygospores formed on the 
mycelium without copulation are similar to the zygospores in struc- 
ture and appearance. The family includes seven genera, includ- 





FiG. 34. — Fly cholera fungus (Empusa musca). i, Fly enveloped in mycelium; 
2, fungus between hairs of the fly; 3, conidiophores and conidiospores; 4, germina- 
tion of spores; 5, formation of egg in Empusa sepulchralis. {After Thaxter.) See 
Henri Coupin, Atlas des Champignons, Parasite set Pathogenes de 1' Homme et des 
Animaux, 1909. 

ing Empusa and Entomophthora, which may be chosen as types for 
discussion. 

The mycehum of Empusa musccB (Fig. 34) is parasitic in the 
bodies of flies, destroying them in large numbers by an epidemic in the 
fall, known as fly-cholera. The short hyphae frequently bud like 
yeast cells. The conidiophores break through to the surface of the 
insect's body, where the conidiospores 18 to 25/x broad by 20 to 30/^ 
long are forcibly discharged. These spores bore their way through the 
chitinous covering of a healthy fly by means of a germ tube and the 



MOULD FUNGI 105 

hyphffi which enter the body of the tly bud hke yeast cells, which are 
carried to all parts of the insect's body. Later the parasitic hyphse 
arise from the gemmae. Resting spores are unknown. 

Entomophthora is a genus of fungi inclusive of thirty species found 
on various insects in Europe and North America. Entomophthora 
sphcerosperma has a richly branched nutritive mycelium, which grows 
through the body of insects. After the death of the host, the hyphae 
break through the surface in connected strands part of which attach 
the larva, or insect's dead body, to the substratum and part form a 
thick white mantle over the surface. 

The conidiophores are in branching bundles. The conidiospores 
are elongated ellipsoidal, 5 to 8ju broad by 15 to 26ju long. Secondary 
and tertiary conidia are found. The resting spores produced as azy- 
gospores are spheric and 20 to 35^1^ broad with a smooth yellow wall. 
It grows on larvae, especially frequent on the cabbage worm Pieris 
brasskce in Europe and North America. 

BIBLIOGRAPHY OF THE ZYGOMYCETALES 

This is not intended to be a complete list of the works dealing in whole or in 

part with the mould fungi, but only a list of the works which may prove helpful to 

the student of mycology. 

Rainier, G.: Etude sur les Zygospores des Mucorinees, These pr^sent^e a I'l^cole 
de Pharmacie. Paris, pp. 136, pis. i-ii; Observations sur les Mucorinee. 
Annales des Sciences naturelles, ser. 6, 1-15: 70-104, pis. 4-6. Sur les zygo- 
spores des Mucorinees. Annales des Science naturelles, vi ser., I: 18, 1883; 
Nouvelles observations sur les zygospores des Mucorinees, do., I: ig, 1884. 

Blakeslee, Albert F. : Sexual Reproduction in the Mucorineae. Proceedings 
American Academy "Arts and Sciences, xl: 205-319 with 4' plates and bibli- 
ography, The Biological Significance and Control of Sex. Science, new ser. 
x.xv: 366-384, March 8, 1907; Papers on Mucors (a review). Botanical Gazette, 
47: 418-423, May, 1909; Heterothallism in Bread Monld, Rhizopus nigricans. 
Botanical Gazette, 43: 415-418, June, 1907; A Possible Means of Identifying 
the Sex of (+) and ( — ) Races in the Mucors. Science, new ser. xxxvii: 880- 
881, June 6, 1913; On the Occurrence of a Toxin in Juice Expressed from the 
Bread Mould, Rhizopus nigricans. Biochemical Bulletin II: 542-544, July, 
1913; Conjugation in the Heterogamic Genus Zygorkynchiis. Mycologisches 
Centralblatt II: 241-244, 1913; Sexual Reactions between Hermaphroditic and 
Dioecious Mucors. Biological Bull., xxix: 87-102, August, 1915; Zygospores 
and Rhizopus for Class Use. Science, new ser. xlii: 768-770, Nov. 26, 1915. 

Brefeld, O.: Botanische Untersuchungen liber Schimmelpilze, Heft i, Zygomy- 
ceten, pp. 1-64, Taf, 1-6, 1872; Untersuchungen aus den Gesamtgebiete der 
Mykologie, ix, 1891. 



Io6 MYCOLOGY 

Buchanan, Estelle 1)., and Buchanan, Robert E.: Household Bacteriology, 

1914: 66-72. 
DE Bary, a.: Comparative Morphology and Biology of the Fungi and Bacteria, 

1887: 144-160. 
Englee, a. and Gilg, Ernst.: Syllabus der Pflanzenfamilien, 7th Edition, 191 2: 

37-38. 
Gortner, Ross A. and Blakeslee, A. F. : Observations on the Toxin of Rhizopus 

nigricans. American Journal of Physiology, xxxiv: 354-367, July, 1914. 
Jorgensen, Alfred: Microorganisms and Fermentation, 3d Edition, 1900: 97- 

115- 
Keene, Mary L.: Cytological Studies of the Zygospores of Spordinia grandis. 

Annals of Botany, xxxviii: 455, 1914. 
Klocker, Alb.: Fermentation Organisms, 1903: 170-186. 
Lafar, Franz: Technical Mycology, II, part i: 1-30, 1903. 
Lendner, Alf.: Les Mucorinees de la Suisse. Materiaux pour la Flore Crypto- 

gamique Suisse III, Ease, i: 1-177, 1908. 
Schroter, J.: Mucorineae, Die natlirlichen Pflanzenfamilien, I, Teil i. Abt. 119- 

142, 1897. 
Stevens, F. L.: The Fungi which Cause Plant Disease, 1913: 101-108. 
Swingle, Deane B.: Formation of the Spores in the Sporangia of Rhizopus nigri- 
cans and of Phycomyces nitens. Bureau of Plant Industry No. 37, 1903 with 

6 plates. 
Underwood, Lucien M.: Moulds, Mildews and Mushrooms, 1899: 24-28. 
VON Tavel, F.: Vergleichende Morphologic der Pilze, 1892: 25-40. 
Wettstein, Richard R. von: Handbuch der systematischen Botanik, 1911: 160- 

164. 



CHAPTER XII 

OOSPORE-PRODUCING ALGAL FUNGI 

ORDER II. OOMYCETALES 

The fungi of this order were derived probably from some ancestor, 
or ancestors, which through the loss of chlorophyll became dependent 
on extraneous supplies of organic food. If we look for such an ancestral 
form among the algae, we find that it must have been related to Vau- 
cheria, if not identic with that filamentous siphonaceous green alga 
with reproductive organs, as oogonia and antheridia. Vaucheria is a 
unicellular filamentous sparingly branched cell with a thin cell wall and 
multinucleate. Hence it is sometimes called a coenocyte. Similarly, 
the structural features of the more primitive Oomycetales are like 
Vaucheria, but the absence of chlorophyll is distinctive. The forma- 
tion of non-sexual sporangia with the formation of zoospores, or swarm 
spores, known as zoosporangia is a feature of the fungi of this order. 
As there is a pronounced difference between the male and female sexual 
organs, oogamous reproduction is the rule. The oogonium is compara- 
tively large and contains one or more oospheres, which are fertilized 
by the sperm cell, which swim to it by cilia, creep to it, or are carried 
into the oogonium through a fertilization tube. Sexual reproduction in 
these fungi has been investigated cytologically by a number of students, 
and they have found that the nuclear changes concomitant with fertili- 
zation are characteristic. Albugo Candida, A. lepigoni, Peronospora 
parasitica, Plasmopara, Pythium and Scleras para show a single large cen- 
tral oosphere with a single nucleus, while the remaining nuclei pass from 
the gonoplasm into the periplasm. A process is sent into the oogonium 
from the antheridium and a single male nucleus passes into the oogo- 
nium. A cell wall is developed about the oospheres and the male and 
female nuclei unite, while the periplasm is used in the formation of the 
spore wall (episporium). The ripe oospore has a single nucleus in 
Peronospora parasitica, while in Albugo, it becomes multinucleate after 
nuclear division. A central oosphere (gonoplasm) surrounded by peri- 

107 



Io8 MYCOLOGY 

plasm occurs in Albugo blitl and .1. portulacce and the oosphere is 
multinucleate and the' nuclei present fuse in pairs with a number of 
sperm nuclei which enter from the antheridium. The oospore which 
arises is multinucleate. This method is considered by mycologists to 
be the primitive one as displayed in these two species, the uninucleate 
oospheres of the first-named species having been derived from the multi- 
nucleate. An intermediate position is occupied by Albugo tragopogonis, 
where at first the oosphere is multinucleate but by the degeneration of 
all but one female nucleus becomes uninucleate. Claussen^ finds that 
Sa'prolegnia monoica develops both antheridia and oogonia, the latter 
at first being filled with protoplasm and many nuclei which wander to 
the periphery and undergo degeneration with a few nuclei left over. 
These nuclei divide once mitotically. Around these daughter nuclei 
the protoplasm collects to form the egg cells. Each egg has a single 
nucleus near which is the coenocentrum of Davis, but which Claussen 
thinks is a true centrosome. The simple or branched antheridia form 
germ tubes which enter the wall of the oogonium and a single male 
nucleus fuses with the nuclei of the egg cells to form the oospore. 
Claussen contrasts the life cycle, as determined by his investigations, 
with those of Trow in the following diagrammatic presentation: 

Trow Diploid Haploid Diploid 



/ Antheridium — Male nucleus \ 

/ \ 

Oospore, Mycelium Oospore 

Multinucleate \ / 

\Oogonium — Egg cell — Egg nucleus/^ 

Claussen Haploid Diploid. 

Strasburger considers that the superfluous nuclei in the oogonia and 
the antheridia are comparable with the superfluous egg nuclei of certain 
of the brown seaweeds belonging to the family Fucace^. When the 
oospores germinate, they either produce directly a mycelium, or give 
rise to zoospores. The fungi of this order are essentially parasitic, 
being found in this condition as endophytic parasites, or as endozoic 
parasites on fishes and insects and Euglena. 

1 Claussen, P.: Ueber Eintwicklung und Befructung bei Saprolegnia monoica. 
Festschrift der Deutsch. Bot. Gesellsch., xxvi; 144-161 with 2 plates, 1908. 



OOSPORE-PRODUCING ALGAL FUNGI IO9 

Key to Families of the Order Oomycetales 

A. Zoosporangia, oogonia and antheridia present; conidia absent. 

(a) Mycelium well developed. 

1. Antheridium forming motile spermatozoids, which enter the 
oogonium. Family i. Monoblepharidace^. 

2. Antheridium not forming spermatozoids, fertilization through 
an antheridial tube, or beak. Family 2. Saprolegniace^. 

(b) Mycelium poorly developed, sometimes represented by a single 
cell. 

1. Fruit body as a single cell or by division forming a sporangial 
sorus; parasites on algae, protozoans, rarely on flowering 
plants. Family 4. Chytridiace^. 

2. Fruit body through division a chain of cells which develop 
sometimes into zoosporangia, sometimes into antheridia and 
oogonia. Family 5. Ancyclistace^. 

B. Conidia present. Family 3. PERONOSPORACEiE. 

The following descriptions of the above five families are presented 
in order to introduce the student to the characters which fundament- 
ally distinguish them. Therefore, all generic keys are omitted because 
the introduction of them under each family would increase the size of 
the book unduly. 

Family i. Monoblepharidace^. — This family is represented by 
the genera M onoblepharis and Gonapodya. The genus Monoblepharis 
is represented by two species of which M. sphcBrica is the most com- 
mon. It is an aquatic fungus found growing saprophytically on dead 
animal and plant parts under water. The hyphae of the mycehum 
are tubular, branched and unicellular. The swarm spores (zoospores), 
which are formed much as in Saprolegnia, have only a single flagellum. 
The oogonia are either terminal in position or interstitial and there is 
no differentiation of an outer periplasm, but the whole protoplasm 
of the oogonium contracts to form an oosphere. Later a pore appears 
at the apex of the oogonium through which the uniciliate spermatozoids 
enter to fertilize the egg cell. The antheridium in M. sphcBrica appears 
as a penultimate cell immediately below the oogonia. An opening is 
formed at the top through which the spermatozoids escape. The 
oosphere on fertilization becomes an oospore. Because of the aquatic 



no MYCOLOGY 

habit and formation of motile spermatozoids, Brefeld considers Mono- 
blepharis to be the most primitive of the Oomycetales. 

Family 2. Saprolegniace^. — The members of this family, as 
their name indicates, are saprophytes on both dead plants and animals 
in water with the exception of the fungus which causes the salmon 
disease and it is both a saprophyte and a facultative parasite. The 
hyphae in the vegetative condition are relatively large, arising from 
delicate rhizoids which penetrate the substratum. Swarm spores 
which are biciliate are formed in terminal, long, tubular zoosporangia 
opening by an apical pore through which the zoospores crowd their 
way out into the water. Sometimes, as they escape, they collect into 
ball-shaped masses which are caused to slowly roll about by the activity 
of the cilia. The female sexual organs, the oogonia, are terminal on 
the branches of the thallus hyphae. Several oospheres without dis- 
tinction of periplasm are formed inside of a single oogonium, and 
sometimes, as many as thirty or forty are found. The antheridia, 
which are club-shaped, are formed on slender branches of the mycelium 
which also bear the oogonia, or which are distinct from those 
which are oogonial bearers. These antheridia approach the oogonia 
and an antheridial beak is formed which penetrates the wall of the 
oogonium and comes into contact with the oospheres by growing from 
one oosphere to another. Sometimes the antheridia, as in Saprolegnia 
monilifera, are not produced at all and the oogonia develop partheno- 
genetic oospores which germinate after a rest period of a few days to 
several months. The series representing reduction in sexuality begins 
with such forms as Saprolegnia monoica with an oogonium and an 
antheridium which develops a fertihzing process through Achlya 
polyandra, which forms antheridial branches which do not touch 
the oogonia, to Saprolegnia monilifera without any trace of antheridia. 
Androgynous forms are those in which the same hyphal branch 
develops both antheridia and oogonia and the diclinous species 
like Saprolegnia dioica and Achlya oblongata ar.e those in which the 
antheridia and oogonia are borne on distinct branches. 

Saprolegnia ferax usually attacks only fishes, tadpoles and the 
spawn of frogs. It appears on aquarium-kept fishes on the sides of 
the body at the tail end, or among the gills. In the latter place, if 
abundant, it frequently causes asphyxiation and before this state is 
final the fish turns over on its back and rises to the surface. In the 



OOSPORE-PRODUCING ALGAL FUNGI III 

experience of the writer, immersion of the diseased fish in strong brine 
in many cases brings about a cure, if the growth of the fungus is not 
too great, Petersen'^ observed a sick bream in the lake of Fure So 
with a wound quite overgrown with Saprolegnia hyphge and he has 
found frog eggs which were attacked, the hyphae growing in the jelly 
around the eggs, penetrating into them. The fungus can be raised in 
the laboratory on dead fishes by allowing tap water to slowly flow over 
them in a jar. A few days are necessary to secure a copious growth. 
Frogs which die under the ice in winter for lack of oxygen float to the 
surface in the spring entirely covered by this fungus. It thrives 
best in the early stages of decay, for as putrefaction advances bacteria 
and infusoria increase to such an extent as to check the growth of the 
fungus. When air insects, such as gnats, fall into lake or pond water 
in great numbers, species of Saprolegnia, Achyla and Aphanomyces 
appear in great numbers and seem to form a gray felt on the surface. 

The vegetable materials on which the Saprolegniace^ mostly Hve 
are branches and shoots of trees, except Salix, owing to presence of 
salicin, which fall into the water. Second in importance are half- 
rotten rhizomes of Calla, half-rotten leaves and leaf stalks of Nuphar 
and Nyniphcea and other parts of aquatic plants which float on the 
surface. Species of the genus Achlya are mostly associated with such 
materials. Achlya polyandra have been repeatedly found by me on the 
fruits of Osage oranges which have fallen into the pond at the Univer- 
sity of Pennsylvania. The most favorable environmental conditions 
seem to be the absence of air about the hyphae, quiet, still, pure water, 
that does not contain much iron and a relatively open light surface. 
Low temperature conduces to the formation of oogonia, which also 
keeps in check other competing organisms (Fig. 35). 

Family 3. Peronosporace^. — This family is rich in parasitic 
forms which may be accounted as the cause of important diseases of 
cultivated plants. The hyphae of the mycelia are irregularly and copi- 
ously branched and are found mainly in the intercellular spaces of the 
host tissue sending short branches called haustoria into the adjoining 
living cells. These haustoria maybe glohulsLV (Albugo = Cystopus), 
club-shaped (Peronospora corydalis), branched (Plasmopara) (Fig. 36), 
or branched and snarled {Peronospora). Septa are absent except 

1 Petersen, Henning E. : An Account of Danish Fresh-water Phycomycetes. 
Annales Mycologici, viii, No. 5, 1910. 



112 MYCOLOGY 

when the reproductive organs are formed. Non-sexual spores, or 
conidiospores, are borne on conidiophores which may remain within 
the host (Albugo = Cystopus), or grow beyond the surface. They may 
be either simple or branched. These conidiospores either germinate, 
as in Phytophthora infestans and Peronospora nivea by means of zoo- 




Fig. 35. — I, Zoosporangium of Achlya racemosa; 2, escape of zoospores; 3, fly- 
covered by mycelium; 4, zoospores of fungus; 5, Achlya ferax with zoosporangia and 
zoospores; 6, Achlya proUfera, 24 hours after germination of zoospores. 7, Achlya 
monoica, with antheridia and oogonia; 8, Achlya conlorta. {After Henri Coupin, 
Atlas des Champignons Parasites el Pathogenes de I' Homme et des Animaux, pi. xviii, 
1909.) 



spores which escape or by the protoplasm escaping {plasmato parous), as 
in Peronospora densa, or by germ tubes, which in some species {Perono- 
spora lactuca) appear at the end of the spore (acroblasfic) , or at the 
side of the conidiospore (pleuroblaslic) , as in Peronospora radii. The 
oogonia and antheridia, which are also present, are formed in the 



OOSPORE-PRODUCING ALGAL FUNGI 



113 



tissues of the host. The different kinds of nuclear fusion, which 
accompany fertiUzation, have been described previously. The oospore, 
which is formed, acts as a zoosporangium in some cases for it gives 
rise to numerous spores; or in other cases it produces a germ tube. 
In most of the forms, the oogonium contains a mass of protoplasm 
known as the oosphere. This is divisible into an outer clearer por- 




FiG. 36. — Plasmopora vilicola. A, Conidiophore with conidiospores (nearby 
oospores); B, Haustoria; C, Swarmspore formation. A, 950/1; B. C, 600/1. {After 
Millardcl in Die naliirlichen Pflanzenfamilien I. i, p. 115), 



tion, the periplasm, and a denser more granular central portion, the 
gonoplasm. After fertilization, the oospore develops a thick wall of 
two layers, an extine and intine, and becomes a resting spore. It 
accumulates fatty substances, which are utilized when the spore 
germinates in the spring after a long winter's rest. The family has 
had many revisions and in order to simplify matters Pythium and 
Albugo (Fig. 37), which are placed in separate families by some 
8 



114 



MYCOLOGY 



authors, are placed in the family Peronosporace^. Details of the 
important forms which cause plant diseases will be given in the third 
part of this book. These fungi will be referred to under each genus 
following the systematic generic key which is here given. 

Generic Key of the Family. PERONOSPORACEiE 




Mycelium of these fungi parasitic or saprophytic in plant tissues; 
zoosporangia as distinct organs producing biciliate zoospores. 

Zoospores formed out of protoplaem 

which escapes out of the conidia. i. Pythium. 

Zoospores formed within the zoosporangia. 

2. Pythiacystis. 

Zoospores elongate. 3. N emato sporangium . 

^_^ Mycelial hyphae branching non-septate 

/ ^ usually coarse, of strictly parasitic habit. 

Conidiophores short, thick, subepidermal, 
conidia in chains. 4. Albugo 

Conidiophores longer superficial, simple 
or branched, conidia not in chains. 
Conidiophores scorpioid cymosely 
branched conidiospores developing 
swarmspores. 5. Phylophthora.^ 

Conidiophores simple, or branched 
monopodially; conidia sprouting as a 
plasma, or by swarm spores. Con- 
idiophores regularly branched. 

Conidiophores simple erect with a 
swollen end (basidia-like) bearing 
short sterigma-like branches of equal 
length. 6. Basidiophora. 

Conidiophores with lateral branches developed normally of 
unequal length. Conidiophores stout, with few branches, 
oospore united to wall of oogonium. 7. Sclerospora. 

Conidiophores slender, freely branched persistent; oospore 
free. [ 8. Plasmopara. 

Conidiophores with forking branches; conidiospores sprout- 
ing with a germ tube. Upper end of conidiospore with a 




Fig. 37. — White rust 
Cystopus (Albugo) portula 
cecB, on purslane, Portulaca 



oleracea 
Harbor, 
1915-) 



(Cold Spring 
L. I., July 24, 



OOSPORE-PRODUCING ALGAL FUNGI 



115 



papilla through which the germ tube grows (acroblastic). 

g. Bremia. 
Conidiospores without papilla; pleuroblastic. 10. Peroiwspora. 

The most important species of these genera from the standpoint of 
the plant pathologist are the following enumerated below with their 
common English names where such have been given. 



English name 



Host plant 



Pythium de Baryantim 

Pythiacystis citriopthora 

Albugo {Cystopus) Candida... 
Albugo (Cystopus) portulaca; . 

Phytophthora cactorum 

Phytophthora infestans 

Phytophthora phaseoU (Fig. 

44)- 
Plasmopara cubensis 



Damping-off fungus.. . . 
Brown rot of lemon.. . . 
White rust of crucifers. 
White rust of purslane. 
Mildew of succulents.. . 
Late blight of potato.. . 



Plasmopara Halstedii 



Plasmopara viticola ... 

Bremia ladiica 

Peronospora effusa 

Peronospora parasitica Downy mildew of crucifers! 

Peronospara Schleideniana. . . Onion mildew 



Downy mildew of beans. 



Seedlings 
Lemon fruits 
Cruciferous plants 
Portulaca oleracea 
Cacti, etc. 
Potato 
Lima-bean 



Downy mildew of cu- Cucumber 
cumber. 



and 



Downy mildew of grape. . 
Downy mildew of lettuce. 
Mildew of spinach 



Helianthus annuiis 

H. tuberosus 
Grape vine 

Cynara, Cineraria, Lactuca 
Spinach 
Cabbage 
Onion 



CHAPTER XIII 
OOMYCETALES (CONTINUED) 

Family 4. Chytridiace.e. — This family according to some authors 
is made to include six families which are here reduced to six subfamilies. 
It includes fungi of short vegetative duration, which may be a few days 
in length. The swarm spores quickly give rise to new generations. 
The resting period is represented in the case of the endophytic para- 
sites by the time which elapses between the growth of two successive 
crops of the host plants. The majority of the species of the family 
are true parasites, partly endobiotic, partly epibiotic, and a few 
are saprophytes. Half of the plant parasites live in fresh-water 
algae, nearly as many in flowering plants, some of which are in 
aquatic plants, some in swamp plants. About ten species are found 
on marine algse. All species are microscopically small, yet they 
cause galls, dwarfing, dropsy and crusts of the host plants. The 
mycelium is absent or in the form of slender protoplasmic filaments, 
occasionally as distinct one-celled hyphae. The cell, which produces 
the fruit body, frequently serves as the chief nutritive organ. Later, 
it divides to form zoospores. The true mycelium has weak develop- 
ment. The short germ tube merely serves as an organ by which the 
parasite gains entrance to the host cell, and in the endophytic forms, it 
disappears quickly, but in the epiphytic species, it serves as an haustor- 
ium, sometimes with rhizoidal extensions. In the better-developed 
forms of Cladochytrie^, the slender mycelium serves to carry the 
fungus from cell to cell of the host. The sporangia are always zoo- 
sporangia which develop swarm spores, or zoospores. They are thin- 
walled and quickly mature, or they are thick-walled and form resting 
sporangia. Sexual spores are formed in only a few types and the differ- 
ence between antheridia and oogonia is morphologically little pro- 
nounced. The swarm spores have as a rule a single flagellum, rarely 
do they have no such locomotory appendages. The sexually produced 
oospores have the appearance of resting sporangia with the empty 
antheridium attached as an appendage. Few of these fungi attack our 

116 



OOMYCETALES II7 

cultivated plants, but where the attempt is made to grow alga^ and 
other water plants, the fungi of this family occasionally do considerable 
damage. 

As an example of the first subfamily Olpide.e, may be chosen 
Olpidiuni endogenum, which lives in the cells of desmids and kills 
them. The zoosporangium found in desmid cells are oblate spheroids 
and develop a long tube which projects out of the desmid cell through 
which the zoospores with a single cilia escape into the water. O. ento- 
phytum is parasitic in such filamentous algse as Vaucheria, Clado- 
phora, Spirogyra. Olpidiopsis saprolegnm lives in the elongated 
cells of Saprolegma,YiXod\xcmg enlargements in the hyphae of the fun- 
gous host. The swarm spore bores a hole in the cell wall of its host 
and swells out into a zoosporangium which develops a tube through 
which the biciliate swarm spores escape into the water. 

The subfamily Synchytrie^ includes most of the fungi which 
attack the higher plants. Such are Synchytrimn decipiens on the 
hog peanut (Amphicarpea monoica); S.fulgens on the evening primrose 
{Oenothera biennis); S. stellarice on Stellaria; S. succiscB on Succisa 
pratensis; S. taraxaci on dandelion; S. vaccinii causing a gall on cranber- 
ries, Pycnochytriiini globosum on violet, wild strawberry, blackberry and 
maple seedlings. P. myosotidis occurs on certain members of the 
borage and rose families. 

Cladochytrium tenue of the subfamily Cladochytrie^ lives in the 
subaquatic tissues of the sweet flag, Acorus calamus, flag Iris 
pseudacorus and a grass, Glyceria aquatica. Its mycelium is widely 
distributed in the cells of its hosts. Spheric sporangia 18 fx wide and 
sometimes 66/x are formed as intercalary enlargements of the mycelium, 
or they are formed at the end of the hyphae, with a colorless supporting 
cell. They give rise to a short tube-like mouth which breaks out of 
the host cell. The zoospores are uniciliate. 

Representing the Oochytrie^ is an interesting fungus first fully 
investigated by Nowakowski, namely, Polyphagus euglencE, which 
attacks the cells of Euglena, a unicellular animal. Its mycehum con- 
sists of a. central enlarged portion from which run out in a number of 
directions branches which end in extremely fine points which penetrate 
the cells of Euglena. The enlarged central portion develops a swollen 
tubular outgrowth into which its protoplasm wanders. The contents 
of this outgrowth then divide into numerous uniciUate swarm spores 



Il8 MYCOLOGY 

which escape into the water. Under certain conditions a cyst appears 
in place of a zoosporangium. This is thick-walled and of a yellow 
color and enters a period of rest. After the rest period, the membrane 
of the cyst rupture and a sporangium appears. Cysts may arise 
by a kind of sexual union where two unlike mycelia fuse and the 
protoplasm of both flows out to form a cyst between the original cells. 
Urophlyctis pulposa attacks leaves and stems of Chenopodium and 
A triplex species. U. alfalfcE grows in the roots of the alfalfa in 
South America and Germany. 

Family 5. Ancyclistace^. — This is a small family consisting 
of fungi whose mycelium is very sHghtly developed and not easily 
distinguished from the fruit body. In one subfamily Lagenide^, 
the mycelium is entirely absent. In the Ancycliste^, there is a 
rich development of the mycelium which forms lateral tube-like 
branches, which penetrate other cells. The fruit bodies are sac-hke 
and give rise to zoospores. Sexual organs are present as antheridia 
and oogonia, the contents of the former passing over completely into 
the latter. The oospore, which is formed, is found free in the oogonium. 
All of the known menxbers of this family are endophytic parasites and 
the different stages of their development are short-lived. 

Lagenidium entophytum lives in the zygospores of species of Spiro- 
gyra. L. Rabenhorstii parasitizes the cells of Spirogyra, Mesocarpus, 
Mougeotia. L. pygmatim lives in the pollen grains of diverse species 
of Pinus. 

BIBLIOGRAPHY OF OOMYCETALES 

Atkinson, George F.: Damping Off. Bull 94, Cornell University Agricultural 
Experiment Station, May, 1895; Notes on the Occurrence of Rhodochytrium 
spilanthidis Lagerheim in North America. Science, new ser., xxviii: 691-692, 
Nov. 13, 1908; Some Fungus Parasites of Algse. Botanical Gazette, xlviii: 
321-338, November, 1894. 

Clinton, G. P.: Oospores of Potato Blight, PhytopMhora hifeslans. Report Conn. 
Agricultural Experiment Station. Part x. Biennial Report of 1909-1910: 
753~774; Oospores of Potato Blight. Science, new ser., xxxiii: 744-747, 
May 12, 1911. 

Claxjssen, p.: Ueber Eientwicklung und Befructung bei Saprolegnia, monoica. 
Ber. d. Deut. Bot. Gesellsch., xxvi: 144, 1908. 

CoKER, W. C: Another New Achlya. Botanical^ Gazette, 50: 381-382, November, 
1910. 

Davis, Bradley M.: Cytological Studies on Saprolegnia and Vaucheria. The 
American Naturalist, xlii: 616-620. 



OOMYCETALES II9 

DE Bary, a. : Compaialixe Morphology and Biology of the Fungi, Mycetozoa and 

Bacteria, 1887: 132-145. 
DuGGAR, Benjamin M.: Fungous Diseases of Plants, 1909: 135-173. 
Engler, Adolf, and Gilg, Ernst: Syllabus der Pflanzenfamilien, 7th Edition, 

191 2: 38-42. 
Holder, Chas. F. : Methods of Combating Fungous Disease on Fishes. Bull. 

of the Bureau of Fisheries, xxviii: 935-936. 
Jones, L. R., Giddings, N. J. and Lutman, B. F.: Investigations of the Potato 

Fungus, Phytophthora infestans. Bull. 168, Vermont Agricultural Experiment 

Station, August, 191 2. 
Kerner, Anton: The Natural History of Plants, 1895, ii: 668-672. 
Magnus, P.: Kurze Bemerkung iiber Benennung und Verbreitung der Urophlyctis 

bohemica. Centralblatt f. Bakteriologie, Parasitunkunde u. infektions- 

krankhciten, ix: 895-897, 1902; Ueber eine neue unterirdisch lebende Art 

der Gattung Urophlyctis. Ber. der Deutschen Bot. Gesellschaft., xix: 145- 

153, 1901; Ueber die in den KnoUigen Wurzelanswuchsen der Luzerne lebende 

Urophlyctis, do., xx: 291-296, 1902; Erkrankung des Rhabarbers durch Perono- 

spora Jaapiana, do., xxviii: 250-253, 1910. 
Melhus, I. E.: Experiments on Spore Germination and Infection in Certain Species 

of Oomycetes. Research Bull. 15, Agricultural Experiment Station, June, 

1911. 
MiYAKE, K.: The Fertilization of Pythium de Baryanum. Annals of Botany, 

xv: 653. 
Petersen, Henning E.: An Account of Danish Fresh-water Phycomycetes, with 

Biological and Systematical Remarks. Annales Mycologici, viii: 494-560, 1910. 
RosENBAUM, J.: Studies of the Genus Phytophthora. Jour. Agric. Res. 8: 233-276, 

with pis. 7 and key, 191 7. 
Spencer, L. B.: Treatment of Fungus on Fishes in Captivity. Bull. Bureau of 

Fisheries, xxviii: 931-932, 1910. 
Stevens, F. L.: The Fungi "Which Cause Plant Disease, 1913: 66-101. 
Trone, a. H.: On the Fertilization of Saprolegnieas. Annals of Botany, xviii: 541. 
VON Tavel, F.: Vergleichende Morphologic der Pilze, 1892: 5-25. 
Wager, H.: On the Fertilization of Peronospora parasitica. Annals of Botany, 

xiv: 263, 1900. 
Wettstein, Richard R.v.: Handbuch der systematischen Botanik, 191 1: 158-160. 
Wilson, Guy West: Studies in North American Peronosporales V. A Review of the 

Genus Phytophthora. Mycologia, vi: 54-83, March, 1914. 
ZiRZOW, Paul: A New Method of Combating Fungus on Fishes in Captivity. 

Bull, of the Bureau of Fisheries, xxviii: 939-940, 1910. 
ZoPF, Wilhelm: Die Pilze, 1890: 282-313. 
Wager-, H.: On the Structure and Reproduction of Cystopus candidus. Annals 

of Botany, x: 295, 1896. 



CHAPTER XIV 

HIGHER FUNGI 

SUBCLASS MYCOMYCETES 

The higher true fungi are characterized by a mycelium in which the 
hyphae, as a rule, are permanently multicellular by the formation of trans- 
verse septa dividing the hyphal length into short cells. Some mycolo- 
gists, among them Brefeld, think it important to call the fungi which 
are transitional between the Phycomycetes and the Mycomycetes 
proper by the name MESOMYCETES, but the distinction between 
these intermediate forms and the higher fungi, being at times difficult 
to make, the writer has thought it best not to use the name MESOMY- 
CETES, as that of a subclass. The student will see the justice of this 
viewpoint as the discussion proceeds. 

Of unsatisfactory position in the fungous system are two families 
of fungi, which Brefeld includes in the subclass MESOMYCETES, 
which will illustrate his point of view as to transitional forms. Under 
HEMIASCINEiE, as a suborder, he includes the families Ascoideace^e 
and ProtomycetacEtE. Engler considers that these families have a 
doubtful systematic position. They show affinity to the PHYCOMY- 
CETES, and yet, they have septate hyphae and a sporangium, known 
as an ascus, which contains an indefinite number of spores, hence their 
closer affinity to the fungi of the order ASCOMYCETALES. The first 
family is represented by Ascoidea ruhescens which lives on wounded 
beech tree trunks, particularly in the sap which flows from the wounds. 
It forms a brown felt-like growth. The richly septate hyphae cut off 
laterally and terminally conidiospores and sporangia are formed in 
a series, so that as the numerous derby-hat-shaped spores are dis- 
charged and the sporangium is emptied of its contents a new sporangium 
forms inside of the walls of the old one, so that ultimately a sporangium 
may appear to arise out of a receptacle with a wall composed of three 
or four layers. In old cultures, the fruit-bearing hyphae may be united 
to form Coremia. The genus Dipodascus belongs to this family. The 

I20 



HIGHER FUNGI 121 

family PROXOMYCETACE.f:; is represented by the {genera Prolotnyces, 
Monascus and Thclebolus. Protomyccs is a genus of fungi parasitic 
in the higher plants; for example, P. macrosporus lives in Umbelli- 
FER^, P. pachydermus in Taraxacum. The coprophilous fungus 
Thclebolus stercoreus lives on the excrement of rabbits. It has a large 
rounded sporangium surrounded by a cushion of hyphge. Numerous 
spores suggestive of the moulds are formed within this sporangium. 

ORDER III. ASCOMYCETALES.— The fungi of this order are 
characterized by a mycelium which lives either saprophytically, or 
parasitically, with animals or plants. It has with few exceptions a 
rank, or exuberant, development sometimes with apical growth. The 
hyphae are septate and the cells are uninucleate, or plurinucleate. The 
reproduction of the majority of species is through endogenous spores 
known as ascospores, which are formed in definite numbers, usually 
eight, sometimes less (four, two, one), and sometimes more (sixteen, 
thirty-two, sixty-four, etc.) inside of a sporangium known throughout 
the order as an ascus (dcr/cos = wine-skin, water bottle). Frequently, 
they are called sac fungi, because of the sac-like ascus. The asci are 
found either isolated, or more generally, they are in fruit bodies where 
the asci are usually arranged along with the paraphyses between them 
in definite layers, which may be termed ascigeral. The paraphyses 
may assist in the discharge of the spores, but more usually their func- 
tion is that of packing in which they serve also for the protection of 
the adjacent asci. The fruit body is an apothecium, when it is open 
with the ascigeral layer wholly exposed. Such apothecia may be 
platter-like, saucer-shaped, cup-shaped, or goblet-shaped, and either 
sessile, or stalked, the length of the stalks being a variable character. 
The perithecium is a closed fruit body sometimes produced under 
ground where it remains subterranean. It may be entirely closed with 
no opening (cleistocarpous), or it may open by a pore at the top. 
This pore may be borne directly at the top of the rounded perithecium, 
or the perithecium may be drawn out into a larger, or a shorter neck, 
so that it becomes flask-shaped, or bottle-like. A narrow canal may 
lead through the neck, which may be straight, or variously curved. 
Sometimes the paraphyses, which extend through the neck and out 
of the pore, are designated periphyses. As accessory fruit forms, we 
find the conidiospores, which are of various forms, and which are 
borne singly, or in chains, at the ends of vertical hyphae (conidio- 



122 MYCOLOGY 

phores), or they are inclosed fruit l)odies willi terminal pores known 
as pycnidia (pycnidium), and in such the conidiospores are termed 
pycnidiospores, or pycnospores. The hyphae also break up into a 
disconnected series of spores known as chlamydospores, or the whole 
of the hypha set aside for reproductive purposes may break up into a 
connected series of spores, the oidiospores. Where the conidiophores 
are united together into strands, a coremium is formed. Sclerotia, 
or condensed masses of resting hyphae, are not unusual in the order. 
, Certain ascomycetous fungi are lichen fungi, as they are parasitic on 
green algae and with them form the lichen thallus, which bears a certain 
nutritive relation with the organic or inorganic substratum, so that 
we may distinguish the crustaceous, foliose and fruticose kinds of 
Hchen thalH. Where such hchen fungi and others of the order ASCOMY- 
CETALES live on the surface of bark, they are epiphleoidal; where 
beneath the surface, hypophleoidal; where they live on rock surfaces, 
they are epilithic; in rock holes, hypolithic; and on the surface of the 
earth, they are epigeic; below the surface, hypogeic. The growth on 
the surface of animals is ectozoic, in animals endozoic. The growth on 
the surface of leaves and other plant parts is designated epiphytic or 
cpiphyllous; inside the plant, as endophytic, or endophyllous. Zoospores 
are never formed in any of the fungi of the order. A few are aquatic. 
That sexuaHty exists in forms of the ASCOMYCETALES has been 
determined only recently and these discoveries confirm the views of 
de Bary, who claimed that the process existed in this order, although 
Brefeld and his disciples claimed the contrary. Thanks to the epoch- 
making research of R. A. Harper, seconded by that of Claussen, J. 
P. Lotsy, Baur, Darbishire, Guillermond and others, the fact that 
sexuality exists has been proven indubitably. The first type displayed 
by Pyronema, Boudiera and related genera is where a multinucleate 
carpogonium with a trichogyne is fertilized by a multinucleate 
antheridium. A uninucleate antheridium unites with a uninucleate 
oogonium in the Erysiphace^. The sexual organs are more or less 
reduced in .many genera and in some of the ASCOMYCETALES, 
they are wanting completely. In the development of the sexual 
organs and in the behavior of the egg-cell, there is represented here a 
type of sexual reproduction which has its closest parallel in the red 
algje (RHODOPHYCEiE). There is a suggestive similarity between 
the structure of the sexual organs and the process of development 



HIGHER FUNGI 1 23 

following fecundation in SphcBrotheca, Pyronema and Collcma, and in 
such red algae as Batr actios permum, Nemalion and Dudresnaya. A 
sketch of the process will not be amiss. The antheridia and oogonia 
arise in Pyronema from the apical cells of thick hyphal branches, 
which arise vertically from the substratum. These organs stand side 
by side. Soon a trichogyne is formed on the oogonium, as a papillar 
outgrowth, and subsequently it is cut off from the oogonium proper by 
a transverse wall. The antheridium and oogonium are multinucleate 
from the start and a broad stalk cell is cut off from the base of the 
oogonium. The tip of the trichogyne curves over to meet the tips of 
the antheridium, and the wall between them is dissolved enough to 
form a pore by which the cytoplasm of one organ becomes continuous 
with the cytoplasm of the trichogyne in which the nuclei have already 
disintegrated. The antheridial nuclei migrate into the trichogyne, and 
while this is happening the nuclei of the oogonium move to the center, 
where they become collected into a dense, hollow sphere. Now the 
basal wall of the trichogyne breaks down and the antheridial nuclei 
pass into the oogonium and become mingled with those of the egg cell. 
The antheridia and carpogonial nuclei now become paired without 
fusing. Out of the oogonium grow ascogenous hyphae and the paired 
nuclei pass into them. The young ascus develops from a penultimate 
cell of a bent ascogenous hypha with two nuclei which fuse, after the 
ascus has been formed and this fusion represents a sexual process. The 
end cell of the ascogenous hypha and the stalk cell are uninucleate, 
and these two cells may fuse to form a binucleate cell out of which a 
penultimate cell may arise. This single nucleus of the ascus then 
divides to form the series of eight ascospores usually found in the ascus. 
The synapsis stage of this single nucleus is immediately followed by a 
reduction division. 

Claussen^ has found that the formation of the ascus is not as simple 
a process, as described by Harper, and he has added materially to our 
knowledge by his reinvestigation of Pyronema confluens (Figs. 38, 39 
and 40). He finds that the conjugate nuclei do not fuse in the asco- 
gonium (carpogonium), nor in the ascogenous hyphae, nor in the pen- 
ultimate cell, nor when the tip cell of the ascogenous hook fuses with 
the stalk cell to form a binucleate cell. He finds that the penultimate 

1 Claussen, p.: Zur Entwickelungsgeschichte der Ascomyceten, Pyronema con- 
fluens. Zeitscrift fiir Botanik, 4, Jahrgang, Heft: 1-64 with 6 plates. 



124 



MYCOLOGY 



cell mav 




Fig. 38. — Diagrammatic representation of the 
observed methods of Ascus formation. {After 
Claussen, Ziir Enlivicklungsgeschicte den Ascomy- 
ceten, Pyronema conflucns, Zeilschr. fiir Bolanik 
4 Jahrb., 1912.) 



)enultiniatc, Up and stalk cells 
and this another, and during 
this process of proliferation, 
the nuclei derived by descent 
from the antheridial nuclei 
remain distinct from those 
of the ascogonium (carpogo- 
nium). Even the two nuclei 
derived from the tip and 
stalk cells show this dif- 
erence, and their descendants 
remain distinct with the pro- 
liferation of a new hook with 
stalk cell. The series of ac- 
companying figures taken 
from the paper by P. 
Claussen will enable the 
student to understand the 
process better than a lengthy 
description. 

The antheridia and 
oogonia of Sph(Erothe.ca arise 
as lateral branches of neigh- 
boring myceUai filaments. 
The oogonium is cut off from 
the rest of the hypha by a 
transverse septa, and pos- 
sesses a single nucleus. The 
antheridial branch appears 
quite near its base and grows 
upward pressed closely to the 
side of the oogonium. The 
antheridial cell with one 
nucleus is also cut off by a 
transverse septum. This 
nucleus now divides and one 
of the two nuclei passes into 
the attenuated end of the 



HIGHER FUNGI 



125 



antheridium, which is cut off by a partition wall. The walls 
between the two organs are dissolved and the male nucleus passes 
through the opening formed wanders toward the egg nucleus with 
which it fuses. Immediately after fertihzation, the oogonium begins 
steady growth, and some of the outer cells formed become the cover 




Fig. 39. — Diagrammatic representation of the development of the ascogenous 
hyphal system. {After Claussen.) 

cells of the perithecium. But ascogenous hyphae are formed, which 
contain two nuclei, then four nuclei by division with karyokinetic 
figures. Two of the nuclei wander to the curved side and this is cut 
off by two partition walls to form the binucleated penultimate cell, 
which becomes the mother cell of the ascus. The two nuclei of the 



126 



MYCOLOGY 



ascus now unite. The fusion or nucleus then divides to form those 
of the eight ascospores, and the walls of the perithecium grow to inclose 
the asci thus formed, including the paraphyses, which develop between 
the asci. 

All of the typic ASCOMYCETALES have uninucleate hyphal cells, 
while the ascogenous hyphse are binucleate, and in this case the nucleus 
has a double chromosome number. Hence is suggested an alternation 
of generations. 

The life cycle of Pyronema may be displayed in a graphic form 
beginning with the ascospore and ending with its production again. 
The diploid, or twenty-four chromosome condition, may be repre- 
sented by the double lines. This life cycle is contrasted with the 
well-known one of the fern where a well-marked alternation of genera- 
tion is shown. 



Fern 
Spore 



(After Claussen) 



Pyronema 
Spore 



Prothalluim 

/ \ 

Antheridium Archegonium 

I. I 

Spermatozoid Egg cell 

I I 



Mycelium 
Antheridium Ascogonium 

I 1 

T. i 

Antheridium Ascogonium 



Sperm nucleus ^Egg nucleus (Sperm) Nucleus (Egg) Nucleus 



\ 



/ 



Sporophyte 

il 

Spore mother cell 



4 Spores 



Ascogenous hyphge 

h 

Uninucleate ascus 



4 Nucleate ascus 



Brown, in his studies of Leotia, has shown that the asci are formed 
at the tips of the ascogenous hyphae in several different ways (Fig. 
41). In some cases, to quote him, "a hypha forms a typical hook, 



HIGHER FUNGI 



127 




Fig 40. — Diagrammatic representation of the development of the ascogenous 
hyphal system and of the mature ascus. (After Claiissen.) 



128 



MYCOLOGY 




Fig. 41. — 9, Vegetative hyphse giving rise to storage cell; 10, paraphyses grow- 
ing out from storage cells; 11-14, fusion of nuclei in storage cell; 15, 16, nucleus with 
two nucleoli in storage cell; 17, large storage cell with single very large nucleus; 18, 
storage cell with very irregularly shaped nucleus; 19, storage cell containing one 
large and two small nuclei; 20, an irregularly shaped storage cell; 21, 22, tip of as- 
cogenous hypha with two nuclei; 23, two nuclei in tip of hypha have divided to four; 
24, walls have come in, separating sister nuclei; 25, hook in which there is no wall 
cutting off uninucleate ultimate cell; 26, hook in which two nviclei have fused to 



HIGHER FUNGI 



129 



consisting of a binucleate penultimate and a uninucleate ultimate and 
antepenultimate cell. In this case, the two nuclei of the penultimate 
cell may fuse to form the nucleus of- an ascus, or they may divide and 
give rise to four nuclei of another hook. The uninucleate ultimate 
cell usually grows down and fuses with the antepenultimate cell, 
after which the nuclei of the two cells may give rise to the nuclei of 
another book or they may fuse to form an ascus. The walls separating 
the nuclei may fail to be formed without affecting the fate of the nuclei. 
In this process there is a conjugate division comparable to that in the 
rusts. Frequently the ascogenous hyphae- do not become markedly 
bent, and in this case, when the two nuclei in the tip divide, a wall 
may separate two pairs of sisters. Either of these pairs may divide 
and give rise to the nuclei of another hook or fuse to form the nucleus 
of an ascus. Any of the methods described above by which the number 
of asci is increased may be repeated many times. Large storage 
cells are formed in rows which give rise to the paraphyses. They are 
at first multinucleate but the nuclei fuse as growth proceeds. This 
process continues until often the cells contain a single very large nucleus 
many times the size of the largest nucleus in the ascus. The nuclei 
are very irregular." 

Blackman, V. H. AND Fraser, H. C, Jr.: Fertilization in Sphjerotheca. Annals 

of Botany, 19: 567-569, 1905. 
Brown, W. H. : The Development of the Asocarp of Leotia. Botanical Gazette, 

50: 443-459- 
Claussen, p.: Zur Entwickelung der Ascomyceten Boudiera. Bot. Zeit., 68 

(1905): Zur Entwickelungsgeschichte der Ascomyceten Pyronema confluens. 

Zeitschrift fiir Botanik, 4 Jahrgang, Heft i: 1-64; Ueber neuere Arbeiten zur 

Entwickelungsgeschichte der Ascomyceten. Bar. der. deutsch. Bot. Gesellsch. 

Jahrg., 1906, Band xxiv: 11-38 with complete bibliography. 
Engler, A. AND GiLG, Ernst.: SyUabus der PflanzenfamiUen, 1912: 47. 



form nucleus of ascus, and tip has fused with stalk of hook; 27, ultimate cell has 
fused with antipenultimate; nucleus of latter has migrated into former, which is 
growing out to give rise to ascus or another hook; 28, two nuclei of penultimate cell 
have fused to form nucleus of ascus; ultimate cell has fused with antepenultimate 
and nucleus of latter has migrated into former, which has grown out to form another 
hook; 29, bmucleate penultimate cell has given rise to hook; ultimate cell has fused 
with penultimate, and the two nuclei have fused; ultimate cell has not developed 
further; 30, binucleate penultimate cell has formed ascus, which fusion product of 
ultimate and antepenultimate has given rise to second ascus; 31, diagram illustrating 
multiplication of number of asci by method shown in 26-30; 9-20 Xr400. 21-30 X 
2100. (Aftey Brown. William H., The Development of the Ascocarp of Leotia. Botanical 
Gazette, 50: 443-359, Dec, 1910.) 
9 



I30 MYCOLOGY 

Fraser, H. C. J. AND Welsford, E. T.: Further Contributions to the Cytology of 
the Ascomycetes. Annals of Botany, xxii (1908). 

GuiLLERMOND, A.: La quest, d.l. sex chez. 1. Asc. et les. rec. trav. Rev. gen. de 
Bot., XX (1908): Recherches Cytologique Taxonomique sur les Endomycetes. 
Rev. gen. de Bot., 21: 353-39; 401-419 (1909) and a number of papers on the 
same subject in vol. 20. 

Harper, Robert A.: Die Entwicklung der Peritheciums bei Sphasrotheca Cast- 
agnei, Ber. d. Deutsch. Bot. Gesellsch., 13: 475-1895; Kerntheilung und 
freie Zellbildung in Ascus Jahrb. f. wiss. Bot., 30: 249-284, 1897; Cell Division 
in Sporangia and Asci. Annals of Botany, 13: 467-524, 1899; Sexual Repro- 
duction in Pyronema confluens and the Morphology of the Ascocarp. Annals 
of Botany, 14: 321-400, 1900. 

MoTTiER, David M.: Fecundation in Plants. Publ. 51, Carnegie Institution of 
Washington, 1904. 

Sands, M. C: Nuclear Structure and Spore Formation in Microsphasra alni. 
Trans. Wise. Acad. Sci., 15; 733-752; Botanical Gazette, 46:79. 

Ward, H. Marshall:: P'ungi, Encyclopedia Britannica, nth Edition. 

Wettstein, Richard R.v.: Handbuch der systematischen Botanik, 1911: 169-172 



CHAPTER XV 
SAC FUNGI IN PARTICULAR (YEASTS, ETC.) 

Suborder A. Protoasciineae.— The fungi of this suborder are charac- 
terized by the absence of definite fruit bodies, that is the asci are not 
enclosed, but are free and at the ends of hyphae. Usually they are of 
unequal length. Four is the typical number of ascospores in each 
ascus. These are one-celled and may increase in number by gemmation. 

Family i. Endomycetace^. — This family is a small one of four 
genera of saprophytes and parasites. The two species of the genus 
Podocapsa are parasitic on Mucorace^, Eremascus albus, the single 
species of that genus grows on spoilt malt extract. The genus En- 
domyces with five species is represented by the cosmopolitan Endo- 
myces decipiens, which forms a snow-white parasitic growth on the 
toadstool Armillaria meltea. Its hyphae are branched richly and the 
asci are pear-shaped and borne singly at the ends of the branches, 
each producing four helmet-shaped ascospores, 6 to S/jl broad and s^u 
high. Conidiospores are more frequently foimed than ascospores. 
Oidiospores are also found, as well, as chlamydospores. Oleina nodosa 
and O. lateralis are the two species of the fourth genus. The first 
grows in ohve oil. 

Family 2. ExoASCACEifc.— This family includes parasitic fungi 
which cause abnormalities of more or less marked character of the 
leaves, fruits and branches of mostly woody plants. The malforma- 
tions are in the nature of witches' brooms of the smaller branches, 
leaf curls, and deformed fruits, such as the plum pocket. Stone fruits 
are especially subject to attack and in some cases the stone formation 
is suppressed entirely. The myceUum may be deep-seated and 
perennial, or it may be subcuticular, or sometimes found growing 
between the epidermal cells, as in Magnusiella flava, while in other 
forms, the hyphae may be below the epidermis and grow throughout 
the leaf tissue. The asci are generally formed on the surface of the 
host breaking through from the more deep-seated mycehum beneath. 
They are generally stalkless and arranged in close proximity to each 

131 



132 



MYCOLOGY 



other without paraphyses, so that they form a velvety layer on the 
surface of the host plant. Eight ascospores are generally found, as in 
the genus Exoascus, but in Taphr'ma (Taphria) the number may be 
increased considerably by budding, so that the whole ascus will be 



-::#\ 



■^h 



y , ,; ff 





^^^ ^rrf^f 



Fig. 42. — Exoascus and Taphrina. A-F, Exoascus pruni, A. Appearance on 
diseased twig; B, cross-section of diseased fruit; C, mycelium in tissues of host; D, 
young asci; E, mature ascus with spores; F, germination of spores; G, E, Exoascus 
alnitorquus; H, Taphrina aurea, ripe and unripe asci; J, Taphrina Sadebeckii. See 
Die naturlichen Pflanzenfamilien I. i, p. 159. 



crammed full of them (Fig. 42). The ascospores are generally ellip- 
soidal and always one-celled with colorless, yellow, or orange contents. 
The perennial mycelium is responsible for the formation of witches' 
brooms in a variety of trees and woody plants. Most of them are the 



SAC FUNGI IN PARTICULAR - 1 33 

result of the parasitism of species of Exoascus. The "hexenbesen" 
are brush-Uke, or tufted masses of branches, which suggest the presence 
of other plants (Uke the mistletoe) parasitically or epiphytically 
growing. They result mainly by the infection of a bud which de- 
velops a branch with increased growth. On this branch, all dormant 
buds are stimulated to activity and the whole infected system of 
branches consists of negatively geotropic branches. These brush- 
like excrescences are called the thunder-bushes, and are -sometimes 
nest-like in appearance. An anatomic study shows that the parenchy- 
matous tissues — pith, hypodermis, etc. — are greatly increased; wood 
and bark are traversed by abnormally broad medullary rays, the ducts 
have short members, the wood fibers wide lumina, which are sometimes 
thin-walled and septate. The bast fibers are few, or entirely wanting. 
The cork cells are enlarged and retain their protoplasmic contents a 
longer time. The form of the witches' brooms are various. Many 
of them are pendent, some are nest-like, owing to the death of some of 
the branches. In some the branches are elongated, while some have 
short twigs. The end of the original branch from which the lateral 
branches developed usually dies and its food substances are absorbed 
by the hypertrophied branches. The family includes three genera, 
distinguished, as follows: 

A. Asci found at the end of intercellular mycelial branches. 

I. Magnusiella. 

B. Asci developed on a more or less subcuticular ascogenous mycel- 
ium. 

(o) Asci eight- (exceptionally four-) spored. 2. Exoascus. 

ib) Asci many-spored by gemmation of the spores. 3. Taphrina. 

The genus Magnusiella comprises five species, four of which are found 
in Europe and two in America. Magnusiella flava forms small pale 
yellow specks on the leaves of the gray birch, Betula populifolia in 
North America. The genus Exoascus includes about thirty species 
arranged in two subgenera, the first of which includes those species which 
deform fruits, which form witches' brooms, and the second those which 
cause a spotting of the leaves of various plants. It would lengthen 
this book unduly to enumerate all of the species of Exoascus with an 
account of the deformities of branches and fruits which they produce. 
Only a few of the more important species will be enumerated here, 



134 



MYCOLOGY 



and the diseases which they cause will be described later. Exoascus 
pruni (Fig. 42) is the cause of an important disease of plum trees, 
producing the so-called plum pockets. It also attacks Pruniis domestica 
and P. padus in middle Europe, and P. domestica and P. virginiana in 
North America. Exoascus communis attacks the fruits of several 
American species of Prunus among them P. maritima. Exoascus 
alnitorquus infests the pistillate spikes and cones of species of alder 
(Alnus), such as Alnus glutinosa and A. incana in middle Europe, and 
A. incana and A. rubra in North America, causing an enlargement of 
the fruit scales into twisted, tongue-like, reddish outgrowths. Exoascus 
deformans is the cause of peach-leaf curl. Exoascus cerasi is responsible 
for the formation of witches' brooms on the cherry. The genus 
Taphrina causes witches' brooms and leaf spots. Taphrina purpuras- 
cens attacks the leaves of a North American sumac, Rhus copallina, 
causing a puckering of the leaves with the formation of a reddish- 
purple color. T. aurea (Fig. 42) forms yellow blotches on the leaves of 
several European and North American poplars, viz., Populus nigra and 
P. italica of Europe, and P. Fremontii, P. grandidentata and P. deltoides 
of North America. T. Laurencia causes witches' brooms on a fern in 
Ceylon, Pteris quadriaurita. 

Suborder B. Saccharomycetiineae. — A true filamentous mycelium 
is absent in the fungi of this suborder. The plants are single-celled 
and reproduce by budding, or gemmation. Occasionally under ex- 
perimental treatment where the culture media are varied, the cells 
develop into hyphae and together form a myceHoid growth. Spore 
formation consists in a single cell, developing one to eight spores. 
It, therefore, may be looked upon as an ascus and the spores are as- 
cospores. Many of them cause fermentation. 

Family i. Saccharomycetace^. — Many species of the genus 
Saccharomyces are called generically yeasts, and are of economic 
importance, because they induce the alcoholic fermentation of car- 
bohydrate substances. The action is accompl shed through a soluble 
enzyme formed in the protoplasm of the yeast cell, and first isolated 
by Buchner by grinding the yeast cells in sand and extracting the 
ferment zymase. The general shape of yeast cells is oval, ellipsoidal, 
and pyriform (Figs. 43, 44). The cell wall is well defined and consists 
of modified forms of cellulose which may be called fungous cellulose, 
because it does not react to the reagents used for true cellulose. This 



SAC FUNGI IN PARTICULAR 



135 



much can be said that the wall consists of a carbohydrate, probably 
some isomer of cellulose. Lining the inner surface of the cell wall is a 
layer of protoplasm which may be called the ectoplasm, which probably 
serves as an osmotic membrane. The cytoplasm fills the rest of the cell 
with the exception of spaces occupied by the vacuoles of glycogen, 
nuclear vacuoles, oil globules, the nucleus and nuclear granules. The 
glycogen is gradually used up as it probably serves as reserve food, 
the same as starch in the higher plants. These glycogen vacuoles 
generally coalesce until one large vacuole may almost fill the cell. 










J 

6 7 8 12 

Fig. 43. Fig. 44. 

Fig. 43. — Yeast cell, Saccharomyces cerevisicB. {After Marshall.) 
Fig. 44. — Yeast, Saccharomyces cerevisicB. i-io. Young cells with nucleus, 
showing its structure; 6-8, division of nucleus; 11-13, cells after twenty-four hours" 
fermentation with large glycogenic vacuole filled with lightly colored grains. {After 
Marshall, Microbiology, Second edition, p. 62.) 

the cytoplasm and nuclear bodies being pressed against the cell wall 
and forming a thin protoplasmic hning to the inner cell wall surface. 
Wager 1 in 1898 demonstrated the nuclear apparatus in a number of 
yeast species. The nuclear apparatus consists in the earliest stages of 
fermentation of a nucleolus in close touch with a vacuole (Fig. 44, No. 4) 
which includes a granular chromatin network suggesting a similar struc- 
ture in the higher plants. The vacuole may disappear and then the 
chromatin granules are scattered through the protoplasm, or are gathered 
around the nucleolus, which is present in all of the cells, as a perfectly 
homogeneous body. Numerous chromatin vacuoles are often found 

1 Wager, Harold: The Nucleus of the Yeast Plant. The Annals of Botany 
.xii: 400-539- 



136 



MYCOLOGY 



in young cells and these ultimately fuse to form a single vacuole which 
occurs in the cells during the earher and the later fermentation. The 
process of budding is associated with the stretching of a network of nu- 
clear granules and its final constriction in the neck between the mother 
and the daughter cell. The nucleolus moves to the constriction where 
it becomes dumbbell- 
shaped, one half press- 
ing into the daughter 
cell (Figs. 44 and 45). 
There are no stages of 
karyokinesis dis- 
played, but by the sim- w^ f 1,«k W /<^ 
pie process described ^^ -"^ ^^^ ^ ^^ 
above the daughter 
cell receives approxi- 
mately one-half of the 
nuclear substance of 



r^ 



^ 



y^^r. 





Fig. 45. Fig. 46. 

Fig. 45. — Young yeast cells, Saccharomyces ellipsoideus, with nuclei and division 
of nuclei. (After Marshall, Microbiology, Second edition, p. 64.) 

Fig. 46. — Yeast, Saccharomyces cerevisice, the variety known as brewers' bottom 
yeast; a, spore formation; h, elongated cells. {After Schneider, Pharmaceutical Bac- 
teriology, p. 144.) 

the mother cell. In spore formation, the chromation which is scattered 
through the cytoplasm is absorbed more or less completely into the 
nucleolus which elongates and divides by a constriction in its middle 
part. Subsequent divisions result in the formation of four nucleoli 
around which protoplasm collects and thin membranes which become 
the walls of the ascospores which remain at first small, but later increase 
in size (Fig. 46). The formation of spores can be secured by taking 






Q^^ 



SAC FUNGI IN PARTICULAR 137 

a Sterile block of plaster of Paris with a saucer-shaped hollow on 
top. This block is placed in sterilized water and the top is seeded 
with vigorous, young well-nourished yeast plants which develop spores 
if kept at 25°C., in from twenty-four to forty-eight hours. The tem- 
perature at which spore formation occurs and the time which it takes 
for sporulation are points which have been obtained by experimenta- 
tion for all the more important species of yeasts. The data which has 
been obtained is used in the physiologic diagnosis, or identification of 
the various kinds of Saccharomycetace^, which react differently 
under experimental treatment. Film formation is also of diagnostic 
importance, where economic yeasts form floating films on the nutrient 
liquid media in which they are grown. The time 
required for the development of the film differs, /^ 
other conditions being equal, with the species of ^^ r^\^(^ 
the yeast and is longer the lower the temperature 
of the culture. Hansen obtained the following data 
for Saccharomyces cerevisicB ; 

Film formation takes place at: 

S3° to 34°C. in about 9 to 18 days. ^ ^/^- 47-— Yeast. 

o i " no,-^ • . ^ i 1 Saccharomyces cerevi. 

20 to 28 C. in about 7 to 11 days. ,-^_ growing repro- 

13° to I5°C. in about 15 to 30 days. duction by germina- 

6° to 7o°C. in about 2 to 3 months. tion, or budding; a, 

single cells; b, bud- 

No formation of film occurred above 34°C. or below ding cells. {After 
5°C. Another point of importance is that species ^IZiJ^X'^'^J'' 
of Saccharomyces form films so that this process is 
not entirely associated with the fungi belonging to the so-called genus 
Mycoderma. In fact some authors recognizing that Saccharomyces 
cerevisicB (Fig. 47) produced films have named that yeast, Mycoderma 
cerevisicB, and have thus confused its identity. 

Hansen in a paper published in 1888 classified the yeasts essentially, 
as follows: 

1. Species which ferment dextrose, maltose, saccharose: Saccharo- 
myces cerevisicB I, S. Pastorianus I, S. Pastoriamis II, S. Pastorianus 
III, S. ellipsoideus I, S. ellipsoideus II. 

2. Species which ferment dextrose and saccharose, but not maltose: 
Saccharomyces Marxianus, S. exiguus, S. Ludwigii S. saturnus. 

3. Species which ferment dextrose, but neither saccharose nor 
maltose: Saccharomyces mali Duclauxii. 



138 MYCOLOGY 

4. Species which ferment dextrose and maltose, but not saccharose 
Saccharomyces n. sp. obtained from stomach of bee by Klocker. 

5. Species which ferment neither maltose, dextrose nor saccharose: 
Saccharomyces anomalus var belgicus, S. farinosus, S. hyalosporus, S. 
memhranifaciens. 

The general chemic phenomena associated with the formation of 
alcohol by fermentation out of sugar may be expressed by the formula: 

CeHioOe = 2C2H6O + 2CO2 

Alcohol Carbon 

dioxide 

The carbon dioxide passes off in bubbles as a gas, while the alcohol 
remains in solution. 

The most important yeast is the beer yeast Saccharomyces cerevi- 
sicB which is a unicellular plant of spheric or elliptic shape 8 to 12/1 
long and 8 to 10// broad. Sometimes the cells formed by budding 
remain connected to form a chain consisting of the mother, daughter, 
granddaughter and great-granddaughter cells. Spore formation is 
characteristic and the size of the spores varies from 2.5 to 6/i. There 
are usually four spores in each cell. The following gives the tempera- 
ture conditions of spore formation in this species: 

At 9°C. no spores develop. 

At 11° to i2°C. the first indications are seen after 10 days. 

At 3o°C. the first indications are seen after 20 hours. 

At 36° to 37°C. the first indications are seen after 29 hours. 

At 37.S°C. no spores develop. 

The temperature limits for film formation are 33° to 34°C. and 6° 
to 7°C. There are a number of races of the common beer yeast, which 
may be separated into the bottom yeasts and the top yeasts. The bot- 
tom yeasts are those which live within the hquid and mostly at the 
bottom even from the start. Some of these yeasts form spores with 
difficulty. The top fermentation yeasts are those which grow on the 
surface of the liquid and cause a brisk'fermentation with a large amount 
of froth, or head, as exemplified by the Munich lager-beer yeasts. 
Yeasts are among the oldest of cultivated plants, as in biblical times 
leavened (yeast-raised) and unleavened bread were known. The 
leaven was a lump of dough kept from one baking to the next. Un- 
leavened bread was simply flour mixed with water and baked, and as 
a result, a hard tough bread was obtained. The .use of yeast as a 



SAC FUNGI IN PARTICULAR 



39 



Starter began in Roman times, but the art was lost until the seventeenth 
century, when it was regained. One of the earliest methods of obtain- 
ing yeast was salt raising, which consisted in adding to a quantity of 
milk a little salt sufficient to delay the growth of bacteria, while the 
yeast found entrance to the milk through the air and grew rapidly. 
This milk was then mixed with dough for the raising process. Bakers 
also sometimes used a brew called barms. Scotch barms were prepared 
by taking hops and flour with other ingredients which were allowed to 



^ '^^ ^ ^^^ 
C^^^ 




Fig. 48. — Saccharomyces ellipsoideus. A common yeast in jams, jellies, etc. 
Budding process is shown in many of the cells as also the vacuoles. Fig. 66, p. 145, 
Schneider, Pharmaceutical Bacteriology, 1912. 



ferment spontaneously, and the fermented material was used in 
bread baking (see page 667). 

Saccharomyces ellipsoideus (Fig. 48) is known as the wine yeast and 
may be classed as a wild species, while the beer yeast is found only in 
cultivation. The vegetative cells are ellipsoidal 6/x long, single, or 
united into a row of loosely connected cells. The cells are two- to four- 
spored. The spores are spheric 2 to 4/i broad. It is important in the 
fermentation of grape juice, gaining entrance from the skin of the 
grape fruit upon which it lives. In the spore form, it overwinters in 
the soil, being blown as dust to the developing grape fruits. The 



I40 MYCOLOGY 

bouquet, or flavor of the wine seems to be clue to the variety of wine 
yeast used in the fermentation of the juice, for every wine-producing 
region seems to have its especial form of wine yeast and the growth is 
different. Some yeasts, such as those of Burgundy and Champagne, 
form a compact sediment, which quickly settles leaving the liquid 
clear, while others remain for a long time suspended and settle slowly. 
Saccharomyces ellipsoideus II is a very dangerous disease yeast, produc- 
ing turbidity in the liquid of bottom fermentation breweries. 

Saccharomyces Pastorianus I was first discovered in the dust of a 
Copenhagen brewery and also in diseased beer. Its growth in wort 
consists of sausage-shaped cells. S. Pastorianus II produces a feeble 
top fermentation. S. Pastorianus III was found in bottom fermenta- 
tion beer affected with yeast turbidity. 

Saccharomyces ilicis and 5. aquiJolU were found on the fruits of the 
holly, Ilex aquifolium. 

Saccharom,yces Vordemanni is similar in appearance to wine yeast, 
its cells being onion-shaped, or pear-shaped. It is present in Raggi, 
which is employed in Java in the manufacture of arrack. It forms 9 
to 10 per cent, alcohol. 

Saccharomyces pyriformis was discovered by H. Marshall Ward to be 
active in the formation of ginger beer in conjunction with Bacterium 
vermiforme, for when these organisms are added to a sugar solution 
containing ginger, an acid beverage with considerable head is formed 
known as ginger beer. 

Saccharomyces exiguus occurs in pressed yeast, and it is capable of 
developing considerable alcohol from dextrose and saccharose solutions. 
Saccharomyces anomalus has been found in impure brewery yeast 
in Hungary, also in Belgian beer, on green malt, on bran, in syrup of 
Althaea, in soil, and on plum fruits. It ferments wort readily forming 
a gray film, a turbidity in the liquid, and an odor like fruit ether. 
The spores are helmet-shaped, suggesting those of Endomyces decipiens, 
which is parasitic on the caps of A rmillaria mellea, a toadstool. Saccha- 
romyces memhranifaciens grows in a gelatinous mass on the injured roots 
of elm trees, in polluted water, and in white wines, where'it destroys the 
bouquet of the wine. It completely consumes acetic and succinic 
acids, and quickly forms gray corrugated films on the surface of wort. 
The organisms of Kefir are Saccharomyces cartilaginosus and S. fragilis. 
Kefir is a beverage prepared originally in the Caucasus region by fer- 



SAC FUNGI IN PARTICULAR 



141 



menting milk. Kefir grains, which include the above yeasts, a Torula, 
and 3 bacteria {Bacillus caucasicus, etc.) are added to the milk as a 
starter. The fermentation of the milk results in the formation of alcohol 
lactic acid and carbonic acid. Mazum (Matzoon) an Armenian drink, 
is prepared by adding a white, fatty cheese-like mass, to milk. The 
starter includes colored yeasts Oidium laclis, mould fungi, a yellow 
Sarcina, Bacillus subtilis, some cocci. Bacterium acidilactici a.nd Saccharo- 
niyces anomalus. The only species of yeast, which can be recognized 
immediately by microscopic examination, is Saccharomyces Ludwigii, 
with its lemon-shaped vegetative cells, on the point of which a wart 
makes its appearance, which is cut off by a septum from the rest of the 
cell. This species is transitional to those included in the genus Schizo- 
saccharomyces. The form of Saccharomyces Ludwigii suggests S. 
apiculatus, which is unequally dumbbell-shaped. The genus Tonda 
according to Hansen includes yeasts similar to Saccharomyces, but 
which do not form endospores, a typical mould growth, and which 
produce alcohol in all percentages. They are widely distributed in 
nature. 

Schroter in Engler's "Die naturlichen Pflanzenfamihen" recognizes 
only two genera in the yeast family, namely, Saccharomyces and Mono- 
spora. The reproductive cells of the former have two to eight (seldom 
one to three) spores and the spores are spheric, or ellipsoidal, while the 
needle-shaped spores of Monospora are borne singly in reproductive 
cells, or asci. Hansen^ considers Monospora to be a doubtful form of 
yeast {Saccharomyces douteux), as also the genus Nematospora. He 
recognizes the following genera: Saccharomyces, whose spores have a 
single membrane and the cells reproduce hyhxiddrng; Zygosaccharomyces, 
where the asci are associated with conjugation; Saccharomycodes, whose 
spores have one membrane and sprout into a promycelium; Saccharo- 
mycopsis, whose spores have two membranes; Pichia with hemispheric 
or angular spores and Villia with citron-shaped spores. Lafar in his 
book on "Technical Mycology" (II, part 2, page 274) gives an analytic 
summary of the genera which he believes should be recognized. The 
position of such genera as Zygosaccharomyces, Saccharomycopsis, 
Schizosaccharomyces with respect to nearly related fungi is presented 
and discussed with a diagrammatic scheme of relationship by 

^ Hansen, E. Chr.: Grundlinien zur Systematik der Saccharomyceten. Centr. 
f. Bak., 1904. 



142 MYCOLOGY 

Guillermond/ who suggests the probable evolution of such forms from 
Eretnascus and Endomyces. Dr. H. Will discusses in Lafar's book 
the family Torulace^e, species of which are widely disseminated on 
field and garden fruits and on plants of all kinds finding suitable condi- 
tions for their growth during the decay of these fruits, and during the 
technic processes of fruit preservation, such as the making of pickles 
and sauerkraut. A number of them will no doubt prove to be budding 
stages of other fungi for our knowledge of them is decidedly imperfect. 
The character of the so-called pink yeast, red yeast, and black yeast is 
even less well known. As they are budding fungi, some have even 
classed them with the genus Saccharomyces. The genus Mycoderma 
was created to include the budding fungi, which form true films and 
which are formed rapidly on nutrient liquids, particularly on beer 
and wine with air between the cells, which are usually short and sau- 
sage-shaped. They are strongly aerobic and form, when exposed to 
the air, a wrinkled skin on the surface of the liquid. Like the true wine 
yeasts, these various species of Mycoderma have their natural habitat 
in the soil and they are carried to their appropriate nutrient substances 
by insects, rain or wind. They are probably not true yeast plants, but 
may represent growth conditions of other fungi, as related to certain 
nutrient materials. Curious chemic activities are possessed by species 
of Mycoderma, for example, the formation of acids and their destruc- 
tion both at the same time. Citric and succinic acids for example are 
consumed by them. 

1 GuiLLEEMOND, M. A.: Rcchetches Cytologiques et Taxonomiques sur les 
Endomycetees. Revue Generale de Botanique, 21: 401-419, 1909. 



CHAPTER XVI 
SAC FUNGI CONTINUED 

Suborder C. Plectasciinese.^This suborder includes fungi with a 
well-developed mycelium on which are developed either on the surface 
of the substratum or within it, as in the subterranean forms, closed 
perithecia without an opening at the top. The wall of the perithecium 
is sometimes called the peridium. The asci are developed on hyphae 
of irregular branching, and in considerable numbers, forming irregular 
layers of the perithecial interior. Each ascus is rounded and three- to 
eight-spored. The spores are one- to many-celled. Condiospores 
occur in a few of the forms, such as Aspergillus, Meliola and Penicillium. 
Many of the fungi of this suborder are saprophytic, but some are de- 
cidedly parasitic, as Thielavia basicola, which destroys the roots of pea 
plants by its parasitic growth and species of the families Terfeziace^ 
and Elaphomycetace^, the mycelia of which form mycorrhiza with 
roots of flowering plants. Economically, the suborder is interesting, 
because it includes the common blue and green moulds and species of 
Aspergillus used in the fermentation industries. The fruit bodies 
of several kinds of Terfezia are used as food by the Arabs of North 
Africa, Arabia, Syria and Mesopotamia. 

Family i. Gymnoascace^. — The fungi of this family are of interest, 
because of the structure of their fruit bodies. In the genus Gymnoascus, 
the spheric asci arise on short lateral branches of hyphae which form a 
dense rounded mass inclosed by loosely branching hyphae, which form 
a basket-like inclosure of the ascus-bearing portion Gymnoascus Reesii 
is coprophilous. Some of the shorter branches of this outer envelop- 
ment are sharp-pointed and spiny. Ctenomyces serratus, the single 
representative of its genus, grows on decaying bird feathers. It 
has branches with short hook-like extremities. The fruit body in this 
fungus is similarly rounded and covered with hyphae that form an 
open basket-Hke peridium. 

Family 2. Aspergillace^. — This family includes fourteen 
genera, the most important of which are Aspergillus, Penicillium and 

143 



144 MYCOLOGY 

Thlelavia. The perithecia are never subterranean. They are usually 
small, spheric, usually closed, and their walls are made up of pseudo- 
parenchymatous hyphge. They rarely open by a pore, more usually 
they break up at maturity to allow the escape of the ascospores. The 
inclosed asci are spheric to pear-shaped and two- to eight-spored. 

The moulds of the genus Aspergillus (Figs. 49 and 50) are usually 
saprophytic, and are found upon decaying vegetables, moldy corn and 
other cereals. After the conidiospores are formed, the color of the 
mould develops and various shades of green, white, blackish-brown, 
brownish-yellow, brown and reddish are found in the different species 
of the genus. The recognition of this genus is made easy by the shape 
of the conidiophores, which are elongated unicellular (unseptate) and 
terminate in a globular swelling, the top of which is covered with a large 
number of closely set stalks, or sterigmata, of variable length and shape 
on which the conidiospores develop. In the related genus Sterigmato- 
cystis, the sterigmata are branched (Fig. 51). The conidiospores are 
spheric, or ellipsoidal, always unicellular with smooth or granular 
walls, and are formed in long chains (concatenation) from each sterigma 
imparting the characteristic color to the whole growth. The perithecia 
are fragile spheres with thin walls which may be yellow {A. herbari- 
orum) dark red {A. pseudo-clavatus) , or even black (A. fumigatus) 
in color. The perithecia and asci are unknown in many of the species, 
so that the classification of the species cannot be based on the characters 
of that organ and of the ascospores. Only about six to ten species are 
known to have perithecia out of a possible total number of 120 species 
included in the genus. This number will probably be considerably 
reduced when these moulds are better known. The accompanying 
figures show some of the specific differences of the conidiophores and 
conidiospore production. The .common green mould, Aspergillus 
herbariorum (= Aspergillus glaucus, Eurotium Aspergillus glaucus) 
grows on many substances such as dried plants in the herbarium, 
(hence its specific name), on old black bread (pumpernickel), on jellies, 
on jams, on old leather, on herring pickle and other objects of domestic 
use. At first the mycelium is white and as the young conidiospores begin 
to form it turns to a pale green, later becoming a dirty grayish green, 
while the feeding hyphse change color to a pale yellow and finally a 
brown color by the deposit of pigment granules. The globular part of 
the conidiophore is 60/x across and crowded with simple sterigmata 



SAC FUNGI CONTINUED I45 

(7M by i4m), bearing prickly, spheric conidiospores 7 to 30^ in diameter 
which are larger than any other well-known species. It produces 
perithecia also with readiness and in abundance. The at first pale 
brown-yellow perithecia, later brown, are about 100 to 200/i in diame- 
ter in closing numerous asci which contain five to eight colorless 
smooth ellipsoidal spores, exhibiting a furrow directed longitudinally 
and 5 to 8/i broad by 7 to IOf^ long. The perithecium develops gradu- 
ally from spirally coiled hyphae. The hyphae of the screw are divided 




Fig. 49. — Aspergillus oryza associated with yeasts in the making of the Japanese 
beverage Sake. Vegetative hyphae (a) and spore-forming hyph« {b. c, d) are shown. 
Fig. 71, p. 152. {Schneider, Pharmaceutical Baderiology, 1912, 19.) 

transversely into as many cells as there are turns of the screw. The 
bottom hyphal cells of the screw send up two or three branches of 
irregular thickness which grow toward the apex. One of these branches 
looked upon as an antheridium grows more rapidly than the others and 
its contents serve to impregnate the inclosed carpogone. These outer 
erect hyphae then branch copiously to completely envelope the carpo- 
gone and the perithecial wall is thus formed. From the carpogone are 
now formed the numerous ascogenous hyph;p, which branch plenti- 



146 MYCOLOGY 

fully and bear terminally asci of a pyriform shape. These contain 
eight grooved ascospores. Aspergillus herbarioriini, as a domestic 
and industrial fungus, is selective. It does not thrive on liquid sac- 
charine media with mineral salts and inorganic nitrogenous food, while 
black bread and wort gelatin are suitable media. Moderate tempera- 
tures (8 to io°C.) are best for its growth, and it ceases growth entirely 
at blood temperatures. The temperature limits are 7° to 3o°C. with 
optimum at 20 to 25°. It grows on tobacco, cigars, hops, cotton-seed 
meal, acid pickles, and smoked meats. It causes the blackening and 
spoiling of chestnuts and is found on the kernels of various nuts even 
before they are removed from the shell (see Appendix VII, pages 702 
to 721). 

The rice mould, Aspergillus oryzece (Fig. 49), is of practical impor- 
tance as a saccharifying fungus, and it has been cultivated for centuries 
by the Japanese and used by them in the preparation of the rice mash 
for Sake, as well as in the production of Miso and Soja sauce. It grows 
luxuriantly and is usually yellow-green in color turning brown with age 
with large closely set tough conidiophores about 2 mm. tall. The tops 
of its conidiophores are obovate, or spheric. The sterigmata are radially 
arranged producing yellowish-green spheric conidiospores (6 to 7/i) in 
chains. The sterigmata are larger than in A. herhariorum 4 to 5^1 by 12 
to lOjj. . No perithecia have yet been observed. This mould secretes a 
very active diastase and it has been used in the making of pharmaceutic 
preparations, such as Taka diastase, which is used in the dose of 2 to 5 
grains either in tablet, capsule or solution in cases of indigestion im- 
mediately after meals. It converts the starchy food into dextrin and 
sugar. The discovery of this diastase in Aspergillus was made by 
Takamine, a Japanese zymologist, and his product has been used over 
the civiHzed world. 

Aspergillus Wentii, which is readily kept in culture on glucose or 
beerwort agar, is used in the preparation of Tas Gu in Java. It appears 
spontaneously on boiled soy beans that have been covered with leaves 
of Hibiscus and it causes a loosening and disintegration of the firm 
tissues of the bean. The growth of this species is of a pale coffee color 
with conspicuous conidiophores about 2 to 3 mm. in height, their thick 
brown heads up to 200/i in diameter are on pale smooth stalks. The end 
of the conidiophore is globular 75 to 90/x in diameter and is covered 
with slender simple sterigmata (4^ by 15/x) which bear small globular 
to elongated conidiospores, 4 to 5/1 diameter. The mycelium at first 



SAC FUNGI CONTINUED 147 

is snow-white; later it becomes reddish brown. The discovery of 
perithecia is yet to be made. 

Aspergillus flavus plays an important part in the cocoon disease of 
silkworms. The stipe portion of its conidiophore is roughened by 
colorless granules. 

Aspergillus luchuensis, according to Inui, is used in the preparation 
of a beverage Awamori, which resembles whisky and is used in the 
Loochoo islands. 

Aspergillus tokelau is found in Tokelau, or Samoan disease, attack- 
ing the natives of certain of the Pacific islands. An important patho- 
genic species, which causes an epidemic disease of pigeons and lives in 
the human ear and the lungs of various birds, is Aspergillus fumigatus, 
which was the cause of a false tuberculosis of a calf in Philadelphia. 
An autopsy by Ravenel and the writer showed the lung tissue of the 
calf penetrated by the myceUal hyphae of the fungus, and its conidio- 
phores bearing the conidiospores in a fan-Hke manner were seen project- 
ing into the lung cavities almost completely filling them. It, therefore, 
grows well at blood temperature, and if its conidiospores are introduced 
into the arterial circulation of animals they germinate and produce 
serious illness, which may terminate fatally. It also acts injuriously 
in certain fermentation processes carried on at high temperatures as 
certain lactic acid fermentations. It attacks tobacco, decaying 
potatoes, bread, malt and beerwort. It has dwarf conidiophores o.i 
to 0.3 mm. long, with club-shaped globules 10 to 20/x thick, upright 
sterigmata 6 to 15/1 long and with long chains of conidiospores (2 to 3^)- 
Nut-brown globular perithecia are found, 250 to 350M in diameter, in- 
closing oval thin-skinned asci (9 to i4ju) with eight red lenticular tough- 
walled spores (4 to 4.5^)- As a parasite of the human skin it was called 
Lepidophyton. The green mould, which usually grows on malt, is 
Aspergillus clavatus causing a moulding of the substratum. The largest 
species of the group is Aspergillus giganteus, which looks at first super- 
ficially hke a Mucor, but later owing to its grayish-green conidiospores 
it is readily separable from the mucor vegetation. Its sterigmata seem 
to be hollow, communicating with a pore-like opening with the center 
of the conidiophore. No perithecia have been found. Other species 
are .4. nidulans (Fig. 50), which can be cultivated readily, A. varians 
and A. ostianus, the latter distinguished by an ochraceous pigment. 
The black mould Aspergillus niger more properly Sterigmatocystis niger 



148 



MYCOLOGY 



(Fig. 51) has a copious literature. Lafar cites forty workers of recent 
date, who have studied it. The physician finds it as an occupant of 




Fig so — Aspergillus nidulans. A, Mycelium with conidiophores; B, branched 
conidiophore, C, spore chains at end of conidiophore ; D, small conidiophores; E, 
young fruit showing development of covering; jp, hyphae with swollen ends; G, 
hypha from interior of fruit-body; H, hyphae with young asci; J, developing perithe- 
cium. (See Die jtaliirlichen Pflanzenfamilien I. i, p. 302.) 



the human ear in a disease otomycosis. It is associated with the cork 
disease which imparts a taste to bottled wine. It grows well in acid 
substrata, as gall-nut extract, tannic acid and has a decided capacity 



SAC FUNGI CONTINUED 



149 



for producing oxalic acid. It has stiff slender conidiophores several 
millimeters in height. The terminal part can be studied only after 
the bleaching or removal of the dark masses of conidiophores. 







Fig. 51. — Slerigmatocyslis niger {Aspergillus niger) showing conidiophores and coni- 
diospore formation with stages in germination of spores. {After Henri Coupin.) 

The genus Thielavia is represented by a common pathogenic species, 
T. basicola, whose life history and pathogenic character will be de- 



150 MYCOLOGY 

scribed later. It attacks the roots of a large series of plants including 
the tobacco, at least 105 species of plants being attacked according to 
the latest account.^ The parasitic mycelium is intercellular, abun- 
dantly septate and hyaline. It produces conidiospores, which are 
abjointed acrogenously from the conidiophore, and are not as was 
supposed formerly endospores formed by free cell division within an 
endoconidial cell. The first conidiospore is liberated by the differentia- 
tion of its walls into an inner wall and a sheath and by the rupture of 
the latter at its apex. The later conidiospores grow out through the 
sheath of the first and are freed by a spHtting of their basal walls.- This 
same process is probably that of all " endoconidia " in fungi. 

Family 3. Elaphomycetace^. — The fruit bodies of the fungi of 
this family are subterranean with a distinct, mostly thick peridium 
whose surface is marked by a more or less strongly developed rind. The 
asci borne within the closed fruit body are irregularly arranged and 
united into large groups, which are separated by radially arranged vein- 
like masses of sterile hyphae. The asci are spheric, or pyriform, and 
mostly eight-spored. The whole spore-bearing interior of the fruit 
body, when ripe, is transformed into a powdery mass with the sterile 
hyphae remaining as a number of capillitia-Hke threads. There is no 
spontaneous opening of the fruit body at maturity. The family in- 
cludes a single genus, Elaphomyces, which comprises about twenty-two 
species, found mostly in northern Italy, in Germany and France, a few 
in England, northern Europe and North America. Such species, as 
Elaphomyces papillalus, E. atropurpureus from the oak and chestnut 
woods of northern Italy, E. mutabilis with a silvery-white mycelium 
growing in the oak, beech and birch woods of northern Italy, France 
and Germany, E. citrinus with an orange-yellow mycelium, also from 
northern Italy, all have delicate thin rinds which become wrinkled 
when dry, and belong to the section Malacodermei. The section Sclero- 
dermei includes those species with compact brittle rind, which is not 
wrinkled when dry. Here belong E. maculatus with strongly de- 
veloped, green myceUum, surface of fruit body blackish brown with 
greenish markings, found in the oak forests of northern Italy, French 

1 Johnson, James: Host Plants of Thielavia basicola. Journ. Agric. Res., 
vii: 289-300, Nov. 6, 19 16. 

^ Brierley, William B.: The Endoconidia of Thielavia basicola; Zopf, W., 
Vnnals of Botany, xxix: 483-491, with i plate, October, 1915. 



SAC FUNGI CONTINUED 151 

Jura and the Tyrol. E. cerviims, which is found under oaks, beeches 
and pines in Europe and North America, has a fruit body the surface 
of which is brownish yellow, or reddish brown, and is covered with 
numerous pyramid-shaped projections. The inner layer of the peri- 
dium of this species is not veined like E. variegaius, another widely 
distributed species throughout Europe. The fruit bodies of the last 
two species are frequently parasitized by Cordyceps ophioglossoides 
and C. capitatus (see ante, Fig. 21). 

Family 4. Terfeziace^. — The fruit bodies of the fungi of this 
family are more or less deeply subterranean, tuber-like, infrequently 
galleried {Hydnobolites). The fruit bodies differ from those of the 
preceding family in that the interior spore-bearing portion does not 
break down into a powdery mass, hence there is no so-called capillitium, 
and as in that family the fruit body does not open spontaneously. 
The terfas, or kames, of arid Mohammedan countries belonging to the 
genera Terfezia and Tirmania were known to the Greeks and Romans. 
The species of Terfezia are found under and associated with the roots 
of the herbaceous or shrubby forms of Artemisia, Cistus and Helian- 
themum. A North African terfa, Terfezia conis, is found in the moun- 
tain forests of pine and cedar and in the sands of Sardinia from March 
to April. The desert terfas include T. Boudieri, T. Claveryi, T. 
Hajizi and Tirmania ovalispora. Duggar,^ an American mycologist, 
has gathered these fungi at the base of Artemisia herba-alba found 
growing in the sandy soil of small oueds, or stream beds, in southwestern 
Algeria. They are located by the breaking of the soil surface and are 
dug out -by the Arabs with a pointed stick. They form a valuable 
food, as they are rich in protem. 

Family 5. Tuberace^. — General reference has been made to the 
members of this family in a description of the special ecology of the 
EUMYCETES. The mycelium of the truffles is well developed and 
septate, producing mostly subterranean, tuber-like fruit bodies, which 
have more or less numerous chambers lined with the ascigeral tissue 
supported by sterile hyphae. The asci, which are arranged irregularly 
in the ascigeral tissue, are one to eight-spored. The ascospores are 
unicellular, and in the truffles {Tuber) usually spiny. The mycelium 
is subterranean and is connected with the roots of coniferous and 
broad-leaved trees forming the so-called mycorrhiza. The simplest 

' DuGGAR, B. M.: Mushroom Growing, 191 5: 207-217. 



152 



MYCOLOGY 




Vj 



'm^^^m^- 





Fig. 52. — A, Tuher ceslivum frtiit-body; B, Tuber magnatiim fruit-body; C , Tuber 
brumale f. melanosporum, section through fruit-body; D, Tuber excavalum, section of 
fruit-body; E, Tuber ceslivum f. mese7!tericuni, piece of fruit-body near pcridium en- 
larged; G, piece of Tuber excavation enlarged;. H, Tuber rufum, fruit-body magnified 
showing asci and ascospores; J, Tiihrr lirumalc, ascia with spores; K, Tuber magnalum, 
ascus with spores. {See Die natiirlidicu Fjhnizenfamilien I. i, p. 287.) 



SAC PUNGI CONTINUED 1 53 

fruit body in the subfamily Eutuberine.^ is found in Genea liispidula 
where it forms a hollow sphere with definite opening. Generally, it is 
provided with a system of tubes, passageways or galleries, which vary 
in their arrangement in the different genera. These galleries are hollow 
in some, in others filled with hyphje, constituting the vencs externce. 
The sterile supporting hyphte between these passageways constitute the 
vena inferncB. In the subfamily Balsaminace^, the fruit body has a 
single, hollow chamber, or numerous hollow closed cavities. The 
ascigeral layers constitute the walls of these chambers. 

The fungi of the genus Tuber (Fig. 52) are of the most interest 
economically, as several species, such as T. CBstivum (Spring), T. 
brumale, T. melanosporum (^Winter), T. uncinatum (Autumn), T.rufum 
are edible, and are known as truffles (Fig. 52). These species occur in 
deciduous woods of north Italy, France and Germany and elsewhere 
in Europe. They are gathered for food by men (rabassier), who make 
a livelihood by selling the truffles for immediate use, or for canning 
purposes. As the fruit bodies emit a characteristic odor, they are 
located by the aid of specially trained dogs, and pigs, whose keen scent 
enables them to find the underground fruit bodies. As they are dug 
up, the animal is rewarded by his master with some other attractive 
morsel of food, and the newly discovered truffle is placed in a leathern 
pouch slung over the shoulder of the rabassier. The tin cans in which 
the tfuffles (Tuber melanosporum in Perigord mainly) are preserved 
for shipment to all parts of the world are usually labeled with a state- 
ment as to the contents of the can, and with a hunting scene, where the 
man and his truffle dog prominently figure. 

Near here should be placed the family Myriangiaceae repre- 
sented by the genus Myriangium with three species of wide distribu- 
tion. This family has been monographed by von Honel.^ 

ivoN Honel: Sitzungsber. Math. Naturw. Klasse k. Akad. Wiss. Wien., 
118, Abt. i: 349-376, 1909- 



CHAPTER XVII 
MILDEWS AND RELATED FUNGI 

Suborder D. Perisporiineae. — The mycelium of the fungi which 
belong to this suborder is filamentous, superficial, light- or dark- 
colored, rarely forming a stroma. The fruit bodies are superficial, 
spheric to egg-shaped without a pore and break up irregularly. Peri- 
thecia are usually dark-colored and in many cases surrounded by 
accessory hyphae, or suffulcra. The asci are spheric, egg-shaped, or 
elongated, and range within the closed perithecia from one to many 
in number. Paraphyses are usually absent. The following families 
are recognized: 

A. Perithecium spheric, poreless or breaking irregularly at the top. 

(a) Aerial mycelium white, perithecium with appendages or suffulcra ; 
accessory spores belonging to the genus Oidium. 

I. Erysiphaceae. 

(b) Aerial mycelium absent, or dark-colored, perithecia without 
appendages or suffulcra, accessory spores not belonging to 
Oidium. 

2. Perisporiace^. 

B. Perithecium peltate flat, opening at top by a round pore. 

3. MlCROTHYRIACE^. 

Family i. Erysiphace^. — The fungi of this family are popularly 
called "white" or "powdery mildews." During the summer their 
conidial fructifications (Oidium) are found on hops, maples, peas, 
roses and vines imparting to the surface of the host a dusty appearance, 
due to the white conidiospores. Later in the summer, the globular 
dark brown, or black, perithecia appear and these are provided usually 
with appendages, or suffulcra, which are frequently branched in a way 
characteristic of the different genera of the family. The white 
mycelium upon which the fruit bodies arise is truly parasitic, for short 
haustoria are formed which pierce the wall of the epidermal cells, and 
swell out into a bladder-like form for absorptive purposes. The haus- 

i.'54 



MILDEWS AND RELATED FUNGI 1 55 

toria are confined to the epidermal cells in all of the genera of the 
family except Phyllactinia, which forms special hyphal branches which 
enter the stomata, penetrate the intercellular spaces of the leaves and 
finally send haustoria into the cells of the loose parenchyma. With 
the exception of these haustoria, the mycelium of the "powdery 
mildews" is entirely superficial. The conidial forms of the different 
fungi of the family were classified formerly under the name of Oidium, 
but with a more detailed knowledge of their life history, this name has 
been relegated to the synonymy. The conidiospores, which are formed 
in great numbers, are carried by the wind, or by snails in the case of 
Erysiphe polygoni on plants of Aquilegia and are capable of immediate 
germination on reaching the epidermis of a suitable host plant, the 
germ-tube penetrating the outer wall of some epidermal cell. True 
sexual reproduction has been discovered in some of the mildews by 
R. A. Harper, thus verifying the earlier observations of de Bary. 
Sphcerotheca Castagnei serves to illustrate the process. The oogonium 
and antheridium, which are formed where two neighboring hyphse 
approach, each contains a single nucleus. The cell wall between these 
organs is dissolved at the time of fertilization and the male and female 
nuclei unite and a fresh wall is laid down between the two organs. 
Now the wall of the future perithecium begins to form by the develop- 
ment of a number of upright hyphal branches around the oogonium, 
forming a pseudo-parenchymatous tissue, while other branches later 
absorbed grow into the interior of the developing perithecium, while 
the outer wall cells become flattened and darker in color. The fol- 
lowing growth takes place in Sphcerotheca, which develops only a 
single ascus. The carpogonium elongates, divides and a curved row 
of five or six cells is formed. The penultimate cell of this row contains 
two large nuclei, while the other cells of the row have one nucleus each. 
The young ascus develops from this penultimate cell in which the two 
nuclei fuse followed by a rapid increase in size of the ascus, which presses 
against the inner wall cells of the perithecium and absorbs them. 
The nucleus of the ascus finally divides three times, producing the 
nuclei of the eight ascospores, which subsequently are formed by free 
cell formation. From the half-grown perithecium there arise apical, 
equatorial or basal hyphae which grow out as the appendages, or 
suffulcra, which in Phyllactinia are acicular and bulbous at the base 
(^ig- 53)) in Uncinula hooked at the apex and in PodosphcBra and Micro- 



156 



MYCOLOGY 




Fig. 53. — Mildew of chestnut leaves due to Phyllaclinia corylei with ascus and 
perithecium to left. (Martic Forge, Pa., Nov. 2, igiS-) 



MILDEWS AND RELATED FUNGI 



157 



sphara (Fig. 54) dichotomously branched. These appendages prob- 
ably assist in the distribution of the perithecium, serving to attach 
the perithecia to plants, if wind-borne, or to the bodies of insects by 
which they are carried to other plants. The number of asci found in a 
perithecium and the number and character of the spores in the asci 
vary generically (see Appendix VIII, pages 721-726). 

As the fungi of this family are especially suitable for systematic 
study, a key is given not only of the principal genera, but also of the 



anth^ 




Fig. 54. — Lilac mildew, Microsphara alni. A, Perithecium with appendages; 
B, perithecia showing asci (a); C, ascus with ascospores; D, conidiophore (cph), 
bearing conidiospores {c.s.); E, beginning of fertilization; anth, antheridium; car, 
carpogonium; F, later stage of fertilization showing the fusion of two nuclei (/). 
(From Gager with E and F after R. A. Harper.) 



principal species of the different genera. These keys (p. 721) have been 
taken from a monograph of the Erysiphace^ by Ernest S. Salmon, pub- 
lished in 1900, as vol. ix of the Memoirs of the Torrey Botanical Club, to 
which the mycologic student is referred for detailed descriptions of the 
various species. The material for the systematic study is easily kept 
in the dry condition and the perithecium can be studied in situ on the 
dried leaf or other plant parts, and later treated with weak alcohol 



158 MYCOLOGY 

to remove the air, washed and mounted permanently stained, or 
unstained in acetic acid with a ring of asphalt, or in glycerine jelly 
for a study of the asci and ascospores. For a study of the distribution 
of the haustoria and for a detailed examination of the sexual organs,^ 
small pieces (2 by 4 qcmm.) of hop leaves on which myceha of the 
mildew (Sphcerotheca) are found in various stages of development 
should be fixed in weaker Flemming's solution, as described by Zim- 
mermann on page 178 of his "Botanical Microtechnique," and then 
hardened in alcohol and carried through to paraffin. The sections 
should be cut 5 to 7.5^ thick stained with safranin (one to one and 
one-half hours), gentian-violet (one-half to one hour), and orange 
G. (quickly), then treated with absolute alcohol, cleared in oil of cloves 
and mounted in balsam. 

The material for systematic study should be handed to members of 
the class in mycology, mounted and then studied as unknowns by the use 
of the generic and specific keys given in Appendix VIll, pages 721-726. 

Family 2. Perisporiace^. — The aerial mycelium of these fungi 
is superficial black, filamentous, or wanting, or rarely as a firm stroma. 
The perithecia are situated on the aerial myceUum, or on the stroma. 
They are black, + spheric, rarely elongated, poreless, or weathering ir- 
regularly at the apex and without appendages. The wall is mostly 
membranous, or brittle. The asci are clustered and mostly elongated. 
The shapes of the spores are various. Paraphyses are usually wanting, 
and are present in only a few cases. 

The genus Scorias has been described incidentally in a foregoing page 
(72). It is represented in America by a single species, spongiosa, ^h.\c\\ 
lives on beech twigs and leaves associated with some species of wooly 
aphis, or on the ground where the droppings of the aphis in the form 
of honey-dew have collected. Its mycelium is greenish-black, much- 
branched, rigid, septate and the hyphae are glued together by an 
abundant mucilaginous substance forming a loose spongy mass, bearing 
an abundance of pyriform, coriaceous perithecia, which enclose narrow, 
thick-walled, eight-spored asci. Elongate pycnidia and perithecia are 
also frequently seen. 

Family 3. Microthyriace^. — The mycelium of the fungi of this 
family is superficial and dark in color. The perithecia are superficial 

1 Harper, R. A.: Die Entwickelung des Peritheciums bei Sphcerotheca Castagnei, 
Bericht. der Deutsch. Bot. Gesellsch., xiii, Heft. 10: 475-481, 1895. 



MILDEWS AND RELATED FUNGI 



159 



shield-shaped, unappendaged, black, membranous to carbonous 
formed of radiating chains of cells. The asci are four- to eight-spored , 
short and associated with paraphyses. Two fungi which attack the 
cofifee plant are the most important pathogenic species of the family: 




Fig. 55. — A-D, Nectria cinnabarina. A, Stroma of conidia and fruit-bodies of 
fungus; B, stroma in section; C, ascus; D, mycelium with conidiospores; E, F, Neclria 
dilissima; F, conidia layer; G, H, Nectria sinaplica; G, ascus; H, pycnidia-like layer. 
J, Nectria inaiirita; K, Neclria oropensoides coremium. {See Die natiirlichen Pflanz- 
enfamilien I. i, p. 35 7-) 

Scolecopeltis aeruginea and Microthyrium cofcB. There are twenty- 
one genera, and more than 300 species not well understood. 

Suborder E. Pyrenomycetiinaee.— The mycelium is always present 
in these fungi. The perithecia are either located upon the substratum, 



i6o 



MYCOLOGY 



or in the substratum, and are mostly spheric. A wall (peridium) is 
present inclosing the clustered eight-spored asci which arise from the 
interior basal part of the perithecium. The perithecium opens by an 
apical mouth or pore and is either isolated or imbedded in a stroma 
which takes manifold forms. The formation of conidiophores and 
conidiospores varies in the different families and genera. Sometimes 

a distinct conidial layer is formed; at 
other times the conidiospores are 
formed in pycnidia. The suborder 
includes many saprophytic and para- 
sitic fungi found upon plants and 
animals. 

Family i. Hypocreace^. — The 
perithecium of these fungi is spheric 
and opens terminally by a definite 
pore. In color, it may be pale, 
sprightly colored, or colorless, never 
black. Hypomyces with sprightly 
colored perithecia arises from a thick 
crust-hke stroma. It lives parasitic- 
ally on a number of different fleshy 
fungi. For example, Hypomyces 
lactifluorum transforms a species of 
Lactarius into a cinnabarred growth 
roughly resembling a toadstool and 
without gills, while the original color 
of the host is completely lost in the 
higher color produced by the parasite. 
Nectria without stroma has its peri- 
thecia developed on the surface of the 
substratum. N. cinnabarina is a par- 
asite on various deciduous trees (Fig. 
55). Its conidial form known as Tubercularia vulgaris produces flesh- 
colored eruptions through the bark of various host plants. Nectria 
ditissima grows on the beech. Polystigma has a crust-like stroma on 
the leaves of trees of the genus Prunus, while Epichloe typhina con- 
fines its parasitic attack to grasses upon which it develops orange- 
yellow stroma. The genus Cordyceps consists of species which live 




Fig. 56. — Ergot {Claviccps pur- 
purea) on rye head. {After Clinton, 
G. P., Rep. Conn. Agric. Exper. Stat., 
1903-) 



MILDEWS AND RELATED FUNGI 



[6l 




Fig. 57. — A, Balansia claviceps on ear of Paspalum; B-L, Claviceps purpurea; 
B, sclerotium; C, sclerotium with Sphacelia; D, cross-section of sphacelial layer; E, 
sprouting sclerotium; F, head of stroma from sclerotium; G, section of same; H, 
section of perithecium; J, ascus; K, germinating ascosnore: ^. conidiosnores pro- 
duced on mycelium. (See Die nalurlichen Pflanzenfamilien I. i, p. 371.) 



l62 • MYCOLOGY 

parasitically on insects and their larva and some in subterranean fungi. 
The myceHum kills the insect or larva and mummifies it. Out of the 
host grow conidiophores (Isaria) in early stages of development, and 
later stalked stroma, in which on enlarged terminal portions the per- 
ithecia with asci and ascospores are found. C. militaris and C. cinerea 
occur on insects, or insect larvae. C. sinensis is found on caterpillars 
in eastern Asia, while C. ophioglossoides grows on the fruit bodies of 
species of Elaphomyces (see ante, page 70) (Fig. 21). Claviceps is a 
genus of fungous parasites found in the developing caryopses of various 
grasses. Its conidial stage was formerly known as Sphacelia. Claviceps 
purpurea and C. microcarpa are important species and their life his- 
tories will be described in the third part of this book. As ergot, the 
sclerotia of Claviceps purpurea are used in medicine (Figs. 56 and 57). 
Fifty-seven genera and three doubtful ones are recognized and described 
in Engler's Die natiirlichen Pflanzenfamilien. 

Family 2. Dothideace^. — This family comprises twenty-four 
genera among the most important of which is Plowrightia (Fig. 22) 
and Phyllachora. The fruit bodies of these fungi is spheric with definite 
mouth and without distinct peridium, as they are found imbedded in a 
black stroma. Plowrightia includes twenty species of fungi, which 
form stroma in the interior of host plants, and which break through to 
the surface, and form pimples in the center of which the opening to 
the perithecium is found. The spores are egg-shaped, two-celled, 
hyaline, or bright-greenish. Plowrightia ribesia is found on dried 
twigs of species of currants Ribes in Europe and North America. 
P. virgultorum occurs on brick in northern and middle Europe, P. 
Mezerei grows on dead branches of Daphne in middle Europe and Italy. 
P. insculpta is found on dried branches of Clematis vitalba in Bel- 
gium, France, Germany and Italy and P. morbosa is the cause of black- 
knot of the cherry and plum (Prunus) and will be described subsequently. 
Phyllachora is a large genus of some 200 species found mostly on the 
leaves of various plants; P. graminis is the commonest species of cos- 
mopolitan distribution on grasses and sedges. The warty spot of clover 
is Phyllachora trifolii. 

Family 3. Sordariace^. — The perithecia in this family are 
superficial, or deeply sunken in the substratum and often break through 
at maturity. The stroma is usually absent, but when it occurs the 
perithecia are sunken with projecting papilliform beaks. The perithecia 



MILDEWS AND RELATED FUNGI 1 63 

are thin and membranaceous to coriaceous, slightly transparent to 
black and opaque. The asci are usually very delicate, surrounded 
by long paraphyses, or intermingled with them. The dark-colored 
spores are one- to many-celled, surrounded by a hyaline gelatinous 
envelope, or ornamented with hyaline gelatinous spicula. The 
SoRDARiACE^ are entirely saprophytic and grow on manure, hence, 
they are coprophilous fungi. Special mechanical devices are shown by 
the asci for eruptive spore discharge and the distance to which the 
spores are shot may be between 5 and 9 cm.^ 

Family 4. Ch^etomiace^. — This is a small family of two genera, 
ChcBtomium and Bommerella, which are found on waste paper, manure 
and on small living fungi, which resemble the fungi of the family 
PerisporiacecB, if the mouth to the perithecium is wanting. Bom- 
merella has three-cornered ascospores. The perithecia of such forms 
as ChcBtomium spirale and C. crispatum are provided apically with 
masses of spirally wound ha^'rs. 

Family 5. Sph^riace^. — This important family includes parasitic, 
or saprophytic fungi showing exceptional diversity on dead parts. 
They have rounded perithecia with definite opening. The peridium is 
evident, mostly dark-colored, membranous to leathery never fleshy, 
usually free from the substratum, or more or less depressed. A 
stroma may or may not be present. Some authors include a number 
of families which perhaps may be subordinated here and ranked as 
subfamilies. Rosellinia quercina is a disease of oak seedlings. Myco- 
sphcerella fr agarics is the cause of leaf spot of strawberry; M. strati- 
formans produces leaf-splitting blight of sugar cane. Gulgnardia 
Bidwellii is a most important parasite, being responsible for the black 
rot of the grape and G. vaccinii causes cranberry scald. Apple 
scab and pear scab are due to the attack of Venturia pomi and Venturia 
pyrina. A serious disease of sycamore leaves in the spring known as 
anthracnose is caused by Gnomonia veneta. 

Family 6. Valsace^. — The stroma of these fungi is black and is 
formed in the substratum which is more or less altered. The peri- 
thecia have a regular border and take various forms in the different 
genera. The asci are cylindric and long-stalked, alternating with 
paraphyses. Pycnidiospores are formed in pycnidia and conidiospores 

1 Griffiths, David: The North American Sordariace^. Memoirs of the 
Torrey Botanical Club, xi, No. i, May 7, 1901. 



1 64 MYCOLOGY 

on definite conidiospores. Of the ten genera of the family, the 
genera Valsa and Diaporihe are the most important. Both genera 
include about 400 species, which are most saprophytic in wood and the 
bark of woody plants. Valsa oxystoma is the cause of the disease and 
death of the branches of Alnus viridis in alpine regions; Diaporthe 
farinosa grows on the branches of the linden, Tilia americana in North 
America and D. eucalypti on Eucalyptus globulus in California. 

Family 7. Melogrammatace.e. — The stroma are mostly like those 
of the genus Valsa and rarely like those in Diatrype. They are hemis- 
pheric and are formed beneath the bark and later break through to the 
surface, where they are more or less isolated. The perithecia are 
imbedded in the stroma. Conidial fructifications are formed on the 
surface of young stroma, or pycnidiospores are produced in pycnidia. 
The most important genus of this family is Endothia, which is repre- 
sented by the Chestnut-blight fungus E. parasitica, which lives in the 
cambium and inner bark of chestnut trees causing a final girdling of 
the branch and the death of the part beyond the girdled area. It has 
caused untold injury to the forest groves of America, where the chest- 
nut tf-ee abounds, and its morphology and its ravages will be described 
subsequently. 

Family 8. Xylariace^e. — The stroma of these fungi is developed 
strongly and is frequently upright and branched. The perithecia 
are borne in the branched club-shaped portions of the fruit bodies. 
Early in their growth the surface is covered with conidiospores. The 
ascospores are unicellular and blackish-brown. The genus Num- 
mularia, which includes forty species, is represented typically by 
N. Bullardi, which causes black charcoal-like eruptions on thick 
branches of the beech, Fagus. Ustulina, with nine species, includes 
U. vulgaris found on old stems of broad-leaved trees and Hypoxylon 
with about 200 species is confined mostly to damp wood and old 
tree stumps. Xylaria digitata, one of the 200 species of that genus, 
grows on old wood, and X. polymorpha on old tree stumps. This 
family completes the list of pyrenocarpous fungi. 

Suborder F. Discomycetiineae.^ — The discomycetous fungi have a 
filamentous mycelium. Reproduction is by the union of two hyphal 
branches either of similar size, or differentiated into oogonia and anthe- 
ridia. The fertilized egg cell either develops directly into an ascus, 
or it develops ascogenous hyphas from which the asci are formed. 



MILDEWS AND RELATED FUNGI 1 65 

The apogamous formation of fruit also occurs in this suborder. The 
asci are united into definite, usually fiat layers, which are in open 
fruit bodies known as apothecia. Conidiospores are also found in 
some of the forms and the conidiophores are of diverse character. 
The asci are usually eight-spored. The fungi of this suborder are 
either parasitic, or saprophytic in habit, and a few of the fleshy members 
of the family Pezizace^ are edible. 

Family i. Hysteriace^e.^ — The apothecium is elongated and the 
opening is a long wide cleft between the approaching walls of the 
apothecium, so that the ascigeral layer is exposed at the time of the 
spore discharge. 

Some species of the genera Lophodermium and Hypoderma are 
dangerous parasites of leaves; for example, L. pinastri attacks pine 
leaves; L. nervisequum attacks the spruce tree; while Hypoderma 
hrachysporum is found on the white pine, Pinus strobus. Such genera 
as Lophium, Hysterium, and Glonium include species which are sapro- 
phytic on bark and wood. 

Family 2. PHACioiACEiE. — The apothecium is rounded, seldom 
elongated and its walls are separated through a star-shaped opening, 
rarely a cleft-like opening, so that the ascigeral layer is fully open at 
maturity. The family includes such parasites as Nemacyclus niveus 
on coniferous needles; Rhytisma acerinum, which produces black tar- 
like blotches on maple leaves; and R. salicimim, which causes similar 
black areas on willow leaves. Several species of Trochila are found 
on the leaves of different plants. 

Family 3. Pyronemace^. — ^The fruit body is placed on fine 
hyphge or on a felt-like cushion of hyphae. At first it is spheric; later, 
it is flatly expanded. The hypothecium is occasionally feebly de- 
veloped, at other times it is strongly so. The peridium is poorly formed, 
or entirely absent. The most interesting genus is Pyronema. P. 
confliiens has a fruit body i mm. across, and of a yellow or reddish 
color. It is often found in spots where fires have been kindled in the 
woods. The structure of the apothecium and the method of its forma- 
tion following the sexual union of an antheridium and oogonium have 
been described by Harper^ and the essential details have been given 
on a former page of this book {ante^ pages 123 and 126). 

^ Harper, R. A. : Sexual Reproduction in Pyronema confluens and the Mor- 
phology of the Ascocarp. Annals of Botany, 14: 231-400, 1900 



i66 



MYCOLOGY 



Family 4. Ascobolace^. — The apothecia of the fungi of this 
family are unstalked. They are superficial and grow up on manure. 
The peridium is mostly thin, or wanting, and the hypothecium, which 
is well developed, consists of rounded parenchyma-Uke cells. In 
Ascoholus, the ascospores are discharged from the asci by a squirting 




Fig. 58. — A, B, Lachnea ^culellala. A, Habit, B, ascus with paraphysis; C, D, 
Lachnea hemispharica; C, habit; D, ascus with paraphysis; E, Sarcosphara arenosa 
habit; F, G, Sarcosphara coronaria; F, ascus; G, habit; H, Sarcosphcera arenicola 
ascus with paraphysis. {See Die nalurlichen Pjlanzenfamilien I. i, p. i8i.) 



action, and this is accomplished probably by the pressure of the cell 
wall upon the cell sap. The end of the ascus breaks open suddenly, the 
ascus collapses, and the eight spores are discharged simultaneously 
along with the cell sap. In Ascoholus, which is related to Pyronema, 
the ascogonium is at first multicellular, but all the cells empty their 



MILDEWS AND RELATED FUNGI 



167 



contenls into a single large one, from which the ascogenous hyphiB 
then arise. 

Family 5. Pezizace^. — ^The apothecia of this family are saucer- 
or cup-shaped, sessile or stalked, arising from a mycelium which is 
found in the substratum. The peridium and hypothecium consists 
of rounded cells and they are of fleshy, or leathery consistency. The 
asci, which are usually eight-spored, are separated by distinct para- 
physes. The spores are usually hyaline. Lachnea and Peziza are 
the most important genera. Lachnea scutellata (Fig. 58) has a 
scarlet to vermilion-red cup, whose margin is beset with a fringe of 




Fig. 59. — Saucer-shaped fruit-bodies oi Peziza re panda. (Photo by W. H. Walmsley). 

large brown bristles. It grows on wet sticks and logs in damp, or wet 
places, especially at the water's edge. L. hemisphcerica has a cup i to 4 
cm. wide with a bluish-white to gray disk and with brownish outside 
bristles which fringe the margin of the apothecium. It grows on much- 
decayed wood. Peziza aurantia, which is found in the fall in woods, 
and is edible, has a bright orange cup i to 5 cm. wide, powdery outside. 
At first, it is cup-shaped, then saucer-shaped and irregular. It is 
stemless, or nearly so. The spores are clear, elliptic and strongly 
netted. A woodland form, P. coccinea, is scarlet in color and suggests 
a wine glass in its stalked apothecium. P. badia grows on the 
ground in grassland and woodland, and is also edible. It has a 



i68 



MYCOLOGY 



dark brown to paler brown apothecium, i to 4 cm. across and almost 
stemless. P. ceruginosa is a stalked, green form whose mycelium pene- 
trates the wood of beeches and oaks and imparts to them a copper- 
green color, which makes it valuable for the manufacture of the famous 
"Tunbridge ware." The attempt has been made to extract the pig- 
ment, or to manufacture it synthetically for use as a shingle stain, but 
without much success. P. Willkommii produces on larch trees a disease 
known as larch canker. Other species of Peziza grow on bark (Fig. 59), 
horse and cow manure, and are, therefore, typically coprophilous. 
Family 6. HelotiacE/E. — The apothecia in these fungi are super- 
ficial from the beginning and rarely arise by break- 
ing through the substratum. Sometimes they de- 
velop from a sclerotium {Sclerotinia). In texture, 
they are waxy, leathery and thick, and stalked, or 
unstalked, smooth or hairy. The asci are eight- 
spored. The spores are round, elongated, or fila- 
mentous, and one to eight-celled, hyaline. The 
paraphyses are filamentous. The fringe cup, 
Sarcoscypha floccosa, has a slender, white, hairy 
stem, I to 3 cm. long by 2 to 3 mm. wide, and 
bearing an apothecium 4 to 10 mm. wide with a 
scarlet disk, so that the whole fruit body is goblet- 
shaped. The outside of the cup is covered densely 
with long white hairs forming a fringe at the margin. 
The spores are clear and elliptic 20 by 11//. The 
-Scleroiinia fringe-cup fungus grows on decaying twigs from 
spring to autumn. Sclerotinia is the most impor- 
tant genus economically. It includes about forty 
species. The apothecium arises from a sclerotium. Sclerotinia haccarum 
forms sclerotia in the fruits of Vaccinium myrtillus; S. urnula (Fig. 71) 
in those of Vaccinium vitis-idcea. Sclerotinia Fuckeliana forms sclerotia 
on the grape-vine. Its conidial form was long known as Botrytis cinerea. 
Sclerotinia sclerotioriim (Fig. 60) is parasitic and pathogenic on a number 
of cultivated plants, such as beets, and bears its sclerotia forming on the, 
subterranean parts of these host plants. The black disease of hyacinth 
bulbs is connected with the growth of Sclerotinia hulhosum. Apples, 
pears and stone fruits are attacked by S. fructigena. S. libertiana. 
causes lettuce drop. S. trifoUorum is responsible for the stem rot of 




(After 



MILDEWS AND RELATED FUNGI 1 69 

clover. Other fungi without sclerotia are parasitic and destructive. 
Such are Dasyscypha Willkommn, the cause of larch canker. D. 
Warburgiana is parasitic on cinchona in the tropics. Such genera as 
Coryne, Helotium, Lachnum and Rutstroemia are saprophytic on wood. 

Family 7. Mollisiace^. — ^The fungi of this family differ from 
those of the preceding largely in texture, the former being tougher with 
hyphal cells modified in a fibrous manner. The spores are hyaline. 
Pseudopeziza is the only important germs with its apothecium formed 
beneath the epidermis, which is subsequently ruptured with the pro- 
trusion of a shallow fruit body. The asci show eight unicellular spores. 

Pseudopeziza medicaginis is the cause of alfalfa leaf spot. Ps. 
ribis causes anthracnose of currants. 

The remaining famiUes of the suborder are Family 8, Celidiace^, 
Family 9, Patellariace^., Family 10, Cenangiace^. 

Suborder G. Helvelliineae. — This suborder includes fungi with 
a well-developed mycelium which is filamentous and largely functional 
for nutritive purposes. From this mycelium, which penetrates the 
substratum, arises a fleshy, waxy or gelatinous fruit body, which usually 
possesses a stalk upon which is raised an expanded portion; sometimes 
club-like, in other forms constituting a distinct pileus. The expanded 
part, which may be smooth and gelatinous, wrinkled or with variously 
contorted folds, or of deep pits separated from each other by anastomos- 
ing ribs, is covered with the ascigeral layer, which consist of asci and 
paraphyses standing on end-like pahsade tissue. The asci are typically 
eight-spored, rarely, two-spored, and open at the apex through the 
removal of a lid, or through a tube-like mouth. The ascospores are 
unicellular, or multicellular. 

FAivnLY I. Geoglossace^. — The fruit body is fleshy, waxy, or 
gristly, and is separable into a stalk, or stipe, and an enlarged fertile 
portion, the pileus, which is club-shaped or knobbed, and its color is 
some shade of yellow, green, or black. The asci are club-shaped, 
opening by a pore at the apex. This family includes twelve genera, 
and it has been carefully monographed by Massee.^ 

Geoglossum hirsutum is an American ground form with pileus flat 

and black, 2 to 3 cm. long and i to 2 cm. wide. It is wrinkled and 

hairy (Fig. 61). The stem is 6 to 8 cm. tall, black soUd and hairy. 

■'Massee, George: A Monograph of the Geoglosseae. Annals of Botany, ii; 

225-306 with 2 plates, 1897. 



lyo 



MYCOLOGY 



The spores are brown, very long and many-celled, loo to 120 by 4 to 
7/1. G. glutinosum, another American species, grows on the ground 
among the grass. It is black and smooth with the ascigerous portion 
one-third the entire length of the fruit body and in shape oblong- 
lanceolate, slightly viscid. The upper portion passes imperceptibly 
into the stalk. The spores are eight in number, arranged parallel to 
each other with obtuse ends and three-septate, 65 to 75 by 5 to 6m, 
and brown in color. 

Leotia chlorocephala is a fungus found in West Virginia, New Jersey 
and Pennsylvania. It is cespitose 
in habit and grows in mixed woods 
on moist ground, from July until 
late frosts. It is green and has a 
gelatinous appearance. The pileus 
is depressed globose, more or less 
wavy and with an incurved border, 
in color a dark verdigris-green. It 
is ecUble. Another species, L. lubrica, 
is found on the ground in woods from 
North CaroUna and Minnesota to 
Massachusetts. It is yellowish, olive- 
green with an irregular hemispheric, 
inflated, wavy cap. 

Family 2. HELVELLACEiE. — The 
fruit body in these edible .fungi is 
fleshy and divided into a hollow stalk 
and ascigerous expanded portion. 
The upper part is cap-Hke and 
covered externally by the ascigeral 
layer. The asci are club-shaped and open by the lifting off of a distinct 
hd. The spores are ellipsoid, colorless, or bright yellow and smooth. 
Five genera are included in the family: Morchella, Gyromitra, Verpa, 
Cidaris and Helvella. This family includes the largest of the sac fungi. 
Some species of Gyromitra weigh over a pound and forms of Morchella 
may grow a foot tall. The cap of Morchella is more or less deeply ridged , 
crosswise and lengthwise and has a delightful odor. The broad stem 
Morel, Morchella crassipes, has a cap 4 to 10 cm. tall and 3 to 6 cm. 
wide at the base, in color tan to tan-brown, with deep pits and wavy to 




Fig. 61. — Geoglossum liirsiUum. 
A, Appearance of fungus; B, asci with 
paraphyses; C, spore. A, natural 
size; B, 300/1; C, 400/1. {Die naliir- 
lichen Pflanzenfamilien I. i, p. 165.) 



MILDEWS AND RELATED FUNGI 171 

irregular ridges, the whole cap being more or less conic. The stem is 
3 to 12 cm. by 2 to 6 cm., white and hollow. The spores are elliptic, 
clear, smooth, 20 to 22 by 10 to 12/x. M. esculenta, the common 
Morel, has a cap 3 to 7 cm. tall and 2 to 4 cm. wide, of a yellowish- 
brown to brown color, covered with very regular ribs with a blunt 
edge. The spores are smooth, elliptic, clear, 14 to 22^ by 8 to 14/i. 
It grows on the ground in woods and forest openings, and is a delicious 
morsel. 

Gyromitra has a more irregular cap more or less inflated and folded, 
the edge united in places with the stem. G. esculenta has a rounded 
lobed pileus, irregular, gyrose-convolute, smooth and bay-red. Its 
stem is stout, stuffed, or hollow. The ascospores are elliptic, yellow- 
ish, 20 to 22M long. It grows in wet ravines, or springy places in the 
vicinity of pine groves, or pine trees. G. brunnea is brown in color and 
is figured by Clements in his "Minnesota Mushrooms," page 143. 

Verpa digitalijormis grows on ground in woods. It has a brown, or 
dark brown, smooth, bell-shaped cap with a long finger-like stem, 
beneath, hence the specific name. Verpa bohemica is the "ribbed 
verpa" and is delicious eating. 

The cap in the genus Helvetia hangs loosely over the stem and it is 
saddle-shaped more or less lobed. The stem is ribbed. The ascigeral 
layer is confined to the upper side of the cap. All of the species are 
edible. Helvella crispa is a common species and has been collected in 
West Virginia, Pennsylvania and New Jersey. It is white or whitish 
in color, while H. lacunosa is gray to almost black. 

Family 3. Cyttariace^. — This family is represented by the 
single genus Cyttaria with a tuber-like stroma in which the apothecia 
are sunken. The stroma, which arises on the antarctic beech, Notho- 
fagus, in South America and Tasmania, is stalked. The asci are cyhn- 
dric and eight-spored. The spores are ellipsoidal and hyaline. The 
paraphyses are filamentous, breaking down into mucilage. The cylin- 
dric asci bear elliptic hyaline spores. Six species have been described 
from Patagonia, Tasmania and Terra del Fuego. 

Family 4. Rhizinace^. — The fruit bodies of the fungi of this 
small family are stalkless and they are fleshy and waxy in consistency. 
Four genera are included. 

Suborder H. Laboulbeniineae. — We owe our knowledge of these 
eccentric or singular fungi to four botanists: J. Peyritsch, G. Lindau, 



172 MYCOLOGY 

Roland Thaxter and J. Faull. They are parasitic on insects, mostly 
beetles, which live in moist situations and are long-lived and hiber- 
nating. They are often highly specialized, as to the parts of the 
insect on which they grow, occurring only on certain joints of the legs 
and on certain legs of the host. The vegetative mycelium is very much 
reduced, consisting of one to a few cells, which are attached to the body 
of the insect and their usually minute size renders them difficult of 
study. The host is not destroyed nor even inconvenienced by these 
fungi which appear as minute, usually dark-colored, yellowish bristles 
or bushy hairs projecting from the chitinous integument of the insect. 
Stigmatomyces BcbH lives parasitically on house flies. The bicellu- 
lar spore with its mucilaginous coat becomes attached at its lower end. 
The upper cell develops an appendage which bears a number of unicel- 
lular flask-shaped antheridia from which the naked spermatia are shed. 
The lower cell divides into four cells which represent the female repro- 
ductive organ, where the carpogonium, or egg cell develops a trichogyne 
to which the spermatia become attached. The three fundamental parts 
of which these plants are composed are a main body, the receptacle; 
one or more spore-producing portions, the perithecia; and lastly, one or 
more appendages which, in the majority of cases, are associated with 
the formation of the male sexual organs. The receptacle is that por- 
tion of the fungus on which the appendages together with the perithe- 
cia, or their stalk cells, are inserted. The sterile appendages, which 
form dense tufts and sometimes are more conspicuous than the main 
plant itself, serve to protect the delicate trichogyne which is subse- 
quently developed. Sometimes, the primary appendage develops a 
spine-Uke process. The male organs and male elements in the Laboul- 
BENiACE^ may be designated as antheridia and antherozoids, the former 
consisting of a single antheridial cell or a group of such cells, the latter 
of a single naked, or thin- walled cell, so that the antherozoids are pro- 
duced either endogenously or exogenously. Among the antheridia 
which produce endogenous antherozoids we may distinguish the 
simple and the compound. A simple antheridium discharges its 
antherozoids through its special pore or opening, the compound an- 
theridium consists of several antheridial cells each of which dis- 
charges its contents into a common cavity from which they es- 
cape. The female organs are formed from a segment of the lower 
cell of the receptacle rarely from the terminal cell. The perithe- 



MILDEWS AND RELATED FUNGI 1 73 

cium, as in many other Ascomycetales, originates from a cell of the 
receptacle situated below the female organ. The procarp consists of 
three distinct parts: the trichogyne, the trichophoric cell and the part 
lowest the carpogenic cell, which is fertilized and undergoes further 
development. FaulP has shown in two species of Laboulhenia that after 
the procarp is mature the carpogonium and trichophoric cell become 
continuous. Meanwhile, the nucleus of the carpogonium is succeeded 
by two which are apparently daughters of the carpogonial nucleus, and 
almost simultaneously the trichophoric nucleus undergoes division. 
Later, a uninucleate trichophoric cell and a uninucleate inferior sup- 
porting cell are septated off from the now four-nucleated fusion cell. 
After further nuclear divisions a binucleate superior supporting cell and 
sometimes a binucleate inferior supporting cell are cut off. The binu- 
cleate ascogonium now begins to bud off asci, or divides into two asco- 
genic cells, each of which contains a pair of nuclei. Up to this stage no 
nuclear fusions have been observed. The nuclei of an ascogenic cell 
divide conjointly, a daughter of each passing into a young ascus. This 
process is repeated at the birth of every ascus. The pair entering the 
ascus soon fuse. The fusion nucleus divides by a reduction mitosis 
after a period of growth and the number of chromosomes is the same 
as in other mitoses. There are two other mitoses prior to spore forma- 
tion, and both are homotypic. The spores are delimited by the method 
characteristic of the ordinary sac fungi. Each ascus in Stigmatomyces 
BcBfi produces four spindle-shaped bicellular spores. In other genera 
eight two-celled spores are formed. It is to be noted in closing that the 
sexual organs of these curious fungi are similar to those of the red 
seaweeds, Floride^. Thaxter^ has done more than any other botanist 
to make this order known systematically. 

Phylogeny oj Ascomycetales. — Atkinson in a philosophic discussion of 
the phylogeny of the Ascomycetales suggests six series or lines of 
development and his suggestions are incorporated in the accompanying 
chart. 

I. Apocarp line from Dipodascus-\\ke forms and by reduction. 

1 Faull, J. H. : The Cytology of the Laboulbeniales. Annals of Botany, 
XXV : 649-654, July, 191 1. The Cytology of Laboulhenia chsetophora and L. 
gyrinidarum. Annals of Botany, xxvi: 355-358, with 4 plates, April, 191 2. 

- Thaxter, Roland: Contributions toward a Monograph of the Laboulbeniaceae 
part I, 1896; part II, 1908, Mem. Amer. Acad, of Arts and Sci. 



174 MYCOLOCxY 

2. Plectocarp line from Dipodascus-like forms, perhaps similar to 
Monascus. 

3. Perispore line arising from Monascus-Ukc prototype, before split- 
ting of archicarp, or from Aspergillace^. 

4. Pyrenocarp line arising near Monascus-like prototype, Laboul- 
BENiALES side near base, and some of the Mycothyriales as reduced 
from Sph^riales. 

Those who adhere to the behef that the AscomycAtales have 
descended from the red algae interpret their belief in three ways: first, 
sac fungi with highly developed trichogyne of the Collema type with cer- 
tain red algae of existing forms; second, sac fungi with highly developed 
trichogyne of the Polystigma type with hypothetic algae with trichogyne 
representing the common original stock of both groups; and third, sac 
fungi with simple generalized copulating gametes of the Gymnoascus 
type with hypothetic algae having a simple procarp representing the 
stock from which both groups started. It will be noted that Atkinson 
believes that the fungi of the Ascomycetales have been derived from 
the simple Phycomycetes, and that thePROXOASCOMYCETES are der'ved 
by descent and degeneration from such a primitive form as Dipodascus, 
Endomyces Magnusii being the nearest known form to the generalized 
condition seen in Dipodascus. The Euascomycetes are derived from 
fungi similar to Monascus and Gymnoascus with generalized archicarp. 
Six distinct lines as previously noted arise from these primitive forms. 
Atkinson gives a chart which is purely provisional, and which suggests 
the probable relationship of the principal groups to each other and to a 
probable common ancestor. 

GENERAL BIBLIOGRAPHY OF THE ASCOMYCETALES 

Atkinson, Geo. F. : Phylogeny and Relationships in the Ascomycetes. Annals 

of the Missouri Botanical Garden, ii: 315-376, February-April, 1915. 
Barker, B. T. P. : The Morphology and Development of the Ascocarp in Monascus, 

with 2 plates. Annals of Botany, xvii: 167, 1903. 
Blackman, H. H. and Welsford, E. J. : The Development of the Perithecium of 

Polystigma rubrum. Annals of Botany, xxvi: 761, 191 2, with 2 plates. 
Brown, Horace T.: Some Studies in Yeast. Annals of Botany, xxviii: 197, 1914- 
Carruthers; D.: Contributions to the Cytology of Helvella crispa, with 2 plates. 

Annals of Botany, xxv: 243, 191 1. 
Clements, F. E.: Minnesota Plant Studies: iv, Minnesota Mushrooms, 1910: 

138-151- 



MILDEWS AND RELATED FUNGI 1 75 

Conn, H. W. : Bacteria, Yeasts and Moulds in the Home, 1903, with 293 pages. 
DuGGAR, B. M.: Mushroom Growing, 1915, pages 188-224, dealing with European 

Truffles, Terfas and Morels. 
Ellis, J. B. and Everhart, J}. M.: The North American Pyrcnomycetes, 1892, 

pages 793, with 41 plates. 
Engler, a.: Die Natiirlichen Pllanzenfamilien, I. Teil, i Abt. : 142-505 with 

separate parts by Ed. Fischer, G. Lindau and J. Schroeter. 
Faull, J. H.: The Cytology of the Laboulbeniales. Annals of Botany, xxv: 

649-654, July, 191 1. 
Faull, J. H.: The Cytology of Laboulbenia chajtophora and L. Gyrinidarum. 

Annals of Botany, xxvi: 325-355, with 4 plates, April, 191 2. 
Eraser, H. C. I. and Ullsford, E. J.: Further Contributions to the Cytology of 

the Ascomycetes, with 2 plates. Annals of Botany, xxii: 331, 1908. 
Eraser, H. C. I. and Brooks, W. E. St. T.: Further Studies on the Cytology of 

the Ascus. Annals of Botany, xxiii: 537, 1909. 
Eraser, H. C. I. and Gwynne-Vaughan Mrs. D. T.: The Development of the 

Ascocarp in Lachnea Cretea, with 2 plates. Annals of Botany, xxvii: 553, 1913. 
Grant, James: The Chemistry of Bread Making, 191 2: 125-152. 
Griffiths, David: The North American Sordariacese. Memoirs Torrey Botanical 

Club, xi, 1901. 
Jorgensen, Alfred: Microorganisms and Fermentation, transl. 3d Edition 

by Alex. K. Miller and A. E. Lennholm, 1900, with 318 pages. 
Kohl, Dr. F. G.: Die Hefepilze ihre Organisation, Physiologic, Biologic and Sys- 

tematik ihre Bedeutung als Giirungsorganismen, 1908. 
Klocker, Alb.: Fermentation Organisms: A Laboratory Handbook, transl. by 

G. E. Allan and J. H. Millar, 1903, with 391 pages. 
Lafar, Dr. Franz: Technical Mycology, transl. by Charles T. C.Salter. II, Part 

I: 99-189: Part II: 191-481. 
Massee, George: A Revision of the Genus Cordyceps. Annals of Botany, ix: i, 

with 2 plates. 
Massee, George: A Monograph of the Geoglosseae. Annals of Botany, 11: 

225-301, 1897. 
Massee, George: The Structure and Affinities of the British Tuberacese, with i 

plate. Annals of Botany, xxiii: 243, 1909. 
Massee, George: Text-book of Fungi, 1906: 261-313. 
Salmon, E. S. : On Endophytic Adaptation Shown by Erysiphe graminis. Annals 

of Botany, xix: 444. 
Salmon, E. S. : On Oidiopsis taurica, an Endophytic Member of the Erysiphaceae. 

Annals of Botany, xx: 187, 1906. 
Salmon, Ernest S. : A Monograph of the Erysiphaceae. Memoirs Torrey Botan- 
ical Club, ix, 1900, pages 287, with 9 plates. 
Stevtens, F. L.: The Fungi Which Cause Plant Disease, 1913: 113-297, with 

bibliography. 
Thaxter, Roland: Contributions toward a Monograph of the Laboulbeniaceie, 

part I, Mem. Amer. Acad. Arts & Sci., 1896; part II, do., 1908. 



1^5 MYCOLOGY 

Thon, Charles: Cultural Studies of Species of Penicillium. Bull. ii8, U. S. 

Bureau Animal Industry, 1910. 
Wager, Harold: The Nucleus of the Yeast Plant. Annals of Botany, xii: 499- 

540, with 2 plates, 1898. 
Wf.ttstein, Dr. Richard R. von: Handbuch der Systematischen Botanik (2d 

Edition), iqii: 168-192. 



CHAriER XVIII 

BASIDIA-BEARING FUNGI (SMUTS) 

ORDER BASIDIOMYCETALES 

The fungi of this order have mostly a strongly developed mycelium, 
multicellular and at times with apical growth. Sexual reproduction is 
entirely absent, yet in the rusts, we find certain nuclear fusions which 
are looked upon by some mycologists as of a sexual nature. The 
characteristic method of reproduction is non-sexual by means of conidia, 
which in the most primitive forms are of indefinite number, 
while in the most highly differentiated forms the conidiospores are 
definite in number two to eight, and are borne on special conidio- 
phores known as basidia (basidium-ia). In many forms, the basidia 
are arranged in definite parts of fleshy fruit bodies and in special layers 
known as hymenia (hymenium-ia). Besides the conidiospores other 
kinds of spores, known as chlamydospores, are formed. Zoospores are 
entirely absent. The fungi of the order are either saprophytes, or 
parasites, and occasionally, they are facultative saprophytes, or faculta- 
tive parasites. None of them live in the water (nicht wasserbewohnend) . 

The Basidiomycetales do not follow the Ascomycetales in the direct 
line of evolution of the fungi. They may be considered to parallel the 
sac fungi. The group is supposed, in this regard, to represent the results 
of extreme simplification; the sexual organs, if ever present, have in 
the phylogenetic history of these fungi long since disappeared and 
simple nuclear fusions function in all probability in lieu of the sexual 
act. 

Key to Suborders of the Basidiomycetales (After Stevens) 

Chlamydospores at maturity free in a sorus, produced intercalary, 
from the mycelium; basidiospores borne on a promycelium and resem- 
bling conidiospores. i. Hemibasidii. 

Chlamydospores absent, or when present, borne on definite stalks. 

Basidia septate, arising from a resting spore, or borne directly on a 
hymenium. 2. Protobasidii. 

Basidia non-septate, borne on a hymenium. 3. Eubasidii. 
177 



178 MYCOLOGY 

Suborder Hemibasidii. — The conidiophore, or more correctly the 
basidium, arises from the chlamydospore and bears an indetinite 
and usually large number of basidiospores. All cells of the mycelium 
and the spores, as far as known, are unicellular. The position of this 
suborder in the family tree of the fungi is uncertain. The majority 
of the funguses are strictly parasitic on the higher plants, and their 
mycelia live in the tissues of the same, mostly as intercellular parasites, 
certain hyphae known as haustoria penetrating the interior of the host 
cells. Infection of the host takes place, as a rule, very early and in 
some cases at the time of seed formation, so that the parasitic mycelium 
keeps pace with the growth of the host plants and at definite times and 
places, such as anthers, ovaries and the like, which are mostly de- 
formed, the spore-bearing portion of the fungous parasite appears. 
The spores, which are formed in such places, are known as chlamydo- 
spores, and the mass of spores and diseased host parts are mostly 
black and soot-like. The chlamydospores give rise to a promycelium, 
which cuts off basidiospores. The basidiospores give rise either to 
conidiospores, or they infect some host plant, if deposited upon it at 
the susceptible time. Brefeld first suggested the name Hemibasidii for 
the UsTiLAGiNACE^ and Tilletiace^ which he considered as repre- 
senting the link connecting the lower fungi and the true BASIDIO- 
MYCETALES. Two famiUes are recognized by mycologists, viz., 

USTILAGINACE^ and TlLLETIACE^. 

Family i. Ustilaginace^e. — ^The fungi of this family are all para- 
sitic. They can be recognized readily by the outbreaks of dusty 
material that they produce on certain parts of their hosts, when they 
reach their reproductive stage. An important genus, Ustilago, the 
type genus of the family, derives its name from ustio, a burning. The 
smut of wheat is called locally in England "bunt ear," "black ball," 
" dust brand" and " chimney sweeper." All of these names are indica- 
tive of the sooty-black character of the spores. There are two chief 
phases in the development of a smut fungus, the mycehal phase and 
the spore phase. The hyphae of the mycelium mostly push between 
the cells through the intercellular spaces and form short special branches, 
or haustoria, which enter the host cells and absorb from them nutritive 
material. The mycelium may be locahzed, or it may be spread gen- 
erally throughout the host. Where the mycelium gains entrance to 
the host through the germinating seeds, it remains in the vegetative 



BASIDIA-BEARING FUNGI (SMUTS) 1 79 

condition and without external manifestation of infection until in its 
fruiting stage, when it breaks through the tissues of the host, appear- 
ing at the surface. In perennial plants, the mycelium may live in the 
perennial parts, each year extending into the new growth. Eventually, 
the mycelium becomes conspicuous in certain organs of the plant. It 
may develop abnormal growths, or cause swellings in the stem leaves, 
flowers (anthers, ovaries), or fruits of the host. Here the hyphae break 
up into chains of spores, which develop thicker walls than the hyphal 
cells from which they arose and are known as chlamydospores (xXayuus, 
xXctfxvdos = a cloak + (rwopa = a seed). The hyphal cells between the 
spores undergo almost complete gelatinization, which gelatinized cells 
are used probably to nourish the developing spores, as at maturity the 
spores lie loosely surrounded in part by the diseased cells of the host 
ready to be discharged as the adjoining hyphal and host cells dry up 
and completely disappear. The chlamydospores, which make up the 
smutty, or sooty masses, are usually thick-walled and, being small, 
4 to 35^t, they are easily disseminated. They are usually spherical, or 
spheroidal, but may be ovoid, eUipsoidal or even oblong. They are 
simple, i.e., consisting of single cells, but they may be united into spore 
balls, which may have an external coating of sterile cells. The galls 
of the chlamydospores may be smooth, or echinulate, or reticulate with 
a network of ridges, or wings. Their color may be yellowish, reddish 
or olive-brown, violet, or purplish, and the dark-colored spores in mass 
may appear to be black or dark amber-brown. Sori are masses of the 
spores that break out singly, or in clusters, on the various organs of 
the hosts. These clusters are protected by their coverings of the tissue 
of the host. The sori may be dusty and easily broken up, while in 
other species, they may be hard and the spore mass is gradually 
disintegrated. 

The wind is undoubtedly one of the principal agents in the dissemi- 
nation of the smut spores, but it was found that no smut spores could 
be demonstrated in spore traps set up at the University of Manitoba 
by BuUer farther distant from the infected fields than 250 yards. Man 
distributes the spores through unclean agricultural methods, such as 
using old grain bags over and over again, and in sowing seed to which 
the smut spores are attached. The threshing machine is an active 
agent in the spread of smut spores, and the farmer should see that his 
machine is carefully cleaned from one operation to another. 



i8o 



MYCOLOGY 




Fig. 62. — Germination of smut spores, a, Chlamydospores; b, basidium; 5, 
basidiospores; d, infection threads; e^ detached pieces of mycelia; /, knee-joints, i. 
Germination of Ustilago avenae in 1/ 50 per cent, acetic acid 24 to 48 hours after being 
placed in liquid. 2. Same as in i but in distilled water. 3. Germination of Ustil- 
ago levis in Cohn's modified solution at end of 24 hours. 4. Same as 3 but at end of 
2 or 3 days. 5. Germination of Ustilago Iritici in Cohn's modified solution. 6. Ger- 
mination of Ustilago striafortnis from red top in 1/ .50 per cent, acetic acid at end of 
2 days. 7. S'ame as 6 except in Cohn's modified solution. {After Bull. 57, Univ. 
III. Agric. Exper. Stat., March, igoo.) 



BASIDIA-BEARING FUNGI (SMUTS) l8l 

Experiments to determine the vitality of smut spores have shown 
that those of the stinking smut of wheat, covered smut of barley and 
oat smut are long-Hved under favorable conditions for seven, or eight 
years, and in a dry condition are resistant to frost. Where vegetative 
reproduction occurs, as in the loose smuts, the spores lose their vitality 
after five to six months. It has also been determined that stinking 
smut spores passing through the bodies of animals lose their power of 
germination in a great majority of cases. Only those passing through 
pigs retain their vitaHty a longer time. The presence of occasional 
viable spores in the manurial offal of animals suggests a danger of 
the spreading of smut diseases through manure applied to fields as 
fertihzers. 

Germination (Fig. 62). — The spores, when placed in a drop of 
water, send out a single hyaline thread several times the length of 
the spore, and this thread, or promycelium, becomes divided into four 
cells by cross-partitions, or septas. Usually the apex of these four cells 
produce one or more elongated thin-walled spores, the basidiospores, 
or sporidea. These basidiospores are pinched ofif at the base, and 
others are formed to take their place. When the basidiospores reach 
the proper host, whether in the seed, seedling, partly grown or mature 
condition, it forms on germination an infection hypha, which bores 
through the surface and enters the interior of the host. Once inside a 
mycelium is formed. 

Modes of Infection. — (i) Certain smut spores, as those of the 
stinking smut of wheat, covered smut of barley, naked and loose smuts 
of oats and others, adhere to the outside of the grains and are sown 
along with the grain. In the soil germination takes place and the spore 
produces a short stout mycelium, which develops secondary, or even 
tertiary spores, which by means of infection threads attack the young 
grain seedlings as they grow upward through the soil. This mode of 
infection is called seedling infection. (2) In the so-called loose smuts 
of wheat and barley, the chlamydospores, which are mature at the time 
of flowering of these commercial grasses, fall upon the female organs 
of the wheat, or barley, and germinating the infection hypha pushes 
its way into the developing grain where it remains dormant as a deli- 
cate mycelium. The normal development of the grain is not inhibited, 
so that when it is planted as seed, the mycelium begins to grow with 
the seedling and keeps pace with the future growth of its host until 



I 82 MYCOLOGY 

the maturity of the spores at the time the wheat, or barley, come into 
bloom. This mode of infection is known as flower infection. A third 
method is shown by the corn smut which may infect its host at any 
time by entering the young and tender parts of the plant. A knowledge 
of these facts is important, for the treatment of seeds will be efficacious 
with smuts, which infect seeds, while it would be useless with infection 
accomphshed by the second and third methods. 

Grain smuts cause a considerable loss to the farmer every year. 
Oat smut, it has been estimated, causes a loss of $10,000,000 per annum 
in the United States. Smut explosions have been recorded recently. ^ 
In the wheat-growing regions of the Pacific Northwest in the summer of 
1 914, 300 threshing machines were blown up or burned by smut ex- 
plosions. Passing into the cylinder of the threshing machine, the smut 
balls were broken up and the highly combustible smut dust oily and 
dry filled the interior of the separator. It is when this condition ob- 
tains, that the explosions and flames occur. The smut dust was prob- 
ably ignited by static electricity in the cyHnder of the threshing machine. 
The drier the conditions, the more static electricity is formed, and the 
easier it is to ignite the smut. 

The family Usttlaginace^ includes eleven American genera. Only 
three genera out of the seven will be considered in this book. They are 
Ustilago, Sorosporium and Tolyposporiiim. The genus UsHlago, of 
which there are about seventy-two American species, is distinguished 
from the other two less important genera by its single spores which 
form dusty masses at maturity without any kind of inclosing membrane. 
Sorosporium has its spores agglutinated into balls which form more or 
less dusty masses. The spore balls are usually evanescent and the 
spores are very dark. The spores are agglutinated into balls in Toly- 
posporium, forming more or less dusty spore masses. The spore balls 
are rather permanent, the spores adhering by folds, or thickenings of 
the outer coat. 

Family 2. Tilletiace^. — The name Tilletia which is that of an 
important genus (Fig. 63) of the family is derived from Matthieu Tillet, 
who published a book in Bordeaux, France, in 1755. The sori form 
dusty spore masses, which break out to the surface, or are imbedded 
permanently in the plant tissues, often without causing any malforma- 

1 AsHLOCK, J. L.: Smut Explosions. The Country Gentleman, April 10, 1915, 
P- 703- 



BASIDIA-BEARING I'UNGI (SMUTS) 



183 




Fig. 63. — Bunt or stinking smut of wheat (Tilletia Irilici). a. Whole head af- 
fected with smut; h, smutted grains; c, normal grains; d, smutted grain broken to 
show spores; e, normal grain divided in the middle; /, chlamydospores enlarged; g, 
germination of a spore. {Draivings by Pool, Venus A., from Bull. 135, Set. Ser. 141, 
Univ. of Tex., Nov. 15, 1909.) 



184 MYCOLOGY 

tion of these parts. In germination, a promycelium is formed, which 
usually gives rise to a terminal cluster of elongated basidiospores, or 
sporidia, which sometimes bear whorls of secondary basidiospores. 
Sometimes the primary sporidia fuse in pairs, and these with or without 
fusing may give rise to infection hypha?; or in nutrient media to a 
mycehum bearing dissimilar secondary sporidia (aerial conidia). As 
in the preceding family the hyphae break up into chlamydospores which 
break through the host tissue, as a sooty mass of dust. When these 
chlamydospores germinate, they give^ rise to an undivided basidium 
with basidiospores borne at the apex not on the side, as in the preced- 
ing family. This is the principal morphologic difference, as the two 
groups of smut fungi approach each other so closely t^iat in external 
appearance they resemble each other. Brefeld described the structure 
and life history of Tilletia tritici {T. caries), the bunt of wheat very 
carefully. In England, this disease of the wheat plant is called in 
various districts pepper brand, smut balls, bladder brand, stinking 
smut, stinking rust (Fig. 63) In the fields, it is difficult to distinguish 
diseased from sound wheat, as there is little to indicate the presence of 
the hidden parasite, but it excites an abnormal development of chloro- 
phyll, so that the spikes of the affected plants are usually greener than 
the healthy ones. The brand spores are found in all the grains of a single 
ear. The burst grains are shorter and wider than healthy ones and 
pointed toward the base. When cracked, a black dust is discharged, 
which under the microscope is seen to consist of reticulate-walled spores 
of an olive-brown. They germinate readily and even after eight and a 
half years, they have been known to grow. On rubbing the black 
powdery mass between the fingers, the smell of herring brine is given 
off, and this decayed fish odor has originated one of the common 
names, that of stinking smut. A curved unicellular basidium arises 
from the chlamydospore on its germination. This produces a bundle 
of elongated condiospores, or basidiospores, according to one's bias. 
Sickle-shaped secondary conidiospores arise from the primary kind. 
The primary conidiospores may unite by bridge-like connections so 
that two united spores look like the letter H. Wheat becomes infected 
in the seedling state, the spores being sown with the grain, and the 
infection hypha which enters the host forms a mycelium which grows 
along with the host until the spores break out again. 

Tilletia is the most important genus. In it the sori may occur in 



BASIDIA-BEARING FUNGI (sMUTS) 1 85 

various parts of the host, usually in the ovaries, where are formed a 
dusty dark spore mass. The spores are simple, separate and originate 
singly at the ends of special hyphse, which almost disappear through 
gelatinization. The spores varies in size from i6/x to 35/1. Fifteen out 
of the fifty-three species recorded by Saccardo have been found in 
North America. The important species are Tilletia fcetens bunt or 
stinking smut of wheat; Tilletia tritici on wheat; Tilletia horrida 
in the ovaries of cultivated rice; Tilletia anthoxanthi in the ova- 
ries of the sweet vernal grass, Anthoxanthum odoratum; and Tilletia 
Maclagani on a wild grass, Panicum vigatum. Urocystis cepulcB is the 
onion smut; Urocystis occulta on the stems and sheaths of rye; Urocystis 
violcB on the stems, rootstocks, petioles and leaves of violets, Entyloma 
crastophilum levis on such grasses as Agrostis, Poa, E. Ellisii forms pale 
white spots on spinach leaves in New Jersey. Entyloma lineatum grows 
on wild rice, Zizania aquatica; Entyloma thalictri on the meadow rice, 
Thalictrum polygamum; Entyloma lobelice or Lobelia inflata; Entyloma 
nymphcece on the leaves of Nuphar advena and Nymphcea odorata. 

The species of Doassansia mostly grow on plants, such as: S a git- 
tar ia, Potamogeton, etc., growing in moist situations. Ten species 
occur in North America. 



BIBLIOGRAPHY OF THE SMUTS 

Arthur, J. B.: Rapid Method for Removing Smut from Seed Oats. Bull. 103, 
vol. xii, Agric. Exper. Stat. Purdue University, March, 1905. 

Clinton, G. P.: The Smuts of Illinois Agricultural Plants. Bull. 57, Agric. Exper. 
Stat. Urbana, March, 1900. 

Clinton, G. P.: North American Ustilagineas. Journal of Mycology, 8: 128-156, 
October, 1902 

Clinton, George P.: North American Ustilagines, Proceedings Boston Society 
of Natural History, 31: 504, 1904. 

Clinton, George P.: The Ustilaginea?, or Smuts, of Connecticut. Bull. .5, 
State Geological and Natural History Survey, 1905. 

Clinton, George P.: Ustilaginales (Ustilaginaceae, Tilletiaceae). North American 
Flora, 7, part I: 1-82, Oct. 4, 1906. 

DiETEL, P.: Hemibasidii. Die naturhchen Pflanzenfamilien, I. Teil, Abt. i, 
1900: 2-24. 

DuGGAR, B. M.: Fungous Diseases of Plants, 1909: 370-383. 

Eriksson, Jakob: Fungoid Diseases of Agricultural Plants, 191 2: 44-62. 

Garrett, A. O.: The Smuts and Rusts of Utah. Mycologia, II: 265-304, No- 
vember, 1910. 



1 86 MYCOLOGY 

Gusspw, H. T. Smut Diseases of Cultivated Plants. Their Cause and Control, 

Bull. 73, Division of Botany, Central Experimental Farm, Ottawa, Canada, 

March, 1913. 
Henderson, L. F. : Smuts and Rusts of Grains in Idaho. Bull. 11, Agric. Exper. 

Stat., Idaho, 1898. 
Hitchcock, A. S. and Norton, J. B. S.: Corn Smut. Bull. 62, Exper. Stat., 

Kansas State Agricultural College, December, 1896. 
Massee, George: Text-book of Fungi; 1906: 313-325. 
Massee, George and Ivy: Mildews, Rusts and Smuts: a Synopsis of the Families, 

Peronosporaceae Erysiphaceae, Uredinacefe and Ustilaginacea?, 1913: 182-205. 
Smith, Worthington G.: Diseases of Field and Garden Crops, 1884: 245-262. 
Stevens, F. L.: The Fungi Which Cause Plant Disease, 1913: 298-323. 
Swingle, Walter T.: The Grain Smuts: How They Are Caused and How to 

Prevent Them. . U. S. Farmers' Bull. 75, 1898. 
Underwood, L. M.: Moulds, Mildews and Mushrooms, 1899: 81-85. 
VON Tavel, F.: Vergleichende Morphologic der Pilze, 1892: 109-120. 
von Tubeuf, K.: Pflanzenkrankheiten, 1895: 289-340. 
VON Wettstein, Richard R. : Handbuch der Systematischen Botanik, 1911: 193- 

195- 



CHAPTER XIX 
RUST FUNGI 

Suborder Uredine^. — -Usually in systematic works placed as 
ORDER UREDINALES. The fungi belonging to this suborder are 
characterized by basidia which are divided either by transverse or 
longitudinal septae. In this character, they are contrasted with the 
EUBASIDII, which have unseptate basidia. Including the rusts this 
suborder embraces some of the most important disease-producing 
fungi, the study of which concerns the mycologist. 

The uredineous fungi are those which are strictly parasitic and 
which in some cases are so specialized, that their growth is confined to 
the species of a single host. Those fungi in which the different stages 
of the life cycle are passed on the same host are known as autoecious, 
while those which grow on two or more hosts are known as heteroecious. 
The plant on which the final stage is passed is called the final host, 
while the other plant on which some of the stages occur is designated 
the alternate host. So speciahzed is the nutrition of the rust fungi, 
that they never have been grown on culture media off the host 
plants on which they live. Hence, they are obligate parasites. The 
myceUum is septate, much-branched, usually ramifying between or in 
the walls of the cells and sending haustoria into the cell cavities. 
The reproductive spores are borne in more or less definite clusters, or 
sori, below the surface of the host, or rarely singly, and the spores are 
set free by the breaking open of the overlying tissues of the hosts. 

Five different kinds of spores may be found in the uredineous fungi, 
but they are not all present in every genus (Fig. 64). The final spore 
form is known as the teliospore, or teleutospore, which determines the 
name which is to be appHed to the parasite. Such spores are borne 
in a sorus known as a teUum. When these teliospores germinate, they 
produce a four-celled promycelium known as a basidium, and this 
abstricts sporidia, or more properly basidiospores, which are minute, 
thin-walled spores without surface sculpturings. These are succeeded 
by spermogonia (spermogonium), which are now called by most 

187 



I 88 MYCOLOGY 

American mycologists, pycnia (pyciiium), in which spermatia, or 
pycniospores, are formed. Pycnia indicate the nature of the life cycle 
and furnish positive characters for identification. Arthur has shown 
that if pycnia and urediniospores are found arising from the same 
mycelium, aecidia do not occur in the cycle; and if pycnia and telio- 
spores are found there are neither uredinia nor secia in the life cycles. 
These pycnospores are accompanied or succeeded by aeciospores 
(aecidiospores), which appear in the cluster cups, or aecia in long chains. 
The peridia of the different kinds of aecia are variable, and hence 




Fig. 64. — Spore forms of wheat rust, Pucainia graminis. A, Section through 
barberry leaf showing pycnia on upper surface and secia on lower; B, two uredinio- 
spores; C, germinating urediniospore ; D, teliosorus showing several teliospores; E, 
single two-celledjteliospore ; F, germinating teliospore with four-celled basidium and 
two basidiospores; G, basidiospore growing on barberry leaf. {Adapted from deBary.) 

mycologists have described four different kinds of form genera: Cceoma 
= peridium absent; Mcidiiim = cup-shaped and peridium toothed; 
Roestelia = peridium elongate and fimbriate; Peridermium = peri- 
dium irregularly split and broken. Urediniospores (uredospores) 
succeed the aeciospores and they appear in sori known as uredinia 
Curedinium). Amphispores are special forms of urediniospores formed 
in arid, or semi-arid climates and usually have a thick cell wall and a 
persistent pedicel. They are in the nature of a resting spore. Meso- 
spores are exactly of the same nature as the two-celled teliospores, but 
they arise merely by the omission of the last nuclear division, and hence. 



O I II III an Eu-form 



RUST FUNGI 189 

have only one cell. These different kinds of spores, representing stages 
in the life histories of the different genera and species of rusts are 
designated, as follows: O = pycnium; I = aecium; II = uredinium; 
III = telium. The determination of the presence or absence of these 
spores in the various life histories has been made for a large number of 
rusts, and we are now in a position to tabulate the results of this study 
and to give names to the different forms of rust life cycles which have 
been found. We call a fungus possessing: 

Auteu-form, if all four kinds are found on one plant 

(Ex. Puccina Asparagi on Asparagus officinalis). 
Hetereu-form, if O, I occur on one species and II, III 

} on another (Ex. Puccinia gramiitis is on wheat and 

I barberry). 
O I III an opsis-form (Ex. Gymnos porangimn Jutiiperi-virginiance, O, I on 

apple, and III on red cedar). 
O II III a Brachy-form (Ex. Puccinia suaveolens on Canada thistle). 
[O] III a Micro-form pycnia (spermogones) sometimes absent (Ex. Puc- 

cinia ribis on currant). 
A Lepto-form is one, of whatever kind, in which the teliospores 
grow as soon as mature without any period of rest, as Puccinia malva- 
cearuni on hollyhock. W. B. Grove in his "British Rust Fungi," 
page 40, gives a diagram which represents all of the possible life cycles 
of the different forms of rust fungi. It is reproduced here (Fig. 65). 
As a fungus which shows a complete life history passed on two dis- 
tinct host plants, we will take the black rust of cereals, Puccinia 
graminis (Fig. 64), first carefully studied by the German botanist, 
Anton de Bary, in 1864-65. It infests all the common cereals, wheat, 
rye, barley and oats, also many grasses. It appears on the wheat 
plant, when the host is about ready to produce its spikes of flowers. It 
appears on the leaves and culms of the wheat plant, as orange-red 
lines, which represent cracks in the epidermis of the host exposing the 
sori, or uredinia filled with rust-red spores, urediniospores. These 
summer spores are yellowish and their surface spinulose with four equa- 
torial germ pores. These urediniospores may follow each other on 
several crops during the early summer. This summer stage is succeeded 
by the autumn stage in which the sori become filled with stalked, 
' two-celled, dark-colored spores with thick walls. The common name 
of this stage is "black rust." Wintering in the open these two-celled 
teliospores germinate. Each of the two cells may sprout out a pro- 
mycelium, or only one may do so. This basidium (promycelium) is 



I go 



MYCOLOGY 



upright and divided transversely into four cells, each of which cuts off 
a basidiospore. These basidiospores are blown to the leaves, twigs, or 
fruits of the barberry where a mycelium is formed. Later pycnia 
(spermogonia) appear on the upper side of its leaf. These are accom- 
panied by round, fringed depressions, the cluster cups or ascia, which 
appear in the spring on the lower side of the leaves. The agciospores 
are arranged in chains. These spring spores, aeciospores, are carried to 
the wheat plant where they induce the characteristic rusted appearance 



basidium 



teleutospore 



basidiospore 




uredospore 

mycelium 
secidiospore 

fusion-cell 

Fig. 65. — Relations of various spore forms of rusts to each other. {After Grove, W. 
B., The British Rust Fungi, 19 13, 40.) 



of the cereal. The wheat plant is not killed by the attack of the fungus 
which, however, prevents the reserve foods from being properly stored 
in the grains; hence, they are mushy and unfit for storage, or for bread- 
making purposes. It has been recently shown that in Australia and the 
plains of India, where the barberry is unknown, the black rust of wheat 
does serious damage. Three methods are open to the wheat rust to 
winter over: (i) The fungus may winter by its urediniospores, (2) by a 
perennial mycelium, (3) by Eriksson's mycoplasm. Arthur, in Amer- 
ica, and others have shown that it winters by its urediniospores, or 



RUST FUNGI 191 

amphispores, as they have been termed by some, but in conversation 
with Arthur he insisted that the perennating spores are typical uredinio- 
spores, so that the postulation of a perennial mycelium, or a hibernating 
fungous protoplasm in the cells of the grain (mycoplasm) is unneces- 
sary. Eriksson has proved that in Sweden six forms of Puccinia 
graminis may be distinguished; which he enumerates as follows: 

A. Not distinctly fixed (occasionally going over to other forms of 
grass): (i) f. sp. tritici on wheat (seldom on rye, barley and oats). 

B. Distinctly fixed (firmly confined to the indicated species): (2) 
f. sp. secalis on rye, barley and on couchgrass, Agropyron repens, Ely- 
mus arenarius, Bromus secaUnus and others; (3) f. sp. avenae on oats 
arid on Avena elatior, Dactylis glomerata^ Alopecurus pratensis, Milium 
efusuni and others; (4) f. sp. poae on Poa compressa and P. pratensis; 
(5) f. sp. airae on Aira ccespitosa and ^4. hottnica; (6) f. sp. agrostis on 
Agrostis canena and A. stolomfera. An oat plant infected with this rust 
can in its turn infect wheat, rye, barley and so forth. The black rust 
of cereals is the classic example of an heteroecious rust. 

The asparagus rust, Puccinia asparagi, may be used to illustrate the 
life history of an autoecious species. All the spore forms are pro- 
duced on stems and twigs. The aecia appear in long, light green cush- 
ion-like areas, which are short cylindric with a white peridium. The 
aeciospores are orange-colored and the wall is hyaline. The pycnia 
appear in yellow clusters followed by the aeciospores in early sum- 
mer. The uredinium is filled with yellowish-brown, thick-walled uredi- 
niospores w'ith three or four germ pores. The black rust stage (telium) 
appears later in the season, when the two-celled stalked teliospores push 
out from beneath. The whole life cycle is passed on the asparagus 
plant. 

Cytology of the Rusts. — According to the earlier researches of 
V. H. Blackman (1904), A. H. Christman (1905), O. H. Blackman and 
Miss H. C. Fraser (1906), Edgar W. Olive (i9o8),Kurssanow (1910) and 
Dittschlag (191 6), supplemented by the research of other botanists, a 
flood of light has been thrown on the nuclear behavior in the rusts, and 
accordingly on their sexuality, or non-sexuality. Blackman discovered 
in Phragniidium violaceum (Fig. 66), that in the formation of the 
aecidium, there was a fusion of two cells by which the nucleus of one 
passed over into the adjoining cell. In the formation of spores the 
paired nuclei of the fusion cell divide side by side and simultaneously 
(conjugate division) so that we find that the basal cell, the aecio- 



192 



MYCOLOGY 



pores and intercalary cells all have two nuclei, which are not sister 
nuclei. The upper cell, cut off from the fusion cell, is the secio- 
spore mother cell; the lower grows a little longer and then divides again 
in the same way, and thus a vertical series of aeciospore mother cells is 
formed, the oldest at the top. Each of the aeciospore mother cells. 




Fig. 66. — A, Chain of young jeciospores of Puccinia caricis; a, fusion tissue; 
b, basal (fusion) cell with conjugate nuclei; c, asciospore mother-cell; d, intercalary 
cell; e, young aeciospore; B, germinating teciospore of P. caricis; C, teliospore of P. 
caricis; D, formation of teliospores of P. falcaria {after Dittschlag); E, development 
of aecium {after Blackman) of Phragmidium violaceum; e, epidermal cell; s, sterile 
cell; below these cells a nucleus is seen migrating into the adjacent cell /; F and G, 
conjugation of two female cells to form basal cell of aeciospore chain {after Ditlschlog). 
In G the first conjugate division is just completed. {Adapted frotn Grove, British 
Rust Fungi.) 

as soon as it is formed, cuts off by conjugate division a small cell below, 
called the intercalary cell; this sooA disorganizes and disappears, while 
the other portion remains as the aeciospore. The succeeding uredinio- 
spores have two nuclei in the conjugate condition and this is continued 
over into the cells of the young teliospores (Figs. 67 and 68). Before 



RUST FUNGI 193 

the teliospore reaches maturity, the nuclei fuse, and the uninucleate 
condition then continues again until the formation of the gecia. In the 
micro- and lepto-iorms, which have no aecium or uredinium, we find that 
the association takes place at points in the ordinary mycelium, but 




Fig. 67. — Portion of a section of cedar apple about 5 mm. below a teliosorus. 
Note (i) Binucleate intercellular mycelium; (2) the haustoria in various stages of 
development; (3) the doubling of nucleoli in the nuclei of some of the parenchyma 
cells of the host. Material collected on March 31. {After Reed, H. S., and Crabill, 
C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 1915.) 

always before the formation of the teliospores. Whether the 
association of nuclei in the ordinary mycelium takes place by the 
migration of a nucleus from one cell to another, or whether two daughter 
nuclei become conjugate in one cell has not been settled definitely. 
The pycnospores are probably abortive male cells. They have never 
13 



194 



MYCOLOGY 




Fig. 68. — Portion of a teliosorus of cedar apple in February showing mycelia 
stroma and the binucleate condition of the cells of young teliospores. (After Reed, 
H. S., and Crahill, C. H., Techn. Bull, g, Va. Agric. Exper. Stat., May, IQ15.) 



teleutospore 



basidiospores 



uredospoTe. 




SPOEOPHYTE 

(2?i generation) 



uredospore 



aecidiospore 
intercalary cell 



GAMETOPHYTE 

(n generation) 




spermatium 

$ gamete 



gametes 



fusion-cell 



Fig. 69. — Diagram of the alternation of generations of a typical rust. {After Grove, 
W. B., The British Rust Fungi, 1913, 27.) 



RUST FUNGI 



195 



been known to germinate, and the large size of their nuclei suggests that 
we arc dealing with male cells. 

The mature tcliospore, which may be looked upon as a spore 
mother cell, has a single fusion nucleus. "The fusion nucleus is large, 
round and (when unstained) perfectly clear and homogeneous, but for 
its nucleolus, so that it looks like a vacuole; it occupies almost invari- 
ably the middle of a cell. The dense chromatin mass is loosened out 
into a kind of spireme which becomes shorter and thicker; the nuclear 
membrane then disappears, and the spireme thread splits longitudi- 
nally, though the splitting is often indistinct. It then divides trans- 
versely into segments which become arranged, or strung out, on a 
spindle (sometimes, but more rarely, in an equatorial plate) ; then the 
daughter nuclei are formed at the poles, and the next division, which 
is homotypic, follows immediately" (Harper and Holden, 1903; 
Blackman, 1904). These nuclei are found in each of the four cells 
which form the basidium, and ultimately, they pass into each of the 
four basidiospores which are uninucleate and haploid. 

The alternation of generations which has thus been determined by 
the various cytologic studies of recent years may be displayed in a 
diagram adapted from Grove (Fig. 69). 

The same life cycle may be represented in another way. 

Basidiospore 



Gametophyte 
(w generation) 



Sporophyte 
(2« generation) 



Mycelium 



Pycnium 



Female cells Pycnospores 



Fusion cell 

II 
.^ciospore mother cell 

. ^ \ 

iEciospore Intercalary eel 

Urediniospore (repeated) 

Teliospore 



Jicium 



0000 
4 Basidiospores 



196 MYCOLOGY 

EndophyUum sempervivi which attacks the house leek, Semper- 
vivum, and causes its rosette of normally spreading leaves to stand 
erect, shows a somewhat different condition, which has led to the sup- 
position that it represents the primitive life cycle of the higher ure- 
dineous fungi. Its life history has been investigatecl by Hoffman 
(191 1). The spores mature on the house-leek leaves in April and 
May. They germinate at once in the secidioid telium and a four- 
celled basidium is formed; hence, the spore looks like an seciospore 
and partakes of the nature of a teliospore and may be called an secio- 
teliospore. Each basidium produces four basidiospores on long sterig- 
mata, and they are blown to the leaf of a house leek, where they 
begin growth at once by boring through the cuticle, and the mycelium 
then grows through the intercellular spaces of the host sending haus- 
toria into the cells, growing down to the base of the leaf and into the 
axis up to the growing point, where it perennates until the following 
spring, when it enters the freshly formed leaves, which become yellow, 
longer and more erect. 

Pycnia are formed in March and April followed by aecio-telia, 
which repeat the cycle. Hoffman has established the most interest- 
ing point about this rust, that the aecio-teliospore chain arises from a 
cell produced by the fusion of two adjacent cells of the spore bed 
after the manner described by Christman except the conjugating cells 
were not in any definite plane. The binucleate secio-teliospores then 
become uninucleate by the fusion of the conjugate nuclei. The for- 
mation of the basidiospores from these oecio-teliospores probably 
follows a reduction division. 

Kunkel (191 4) has shown that a study of the binucleate seciospores 
of CcBoma nitens during germination shows that they become uninu- 
cleate previous to the production of the promycelia. The normal ger- 
mination of the aecio-teliospore consists in the pushing out of a germ tube 
into which the protoplasmic contents of the spore passes. The nucleus 
which travels out into the tube divides producing two nuclei which may 
divide again immediately and cell division may follow at once, but in 
other cases the four nuclei of the promycelium (basidium) may be 
present before cross walls are formed. Ultimately, four cells are found 
filled with protoplasm and uninucleate. The basidiospore arises as an 
enlargement of the sterigma and the nucleus enters when it is one-half 
developed. Cceoma nitens although like EndophyUum sempervivi in 
some respects is more primitive, since it possesses a simpler aecium. 



RUST FUNGI 197 

Phylogeny of the Uredine^ (Uredinales) 

In looking for the primitive types of rust fungi, it has been assumed 
by some mycologists, that, as the rusts are a specialized group of para- 
sites, the most primitive forms will be found on hosts which are lowest 
in the phylogenetic scale of the higher plants. This consideration 
would place Uredinopsis, which grows upon ferns, as one of the primi- 
tive rusts, while many of the more advanced types of Puccinia are found 
upon the Composite. The absence of a germ pore is considered primi- 
tive, as instance its absence in the aecio-teliospore of EndophyUum. 
When these first appeared, they were numerous and indefinitely scat- 
tered, while in the higher rusts, they are reduced in number and 
restricted to a definite part of the cell wall. The formation and ger- 
mination of teliospores approaches that of the smuts a more primitive 
group, hence the formation of a basidium and basidiospores must 
have been inherited by both from their ancestors. Now among the 
red algge, such as Grifjithsia, the sporophyte bears tetraspores, these 
develop into a thallus which bears the gametes. Hence one would look 
for the ancestors of the UREDINE^ among red algge. Again, it has 
been suggested that the female cells of the ascium have a trichogyne, 
such as the red seaweeds (Florideae) possess. In the rusts, it has become 
abortive. 

The Endophyllace^ are considered by Grove to constitute the 
starting point from which the varied forms of the Pucciniace^ have 
been derived. In EndophyUum, we have seen that the seciospore, which 
is the product of the fusion cell, is also the teliospore from which the 
basidium and basidiospores arise. The aecium is accompanied by the 
pycnium here. The first stage of evolution was the separation of this 
spore form into two: one the geciospores, germinating like conidio- 
spores; the other, the teliospore, germinating with the formation of a 
basidium and basidiospores. Pucciniopsis suggests these stages. The 
summer spores are probably modified geciospores formed as a device 
for repeating the spore generations without the intervention of another 
fusion cell. The fusion of the two nuclei in the teliospore is from a 
cytologic standpoint paralleled by a similar fusion in the BASIDIO- 
MYCETALES, for a division into four basidiospores follows in both 
cases, although the mechanism is different. The paired condition 
of the nuclei found in the ascogenous hyphae of the ASCOMYCETALES, 
such SLsPyronema confluens investigated by Claussen (1912), and in the 



198 MYCOLOGY • 

formation of the ascus, the two nOn-sister nuclei fuse after which the 
fusion nucleus divides, the first division being heterotypic (meiotic, 
reducing, possessing synapsis and diakinesis stages), and the two fol- 
lowing ones, which result in the formation of eight ascospores, are 
homotypic. From this point of^view, the ascus is a spore mother cell 
comparable to the teliospore of the rust fungi, but forming an octad, 
not a tetrad of spores. The probable phylogeny and relationship of 
the Uredine^ to the other groups has been set forth in a family tree 
by Grove. 

Arthur, who has studied the rusts carefully for many years, pro- 
posed at the International Congress of Botanists held in Vienna in 
1905 an arrangement of the famihes, genera and species of the rusts, 
which differs materially from the older classifications. 

As this classification of Arthurs has not been elaborated in detail, 
it has been considered best to follow the arrangement of families, sub- 
families and genera given in Engl er and Gilg's "Syllabus der Pflanzen- 
familien" (7th Edition, 191 2) as following the conservative and 
older treatment. 

Family Endophyllace^. — The teliospores are abstricted suc- 
cessively in long rows and are surrounded by a peridium which is 
formed like that of a typic aecidium of Puccinia from the peripheral 
cell rows, but is sometimes less strongly developed. These teliospores 
are perhaps more correctly called aecio-teliospores, as they are separated 
from each other by intercalary cells like true seciospores and arise 
from a fusion cell, but they germinate by the formation of a basidium 
and basidiospores like true teliospores. The germ pores are impercep- 
tible and the spore wall is colored. Pycnia are present and both kinds ■ 
of sori are subepidermal. 

Endophyllum sempervivi lives parasitically on the house leek, Sem- 
pervivum tedoruni, and several other species of Sempervivum in Europe 
from April to August. It has been proved by de Bary, Hoffmann and 
others, that the basidiospores produced by the secio-teliospores infect 
the leaves of the house leek and from them arises a mycehum which 
lives over the winter in the stem. The following spring, it forms 
pycnia and secio-teliospores and the affected leaves are more erect 
than normal ones, twice as long, narrower and yellowish at the base. 

Family MelampsoracetE.— The tehospores are unstalked, one- to 
four-celled, but placed singly on dilated hyphie in the tissues of the 



RUST FUNGI 199 

host, or arranged side by side in flat crusts. Germination of the teHo- 
spore results in the formation of a four-celled basidium, each cell of 
which forms a single basidiospore. The secium is typically without a 
peridium, hence, a cseoma and the urediniospores appear in long chains 
without a peridium, or arising singly, and then mostly surrounded 
by the peridium, or mixed with paraphyses. 

The genus Melampsoropsis includes fungi whose teliospores are in 
cushion-like layers, which break through the epidermis of the host. 
M. ledi has its teliospores on Ledum and its aecia on the spruce, Picea 
excelsa, in Europe, and on P. rubra in this country. The secia of Cronar- 
tium have a broad, inflated irregularly torn peridium. The uredinium 
is enclosed in a hemispheric peridium, which opens at the summit by a 
narrow pore. Its teliospores are abstricted in long chains and remain 
united into cylindric columns, which are horny when dry. The 
European C. asclepiadeum has its gecia on the branches of Plnus sihestris 
in May and June, and its urediniospores and teliospores on PcBonia 
officinalis in gardens, as also on Vincetoxicum, Cynanchum and Verbena. 
C. quercmim has its aecia on Pin us and its urediniospores and teliospores 
on at least twenty species of oak in North America. C. ribicola is a 
dangerous parasite called the white pine blister rust and against it the 
United States Government has an active quarantine. Its aecium is con- 
fined to the five-leaved pines, one of which is Pinus strobus, our eastern 
white pine. These are found in the months from March to June. The 
urediniospores and teliospores grow on the currants, Ribes nigrum and 
R. rubrum. The fungi of the genus Melampsora are mostly heteroecious. 
There are seven species recorded for North America. Of these Melam- 
psora meduscB causes the poplar rust. The aecium occurs on the larch, 
Larix, and its urediniospores and teliospores on Populus deltoides, P. 
tremuloides and P. balsamifera. Calypfospora is a genus of rusts, the 
life history of which has been investigated by Hartig, Kuhn and 
Bubak. In July to September, the teliospores appear on the stems of 
Vaccinium vitis-idcBa, where the stem becomes swollen and elongated 
and at first of a pink color passing to brown. It occurs on other species 
of Vaccinium, including V. pennsylvanicum in the United States. The 
aecia are found in Europe on leaves of Abies pectinata and in America 
on A . balsamea. 

Family Coleosporiace^. — The aecium in this family has a perid- 
ium. The flattish, linear pycnia are subepidermal dehiscing by a 



MYCOLOGY 



slit. The teliospores consist of four superimposed cells. There is a 
North American species of this family, Gallowaya pini (formerly Coleo- 
sporium pini), which has teUospores only and these on the leaves of 
Pinus inops, i.e., on trees of the same order on which Coles porimn has 




A 

Fig. 70. — A-D, Uromyces pisi. A, Ascidia on deformed leaves of Euphorbia 
cyparissias; B, ascidia enlarged; C, teliosori on leaves of Pisum sativum; teliosori 
enlarged; E and F, Uromyces Irifolii on Trifolium hybridum. {After Dietel, Die 
natiirlichen Pflanzenfamilien I. lA**, p. 55.) 

its aecia. In Coleosporium, the teUospores are adherent closely with a 
rounded, thickened, gelatinizing pore. The long sterigmata bear 
large, ovate, flattened sporidia. The orange rust of asters and golden 
rods,^'C. solidaginis is reported to cause a sickness of horses, some- 



RUST FUNGI 20I 

times resulting in the death of the animals. Its urediniospores and 
teliospores are on compositous plants and its aecial stage on the pitch 
pine, Pinus rigida, this stage being known in the older books as 
Peridermium acicolum. The species of the genus are all heteroecious, 
and ascial stages, whenever found, occur on species of Pinus and 
are referable to the form genus Peridermium. Arthur and Kern 
enumerate twenty-seven species of Peridermium, ranging from Mexico 
to Alaska, and from the Atlantic to the Pacific coasts. The species 
are all secia of species belonging to tehal genera, but they cannot 
be always satisfactorily assigned because of incomplete knowledge 
regarding them. The genus Peridermium embraces all aecial forms 
possessing peridia, inhabiting the Pinace^ and Gnetace^. Only 
three of the twenty-seven American species have been associated with 
telial forms as follows: 

Peridermium pini connected with Coleosporium campanulcc on 
Campanula. 

Peridermium cerebrum connected with Cronartium on oak. 

Peridermium elatinum connected with Melampsorella cerastii. 

Family Pucciniace^. — In this family, the teliospores usually con- 
sist of a single cell, or a vertical row of superimposed cells sometimes 
united into a small bead-like cluster. The teliospores are borne on a 
simple, or a compound pedicel. The urediniospores are single, on 
hyaline, deciduous stalks. The secia usually have a peridium. The 
most important genera of the family are: Uromyces, Puccinia, Gymno- 
sporangium, Gymnoconia (Fig. 71) and Phragmidium. 

The rusts belonging to the genus Uromyces have one-celled winter, 
or teliospores, which are egg-shaped, individually separated and massed 
in small, open spore groups. The important pathologic species are the 
clover rust, Uromyces trifolii; the rust of beans, U . appendiculata; beet 
rust, U. betcB; carnation rust, U. caryophyllinus (Fig. 70). The largest 
genus of the rusts, Puccinia, has usually two-celled teliospores, although 
unicellular ones may occur in some species. The principal cereal or 
grain rusts may be enumerated first, as they are fairly well known, 
owing to the researches of Eriksson and others: 

Black Rust of Cereals, Puccinia graminis (Fig. 64) with its aecium 
on the barberry, Berberis vulgaris. Six forms of this species may be 
distinguished: (i) f. sp. h-itici on wheat (seldom on rye, barley 
and oats); (2) f. sp. secalis on rye, barley and couch grass, Agropyron 



202 MYCOLO&Y 

repens, Elymns arenarius, Bromus secalimis and others; (3) f. sp. 
avencB on oats and Avena elqtior, Dactylis glomerata, Alopecurus praten- 
sis, Milium efusum, etc.; (4) f. sp. po(B on Foa compressa and P. praten- 
sis; (5) f. sp. airce on Aira ccBspitosa and A. hottnica; (6) f. sp. agrostis on 
Agrostis canina and A. stolonijera. 

Brown Rust of Rye, Puccinia dispersa, with its cluster cups on 
Anchusa arvensis and A. officinalis. 

Crown Rust of Oats, Puccinia coronifera, with its secium on the 
buckthorn, Rhamnus cathartica. Of this species there are eight 




Fig. 7 1 . — A-C, Gymnoconia interstitialis. A , ^cidia on leaf of Rubus canadensis; 
B, piece of leaf enlarged; C, teliospore; D, teliospore oi Sphenospora pallida, 500/ i. 
{After Dieiel: Die naturlichen Pflanzenfamilien I. lA**, p. 70.) 



speciahzed forms, as follows: (i) f. sp. avencB on oats; (2) f. sp. alope- 
curi on Alopecurus pratensis; (3) f. sp. festuccd on Festucas; (4) f. sp. 
lolii on rye grass, Lolium perenne; (5) f. sp. glycericB on Glyceria aqua- 
tica; (6) f. sp. agropyri on Agropyron repens; (7) f. sp. epigm on Cala- 
magrostis epigeios; (8) f. sp. hold on Holcus lanatus. 

Crown Rust of Grasses, Puccinia coronata, with its aecium on Rham- 
nus frangula. Three special forms of this rust are known: (i) f. sp. 
calamagrostis on Calamagrostis ariindinacea; (2) f. sp. phalaridis on 

1 Arthur, J. C. and Kern, F. D.: North American Species of Peridermium, 
Bull. Torr. Bot. Club, 33: 403-43''^i iyo6. 



RUST FUNGI 



203 



Phalaris armidinacca; (3) f. sp. agrostis on Agrostis vulgaris and A, 
sfolonifera. 

Yellow Rust of Wheat, Puccinia glumarum, without any known 
aecial stage. It has according to Eriksson the following specialized 
forms: (i) f. sp. tritici on wheat; (2) f. sp. secalis on rye; (3) f. sp. 
hordei on barley; (4) f. sp. Elymi on elymus arenarius; (5) f. sp. 
agropyri on couch grass, Agropyron repens. 




Fig. 72. — Hollyhock rust, Puccinia tnalvacearum. {Nantucket, August 19, igis.)' 



Brown Rust of Wheat, Puccinia triticina, with aecia unknown. 

Dwarf Rust of Barley, Puccinia simplex. 

Timothy Rust, Puccinia phlei-pratensis. Experiments to get this 
form to infect barberry leaves have met with indifferent success. 

Chrysanthemum Rust, Puccinia chrysanthemi, on leaves of Chry- 
santhemum sinensc in greenhouses all the year round. 



204 MYCOLOGY 

Dandelion Rust, Puccinia iaraxaci, on the dandelion Taraxacum 
officinale, rather common in Europe, North America, Japan and the 
East Indies. 

Reed Grass Rust, Puccinia phragmitis, with aecia on Rumex crispus, 
R. ohtusif alius and urediniospores and teliospores on reed grass Phrag- 
mites communis. 




Fig. 73. — Roeslelia aurantiaca on fruit oi Amelanchier intermedia corresponding 
to Gymtiosporangium clavipes on red cedar. (Shelter Island, New York, July 16, 
•1915-) 



Ash Rust, Puccinia fraxinata, on leaves and petioles of ash and 
uredinospores and teliospores on salt grass, Spartina Michauxiana. 

Asparagus Rust, Puccinia asparagi, develops all of its spore forms 
on the cultivated asparagus. 

Violet Rust, Puccinia violce, is parasitic on about forty-six different 



RUST FUNGI 



205 



species of violetsjn\\sia/ Europej'^North^and South America. It 
autoecious. 





m 

—.J 

il 




H|^ 


I'i 




1 








Fig. 74. — Witches' broom caused by Gymno- Fig. 75. — A, Protruding fili- 

sporangium Ellisii. {After Harshberger, Proc. form horns of the rust fungus, 
Acad. Nat. Sci. Phila., May, 1902.) Gymonsporangiiim Ellisii on white 

cedar; B, teliospore. (May 27, 
1916.) 

Mint Rust, Puccinia menthcB, is also an autoecious rust. 
Maize Rust, Puccinia sorghi, is widely distributed in maize-growing 
countries. Its secia are less common on various species of O.xalis. 



2o6 



MYCOLOGY 



Rust of Stone Fruits, Puccinia pruni-spinQsa:, occurs on various 
species of the genus Prunus in the southern and central United States. 




Fig. 76.- — Fully expanded cedar apple on red cedar. Long yellow teliosori as 
finger-like projections are seen. (After Jones and Barlholomew, Bull. 257, Agric. 
Exper. Stat., Univ. Wise, July, 1915.) 



The secial stage occurs on Anemone and Hepatica, and is known as 
jEcidium punctatum. 

Hollyhock Rust, Puccinia malvacearum (Fig. 72), is found over the 
world, where the hollyhock, Althcea rosea, is grown. 



RUST FUNGI 



207 




Fig. 77. — Longitudinal section of a partly'gelatinous teliosorus'after the exten- 
sion of the tentacles. (After Reed, H. S., and Crahill, C. H., Techn. Bull. 9, Va. 
Agric. Exper. Slat., May, 1915.) 



208 



MYCOLOGY 



Belonging to the genus Gymnoconia (Fig. 92) is the orange rust 
of raspberry and blackberry which is found throughout the United 
States and Canada. It is also widely distributed in Europe and Asia. 

The genus Phragmidium, which is confined entirely to plants of the 
rose family, is autoecious. Warts are formed on the teliospores by the 
contraction of an outer gelatinous layer which with a rigid middle 
lamina and the arrangement of the germ pores distinguishes Phrag- 




FiG. 78. — Teliospores of cedar apple showing germination with formation of 
basidia (promycelia) and basidiospores (sporidia). {After Reed, H. S., and Crabill, 
C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 1915.) 



midium from neighboring genera. The teliospores are two- to several- 
celled by transverse septa. An important species is the Rust of Roses, 
Phragmidium subcorticium, which has a spindle-shaped teliospore with 
six to eight cells. 

Gymnosporangium is a genus of heteroecious rusts the secia of which 
occur on Rosacea (except one on Hydrangeac^ and one on Myri- 



RUST FUNGI 



log 



cace.e) while the three-, four or five-celled teliospores are found 
on CupRESSiNEiE {Chamcecyparis , Cupressus, Juniperus, Libocedrus). 
One autoecious species is G. bermudianum which produces both its 
ascia and telia on junipers (/. bermudianum) . Kern gives thirty-two 
species as the number for North America and in vol. 7, North American 
Flora, part 3, pages 188-190, gives a useful key for the identification 
of the species. 

Gymnosporangium botryapites causes fusiform swellings on the white 
cedar, Chamcecy parts thyoides, on which swellings the two- to four- 




FlG. 



79- — Cedar rust on apple, roestelia stage with pustules.^ {After Jones and 
Bartholomew, Bull. 257, Agric. Exper. Stat., Univ. Wise, July, 1915.) 



celled teliospores are formed. The aecia occur on two species of shad 
bush: Amelanchier canadensis and A. intermedia (Fig. 73). 

In Gymnosporangium nidus-avis, the telia arise from a perennial 
mycelium which often dwarfs the young shoots and causes bird's-nest 
distortions in which usually there is a reversion of the leaves to the 
juvenile form, sometimes causing gradual enlargements in isolated 
areas on the larger branches of Juniperus virginiana with gecia on 
several species of Amelanchier (Fig. 73). 

Juniperus communis is the host of the telial stage of G. clavaricBforme, 
which appears on long fusiform swellings of various-sized branches, 
14 



MYCOLOGY 



scattered, or aggregated and its aecia on seven species of Amelanchier , 
one each of Aronia and Cydhnia. 

Gymnosporangium Ellisii (Figs. 74 and 75) in its telial form distorts 
the younger branches of the white cedar, ChamcBcyparis thyoides, pro- 




FiG. 80. — Roestelia, or aecia on apple leaf. {After Giddings and Berg, Bull. 257, 
Agric. Exper. Stat. Univ. Wise, July, 1915.) 



ducing numerous fasciations. The aecia and pycnia of this fungus 
are on Myrica. Gymnosporangium globosiim is remarkable in forming 
aecia on eighty-five different species of hawthorn, Cratcegus, while its 



RUST FUNGI 



teliospores appear on irregular spheric swellings or excrescence on 
Jitiiiperus virginiana. 

The mycelium of G. jimiperi-virginiance is annual, or biennial, 
producing globose swellings known as cedar apples on the leaves of the 



— ;: 3= 5 

■ * 

j* 'it J 




p 
*;,^^^^ 









Fig. 8i. — Alagnified view of apple rust roestelia, or aecia. (After Jones and 
Bartholomew, Bull. 257, Agric. Exper. Slat. Univ. Wise, July, 1915.) 

red cedar, Juniperus virginiana. The cluster cups appear on the leaves 
of native species of apples {Mains). 

The most important publication dealing with this disease and giving 



212 MYCOLOGY 

a copious bibliography is one by HowardL. Reed and C. W. Crabill issued 
as Technical Bulletin 9 (May, 1915) by the Virginia Agricultural Experi- 
ment Station. The 106 pages of text are devoted to a careful considera- 
tion of all aspects of the disease, which is prevalent throughout the 
geographic range of the red cedar. The aecia are found on the apple 
and were originally described as RoesteUa pyrata (Schw.) Thaxter, 
and frequently the apple stage is known as the RoesteUa stage (Fig. 
81). Infection of the leaves (Fig. 80) and fruit is only possible 
during their undeveloped condition and not all varieties of apple are 
susceptible. Some are rust free. Such are Early Harvest, Golden 
Pippin, Winesap, while the badly affected varieties are Grimes Golden, 
Smokehouse and York Imperial. The aeciospores are dark brown, 





Fig. 82. — Diagram (left) of aecium (roestelia) of apple rust; right, three Kcio- 
spores from the cup highly magnified. {AfUr Jones, L. R., and Bartholomew, E. T.. 
Bull. 257, Agric. Exp. Stat., Univ. Wise, July, 1915.) 

minutely pitted and almost spheric with thick walls and granular con- 
tents. The first aecia (Figs. 81 and 82) become mature during the 
month of July and viable spores are produced in large numbers during 
this and the following two months (Fig. 83). This is the period of 
infection of the red cedar, and the mycelium formed from these spores 
remains dormant in the cedar leaves until the following spring, when 
the cedar apple (Fig. 76), or gall, is formed out of the parenchyma 
of the red cedar leaf (Fig. 161). Into the gall a vascular strand extends. 
The surface of the galls becomes papillate and in May these papillae 
enlarge into gelatinous horns, or teliosori (Fig. 77), made up of the 
agglutinated stalks of numerous teliospores (Fig. 77), which are two- 
celled and measure 46 to 63/x by 15 to 20/x (Fig. 78). These telio- 



RUST FUNGI 



213 



spores on germination produce a four-celled basidium (Fig. 78), 
or promycelium, from which are cut off basidiospores, which infect the 




partially developed apple leaves, or apple fruits (Fig. 79). The dis- 
ease apparently does little damage to the red cedar trees, but the 



214 MYCOLOGY 

aecial stage devastates the apple orchards found in proximity to red 
cedar trees infected with the rust. Destroying the red cedar trees 
seems to be the only feasible plan of combating the disease. 

BIBLIOGRAPHY OF THE RUSTS 

Arthur, J. C: Cultures of Uredineje. I (1899), Botanical Gazette, 29: 268-276; 
II (1900 and 1901), Journal of Mycology, 8: 51-56; IV (1903), Journal of My- 
cology, 10: 8-21; V (1904), Journal of Mycology, 11: 50-67; VI (1905), Journal 
of Mycology, 12: 11-27; VII (1906), Journal of Mycology, 13: 189-205; VIII 
(1907), Journal of Mycology, 14: 7-26; IX (1908), Mycologia, i: 225-256; X 
(1909), Mycologia, 2: 213-240; XI (1910), Mycologia, 4: 7-33; XII (191 1), 
Mycologia, 4: 49-65; XIII (1912, 1913 and 1914), Mycologia, 7: 61-89; 
XIV (1915), Mycologia, 8: 125-141. 

Arthur, J. C. and Holway, E. W. D.: Description of American Urcdinea;. Bull. 
Lab. Nat. Hist, of State Univ. of Iowa, I, 3: 44-57; Hj 4:"377-402; III, 5: 171- 

193; IV, 5:311-334- 

Arthur, J. C.: Clue to Relationship among Hetercecious Plant Rusts. Botanical 

Gazette, 33: 62-66, January, 1902. 
Arthur, J. C: The Uredineae Occurring upon Phragmites, Spartina and Arundinaria 

in America. Botanical Gazette, 34: 1-20, July, 1902. 
Arthur, J. C: Problems in the Study of Plant Rusts. Publ. 22, Botanical Society 

of America, Dec. 31, 1902, 1-182. 
Arthur, J. C: Taxonomic Importance of the Spermogonium. Bui. Torr. Bot. 

Club, 31: 125-159, March, 1904. 
Arthur, J. C: Terminology of the Spore Structures in the Uredinales. Botanical 

Gazette, 39: 219-222, March, 1905. 
Arthur, J. C: Amphispores of Grass and Sedge Rusts. Bull. Torr. Bot. Club, ^,2: 

35-41, 1905. 
Arthur, J. C. and Kern, F. D.: North American Species of Peridermium. Bull. 

Torr. Bot. Club, 33: 403-438, 1906. 
Arthur, J. C: Eine auf die Struktur und Entwicklungsgeschichte begriindete 

Klassifikation der Uredineen. Rusultats Scientifique du Congres international 

de Botanique Wien, 1905: 331-348, 1906. 
Arthur, J. C: New Species of Uredinese. Bull. Torr. Bot. Club, I, 23: 661-666, 

December, 1901; II, 24: 227-231, April, 1902; III, 31: 1-8, January, 1904; 

IV, 33: 27-34, 1906. 
Arthur, Joseph C: Uredinales. Coleosporiaceas, Uredinaces, ^cidiace^ (pars). 

North American Flora, 7, part 2, 1907; /Ecidiacese (continuatio), 7, part 3, 191 2. 
Arthur, J. C: On the Nomenclature of Fungi Having Many Fruit Forms. The 

Plant World, 8: 71-76; 99-103. 
Blackman, H. v.: On the Fertilization, Alternation of Generations, and General 

Cytology of the-Uredinese. Annals of Botany, xviii: 323-373) i904- 
Blackman, H. V. and Eraser, Miss H. C: Further Studies on the Sexuality of 

the Uredinea;, with 2 plates. Annals of Botany, xx: 35-47, 1906. 



RUST FUNGI 215 

Carleton,. Mark A.: Investigations of Rusts. U. S. Dept. Agr., Bureau of Plant 

Industry Bull. 63, 1904. 
Carleton, Mark A.: Lessons from the Grain Rust Epidemic of 1904. U. S. Ucpt. 

Agr., Farmers' Bull. 219, 1905. 
Cheistman, a. H.: Sexual Reproduction in the Rusts. Botanical Gazette, xx.xix: 

267-274, 1905. 
Christman, a. H.: Observations on the Wintering of Grain Rusts. Trans. Wise. 

Acad. Sci., 15: 98-107, 1905. 
Coons, G. H.: Some Investigations on the Cedar Rust Fungus, Gymnosporangium 

juniperi-virginianas. Ann. Rep. Neb. Exp. Sta., 25: 217-245, pis. 1-5, 191 2. 
DE Bary, Anton: Comparative Morphology of the Fungi Mycetozoa and Bacteria, 

1887: 274-286. 
DiETEL, P.: Uredinales. Die natiirlichen Pflanzenfamihen I, Teil i, Abteilung**: 

24-81, 1900. 
DuGGAR, Benjamin M.: Fungous Diseases of Plants, 1909: 384-438. 
Eriksson, Jakob: Fungoid Diseases of Agricultural Plants, 191 2: 63-89. 
Eriksson, Jakob: On the Vegetative Life of Some Uredineae. Annals of Botany, 

xix: 55. 
Freeman, E. M.: A Preliminary List of Minnesota Uredineae. Minn. Bot. Studies, 

2, part 4: 407, 1901. 
Grove, W. B.: The British Rust Fungi (Uredinales): Their Biology and Classifica- 
tion, 1913, pp. i-x + 1-412. 
Heald, F. D.: The Life History of the Cedar Rust Fungus Gymnosporangium 
juniperi-virginianas. Ann. Rep. Neb. Agric. Exp. Sta., 22: 105-113, pis. 1-13, 
1909. 
Hoffmann, A. W. H.: Zur Entwicklungsgeschichte von Endophyllum sempervivi. 

Centralbl. fur Bakteriologie, 2, abt. 32: 137-158, 191 2. 
Hume, H. Harold: Some Peculiarities in Puccinia Teleutospores. Botanical 

Gazette, 1899: 418-423. 
Kern, Frank D. : A Biologic and Taxonomic Study of the Genus Gymnosporangium. 

Bull. N. Y. Bot. Gard., 7: 391-494, pis. 151-161, 1909-1911. 
Kern, Frank D.: Gymnosporangium. North American Flora, 7, part 3: 188-21 1. 
Klebahn, H. : Die wirtswechselnden Rostpilze, 1904. 

Kunkel, Louis Otto: Nuclear Behavior in the Promycelia of Caeoma nitens 
Burrill and Puccinia Peckiana. Howe Amer. Jour. Bot., i: 37-47, January, 
1914. 
KURSSANOW, L.: Zur Sexualitat der Rostpilze. Zeits. Bot., 2: 81-93, iQio- 
Magnus, P.: Weitere Mittheilung iiber die auf Farnkrantem auftretenden Uredi- 
neen. Berichten der Deutschen Botanischen Gesellschaft, xix. Heft 10: 578- 
584, 1901. 
Magnus, P.. Ueber eine Function der Paraphysen von Uredolagern, nebst einen 
Beitrage zur Kenntniss der Gattung Coleosporium. Berichten der Deutschen 
Botanischen Gesellschaft, xx. Heft 6; 334-339, 1902. 
Massee, George: Diseases of Cultivated Plants, 1910: 289-338. 
Massee, George and Ivy: Mildews, Rusts and Smuts, 1913: 52-182. 
McAlpine, D.: The Rusts of Australia. Dept. Agric. Victoria, 1906. 



2l6 MYCOLOGY 

Olive, Edgar W.: Sexual Cell Fusions and Vegetative Nuclear Divisions in the 

Rusts. Annals of Botany, xxii: 331-360, 1908. 
Olive, Edgar W. : Origin of Heteroecism in the Rusts. Phytopathology, i: 139- 

149, October, 191 1. 
Olive, Edgar W.: Intermingling of Perennial Sporophytic and Gametophytic 

Generations in Puccinia Podophylli, P. obtegens and Uromyces Glycyrrhizas. 

Annales Mycologici, ii: 297-311, August, 1913. 
Pritchard, F. J.: A Preliminary Report on the Yearly Origin and Dissemination 

of Puccinia graminis. Botanical Gazette, 52: 169-192, 1911. 
Reed, Howard S. and Crabill, G. E.: The Cedar Rust Disease of Apples Caused 

by Gymnosporangium juniperi-virginianse. Tech. Bull. 9, Virginia Agric. Exper. 

Stat., 1915. 
Sappin-Trouffy, P.: Recherches histologiques sur la famille des Uredinees. Le 

Botaniste, 5: 59-244, 1896. 
Stewart, Alban: An Anatomical Study of Gymnosporangium Galls. Amer. 

Journ. Bot., 2: 402-417 with i plate, October, 1915. 
Sydow, Paul H.: Monographia Uredinearum seu-specierum omnium ad hunc usque 

diem descriptio et adumbratio systematica auctoribus, 1904. 
Tulasne, L. R.: Second Memoire sur les Uredinees et les Ustilaginee. Ann. Sci. 

Nat., iv. 2: 77, 1854. 
von Tavel, Dr. F.: Vergleichende Morphologic der Pilze, 1892: 123-133. 
VON TuBEUF, Dr. Karl F.: Pfianzenkrankheiten, 1895: 340-434. 
Ward, H. Marshall: Illustrations of the Structure and Life History of Puccinia 

graminis. Annals of Botany, ii: 217 with 2 plates. 
Ward, H. Marshall: On the Relation between Host and Parasite in the Bromes 

and their Brown Rust, Puccinia dispersa. Annals oT Botany, xvi: 233, 1902. 
VON Wettstein, Dr. Richard R., Handbuch der Systematischen Botanik, 1911: 
196-202. 

Suborder Auricularine^. — Family Auriculariace^. — ^The 
fungi of this family are saprophytes, or v^^ood-inhabiting parasites. The 
basidia are borne directly on the mycelium, or in variously formed fruit 
bodies in which the basidia form a layer. The basidia are transversely 
divided into four cells. Auricularia includes about forty species of 
which the best known is, Auricularia (Hirneola) Auricula Judce, the Jew's 
ear fungus, which develops its fruit body on rotten wood. When wet, it 
is gelatinous; when dry, it appears as a dry crust. It is a rather gelatin- 
ous, flabby-looking, thin expanded cup or saucer-shaped fungus of 
a brownish color when expanded smooth inside, veined and plaited so 
as to have the resemblance to a human ear. It grows on a variety of 
trees: elm, maple, hickory, balsam, spruce and alder and up to 1900, 
it had been collected in Ohio, Maryland, Indiana, New Jersey, Pennsyl- 
vania and West Virginia. Outside it is velvety and grayish-olive. 



GELATINOUS FUNGI 217 

Auricularia (Hirneola) polytricha is the "Mu-esh" of the Chinese, who 
gather it as an article of food, in fact oak boughs are cut and allowed to 
decay to raise the fungus. 

Family Pilacrace^. — ^This is a small family of two genera, Pila- 
crclla and Pilacre, with spheric stalked fruit bodies. The basidia are 
in capitate clusters and surrounded at first by a peridium-Uke wall, 
which breaks at maturity. 

Suborder Tremelline^. — Family Tremellace^. — This family 
includes twelve genera, of which Trcmella is the most important. The 
majority are widely distributed and live saprophytically on wood, where 
they appear as soft, trembhng, gelatinous masses, when moist, becoming 
rigid and horny when dry. The basidia are longitudinally divided by 
two septa. The four portions thus formed each bear a terminal basidio- 
spore. Some species of Tremella produce conidiospores. Tremella 
frondosa has been used as food, but as such is unsatisfactory. Tremella 
foliacea is of a smoky-brown color, cold, clammy and trembles in the 
hands. When stewed, it becomes a shmy mess relished only by the 
Chinese. Tremella mesenterica is brain-like in its convolutions, ge- 
latinous in texture and usually the size of a walnut, and of an orange-red 
color. 



CHAPTER XX 
FLESHY AND WOODY FUNGI 

Suborder Eubasidii. — The fungi of this suborder are characterized 
by the undivided (unseptate) basidia, more or less club-shaped with 
generally four, rarely six, eight, or two apical sterigmata each of which 
bears a basidiospoi-e (Fig. 92). These fungi are usually fleshy and the 
spores are borne openly on wrinkles, ridges, gills, in pores, on spines, 
or in closed fruits, which open regularly, or irregularly, by splitting. 
Many of the forms are edible, some are inedible, because of toughness, 
or woodiness, while others are poisonous. 

Cytology. — Recent studies by Juel (1897), Maire (1900), Ruhland 
(1901), Harper (1902), Levine (1913) have shown that as a general 
thing the hyphal cells of the mycelium in the HYMENOMYCETES 
and GASTEROMYCETES are binucleate, and sometimes, as in Cop- 
rinus radiatus, uninucleate. The cells of the young carpophore are 
binucleate, but as the fruit body matures, the majority of the cells in 
the stipe and pileus are multinucleate, but this condition arises from 
the amitotic fragmentation of the two nuclei originally present in each 
cell. The subhymenial cells from which the basidia spring and the 
paraphyses are always binucleate. All the cells, which are concerned 
directly with the production of basidiospores, are binucleated through- 
out their development. The multinucleated condition above noted 
arises in cells of strictly limited development and are found in the organs 
of nutrition, support, transportation, etc. Maire found that the pairs 
of nuclei divide simultaneously, as conjugate nuclei, so that in the suc- 
cessive cell generations which arise in the development of the carpo- 
phore the two nuclei in each cell are of widely separated nuclear ances- 
try, duplicating exactly the condition found in the rusts previously 
described. The young basidium contains only two nuclei just as in 
the teliospore of the rust. These two nuclei fuse to form the primary 
nucleus of the basidium which then divides twice to furnish the nuclei 
for each of the typically four basidiospores. Levine (191 3) who has 
studied this nuclear division in a number of species of Boletus, finds the 

218 



FLESHY AND WOODY FUNGI 219 

long axes of the spindles in both divisions are commonly transverse to 
the long axis of the basidium. The spores in all of the forms studied 
by him are uninucleate at first. Just when the mycelial cells become 
regularly binucleate has not been certainly ascertained except in a few- 
forms. Presumably in Coprinus radiatus the uninucleate spores give 
rise to uninucleate hyphal cells, but Levine finds in his Boletus studies 
that the primary spore nucleus divides at once to form two nuclei. 
Presumably, the nuclear division in other forms may be delayed, until 
the primary mycelium has arisen. An alternation of generations com- 
parable to that of the rusts is also present in the Hymenomycetes and 
Gasteromycetes. The sporophyte begins at some indefinite point in 
the mycelium and extends through the development of the carpophore. 

A. Hymenomycetes. — The undivided basidia of these fungi bear 
four basidiospores perched on corresponding points, or sterigmata. 
These basidia spring directly from the mycelium in the primitive forms, 
but in the more highly evolved types, the basidia are borne on definite 
layers (hymenial layers) together with the paraphyses and cystidia 
characteristic of some of the forms. The hymenia are carried by special 
fruit bodies which differ structurally in the different f amiUes. These 
fruit bodies arise from a profusely branched mycelium, which radiates 
through the organic substratum, which may consist of leaf mold, rotten 
wood, dying tree trunks, and manurial waste. The hyphal cells are 
frequently united by clamp connections which probably give greater 
strength to them. Such are the saprophytes. Some of the hymeno- 
mycetous fungi are parasites and five in the bark and wood of trees, 
and some few are parasitic on the woody parts, leaves, flowers and 
developing fruits of certain shrubs. Sometimes, as in Armillaria mellea, 
the hyphae become united in strands with apical growth. These strands 
are known as rhizomorphs and serve in part as the resting organs. True 
sclerotia are also formed. The fruit bodies take various forms. The 
most highly developed types with stalk, cap and gills are known as 
toadstools. Some of the simple forms are club-shaped. Others have 
spines and pores instead of gills over which the hymenia are spread. 

Family i. Dacryomycetace^. — The fruit body is gelatinous, or 
cartilaginous, and of different shapes. The whole surface of the fructi- 
fication is covered with a paHsade-like layer of long club-shaped basidia 
which bear two-forked basidia, each fork with a basidiospore. Conidio- 
spore formation occurs in a number of forms. The important genera 



220 



MYCOLOGY 



are Dacryomyces, Guepinia, Calocera. Dacryomyces deliquescens forms 
gelatinous, or gristly, lumps on tree stumps. Guepinia peziza is sapro- 
phytic on oak stumps. Calocera viscosa is a branched upright form 
suggesting the true coral fungi. 

Family 2. Exobasidiace^. — The mycelium of the fungi of this 
family Hves parasitically in the chlorenchyma of many shrubs. The 
fruit body is a thin basidial layer, which breaks out of the tissues of the 
host. Each basidium develops four basidio- 
spores; rarely 5 to 6 are formed. Some of the 
species form galls on the stems, leaves and 
flowers of ericaceous shrubs, such as species of 
Vacciniiim, Rhododendron, Azalea, Andromeda, 
etc. There are two genera: Exobasidium (Fig. 
84), with eighteen species; and Microstroma, 
with two species. Exohasidium caccinii (Fig. 
84) develops swellings on the leaves of species 
of Vacciniiim of a whitish-red color. Its 
basidia are club-shaped with four sterigma 
and four basidiospores. The basidiospores are 
spindle-shaped, 14 to i6yu long by 2 to 3^ 
broad, colorless and smooth. Exohasidium 
rhododendri forms enlargements of the leaves 
of species of Rhododendron of greater or less 
size; colored white, or flesh-colored. Ex- 
Fig. 84.— Floral gall ohasidium ledi occurs on Ledum in Finland. 

produced on flowers of 

huckleberry, Gaylussacia Exohasidium andromedcB grows on leaves and 
resinosa, by Exohasidium ^^j^g ^f gpecies of Andromeda in Europe and 

vaccina. Note enlarged ° , '- ,.,. ... 

and swollen calyx. (Pine America. Exooasidium AzalecB IS found on 

mTT^' f ^i6T"^' ^' ■^" ^P^"^^ ^^ ^"^^^^^^ ^^ ^^^^^ America. E.v- 
obasidium lauri forms widely spread, yellow 
then brownish, horny, or club-like galls on the stems of the laurel in 
Italy, Portugal and the Canary Islands. Exohasidium Warmingii 
attacks the living leaves of Saxifraga aizoon in Greenland, Tyrol and 
north Italy. 

Family 3. Hypochnace^. — The hymenium is cobwebby. The 
basidia have two, four or six sterigmata. Cystidia are sometimes present. 
Hypochnus occurs on old stumps, on leaves and on mosses. Tomen- 
tella is another genus. 




FLESHY AND WOODY FUNGI 221 

Family 4.. Thelephorace.^. — Fruit bodies of a simple type are 
found in this family. They form on three trunks, either flat 
leathery crusts with the hymenium on the smooth upper surfaces, or the 
flat fructifications are raised above the substratum and have bracket- 
like outgrowths, which show an overlapping arrangement with the 
hymenial layer on the under side. The important genera are Corticium, 
Stereum and Thelephora. In Corticium, the fructification is leathery, 
membranous, fleshy, rarely wholly gelatinous, crust-like, growing resu- 




FiG. 85. — a piece of old oak timber rotted by Slereum fruslulosum showing scat- 
tered frvtiting bodies. {After von Schrenk, Hermann, Bull. 149, U. S. Bureau of 
Plant Industry, 1909.) 



pinate. The hymenium is smooth, or pimply, and consists of club- 
shaped basidia with four basidiospores. The species are mostly 
found on wood. C. vagiim-solani in its sterile form is known as Rkiz- 
octonia, which apparently has been found on sugar beet, bean, carrot, 
cabbage, potato, egg plant and a number of other hosts. The hymeno- 
phore of this species is white with short basidia and elliptic spores. 
It frequently entirely surrounds the green stems of its host near the 
ground. The persistent hymenophore of Stereum is leathery, or 



22 2 MYCOLOGY 

woody, attached laterally, or centrally, sometimes as a bracket with a 
smooth hymenium. Stereum hirsutum attacks oak trees in which the 
wood becomes brownish at first and in longitudinal section, white or 
yellow streaks are found, hence the common name white-piped, or 
yellow-piped oak. In the cross-section, these streaks are white specks, 
and another name, that of "fly wood," is apropos. Further decom- 
position follows. The rot of woods, known as partridge wood, where 
the timber becomes speckled with white, is due to Stereum frustulosum 




Fig. 86. — Coral-like fruit-bodies of Clavaria flava. {Photo hy W. H. Walmsley.) 



(Fig. 85). The fruiting bodies are hard and crust-like, light brown to 
grayish , in color. The smothering fungus of seedlings is Thelephora 
terrestris and T.laciniatum. Soft leathery masses are found at the base 
young trees of the hard maple. These are numerous, shelf-like fruit of 
bodies, hemispheric in shape and in -mass may completely surround 
and smother the small tree. Hymenochcete noxia attacks tropic plants, 
such as cocoa, tea, bread fruit, camphor and the like. 

Family 5. Clavariace^. — The fairy clubs, or coral funguses belong 
here. The simple, or branched, club-shaped or antler-like hymeno- 



FLESHY AND WOODY FUNGI 323 

phores are fleshy, leathery, cartilaginous, or waxy. The basidia are 
clavate, interspersed with cystidia and bear one to four sterigmata. 

Pistillaria, Typhula, Clavaria and Sparassis are important genera. 
Many of the species of Clavaria are edible (Fig. 86), but some of them 
are tough and leathery. The color varies, as noted in the enumeration 
of common American species given below: 

Clavaria flava (paleyellow) (Fig. 86). 

Clavaria aurea (golden). 

Clavaria botrytes (red-tipped). 

Clavaria cristata (crested). 

Clavaria cinerea (ashen). 

Clavaria aurantio-cinnabarino (orange-red) . 

Sparassis crispa, a common species, has its hymenial ridges pro- 
jecting and much convolute, suggesting a mammalian brain. It is too 
tough to be edible. 

Family 6. Hydnace^. — The highest forms of this family possess 
the form of a mushroom, while others are sessile and are resupinate, 
others without a distinct cap are effused. The hymenium is spread 
over with persistent bristles, teeth, tubercles or spines. The most 
important genera are Phlebia, Radidum, Grandinia Irpex and Hydnum 
(Fig. 87). The edible forms are included in the last two genera. 
The forms of Hydnum are extremely variable. The highest forms, 
such as Hydnum repandum, have a cap with a central stipe, while 
in other forms it is lateral, or absent. In some of the lower forms, 
the pileus is resupinate. Projecting spines are covered with the 
hymenial surfaces. A rot of hardwoods in America is due to Hyd- 
num coralloides. H. diversidens with its yellowish-white sporophore 
takes the form of an incrustation,^or bracket with downward-projecting 
spines of unequal length. The hymenium renews itself by a new 
hymenium growing through the old one. It causes a decay of timber 
known as white rot. Hartig gives a careful description of it, as it occurs 
in Europe. H. caput-ursi is a bracket form growing as excrescences on 
living oak trees with its pendulous spines at first white, then becoming 
yellowish and brownish. H. caput-medusce. has pendulous tufts of 
white to gray spines and is found on elms and oak trees. The spiny 
character of H. erinaceum (Fig. 87) suggests a hedgehog, hence its 
specific name. The last three are fleshy and edible. Irpex differs 
from Hydnum in having the spines connected at the base, and in 



224 



MYCOLOGY 



in their being less awl-shaped and pointed. /. obliquus on stumps, /. 
carneus on tulip poplar, /. fusco-violaceus on pine trunks are American 
species.' 

Family 7. Polyporace^. — The fruit body of the fungi of this 
family are of various substance and shape. The hymenium lines the 
inner surface of pores, or grooves, or is spread over the under surface of 
the fruit body. The depressions are either united vein-like grooves, 
tubes, or honeycombed cells, or twisted passages. Concentrically 



■ 


Wt^^^ 


■'^ '^ 




r 


: f 










, I 





Fig. 87. — Fruit-body of Hydnuni erinaceum. {After Patterson, Flora W., and 
Charles, Vera K., Bull. 175, U. S. Dept. Agric, pi. xxxii, Apr. 29, 1915.) 



formed lamellae are found rarely. The consistency of the fruit bodies 
of these fungi is leathery, fleshy and succulent, while in some the fruit 
bodies are woody and perennial. The family is naturally divided into 
four subfamihes, as follows: Merulioide^, Polyporoide^, Fistulin- 
oiDE^, Boletoide^. Each of these subfamilies includes fungi which 
are important economically. 

MERULOIDE.E. — This subfamily includes two genera of interesting 
fungi: MeruUus and Mycodendron. Merulius is represented by sixty- 



PLESHY AND WOODY FUNGI 



225 



three species of which M. lacrymans, the dry-rot fungus, is most impor- 
tant. This fungus is of world-wide distribution, where it attacks 
structural wood work and timbers. It has been so long associated as 
a destructive agent with the structural wood work of men, that it was 
supposed to be an entirely domesticated form and not known to exist 
in the wild form. Recent investigations have shown that it occurs on 
living trees, which when used for structural purposes furnish wood 
which is liable to destruction later on. The mycelium of Merulius 
lacrymans (Fig. 88), usually gains access to dressed boards, joists, or 




Fig. 88. — Immature fruiting stage of dry-rot fungus {Merulius lacrymans) de- 
veloping on the front of a board. {After Clinton, G. P., Rep. Conn. Agric. Exper, 
Slat., pi. xxviii, 1906.) 



rafters by the germination of one of its spores at a point where the beam 
may be in contact with a damp wall. Its mycehum penetrates the wood 
and usually grows lengthwise at first, the water for its extension being 
supplied by larger more tube-like hyphae known as the conductive hyphte, 
which carry water to the extreme end of the mycelial growth. The pres- 
ence of the fungus results in a decay of the wood, which is reduced to a 
brown punky mass, that crumbles between the fingers. When the myce- 
lium comes to the surface of the wood, it forms a white felt-like coyering 
studded with water drops, hence the specific name lacrymans referring 
IS 



226 



MYCOLOGY 



to the tear-like drops of water pressed out of the Hving hyphal cells. 
The mature sporophore is an amber-brown color covered with anasto- 
mosing wrinkles (Fig. 89) over the surface of which the basidia bearing 
basidiospores are borne. Two basidiospores are borne on pointed 
sterigma by each basidium. As the fungi by means of its conducting 
hyphag is independent of local water supplies, it can grow in wood, even 
if protected by an external coat of paint, or varnish, and the builder is 
chagrined to find such wood work crumble away beneath the coats of 
paint. Mycodendron is a curious fungus with a fruit body which 
suggests a muffin stand, or a pagoda with superimposed, rounded. 




-Fruiting stage of dry-rot fungus (Merulius lacrymans). {After Clinton, 
G. P., Rep. Conn. Agric. Exper. Stat., pi. xxviii, 1906.) 



spore-bearing shelves through which the central stalk runs from one-half 
to the next above. Mycodendron paradoxum has been collected on 
wood in Madagascar. 

PoLYPOROiDE^. — This Subfamily includes tough or woody fungi 
found generally on wood as bracket-hke fruit bodies of different 
forms and sizes. The spore-bearing surface, a hymenium, consists of 
furrows, or tubes. In the perennial-fruited forms, the tubes are often 
found in layers. Mycologists have made a natural division of the dif- 
ferent forms of fruit bodies into those which are resupinate, the annual 
peroi^ species, the perennial peroid forms and those species which are 
like the agarics. The various forms are of interest to the scientific my- 



FLESHY AND WOODY FUNGI 227 

cologist, but to the mycophagist they are of use as food. Only one 
poisonous form is known, and that is the medicinal one, Fames laricis, 
but it is so bitter and unattractive, as not to be tempting. Some of 
them are destructive to living trees, to timber used for mine props, and 
structural purposes, and to wood exposed to the weather, or in contact 
with the soil. 

The ease with which the polypores are collected and preserved 
makes them especially suitable for systematic study in the classroom. 
Besides, they retain their characters when dried, so that the keys used 
for their identification can be readily followed. Fortunately also we 
have several manuals which cover the different sections of our country. 
They are reasonable enough in price to be furnished for use in the class- 
room. It is suggested that boxes of the different kinds used for this 
purpose be filled with enough specimens to furnish each member of 
the class in mycology with one specimen of each kind. There should 
be a sufiicient number of manuals of the region, where the botanic 
institute is situated, to supply every two members of the class with 
one, so that the students may use them in groups of two. The 
advertisement of the books is here reproduced for the use of teachers 
of mycology. 

MANUALS OF POLYPORES AND BOLETES 

By William A. Murrill, A. M., Ph. D., Assistant Director of the New York 
Botanical Garden, Editor of "Mycologia," and Associate Editor of "North American 
Flora." 

Northern Poljrpores, November, 19 14. Including species found in Canada and 
the United States south to Virginia and west to the Rockies. 

Southern Polj^jores, January, 1915. Including species found in the United 
States from North Carolina to Florida and west to Texas. 

Western Pol5T)ores, February, 1915. Including species found in the states on 
the Pacific coast from Cahfornia to Alaska. 

Tropical Polypores, March, 1915. Including species found in Mexico, Central 
America, southern Florida, the West Indies, and other islands between North 
America and South America. 

American Boletes, November, 19 14. Including all the species found in temperate 
and tropical North America, both on the mainland and on the islands, south to 
South America. 

As satisfactory keys of the different genera and species of the poly- 
pores and boletes are given in these manuals, and as it is presupposed 
that their use will be adopted, keys of the more common genera and 



228 



MYCOLOGY 



species are not given space in this book. It should be stated, however, 
that Murrill classifies his genera and species differently from the authors 
that have preceded him where many of the new genera were classified 
under the genera Polyporus and Boletus (Fig. 90). The arrangement 
of Murrill seems to be a more satisfactory presentation of these groups 
than those systems which have gone before and is founded on more 
natural characters. The nomenclature which this author adopts in 
the several recommended manuals was f()rcshad(nved in \o\. (>, i)art i 




Fig. 90.~7)<j/«7;(s /,//, ,i\ in three stages of devel. iinnent. {After Patterson, Flora W. , 
and Charles, Vera K., Bull. 175, U. S. Dept. Agric, pi. x.xxi, Apr. 29, 1915.) 

(1907), and part 2 (1908) of the "North American Flora," where keys 
will also be found with the synonymy which has been omitted from the 
manuals. To connect satisfactorily, the old and the new generic and 
specific names, the treatment of the Polyporace^ in the "North 
American Flora" should be consulted. 

Trametes roblniophila is found on decayed spots of living trunks of 
Rohinia pseudacacia from Pennsylvania to Virginia and Missouri, and 
it doubtless causes decay of the wood. T. suaveoleus is found on willow 
trees, where it causes serious decay. It has an agreeable odor. T. 



FLESHY AND WOODY FUNGI 



229 



subiiivosa is occasional on dead deciduous wood in Florida, Louisiana 
and Mississippi. At New Orleans, it was collected on living water 
oak and at Eustis, Fla. on cypress. The species become more abundant 
in tropic America where nine have been found. T. jalapensis was col- 
lected on a railway tie near Jalapa, Mexico. The species of Coriolus 
are annual. It includes Coriolus {Polyporns) versicolor found on all 




Fig. 91. — Piece of dead wood with'sporoiiii-iK , - , .,.. iomenlaius. {After von 
Schrenk, Hermann, Bull. 149, C/.?5. Bureau of Flant Industry, pi. viii, 1909.) 

kinds of dead wood. It causes root rot in many trees and becomes a 
wood parasite of Catalpa. It has a leathery, thin and rigid hymeno- 
phore depressed at the point of attachment. The surface is velvety 
and variegated with two-colored zones. The pores are minute rounded 
with ragged edges, white then yellowish. Polyporus arcularius is com- 
mon in the eastern United States on dead branches and trunks of vari- 



MYCOLOGY 

ous trees. P. caudicimis is one of the most dangerous enemies of shade 
trees in Europe but, fortunately, it is rare in America. 

The genus Fames includes the fungi with corky, woody, or rarely 
punky hymenophore, which is sessile, hoof-shaped, or applanate (Fig. 
91). The substance of the fruit body is white, flesh-colored, or wood- 
colored. The tubes are cylindric and usually thick walled. Fomes 
annosus will live on trunk and roots of coniferous trees, Fomes 
(Pyropolyporus) igniarius causes serious heart rots of trees. It was 
formerly the source of tinder. Dcedalea quercina (Fig. 202) is a corky, 
or woody, species common on oak and chestnut trees. It is at first 
porous, but these pores coalesce to form slits with blunt partitions. 
It is very common about Philadelphia. Lenzites betulinus is common 
on dead deciduous wood. 

FiSTULiNOiDEiE, — The most important genus of this subfamily is 
Fistulina, which comprises about six species. F. hepatica is the com- 
monest form, and is known by its English name beefsteak fungus or, 
in French, langue de hoeiif. The tongue-shaped fruit body projects 
from the tree and is six to ten inches across with a liver-colored and 
sticky gelatinous surface. The mouths of the tubes are closely packed. 
It is edible, when fully mature, its flavor resembhng beefsteak. 

BoLETOiDE^. — The members of this subfamily are tube-bearing 
fungi differing from the Polyporoide^ in their fleshy substance and 
terrestrial habit. They have a cap and stipe like a mushroom, but 
porous tubes instead of gills on the under cap surface. They occur 
usually in forested tracts during summer and autumn. The annual 
hymenophore is usually centrally stipitate. Many of the best edible 
fungi (few of them poisonous) are found in this subfamily, which in- 
cludes, according to Murrill in North America, Central America and 
the West Indies, as far as Trinidad, eleven genera. 

Boletus (Tylopilus) felleus (Fig. 90) is common iji woodlands. It 
is discarded as an edible form, because of its bitter taste. Forty-eight 
species of Ceriomyces are listed by Murrill for America. The genus 
Boletus proper is made to contain only five species, while Strohilomyces 
strobilaceus still retains its old name. This rough shaggy form is 
regarded as edible. 



CHAPTER XXI 

MUSHROOMS AND TOADSTOOLS 

Family 8. Agaricace^e. — The mycelium of the fungi of this fam- 
ily lives in the substratum, which may be the soil, leaf mould, rotten 
wood, old stumps, dead tree trunks, or living trees, as far as the natural 
environment is concerned, and in manures, in the decay of agricultural 
plants in the fields, offal, spent tan bark and rubbish heaps, as far as 
man has influenced the environment. The hyphse may be delicate and 
cobwebby, thread-hke, cord-like, or in strands (rhizomorphs). They 
are always septate, sometimes with clamp connections and their color 
may vary from white to yellow, or brown {Ar miliaria mellea). The 
fruit bodies are mostly fleshy, rarely of membranous, or leathery, con- 
sistency. Usually of an umbelloid form, they may have a sessile cap, 
or pileus, or the stalk, if present, may be attached laterally, although 
it is placed centrally as a general rule. The hymenophore consists of 
radiately arranged veins, folds, or gills (lamellae), which are generally 
free from each other, seldom anastomosing, or dichotomously branched. 
As the popular name toadstool is suggestive of the commonest form 
of these fleshy fungi, a few words of explanation with regard to the 
general structure will be apropos. Attached to the spreading myce- 
lium we find arising vertically the stalk, or stipe. The height of this 
varies in the different genera and species. Sometimes it is enlarged 
at the base, at other times, the stalk is perfectly cylindric. The sur- 
face of the stipe may be smooth, rough, reticulate, or stringy, and its 
center may be solid, stuffed, or hollow, as the case may be. An annu- 
lus, such as is present in the common mushroom, may in other forms 
be absent, or well developed. Placed on the stem, or stipe, above we 
find the cap, or pileus, which is expanded horizontally. It has a 
domed, convex upper surface sometimes with a projecting boss, or 
umbo; in other forms it is depressed (crateriform, umbilicate, etc.). 
The gills, or lamellae, are attached to the lower surface of the pileus. 
They may run from the stipe to the margin, or they may run only 
part way, so that frequently there are secondary gills alternating with 

231 



232 



MYCOLOGY 



the primary ones. The gills may be free from the stipe, adnexed, or 
even decurrent. 

A section of a mature gill shows the following disposition of the 
hyphal layers. The central part of the gill consists of parallel, down- 
ward directed hyphffi, that form the trama. Running out obliquely 
from the trama are shorter cells which constitute the subhymenium. 
The basidia, together with their accompanying paraphyses and cysti- 
dia, form a palisade-like layer (the hymenium) whose cells stand at 

right angles to the tramal hyphae. 
The basidia are furnished with 
sterigma, which bear the basidio- 
spores (Fig. 92). In such forms 
as the common mushroom, the 
gill chamber is at first closed by 
a veil known as the partial veil, 
or velum partiale, which ruptures 
when the pileus expands. The 
part of this membrane attached 
to the stipe becomes the annulus. 
while the other part remains at- 
tached in a shreddy condition 
to the edge of the cap. The 
species of A manita have a univer- 
sal veil which covers the whole 
fruit body, and as this enlarges 
the velum universale is torn trans- 
FiG. 92.-Coprinus siercorarius with versely, the lower part forming 

young and mature sporophores with gills, the death CUp, Or volva, and the 
basidia and basidiospores and cystidia. , ,• . . 

{After Brefeid.) "PP^r P^rt sometimes remammg 

in the form of flaky pieces, which 
are distributed irregularly over the upper surface of the cap (Fig. 93). 
A frill-like annulus is also found at the top of the stipe in the Amani- 
tas. It does not represent a portion of the partial veil in the Amanitas, 
but is a membrane which is formed from a thick, loosely felted 
layer, which separates as elongation proceeds from the surface of the 
stipe, retaining its connection with the stipe where the stalk joins the 
cap. It is pulled away from the stipe by retaining its connection with 
the edges of the pendant gills as a continuous membrane, which covers 




MUSHROOMS AND TOADSTOOLS 233 

the gills. As the pileus expands the membrane becomes detached first 
at the margin of the cap, and it falls down around the stipe, as a frill, 
plaited in delicate folds, corresponding to the former lines of contact 
with the lamellae and is now known as the annulus superus, frill, or 
armilla. Special milk tubes are found in such forms as species of Lac- 
tarius for when these toadstools are wounded a milky fluid oozes out in 
drops. Each basidium usually bears four basidiospores, sometimes 
thereare two. The color of these spores is distinctive, and is used in 




Fig. 93. — Deadly amanita (Amanita mitscaria) showing volva at base of stem 
and frill, like stem ring. {After Chestnut, V. K., Bull. 175, U. S. Dept. Agric, pi. i, 
Apr. 29, 1915-) J 

the classification of the genera of the family. We distinguish the 
white-spored, rosy-spored, ochre-spored (yellow or brown), brown- 
spored, black-spored agarics. 

Buller in his "Researches on Fungi" (1909) has carried on detailed 
studies with numerous species of gill fungi and has studied the physi- 
ology and mechanics of spore discharge and fall. The disposal of the 
hymenium beneath a pileus on gills, the rigidity of the fruit body, the 
growth movements of the fruit body, all faciUtate the distribution of the 
discharged basidiospores. The spores liberated from a pileus in per- 



234 MYCOLOGY 

fectly still air placed above a horizontal sheet of paper fall vertically 
downward and produce a spore print of radiating lines of spores cor- 
responding to the interlamellar spaces. The number of spores liberated 
in Agaricus (Psalliota) campestris (Fig. 94), 8 cm. in diameter, was 
1,800,000,000 spores. Coprinus comatus formed 5,000,000,000 spores. 
Such discharge under normal conditions is continuous, but by exposing 
the gills to ether, or chloroform vapor, it ceases. BuUer determined 
that the four spores on each basidium are discharged successively leav- 
ing the sterigmata a few seconds or minutes of one another, so that an 
entire mushroom will discharge in total about a million spores a minute 




Fig. 94. — Meadow mushroom, Agaricus campestris. A, View of under surface; 
a, annulus; g, gills; B, side view; s, stipe; p, pileus or cap. {From Gager, after W. A. 
Murrill.) 

for two or more days. The rate of fall of hymenomycetous spores ranges 
from 0.3 to 6.0 mm. per second; those of the mushroom shortly after 
they have left the gills fall at a speed approximately i mm. per second. 
The path described by a spore in its fall has been called a sporabola. 
Buller has divided the fruit bodies of the Agaricace^ into two types, 
the Coprinus comatus type and the Agaricus campestris type. The 
deliquescence in the first type is an autodigestion, which renders impor- 
tant mechanic assistance in the process of spore discharge, where the 
process proceeds in succession from below upward, so that autodiges- 
tion refnoves those parts of the gills from which the spores have been 



MUSHROOMS AND TOADSTOOLS 235 

discharged, and permits the spores to fall more easily past the neighbor- 
ing gill surfaces. 

Development of the Fruit Bodies.— Kikmson^ has studied the develop- 
ment of the mushroom {Agaricus {PsaUiota) campestris) (Fig. 94). — 
The youngest stage is the homogeneous primordium 01 the carpophore 
composed of slender, uniform, dense hyphae, intricately interwoven, and 
surrounded by a thin layer of hyphse of a looser arrangement. This 
layer is the universal veil which grows until the form of the fruit 
appears when it is torn into white floccose patches on the pileus. In 
the very young primordium then there is no evidence of a differentiation 
into stem and pileus and at this stage stained longitudinal sections show 
two small deeply stained internal areas near the upper end of the young 
fruit body and some distance from the surface. The hyphae here are 
richer in protoplasm and form an annular area within the fruit body. 
This area now increases in extent and many hyphae grow from its 
upper portion downward to form the primordial layer of the hymenium. 
These downward growing hyphge are slender and terete and taper 
pointed, which enables them to push between the surrounding hyphse. 
Soon after these hymenial hyphse grow downward there is a cessation of 
growth. Just below this area which results in the rupture and separa- 
tion of the hyphse at this point in a corresponding internal annular area, 
forming the well-known "gill cavity" which at first is very minute. 

With the formation of this annular primordium of the hymenium 
the primordia of the stem, veil and pileus are differentiated. The 
period of elongation of the parts after they have been organized follows 
in succession. The marginal veil completes its period of elongation 
first, then the stem, followed by the pileus, and finally, the hymenium 
where in examples studied Atkinson secured two-spored basidia. 

A somewhat similar development takes place in Agaricus Rodmani, 
a form which grows in grassy ground and paved gutters in cities from 
May to July. The sequence of events in the growth of the fruit body is 
given by Atkinson. ^ He finds that the primordium of the fruit body 
is oval in form and homogeneous in structure, consisting of intricately 
woven hyphse. The hymenophore primordium arises as an internal 

^Atkinson, George F.: The Development of Agaricus campestris. Botanical 
Gazette, 42: 215-221, September, 1906. 

2 Atkinson, George F.: Morphology and Development of Agaricus Rodmani. 
Proceedings American Philosophical Society, 191 5: 309-343, with 7 plates. 



236 MYCOLOGY 

annular zone of new growth toward the upper part of the young fruit 
body (basidiocarp) and with its origin the four primary parts of the 
basidiocarp, pileus, stem, marginal veil and hymenophore are differen- 
tiated. By the continued growth and multiplication of hyphae rich in 
protoplasm, which are parallel and directed downward, the hymeno- 
phore primordium becomes more compact to form a level palisade 
zone, and as the ground tissue beneath lags behind in growth, the more 
rapid growth of hymenophore causes a rupture of the ground tissue 
beneath and an annular gill cavity arises. The lamellae project into this 
cavity, as downward-growing radial sahents of the level palisade zone, 
beginning next to the stem and proceeding in a centrifugal direction. 

Cultivation of the Mushroom. — The commercial growing of mush- 
rooms has been placed upon a sure financial basis within recent years 
and around Philadelphia, notably in Chester County, there are large 
concerns which make the culture of mushrooms a specialty. Mush- 
room cultivation is an important business in Europe, especially in 
France where certain of the grades are canned and bottled for export 
trade. Mushrooms are grown in America in long mushroom houses, 
or sheds especially constructed and heated for the purposes of the trade. 
Cellars are also devoted to the industry. Sometimes they are grown 
under the benches of greenhouses devoted to the raising of other plants. 
The beds are so constructed of boards that they rise in tiers of four, or 
five with a central aisle, or in the larger houses there are tiers of beds 
along the walls and in the center of the house with two aisles running 
lengthwise with a cross aisle at the far end or in the middle of the house. 

Stable manure is used as the compost for commercial mushroom 
culture. Bedding straw should also be included with the manure in 
the compost. The manure should be the best that can be obtained. 
It should be thrown into piles about four feet high and forked over 
occasionally to assist the fermentation process, which is assisted further 
by wetting the fermenting mass occasionally until the fermentation is 
completed, which is usually at the end of three weeks. During this 
time all objectionable odor should be lost and the temperature should 
decline to 120° or i30°F. Out of this compost the beds are constructed 
by compressing the mass with blows of a spade, or by a compressing 
board. Growers cover the manure bed with a thin layer of garden soil 
one to one and a half inches deep. This operation is known as casing, 
and is performed after the spawning operation has been completed. 



MUSHROOMS AND TOADSTOOLS 237 

Spawning consists in breaking up the bricks of spawn into about ten 
pieces and one piece of spawn, which consists of hard manure pene- 
trated by the mushroom hyphae, is used for each square foot of bed 
space. The piece of spawn should be covered by about one inch of 
compost which should have a temperature of 70° to 75°F. The casing 
soil should be well moistened by repeated sprinkhng, and not by a sud- 
den drenching. Under favorable conditions, such a bed should come 
into bearing in from six to eight weeks after spawning, and during the 
period of production constant care in the matter of watering is neces- 
sary to keep the beds up to the maximum conditions of production. 
The making of spawn is an art in itself and the process is fully described 
in a recent book by B. M. Duggar on "Mushroom Growing," published 
in 191 5 by Orange Judd Company, New York. Duggar also ascer- 
tained in his studies of the mushroom that fragments of growing mush- 
rooms obtained under aseptic conditions could be made the starting 
point for pure cultures of spawn. This is based on the fact, that a 
small piece of the inner stipe tissue of a fresh mushroom will, when 
placed on any suitable sterile nutrient medium, promptly develop a 
mycelium. The method of making pure cultures is described in Bulle- 
tin 85, Bureau of Plant Industry, United States Department of Agri- 
culture and in Duggar's "Mushroom Growing" and need not be re- 
peated here. 

Chemistry and Toxicology of Mushrooms. — With the increase 
in the cost of hving and in our population, which is beginning to feel the 
shortage of food supplies, earnest attention has been directed to foods, 
such as the edible wild fungi, which are frequently abundant during the 
summer months. One phase of this study has been the investigation 
of the food value of mushrooms and toadstools. Chemical analyses 
have been made to ascertain what they contain. It has been found, 
that such a fungus as Polyporus sulphureus, has over 70 per cent, of 
water, while species of Agariciis and Coprinus have fully 90 per cent, 
of water. As to nitrogen, although the proportion of this element in 
the dry matter of different fleshy species varies from 2 to 6 per cent., it 
has been found that much of the nitrogen is present in the form of non- 
protein substance of a very low food value and some of it enters into 
the composition of a substance closely related to cellulose. Thus, not- 
withstanding the fact that Coprinus comatns contains 5.79 per cent, of 
nitrogen, we find only 0.82 per cent, as available (digestible) proteins, 



238 



MYCOLOGY 



SO that the food value of this form is less than had formerly been sup- 
posed. The fatty substances soluble in ether are present to the amount 
of 4 to 8 per cent. The carbohydrates (cellulose, glycogen, trehalose, 
mannite, glucose, etc.) make up the largest part of the dry matter of 
the mushroom. Starch usually present in higher plants is absent in 
these fungi. The ash varies greatly, varying from i,o8 to 15 per cent. 

with potassium as the most 
abundant element. Sulphuric 
acid occurs in the ash of all fungi, 
with 1.58 per cent, in the ash of 
Hehella esculenta. 

The poisonous substances are 
alkaloids, such as choline, found 
in Amanita muscaria, Hehella 
esculenta and other fungi, neurin 
(deadly), muscarin, the most 
dangerous alkaloid found in toad- 
stools, as in Amanita muscaria 
(Fig. 93). Phallin, a deadly 
poison, found in Amanita phal- 
loides, is albuminous in nature. 
Helvellic acid, a deadly poisonous 
substance, occurs in Helvetia es- 
culenta, especially in old decaying 
specimens. The symptoms of 
poisoning with muscarin are long 
delayed. They may be summed 
up in the words of Mr. V. K. 
Chestnut (Circular No. 13 Divi- 
sion of Botany, United States 
Department of Agriculture) : 
"Vomiting and diarrhoea almost 
always occur, with a pronounced flow of saliva, suppression of the 
urine, and various cerebral phenomena beginning with giddiness, 
loss of confidence in one's ability to make ordinary movements, and 
derangements of vision. This is succeeded by stupor, cold sweats, 
and a very marked weakening of the heart's action. In case of rapid 
recovery, the stupor is short and usually marked with mild delirium. 




Fig. 95. — Deadly amanita, Amanita 
phalloides, showing death cup, or volva, at 
base of stipe. {From Gager, after E. M. 
Kiltredge.) 



MUSHROOMS AND TOADSTOOLS 239 

In fatal cases, the stupor continues from one to two or three days, 
and death at last ensues from the gradual weakening and final stop- 
page of the heart's action." Fortunately an antidote has been found 
in the hypodermic injection of atropine in doses of one-hundredth to 
one-sixtieth of a grain. Strong emetics should also be used to rid the 
stomach of the offending food. The action of phallin from Amanita 
phalloides (Fig. 95) for which no antidote is known except the adminis- 
tration of emetics and the transfusion of blood into the patient, which 
may be of little avail is best summed up in Chestnut's account: "The 
fundamental injury is not due, as in the case of muscarin, to a paralysis 
of the nerves controlling the action of the heart, but to a direct effect 
on the blood corpuscles. These are quickly dissolved by phallin, the 
blood serum escaping from the blood-vessels into the alimentary canal, 
and the whole system being drained rapidly of its vitality. No bad 
taste warns the victim, nor do the preUminary symptoms begin until 
nine to fourteen hours after the poisonous mushrooms are eaten. There 
is then considerable abdominal pain and there may be cramps in the 
legs and other nervous phenomena, such as convulsions and even lock- 
jaw, or other kinds of tetanic spasms. The pulse is weak, the abdom- 
inal pain is followed rapidly by nausea, vomiting, and extreme diarrhoea, 
the intestinal discharges assuming the rice-water condition characteristic 
of cholera. The latter symptoms are maintained persistently, generally 
without loss of consciousness, until death ensues, which happens in 
from two to four days." 

B. Gasteromycetes. — -The fungi known as the Gasteromycetes 
{yaarrip = belly, sac -f /jlvktjs = fungus) have the basidial layers, or 
hymenium, enclosed within a peridium, as in the common puff-ball. 
The shell or hull enclosing the masses of spores is called the peridium, 
which is a simple uniform layer in some genera (Scleroderma), or it con- 
sists of two distinct layers, the exoperidium and the endoperidium. 
The earth-star (Geaster) has a thick outer peridium, which splits in a 
stellate manner, later becoming reflexed. The exoperidium in such 
genera as Bovista and Lycoperdon is a loose pliable coat often having 
spines and warts. Many of the genera are stalkless, but other genera, 
such as Tylostoma, are stalked. Inside of an unripe puff-ball, we find a 
white fleshy mass of soft cellular matter, the gleba. As the fruit 
bodies grow they become chambered. The chambers, in countless 
numbers, are narrow, irregularly curved and branched, separated from 



240 MYCOLOGY 

each other by curved plates of tissue which anastomose in every direc- 
tion. The walls of the chambers consist of layers of branched hyphse 
bearing the basidia which line the interior walls of the cavities and con- 
stitute the hymenium. Each basidium usually bears four spores. 
The way the spores are borne on the basidia is characteristic. They are 
almost sessile in Geaster, in Bovista they are found on long sterigmata. 
Mitremyces may have as many as a dozen basidiospores, which are 
sessile and lateral. 

When the puff-ball reaches full size and ripens, the tissues become 
moist, deliquesce and change in color. The tissues are absorbed and 
disappear and the whole mass dries up, leaving the interior sur- 
rounded by the peridium filled with a dry dusty mass usually con- 
sisting of slender threads (the capillitium) and countless multi- 
tudes of ripe spores. The threads of the capillitium are absent in many 
genera, but when present they are characteristic and used as important 
points in the classification. There are two distinct kinds of capillitial 
threads. In one kind, the threads are long hair-like strands, simple, 
more or less branched and interwoven, proceeding from the inner walls 
of the peridium, or from the centrally placed columella. The second 
type, characteristic of Bovista, Bovlstella and Mycenastrum, has rela- 
tively short and branched threads entirely separate and distinct from 
each other and are not connected with the peridium nor the columella. 
The bird-nest fungi are characterized by the thickening of the walls of 
the glebal chambers to form separate little seed-hke bodies enclosing the 
spores. These are known as peridioles. The ripe spores in some are 
smooth, some are spinulose, while in shape they are globose, oblong or 
oval. 

The most primitive forms of these fungi are probably the subter- 
ranean forms included in the family Hymenogastrace^. In one 
classification of the Gasteromycetes, the division of the famihes is 
based on whether the sporophore is borne above or below the ground. 
The family Hymenogastrace^ with subterranean fruit bodies belongs 
to one division, all of the other families to the other division. 

Family i. Hymenogastrace^. — The subterranean fruit bodies of 
these fungi suggest those of the families Terfeziace^ and Tuberace^ 
among the ASCOMYCETALES, but the spores of the two latter 
families are borne in asci, and are known as ascospores, while those of 
the former family are borne on basidia and are known as basidiospores. 



MUSHROOMS AND TOADSTOOLS 24 1 

Most of the forms are irregularly globose and grow under trees, some- 
times their association with certain kinds of trees suggesting a para- 
sitic attachment. They are often found in sandy places, where they 
are exposed frequently by rain erosion. The mycelium of these fungi 
is filamentous, or cord-like. The gleba is richly chambered and the 
walls of the glebal chambers are lined with the hymenium. Cystidia 
are often found between the basidia. The fruit bodies are variously 
shaped. In Lycogalopsis, they are hemispheric; in Phyllogaster, pear- 
shaped; in Cauloglossum, club-shaped; some are stalked and suggest 
the shape of the Agaricace^. 

Very few of the forms are known commonly, and of the dozen Cali- 
fornian species, many are known imperfectly by a single collection. 
Gaiitieria and Sclerogaster have each a single species in California; 
Hymenogaster and Octaviana are represented by two Californian species, 
while Hysterangium and Melanogaster have three species in California. 
Two species of Rhizopogon and one of Melanogaster are found in South 
Carolina. The climate probably has something to do with this 
distribution. 

Family 2. Tylostomace^. At first, the fruit body is subter- 
ranean, later as in Tylostoma niammosa, a form found in heathland, it is 
raised on a stalk not prolonged as an axis. The peridium is double, the 
outer one falUng off at maturity, the inner one is thin. The uncham- 
bered gleba possesses well-developed capilUtial threads, which are con- 
nected with the inner wall of the endoperidium. The basidia in 
Tylostoma are unicellular, club-shaped and bear four laterally placed 
spores, one above the other on well-developed sterigmata, thus differ- 
ing from the other two basidiomycetous fungi. 

Family 3. Lycoperdace^. — -The fruit body from the beginning is 
epigaeic. Its gleba is chambered richly and the inner walls of each 
chamber are lined with a hymenium. The peridium is differentiated 
into an outer and an inner peridium. The gleba, when ripe, breaks 
down into powdery spores and richly branched capilHtial threads. This 
family contains some of our most delicious and important food species, 
if they are taken before fully mature. The genus Ly coper don, in which 
the true peridium opens by an apical mouth, includes over one hundred 
species, which in America can be divided into the purple-spored series, 
and the olive-spored series. Lycoperdon atropurpureum is found in sandy 
pastures, woods and bushy places commonly in the months from August 
16 



242 



MYCOLOGY 



to October. It is an extremely variable species, Lycoperdon gemma- 
turn, an olive-spored species, has a turbinate shape, its outer peridium 
being marked with long, thick, erect spines, or warts of irregular shape 
with intervening smaller ones, whitish, or gray in color. The larger 
spines fall away first imparting to the surface of the peridium a reticu- 
late appearance. It often grows cespitosely on the ground, or rotten 
tree trunks in woodlands. Lycoperdon pyriforme is another common 
species found in woods and clearings on the ground, or on decaying 
wood. It is edible, tender and of second-class flavor when young. 




Fig. 96. — Fruit-body of Calvatia cyalhiformis. {Photo, by IF. H. Wahnsley.) 



The largest puff-balls are included in the genus Calvatia (Fig. 96), 
which differs from Lycoperdon in the absence of an apical mouth and 
a regular dehiscence. The fruit bodies are globose, or top-shaped, aris- 
ing on the surface of the ground from subterranean, cord-like hyphae. 
Calvatia cyathiformis (Fig. 96) which is edible, if eaten when white in- 
side, grows in open grassy fields and lawns and reaches a diameter of 
three to six inches. Calvatia gigantea, the giant puff-ball, grows in 
pastures and meadows. Usually the fruit bodies are ten to twenty 
inches in diameter and even larger. The genus Bovista has a fragile 



MUSHROOMS AND TOADSTOOLS 243 

exoperidium, and in the absence of a sterile base and the fact that the 
fruit body separates easily from the place of attachment it is distin- 
guished from Lycoperdon. Because they are readily detached and 




Fig. 97. — Specimen of Geaster fornicatus from Carleton Rea, England. {After Lloyd, 
J. U., and C. G., Bull. 5, Lloyd Library, June, 1902, Mycological Series No. 2.) 

readily blown about, they are called "tumblers." Catastoma has an 
outer peridium which splits by a circular Hne of cleavage, so that the 
upper part is dislodged carrying along with it the inner peridium which 



244 MYCOLOGY 

opens by a mouth that is situated at the actual base of the plant as it 
grows. The lower part remains as a saucer-shaped body in the soil. 
A capillitium is present. Catastoma circumscissum is the common species. 

The earth stars are included in the genus Geaster, where the peridium 
consists of three persistent coats, the two outer adhere and split into 
leathery, stellate divisions exposing the parchment-like inner peridium, 
which opens by an apical pore (Fig. 97). It has a columella. The spores 
are dark brown and mixed with the simple capillitial threads. Geaster 
hygrometricus is the common species. It grows in sandy soil and in dry 
weather its segments are strongly recurved, but in wet weather they 
expand, hence the plant is sometimes dubbed poor man's weather 
glass. Astr(Eus, which resembles Geaster, is distinguished by the 
absence of a columella and by the long capilUtial threads which are 
much branched and interwoven. 

Family 4. Nidulariace^. — The following account of the family 
of bird's-nest fungi is taken from Bulletin 175, United States Depart- 
ment of Agriculture, on "Mushrooms and Other Common Fungi" by 
Flora W. Patterson and Vera K. Charles. Dried material of these 
fungi might be kept for use by the class in the systematic study of the 
higher fungi with the following key at hand. The types should be 
used as unknowns. 

Members of the family Nidulariace^ are represented by small, 
leathery, cup-shaped plants growing on old sacking, manure, earth, and 
decaying or dried wood. The common name is suggested by the form 
of the peridium, which is cup-shaped and contains many small, lenticu- 
lar bodies (peridiola) resembhng eggs. The mouth of the peridium is at 
first covered by a membrane (epiphragm), which later becomes ruptured 
and exposes the peridioles. In Cyathiis and Crucibulum, the peridi- 
oles are attached to the inner wall of the peridium by elastic cords 
called funiculi. The spore-bearing tissue and spores are never resolved 
into a dusty mass, as in many Gasteromycetes, but persist in the 
form of peridiola which contain the spores, which are hyaline and 
ellipsoidal to subglobose. 

Key to Nidulariace^ 

Peridium with several to many sporangioles: 
Peridium torn at the apex in opening— 

Sporangioles not attached to the inner wall of the peridium. Nidiilaria. 



MUSHROOMS AND TOADSTOOLS 245 

Peridium opening by a deciduous membrane — 

Sporangioles attached to the inner wall of the peridium — 
Peridium of three united layers and spores mixed with 

filaments Cyalhua. 

Peridium of a single layer and spores not mixed with 

filaments Crudbnlmn. 



Cyathus 

In Cyalhiis the peridium is cup-like and composed of three layers. 
The apex is covered by a white membrane, which bursts, disclosing egg- 
like bodies, the peridiola, which usually fill about one-half of the cup. 
The peridiola are attached to the inner wall of the peridium by an elastic 
cord, which is attached to each peridiolum in a depression on one side. 

Cyathus stercoreus 

Peridium cylindrical, campanulate to infundibuliform, sessile or with an elon- 
gated base, light brownish, at first with shaggy, matted hairs which disappear in age, 
interior smooth and nonstriate; peridiola black. 

Cyathus skrcoreus is an exceedingly common species and is to be found growing 
on manure or in heavily manured places. It is subject to considerable variation in 
size and form. 

Cyathus striatus 

Peridium obconic, exterior even, brownish, hairy, interior striate, lead-colored; 
apex truncate, covered by a white membrane, which is at first strigose; peridiola 
compressed, subcircular. 

Plant one-half to three-fourths inch in height and about three-eighths inch in 
diameter. 

Cyathus vernicosus 

Peridium bell-shaped, subsessile, base narrow, broadly open above, exterior at 
first brownish, silky tomentose, becoming smooth, interior dull lead color, smooth. 
Differs from Cyathus striatus in the even, non-fluted inner surface of the peridium and 
in the larger peridiola. 

Plant about one-half inch in height and about three-eighths inch in diameter. 



Crucibulum 

In Crucibulum the peridium is cup-shaped and consists of one thick 
fibrous layer, Hned by a very thin, smooth, and shining layer. The 



246 MYCOLOGY 

mouth when young is covered with a yellowish tomentose membrane, 
the peridiola are more numerous than in the preceding genus, and each is 
Attached to the peridium by an elastic cord which springs from a pro- 
jection on the peridiolum. The plants are smaller than in the genus 
Cyathus. 

Crucibulum vidgare 

Peridium yellowish-brown, becoming paler with age, outer surface when young 
velvety tomentose, inner surface smooth and shining; mouth at first closed by a yel- 
lowish membrane, which ruptures and exposes the peridiola. Peridiola biconcave, 
with a projection on one side from which originates the elastic cord which attaches 
the peridiola to the peridium. 

Plant about one-fourth inch in height and about the same in diameter. 

Family 5. Sclerodermace^. — The fruit bodies of the fungi in- 
cluded in this family are subterranean, or epigeic, globose, sessile, or 
occasionally with a root-like stalk. The peridium is generally simple, 
thick, rough, warty, or scaly, opening irregularly at maturity. The 
gleba consists of rounded basidia-bearing parts, which are separated by 
sterile veins or strands of hyphge. The individual basidia are pear- 
shaped to club-shaped with spores which are often lateral in position. 
The capilhtiiim is rudimentary. Scleroderma is the most common genus 
with sessile fruit bodies and thick, hard, leathery peridium, frequently 
warty. It usually bursts at the apex into stellate lobes. Scleroderma 
geaster grows in sandy woods, banks or along roadsides. S. vidgare 
is common in dry situations, or hard ground, along cinder paths and 
gravel walks. 

Family 6. Sph^robolace^. — The fruit body is on the surface of 
the ground. The periphery of the gleba is furnished with a palisade- 
like layer of radially arranged turgescent cells. The basidia-bearing 
portion of the gleba is penetrated by sterile veins, or hyphal strands. 
When ripe the gelatinous gleba is forcibly ejected from the fruit body by 
the inversion of the pahsade-like layer. The family includes a single 
genus, Sphcerobolus, of five species. The best-known species is S. car- 
pobolus of cosmopolitan distribution. 

C. Phallomycetes. — The carrion fungi, stink-horn fungi, or dead- 
men's fingers, resembles the button stage of the Amanitas, and the puff- 
balls when still young, but later the outer wall is ruptured and the stem 
elongates carrying upward the sporogenous tissue as a terminal cap, or 
enlargement. The subterranean mycehum is cord-hke and from it the 



MUSHROOMS AND TOADSTOOLS 



247 



fruit body arises which has a pcridium of two or three layers. The 
outer peridium is leathery and tough, while the inner peridium is gelat- 
inous at maturity. The outer peridium remains at the base, as a 
cup called the volva. The sporophore, pileus, or cap, is raised up on the 
end of a stalk, or stipe, which is usually spongy in character. The 
sporophore takes a variety of forms, but in all cases, its outer surface at 




y^'"- 



Fig. 98. 



-Clathrus cancellatus, fully mature fruit-body, natural size. {After Ed. 
Fischer, Die naliirlichen Pflanzenfamilien I. lA**, p. 282.) 



first represents the hymenium which deliquesces at maturity, so that the 
minute spores are imbedded in a greenish, fetid sUme, which gives off a 
penetrating, nauseating odor, attractive to blue-bottle flies, that lick 
off the malodorous slime with evident enjoyment and are the agents 
by which the spores are distributed. In fact, it has been proved that 
the basidiospores germinate better after passage through the alimentary 



248 MYCOLOGY 

canals of flies. The gleba is the fruiting portion of the phalloid and its . 
bulk appears considerable in the early egg-shaped stage of the fruit 
body. As the carrion fungus matures, it forms proportionately less of 
the fruit body, for it is converted into the greenish, mucilaginous mass 
which is removed by the flies. Some forms like Didyophora have a veil 
that hangs under the pileus and spreads out as a net around the stem. 
Although it is called the veil, it is more correctly the indusium. The 
sporophore in genera like Clathrus (Fig. 98) takes the form of a hollow 
sphere, or of a basket-like lattice, while in other genera it resembles the 
open iron framework of a lantern, a brazier, a crinoid, or storie-lily, an 
octopus, or even a sea-anemone. One tropic form of Brazil has been 
called Pilzblumen by the Germans. The species are not common in 
temperate regions, but in the tropics they are richer in forms and more 
abundant; for example, in Florida the species of Clathrus are common, 
the writer finding four specimens within a quarter of a mile along a road 
across the sand dunes at Ormond. 

Development of the Carrion Fungi. — Several authors have studied 
the development of several forms of the Phallomycetes, notably 
Burt and Atkinson. Burt^ has contributed three papers dealing with 
the genera Anthurus, Clathrus and Mutinus, while Atkinson's studies^ 
are concerned with Ithyphallus and Didyophora. 

Burt finds in the Clathrace^ that the egg consists of cortical and 
medullary systems continued upward from the mycelial strand in the 
earliest stage. The cortical layer gives rise to the outer layer of the 
volva, the cortical plates and the pseudoparenchyma of the receptacu- 
lum. The medullary portion gives rise to the gelatinous masses of the 
gelatinous layer of the volva, to the gleba, and to the gelatinous tissue 
of the chambers of the receptaculum. The elongation of the receptacle 
in Clathrus columnatus (Fig. 98) begins at the base and after its elonga- 
tion the gleba hangs suspended from the arch of the receptaculum by 
medullary tissue constituting the chamber masses of the receptacle. 

In the earliest recognizable stage of Mutinus caninus, the egg con- 
sists of the cortical and medullary tissues of the mycelial strand, 

1 Burt, Edward A.: A North American Anthurus: Its Structure and Develop- 
ment. Memoirs Boston Soc. of Nat. Hist., 3: 487 (1894); The Development of 
Mutinus caninus. Annals of Botany, 10: 343 (1896); The Phalloideas of the United 
States. Development of the Receptacle of Clathrus columnaLus. 

Atkinson, George F.: The Origin and Taxonomic Value of the Veil in Dicty- 
ophora and Ithyphallus. Botanical Gazette, 50: 1-20, January, 1911. 



MUSHROOMS AND TOADSTOOLS 



249 



continued directly upward from the strand. Of these tissues, the 
medullary bundle spreads out at its upper end and forms a dense 
sheaf-like head by repeated branching and anastomosing. The 
cortical layer of tissue becomes the outer wall of the volva; the sheaf- 
like head gradually differentiates into all the other parts of the older 
egg. In such differentiation the central 
column first appears. The formation of 
the gelatinous layer of the volva now begins 
in the periphery of the head. A dense 
dome-shaped mass arises. Along the inner 
surface of the dense zone and next to the in- 
termediate tissue, the rudiment of the gleba 
arises from the clustered swollen ends of 
lateral branches of the tramal tissue. These 
hyphal ends take position in a palisade 
layer facing the intermediate tissues and by 
the crowding in of new hyphal ends (basidia) 
the surface of this layer becomes greatly 
enlarged and thrown into folds and torn 
from the intermediate tissue. The rudiment 
of the stipe arises in the intermediate tissue 
lying next to the central column by the forma- 
tion of deeply staining tissue rich in proto- 
plasm. Somewhat later, masses of tissue in 
the dense and intricately interwoven rudi- 
ment of the stipe show a tendency toward 
gelatinization. These masses mark the 
position of the later chamber-cavities in the 
wall. Toward the upper end of the stipe, 
such masses are in contact with the central 
column, and they mark the position of the 
pits which open into the main central cavity 
of the stipe in mature stages of M. can in us. 

The chamber walls are thrown into folds through a more rapid growth 
of the pseudoparenchyma than that of other parts of the egg. Final 
elongation of the stipe and elevation of the gleba is brought about 
through the straightening out of the folds in the chamber walls. 

The studies of Atkinson deal with the origin of the veil of Dictyo- 




FiG. 99. — Mature stink- 
horn, Diclyophora duplicata. 
{Photo by W. II. Walmsley.) 



2 50 



MYCOLOGY 



phoni (Figs, gg and loo), and llhyphaUiis. From such studies, he 
confirms the making of two genera out of them. His plates show 




Fig. 100. — Diclyophora phallaidea. Fully developed fruit-body with veil 2/3 natural 
size. {After Alf Moller in Die natUrlichen pflanzenfamilien I. lA **, p. 294.) 

that three common forms were examined, viz., Ilhy phallus impudicus, 
Diclyophora duplicata and the Phallus Ravenellii. 

Two families are distinguished: Clathrace^ and Phallace^ 
which may be distinguished as follows: 



MUSHROOMS AND TOADSTOOLS 



251 



Receptacle latticed or irregularly branched, sessile or stalked; 
gleba inclosed within the receptacle. Family i. Clathrace^. 

Receptacle tubular or cyhndric, capitate, with the gleba external. 
Family 2. Piiallace.e. 




Fig. ioi. — A, B, Dictyophora phalloidea. A, Longitudinal section of a fruit-body 
fully stretched beyond volva (natural size); B, longitudinal section of a young fruit- 
body (twice enlarged); G, volva mucilage; a, gleba; H, cap; /, indusium; Sw, stipe; 
Pi, primordial layer between cap and indusium'; Pi, primordial layer between in- 
dusium and stipe; S, S, tissue of stem; B, tissue of base of fruit-body. {After Ed. 
Fischer in Die naliirlichen PJlanzejifamilien I. lA**, p. 295.) 

The first family, according to "Die natiirlichen Pflanzenfamilien, " 
comprises eleven genera of which Clathrtis (Fig. 98), Sinihlum, An- 
thurus are North American. Three species of Clathrus have been col- 
lected in this country. Simhlum rubescens was collected originally on 



252 MYCOLOGY 

Long Island and later in Nebraska, while Anthurus horcalis has been 
found in New York, Massachusetts and Pennsylvania. 

The family Phallace^ is represented in the eastern United States 
by three important and interesting genera, viz., Mutinus, I thy phallus, 
Didyophora (Figs. 99, 100, loi). Mutinus is the simplest form with 
the gleba Ijorne on the upper portion of the stipe without the hanging 
cap. Mutinus caninus has a hollow, perforate stipe reddish in color 
bearing the greenish bad-smelling spore slime over its upper end. 
Ithyphallus impudicus, our commonest species, has a globose volva, 
cylindric, hollow spongy stalk bearing a campanulate pileus, the spore- 
bearing surface being reticulate pitted. Didyophora duplicata, which 
resembles the Brazihan Pilzblumen, D. phalloidea in (Figs. 100, loi) 
the possession of a long white indusium, which hangs down beneath the 
cap like a spread-out hoopskirt. The terminal cap is campanulate 
and after the removal of the malodorous greenish spore slime appears 
reticulate-pitted. The volva is prominent. 

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MUSHROOMS AND TOADSTOOLS 253 

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Fayod, v.: Prodrome d'une histoire naturelle des Agaricinees. Ann. Sci. Nat. 

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2 54 MYCOLOGY 

Ferguson, Margaret C: A Preliminary Study of the Germination of the Spores 

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MUSHROOMS AND TOADSTOOLS 255 

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256 MYCOLOGY 

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25, 1916. 



CHAPTER XXII 
FUNGI IMPERFECTI (DEUTEROMYCETES) 

The life histories of the fungi belonging to this group are imperfectly 
known, and hence, it happens that when it has been established, the 
type is removed from the fungi imperfecti and properly classified with 
some other group. The name Deuteromycetes, also applied to the 
imperfect fungi, is derived from the Greek, devrepos = second. Many 
important parasites are included here, and hence, it has been considered 
important by mycologists to give the characters by which the fungi 
imperfecti are distinguished. 

General Characters. — The mycelium consists of septate, hyaline, or 
pigmented hyphas, or only of chain of yeast-like cells. The hyphas are 
diffuse, or plectenchymatous (irXeKTos = woven). Stromata are fre- 
quently present. The fructification is a single conidiophore, a layer 
of conidiophores, or a conidial fructification (pycnidium). The 
Fungi Imperfecti represent the accessory fruit forms of the ASCOMY- 
CETALES, rarely those of other orders. The mycelium is practically 
the same as found in the sac fungi. The septate hyphae spread over 
the substratum, or penetrate its interior, and the fungi live sapro- 
phytically, or parasitically. The arrangement of the hyphas in various 
ways has suggested the segregation of species and genera. The under 
layer (subiculum = felted stratum of hyphae) is of loose, entangled 
threads, or disc-like bodies, or radially stretching fibrils, aggregated 
loosely. The stroma on the contrary represents compact tissue, cor- 
responding to similarly named structures in the ASCOMYCETALES. 
The fruit layer originates in or on the stroma. 

Reproduction is dependent on exogenously produced spores, known 
as conidiospores. In the simplest cases, the mycelium gives rise at 
indefinite places to outgrowths, which are separated as spores. There 
arise from the mycelium, erect conidiophores which form conidiospores 
in the different species. With an unbranched conidiophore, the conidio- 
spores arise at its apex followed by a second, a third, etc. When the 
end of the conidiophore is globutar, the spores arise on the ends of 
sterigma. By the branching of the conidiophores originate conidial 

258 



rUNGI IMPERFECTI (dEUTEROMYCETES) 259 




Fig. 102. — Phylloslicta pavice on horse-chestnut leaves. (Cold Spring Harbor, L.I., 
July 28. 1915-) 



26o MYCOLOGY 

strands, which suggest the inflorescences of flowering plants. One can 
separate these into monopodial, or sympodial forms. A bundle of coni- 
diophores is known as a coremium {Kopr^na = broom). If the conidio- 
phores are arranged side by side, they form a conidial layer, which 
arises on the upper surface of a stroma. Such a conidial layer may be 
folded, or it may be chambered, the irregular chambered spaces being 
lined with the conidial layer. Finally, the conidial layer may be in- 
closed in receptacles called pycnidium, which correspond to those of 
the Pyrenomycetiine^. The conidiospores are of different sizes, 
hence one can distinguish them as a micropycnidia and as macro- 
pycnidia, and the spores as micro- and macropycnospores. Stylospores 
are those spores borne on a filament {oTxiKos = a column). This term 
is also superfluous. The number of fungi imperfecti surpasses the 
ASCOMYCETALES. 

Systematic Position. — Fuckel includes all those fungous forms 
as fungi imperfecti which have no final fruit forms, such as asci 
and basidia. The name Deuteromycetes of Saccardo is less fortunate 
than that of Fuckel. That many fungi imperfecti represent accessory 
fruit forms of ASCOMYCETALES is known, so that the group is not 
a permanent systematic entity. It is a motley assemblage of hetero- 
geneous forms. As with the large group, so it is with the genera. 
Some of the genera inclose not always related forms, that is of the same 
phylogenetic series. Schroeter calls such genera Formgattungen ( = 
form genera). In the following classification of them, this point of 
view must be kept prominently in view, for a natural classification of 
Fungi Imperfecti is in the nature of things an impossibility. The great- 
est number are saprophytes, useful in the destruction of dead plant 
parts. Many are parasites and produce dangerous diseases in culti- 
vated plants. 

A. Conidia in pycnidia, or chamber-like hollows. I. SPH^ROPSI- 
DALES. 

B. Conidia in conidial layer formed ultimately wholly free. II. 
MELANCONIALES. 

C. Conidia on conidiophores. Single or in coremia. III. HYPHO- 
MYCETALES. 

I. SPH^ROPSIDALES.— The conidia are formed in pycnidia. 
The receptacles are closed or open by a pore, or by a slit suggesting 



FUNGI IMPERrECTI (dEUTEROMYCETES^ 



?6l 



groups of ASCOMYCETALES. Four families are included in this 
order, and these families include a considerable number of important 
genera of fungi, which specifically are the cause of important plant 
diseases. PhyUosticta is a genus, the species of which are confined to 
leaves, and they produce characteristic leaf spots on a great variety of 
plants. The specific name of the fungus is usually derived from that 
of the host plant attacked, as for example, PhyUosticta catalpce, which 




Fig. 103. — Six j3en Davis apples showing apple blotch (Phyllostica solilaria). 
{After Scott, W. M., and Rorer, J. B., Bull. 144, U. S. Bureau of Plant Jndustry, 
March 6, 1909.) 



grows on the leaves of the catalpa. The group has been monographed 
systematically by J. B. Ellis. The spores are small, egg-shaped or 
elongated, unseptate and in color pale green, or hyaline, produced in 
pycnidia. The most important species of this genus are PhyUosticta 
ampelopsidis on the Virginia creeper {A mpelopsis) ; catalpcB on catalpa 
leaves; labruscce on the leaves of the grape; pavi<^ on horse chest- 
nut leaves (Fig. 102); PhyUosticta solitaria E. and E. (Figs. 103 and 
104) is the cause of apple blotch, and violce on violets. The conidio- 



262 



MYCOLOGY 



spores in Phoma are colorless and unicellular. The pycnidia are 
black with a terminal pore and depressed in the tissues of the host. 
The genus is arbitrarily limited to those species in which the spores 
are less than 15^, for the larger spored forms have been placed in the 
genus Macrophoma. The most important species from the pathologic 
viewpoint are out of the iioo species recognized the following: Phoma 
betcB is the cause of the heart rot and blight of beets. Phoma batata 
produces a dry rot of sweet potato; while Phoma solani behaves much 




nrn o 



Fig. 104. — Microscopic characters of apple blotch fungus {Phyllosticta solilaria). 
I, vertical section of pycnidium showing pycnospores; 2, 3, 4, 5, mature pycnospores; 
6, 7, 8, germinating spores; 9, mycelium. {After Scott, W M.. and Rorer, J. B., Bull. 
144, U. S. Bureau of Plant Industry, pi. Hi, March 16, 1909.) 



like the damping-o£f fungus, attacking seedling egg plants near the sur- 
face of the ground. The most destructive fungus of the genus Sphcerop- 
sis is S. malorum which causes the decay of apples, quinces and pears 
and attacks the stem of the apple tree producing characteristic cankers. 
The genus includes about 180 species. The 150 species of the genus 
C oniothyrium are widely spread geographically. The blight of rasp- 
berry canes is due to Coniothyrium Fuckelii, which has only recently 
come into prominence in the United States. The genus Septoria in- 



FUNGI IMPERFECTI (dEUTEROMYCETES) 



263 




Fig. 105. — Septoria leaf spot disease of celery, or celery blight. (After Coons, G. N., 
and Levin, Ezra, Spec. Bull. 77, Mich. Agric. Coll. Exper. Stat., March. 1916. 



SPORES^ 




Fig. 106. — Section through leaf spot of celery blight (Septoria) ^i i-lis) 

in leaf tissue and pycnidium with exuding pycnospores. (After Coons, G. 11., and 
Levin, Ezra, Spec. Bull. 77, Mich. Agric. Coll. Exper. Slat., March, 1916.) 



264 MYCOLOGY 

eludes the fungi which c§iuse the leaf spot of the pear, Septoria pyricola, 
the late blight of the celery S. petroselini (Figs. 105 and 106), the leaf 
blight of the tomato S. lycopersici and the leaf spot of currants, S. rihis. 
The pycnidia in this genus develop under the epidermis of the host 
producing leaf spots. The center of the leaf spot is occupied by the pore 
of the spheric, black pycnidium. Leptothyrium pomi is an imperfect 
fungus responsible for the sooty blotch of the apple and other 
plants. According to Floyd the same fungus causes the fly speck of 
apples. The genus Entomosporium is a small one with closed half- 
spheric, black pycnidia. The spores suggest an insect in being four- 
celled, the cells being arranged cross-like with attenuated extremities 
and swollen bases. Entomosporium maculatum is the cause of the leaf 
blight of the pear and quince. 

II. MELANCONIALES.^ — The mycelium is formed in the interior 
of the host plants. The fruit is in the form of a conidial hymenium, 
which is produced below the epidermis of the host, breaking through 
clefts in the surface of the host as bright or black spots. The conidio- 
phores stand closely together and are simple, or rarely branched, hya- 
line, or rarely dark-colored. Pycnidia are unknown in this group of 
imperfect fungi. The spores are of different shapes, single or in chains. 
The order includes both parasites and saprophytes. The pustule, or 
acervulus, which produces spores in Gleosporium may be extensive 
The short conidiophore arise from or are inclosed within a cushion, 
or stroma, of fungous tissue. The rupture of the epidermis of the host 
is accomplished by the opening of the stroma. The ovoidal, fusiform, 
slightly curved hyahne spores are discharged with the opening of the 
stroma. Some species of Gloeosporium are connected with other genera, 
viz., Glomerella (rufomaculans) , Gnomonia and Pseud opeziza the im- 
perfect stages of which were placed as species under the form genus 
Glososporium, which is the important form pathologically speaking. 
As examples of the form genus Gloeosporium, we have G. ampelophagum 
which causes the anthracnose of the grape; G. venetum which is re- 
sponsible for the anthracnose of blackberry and raspberry, while other 
species attack the linden, walnut, pine and Norway maple. 

In Colletotrichum (Fig. 107) the conidial cushions have a bristly 
border, while the conidiospores are in chains. Colletotrichum Lindemuth- 
ianum causes anthracnose of bean, an important disease in gardens and 
fields (Fig. 107). The cotton is attacked by C. gossypii, citrus fruits by 



FUNGI IMPERFECTI (dEUTEROMYCETEs) 



!65 




4 M 



\ i 




^k 




Fig. 107. — Anthracnose cankers on bean pods (Colletolrichum Lindemidhianum) 
(After Whetzel, H. H., Bull. 255, Cornell Agric. Exper. Stat.) 



266 



MYCOLOGY 



C. glceosporioides, clovers and alfalfa by C. trijolii and the snapdragon 
by C. antirrhini. Usually the diseases on these plants induced by species 
of Colletotrichum are known as anthracnose (Fig. 107). Coryneum Bei- 
jerinckii is a destructive fungus causing the peach blight. Pestalozzia 
Guepini var. vaccinii is a fungus often found upon the cranberry leaves 
and fruits. The conidiospores are three-celled, the terminal cells with 
filiform appendages. The shot-hole disease of plum and cherry is due to 
Cylindrosporium padi. The formation of the acervuli is followed by the 
falling out of the disease areas of the leaf resulting in the formation 

of the characteristic shot-hole. 
The fruit spot of apples is caused 
by C. pomii. 

III. HYPHOMYCETALES. 
— The hyphae are septate, 
branched in or on the substra- 
tum. They are dark, or hyaline, 
separate, or bound into coremia, 
or layer-like cushions. The con- 
idiospores may exist as oidio- 
spores through the separation of 
the hypha. The conidiophores 
are simple, or branched. The 
conidiospores of different shapes 
and colors are borne in a variety 
of ways on the conidiophores or 
their branches. The genera may 
be arranged in three series. 

A. MyceHum and spores light- 
colored: Oospora, Monilia, 
Oidium, Sporotrichum, Botrytis, Cephalothecium, Ramularia, Cercos- 
porella, Piricularia. B . Mycelium dark-colored at least with age ; spores 
generally dark: Fusicladium, Polythrincium, Scoletotrichum, Clado- 
sporium, Helminthosporium, Macrosporium, Alternaria, Cercospora, 
C. Conidiophores in the form of a tuberculate mass, or sporodochium : 
Volutella, Fusarmm. As examples of common disease producing forms 
of the above genera without enumerating all of the more important 
species may be mentioned the potato scab fungus, Actinomyces chro- 
mogenes, the early blight of potato fungus, Macrosporiums olani; the 




Fig., 108. — Sweet-potato stem rot 
{Fusarium balatalis). Section through 
sweet potato showing blackened ring just 
below surface caused by the stem-rot fun- 
gus. {After Harter, L. L., U. S. Farmers' 
Bull. 714, March ii, 1916.) 



FUNGI IMPERrECTI (dEUTEROMYCETES) 



267 



fungus which causes leaf spot of beets, Cercospora beticola. The form 
genus Fusarium (Fig. 109), established by Link in 1809, is one which 
has come into prominence recently as associated with the production 
of serious plant diseases. At least eleven species are found on the 
sweet potato (Fig. 108), and these have been investigated by H. W. 
Wollenweber^ and other mycologists. He finds that the genus has a 
number of vegetative and spore stages the variabihty of which has 
caused confusion, as transfers of mycehum produce a growth quite 
different in general appearance from that derived from spores from the 




Fig. 109. — Spores of two stem-rot organisms. A, Fusarium bataiatis and B. 
F. hyperoxysporum, X500. {After Harter, L. L., U. S. Farmers" Bull. 714, March 11, 
1916.) 



same medium under conditions otherwise identic. 'yVollenweber and 
AppeP have pubUshed a monograph of Fusarium and later Wollen- 
weber has studied the Fusarium problem and similar studies should 
be made of each one of the form genera of the Fungi Imperfecti. 
The genus Fusarium is divisible into sections not only by physiologic 
characters (pathogenicity) but also by morphologic characters (coni- 
diospores, chlamydospores). The section, Elegans, comprises the 
vascular parasitic Fusaria, which are serious enemies of plants, causing 

1 WoLLENWEBER, H. W. : Identification of Species of Fusarium occurring on 
the Sweet Potato, Ipomaa hatatis. Journal of Agricultural Research, II: 251-286 
July 15, 1914. 

^Appel, Otto, and Wollenwebek, H. W.: Grundlage einer Monograph 
der Gattung Fusarium Link Arb. Biol. Anst. f. Land. u. Forst., Bd. 8, Heft, i, 
pp. 1-207; Phytopathology III: 24-50. 



2 68 



MYCOLOGY 




Fig. 1 10. — Violet leaf spot {Fusarium viola), i, Germination of microconidio- 
sporeS; 2, formation of microconidiospores in hanging drop cultures; 3, germination 
of macroconidia; 4, various forms of macroconidia. (.After Mycologia, 2: 19-21, pi. 
xviii, January, 191 o). 



FUNGI IMPERFECTI (dEUTEROMYCETES) 269 

especially wilt diseases. Fusarium oxysporum and T. trichorthecoides 
can produce both tuber rot and wilt of the potato plant. Fusarium 
viola causes violet leaf spot (Fig. no). Ftisarium bat at atis is respon- 
sible for sweet potato stem rot (Figs. 108 and 109). 

The sterile fungus Rhizoctonia, represented in America by two para- 
sitic species Rhizoctonia solani, which is found on at least 165 different 
hosts, and R. crocorum with a limited distribution on alfalfa and potato 
tubers has through the discoveries of Rolfs and Burt been connected 
with a basidiomycetous fungus, Corticium vagum var. solani.^ 

1 Peltier, George L. : Parasitic Rhizoctonias in America. Bull, 189, Agri. 
Exper. Stat. University of Illinois, June, 1916. 



PART II 
GENERAL PLANT PATHOLOGY 

CHAPTER XXIII 
GENERAL CONSIDERATION OF PLANT DISEASES 

The student who would become acquainted with the general 
pathology of plants must have some previous knowledge of other sub- 
jects, especially those which are concerned with the life of the plant. 
To appreciate diseased conditions the normal state of the plant must 
be understood. A study of phytopathology, which as a department of 
scientific inquiry concerns itself with plant diseases, therefore, presup- 
poses that the would-be phytopathologist is acquainted with plant 
morphology, systematic botany (fungi and flowering plants) histology, 
cytology, embryology, genetics, physiology, with bacteriology, zoology 
(especially entomology) chemistry and physics,^ as well as meteorology. 
Plant morphology deals with the general form and gross structure of 
plant parts, such as roots, stems, leaves, flowers, fruits and seeds. The 
student should know the common fungi (see part I), the technique of 
their study (see part IV), as well as the flowering plants, which act as 
hosts to the bacteria and fungi causing disease. Histology is concerned 
with the microscopic details of plants, while cytology treats of cell 
structure and organization. Embryology, as a distinct subject of in- 
quiry, embraces a study of their productive cells and organs. Genetics 
is a new branch of inquiry. As Walter tersely put it, "The study of the 
origin of the individual, which has grown out of the more general 
consideration of the origin of species, forms the subject matter of 
heredity, or, to use the more definitive word of Bateson, of genetics." 
The functions of a plant are considered when we study physiology and 
the chief divisions of that subject treat of the nutrition, growth and 

1 Along these lines see suggestive papers by Ernest Shaw Reynolds: Plant 
Pathology in its Relations to other Sciences. Science, new ser., xxvii: 937-940; 
June 19, 1908. 

271 



272 GENERAL PLANT PATHOLOGY 

irritability of the living plant organisms. A knowledge of insect life 
is essential, as also the chemistry of the plant, of the soils, of the ferti- 
lizers, of the insecticides and fungicides. The physics of sap ascent, 
of osmosis, of turgescence, and of the soil must be studied.^ 

The investigation of malformed organs and cells may be classified 
under the head of Pathologic Morphology, and if the microscope is 
used, it may include Pathologic Histology and Pathologic Cytology. 
Disturbed conditions of the reproductive cells and organs bring about 
anomalies in the offspring, so that genetically speaking freaks, bizarre 
forms, or chimeras arise. Diseased conditions may be traceable to 
disturbed nutrition, to excessive or retarded growth and to abnormal 
irritability. Therefore to be a successful pathologist, one must be a 
good morphologist, histologist, geneticist and physiologist. 

Phytopathology is that phase of botanic inquiry which treats of the 
diseases of plants. Its history dates from about 1850. Disease may be 
looked upon as an unwholesome condition, derangement of, perversion 
of, or departure from the normal in structure, in function, or in both com- 
bined. It is a morbid state. One who studies phytopathology is con- 
cerned with the characteristic symptoms of disease (Symptomatology), 
the interpretation of symptoms (Diagnosis), with the causes of diseases 
(Etiology) and with the remedies (Therapeutics) and prevention of dis- 
ease (Prophylaxis). Recently considerable attention has been given 
prophylaxis, following out the old adage that an ounce of prevention is 
worth a pound of cure. Curative agents are therapeutic agents. 

ETIOLOGY. — At the outset it is important to consider the causes of 
disease. These may be considered under two heads, predisposing and 
determining. 

Predisposing Causes of Disease. — The normal plant can to a cer- 
tain extent ward off the attack of disease, but the power to do so varies 
within wide limits, which may be conditioned upon racial, or individual 
characteristics of resistance. The degree of this resistance determines 
the degree of the immunity of the plant organism. It is well known 
that the normal constitution of plants varies considerably in individ- 
uals of the same variety and among different races and varieties of the 
same species. Some individuals and varieties are constitutionally weak, 
others are strong and resistant to external influences of every descrip- 

iAppel, O.: The Relations between Scientific Botany and Phytopathology. 
Annals Mo. Bot. Gard., 2: 275-285, February, April, 1915. 



GENERAL CONSIDERATION OF PLANT DISEASES 273 

tion. Such plants are designated as cast-iron, or hardy, while the 
others are tender and need constant care and attention on the part of 
the cultivator. Such weakness of constitution, of histologic structure, 
or absence of protecting chemical bodies in the cells of the plant may be 
looked upon, other things being equal, as predisposing causes of diseases. 
Such depend on the hereditary character of the plant, and in case of 
varieties susceptible to disease may be designated hereditary predis- 
position. Immunity, on the other hand, may be hereditary, as in the 
case of the plants of strong constitution, or acquired. Resistance on the 
part of certain plants may be due to the hereditary resistance of the pro- 
toplasm, it may be due to histologic structure, such as the presence of a 
thick cuticle in the resistant form and its absence in the susceptible form, 
for Sorauer has found that the resistance of different carnations was due 
to the thickness of the cuticle. The habit of earliness, or lateness, may 
be the determining factor in resistance. A late variety might be at- 
tacked, because of its growth in relation to the life history of some insect, 
or fungous parasite, while for this reason an early variety might remain 
healthy. Morphologic peculiarities may be effective, for the investiga- 
tions of Hecke and Brefeld have shown that in the varieties of wheat with 
closed flowers, and which are close pollinated, therefore, the spores of 
the loose smut fungus carried by the wind are unable to reach the stig- 
mas, and hence, infection does not take place. Such varieties would be 
smut proof for the simple morphologic reason that their stigmas are not 
exposed to the smut spores. Osterwalder has indicated that varieties 
of pears without an open channel from the calyx to the carpels are pro- 
tected against infection by Fiisarium putrefaciens, while those varieties 
with an open channel from calyx to t"he carpels are susceptible. The 
habit of a plant, as to drying after a rain, may influence its disease 
resistance, as shown by Appel.^ Infection of potatoes by the spores of 
late blight, Phytophthora infestans , is due to the wind carrying the spores 
to healthy plants where in the raindrops on the surface of the leaves 
zoospores are formed. 

The leaves of some varieties dry within half an hour after a rain, 
while on others the leaves do not dry for several hours. Quick-drying 
varieties are less susceptible than the slow-drying ones. In some mem- 
bers of the pea family, the seeds are imbedded in a woolly outgrowth of 

^ Appel, O.: Disease Resistance in Plants. Science, New ser., xli: 773-782, 
May 28, 1915. 
iS 



274 GENERAL PLANT PATHOLOGY 

the inner epidermis of the pod. It has been found that infection of the 
seeds with Ascochyta pisi is facihtated by the presence of the hairs, for 
the fungus grows, as in a culture medium, and infects every seed, while 
in the hairless forms infection takes place only where the seed actually 
touches the infected spot of the pod. 

The presence of certain chemic substances may explain immunity, for 
the disease resistance of Vaccinium vitis idcea is supposed to be due to the 
presence of benzoic acid. So, too, the presence of tannins may increase 
the power of resistance to fungus and insect diseases, as indicated by 
Cook and Taubenhaus.' Enzymes also play an important role in the 
production of chemic substances, which increase disease resistance. 
Such hereditary disease resistance may be made to play an important 
part by breeding and growing the varieties which have been proved to 
be disease resistant. 

Immunity may be acquired by growing the susceptible form at a 
different season of the year from its accustomed one. Grafting has 
been used with success. The method is to graft a non-resistant variety 
on a resistant one, as in the case of the European vine on the American 
vine, which resists the attack of the Phylloxera insect, which devastated 
the European vineyards until this method was adopted. Crossing has 
been resorted to as a second means of increasing disease resistance. The 
weak variety is crossed with a disease resistant form to increase its 
immunity. The third way to obtain immune forms is to select resistant 
individuals and from them breed pure strains. This has been accom- 
plished with some degree of success by Orton with cotton, by BoUey 
with flax, by L. R. Jones with cabbage. It should be emphasized that 
the inheritance of the unit characters and their behavior in the next 
generation is one of the fundamentals of breeding resistant races. 

Determining Causes. — Having considered the general reasons for the 
predisposition of plants to diseases and the immunity of others, it is 
important to describe next the causes which determine disease. These 
may be divided into those of external origin and those ofinternal. The 
external factors of disease are the chemical conditions of the soil, as a 
determining cause, also the physical character of the soil. The influ- 
ence of a superabundance of water, or its absence, is important. Cli- 

^ Cook, Mel T. and Taubenhaus, J. J.: The Relation of Parasitic Fungi to the 
Contents of the Cells of the Host Plants, i. The Toxicity of Tannin, BuU. 91, 
Delaware College Agric. Exper. Stat., Feb. i, 1911. 



GENERAL CONSIDERATION OF PLANT DISEASES 



275 



matic and meteorologic conditions may be influential, when these dis- 
turb the normal life of the plant. Light, heat, cold, rain, dew, hail, 
frost, wind and Ughtning play an important role. The gaseous emana- 
tions from gas pipes, smelter works, smokestacks, including soot, dust 
from cement works, acids, poisons, and dye stuffs, which pollute streams, 
all are determining causes of disease. Traumatism or mechanic injury 
may be of various sorts and the effects are dependent upon the form and 
severity of the injury, or wound. 




Fig. III. — Rose-chafer {Macrodaclylis subspinosus). a. Adult or beetle; b, 
larva; c, d, mouth parts of same; e, pupa, /, injury to leaves and blossoms of 
grape with heetles at work. {From Marlalt in Quaintance, A. L. and Shear, C. L., 
U. S. Farmers' Bull. 284, 1907.) 



Living organisms, whether animal or vegetal, may be the cause of 
disease. All groups of animals may be considered, but the mammals, 
worms and insects (Fig. iii) are of most importance and interest. 
Insect depredations of plants are notorious and insects occupy first 
place in their destructive effects on plants (Fig. 112). Various para- 
sitic flowering plants are known, as well, as the bacteria and fungi, 
for their disease-producing powers. 



276 



GENERAL PLANT PATHOLOGY 



As an internal determining cause, the formation of enzymes under 
abnormal conditions must be reckoned as causal, as well, as nutritive 
disturbances which produce monstrosities and the like. 

Having classified the chief causes of disease, a more detailed descrip- 
tion of these factors should be put in a form available for student use. 
Much of the information is scattered, and part of it is buried in foreign 
botanic and pathologic journals, which can be consulted only in the 
largest scientific hbraries at home and abroad. 




Fig. 112. — Oyster-shell scale {Lepidosaphes ulmi. After Quaintance, A. 
Farmers' Bull. 723, Apr. 26, 1916. 



L., U. S. 



The chemic condition of the soil, as a determining cause of disease, 
may be considered from the standpoint of the normal influence of the 
important soil ingredients, as contrasted with the absence or deficiency 
of such elements. Potassium is usually found in young tissues and dis- 
appears in the older ones. It is associated in some way with the for- 
mation of carbohydrates in the plant such as starch, sugar and cellulose. 
The absence of potassium in the soil causes a cessation of growth, the 
leaves fail to develop the power of forming starch within the greenr 
coloring bodies, or chloroplasts. A plant which has failed to grow for 
months will recover in a few days after potassium salts have been added 



GENERAL CONSIDERATION OF PLANT DISEASES 277 

and after a few hours the formation of starch in the chloroplasts will 
be detected.^ The storage of reserve materials is, therefore, inhibited, 
and one finds in such plants, as the cereals, that the formation of green 
parts is at the expense of the grain, and in the beet, the vegetative part of 
the plant is at the expense of the fleshy roots. Potassium hunger causes" 
in the potato and buckwheat a shortening of the internodes and a 
convex bending of the leaf blades, which are spotted with yellow blotches. 
Calcium is abundant in nature in the form of the carbonate which 
forms the rocks known as marble and limestone. It is chiefly concerned 
in the strengthening of the cell wall, where in such plants as Chara it is 
deposited. It plays an important role in fixing the calcium oxalate 
formed in the metabolism of the plant. Ecologists in Europe classify 
many plants either as calciphile (calcium-requiring), or calciphobe 
(calcium-hating). The apphcation of calcium to soils under certain 
conditions promotes apparently the disease of beets called heart- or 
dry rot. The chlorosis, or icterus, of the grape vine seems to be in- 
creased in soils with a high calcium content. The accumulation of 
oxalic acid in the absence of its fixation by calcium poisons the plant. 
The formation of brown blotches on leaves, the yellowing, or brown- 
ing of pine needles, the death of the root tips of water plants is associated 
with the absence of calcium. 

Magnesium is chemically allied to calcium, but it cannot replace 
calcium in the economy of the plant. It apparently works together 
with nitrogen in the formation of protoplasm, and has an influence in 
the formation of chlorophyll, for plants grown without magnesium have 
yellowish-green chloroplasts, and new cell formation does not proceed 
readily. The absence of magnesium is shown in the pale-green color 
of the chloroplasts, the yellow to orange-yellow blotches on the leaves, 
and the brown spots on the stems. The amount of starch formed by 
the chloroplasts is reduced, the internodes are shortened, the young 
leaves do not unfold. These are symptoms associated with a 
deprivation of magnesium. 

Iron is necessary in the formation of chlorophyll, for if the plant is 
grown in an iron-free solution, it remains permanently etiolated 
(blanched). The diseased condition which arises through the lack of 
the requisite amount of iron is called chlorosis. Too much iron in the 
soil acts poisonously. 

^Hartwell, B. L.: Bull. 165, R. 1. Agric. Exper. Stat., May, 1916. 



278 GENERAL PLANT PATHOLOGY 

Sulphur and phosphorus are of some value in the production of 
albuminous substances by the plant, and in the soil they exist mainly 
as calcium sulphate and calcium phosphate. Phosphorus is in some 
way associated with the formation of the crystalloids, globoids and 
aleurone grains of the plant. Some soils are poor in phosphorus, so 
that the agriculturist must supply phosphates. The_ deficiency_of 
phosphorus is seen in the production of a red coloration in plarits. The 
leaves are blotched with red and later the spots become dark brown. 
The formation of flowers and seeds is partially inhibited. The absence 
of sulphur is manifest in the poor development of the whole plant and 
in the reduction in the amount of fruit produced. 

Nitrogen enters largely into the living substance of the plant, 
protoplasm. It is stored in the form of protein granules and aleurone 
grains. In the life of the plant, it is concerned in the building of young 
tissues, and in the metabohsm of plants, it appears in the form of aspar- 
agin which in the soluble state is conducted through the bast portions 
of the vascular bundles from one part of the plant to another part. 
Some plants have a pecuhar relationship to nitrogen. Such are the 
leguminous plants, which are provided with root nodules, where there 
are nests of bacteria. These bacteria can utiUze free atmospheric nitro- 
gen and later in the involution form as bacteroids, they are absorbed 
by the green plant which is thus enriched with nitrogen. During the 
period of entrance of bacteria into the root hairs, the young seed- 
ling goes through a period of nitrogen starvation, when it appears 
to flag, but later, it regains its active growth and vitality when the 
nodules have been formed. Contrasted with the same leguminous 
species without nodules and when the root systems alone take up 
nitrogen in the form of nitrates, the nodulated plant is larger and 
stronger in every respect. 

A deficiency of nitrogen in the soil can be detected in the case of 
Indian corn and other agricultural plants by a general paling of the 
green color, so that in some cases the plant becomes yellowish-green. 
Klebahn^ indicates that the leaves of beets, buckwheat and potatoes 
assume a yellowish color with a deficiency of nitrogen, and as the leaves 
dry, they become yellowish-brown. The prothaUia of ferns in a nitrogen- 
free nutritive solution do not form meristem or archegonia. Excessive 
supplies of nitrates in their application to cultivated fields stimu- 

1 Klebahn, Prof. D. H.: Grundzuge der Allgemeinen Phytopathologie, 1912: 11. 



GENERAL CONSIDERATION OF PLANT DISEASES 279 

lates in the case of the crops grown upon such fields the development 
of the vegetative organs and, therefore, delays the formation of flowers 
and fruit and the ripening of seeds. Such delay may mean the attack 
of parasitic fungi. For example, a large field of winter wheat which 
had been sown about the end of October was much attacked by stink- 
ing smut (60 per cent.), while the adjacent fields belonging to the same 
farmer, under the same variety of wheat and treated in a similar 
manner, but sown early in October showed no sign of infection. With 
fruit trees, one notices greater frost susceptibility in those plants which 
have received an excessive nitrogen supply. Lipman (Science, new 
ser. xxxix: 728-730, May 15, 1914) has suggested that the poor nitri- 
fying power of soils is a possible cause of "die-back" (exanthema) in 
lemons. It has been a serious disease with the citrus growers of 
Florida and California. 

Physical Character of the Soil.- — The physical character of the soil 
is of great importance as a determining cause of disease. When we 
speak of the physical character of the soil, we refer to the size of its 
particles, the relation of these particles to each other, the presence 
of colloidal bodies, the presence of air spaces associated with the air 
content, the distribution of the water through the soil, the presence or 
absence of organic matter, or humus, the color and temperature of the 
soil. Of greatest importance to the life of the plant is the water 
which is available for the needs of the plant. ^ A too plentiful sup- 
ply of water causes the formation of a wet ball of roots with the 
formation of alcohol. Frequently gardeners fearing that the soil is 
dry, water potted plants with more water than the plants actually 
need, so that the lower part of the soil is continuously saturated with 
water. Alcohol is formed and decay of the roots sets in, because they 
are gradually suffocated. Too little water on the other hand causes 
a drooping or wilting of the plant, and if water is not supplied in 
time permanent wilting and death of the foliage results. But a 
diminished water supply may be decidedly beneficial to plants, as it 
has been found that the formation of flower buds is best initiated by 
preserving a period of rest following a diminished water supply. 
Different plants have different water requirements and these require- 
ments vary with the season of the year and the development of 

* Cf. SoRAUER, Paul, Lindau, G. and Reh, L., transl. by Dorrance, Frances: 
Manual of Plant Diseases, vol. i, parts i and 2. 



28o GENERAL PLANT PATHOLOGY 

the plant. As an illustration of this may be cited the planting of the 
Carolina poplar on the open porous sandy soils of New Jersey. About 
Philadelphia, where the tree is largely planted, it grows rapidly with 
a dense crown of dark-green, foliage leaves. In New Jersey, it grows 
less rapidly, its crown is more open by a wider spacing of the branches 
and the leaves have a greenish-yellow appearance and drop off earlier 
in the autumn than similar trees on the Pennsylvania side of the Dela- 
ware River. This difference is without doubt associated with the water 
requirements of the tree, for on the Pennsylvania soils, it can secure 
abundance of water during the growing season, while in the New Jersey 
sands, owing to their porosity and the rapid drainage of water through 
them, the Carolina poplar does not receive sufl&cient amounts of water 
for its most vigorous growth. 

The experiments of Miinch^ throw important light on the content 
of water and air in the tissues as a determining factor of disease of 
woody plants, such as on forest and fruit trees. He has shown that the 
greater number of the wood-destroying fungi require a large amount of 
air and are able to grow only when a maximum amount is present. The 
air content of the tissues is dependent on the water supply and trees 
with narrow annual rings are more resistant than those with broad ones, 
because the former contain m.ore water and less air relatively. Differ- 
ent annual rings of the same tree may be attacked differently. 

The decayed rings of wood in such trees are always the broad ones. 
The tissues of vigorous branches are rich in water and poor in air and 
infections do not always penetrate to such regions. The healthy bark 
of beech trees in winter-rest contains 19 to 20 per cent, of air and at 
the time of budding the air diminishes to 11 per cent., rising afterwards; 
This is correlated with the canker disease, Nectria ditissima, which in 
Europe does its damage during the winter months, while during the 
vegetative period it ceases. Hence, we have opened here a very profita- 
ble line of investigation to determine the relative amounts of air and 
water with respect to immunity, or its absence. Again, in the irrigated 
districts of America, the fruit trees have only a few diseases due to 
species of Valsa and other species of fungi. Defective irrigation may 
bring about the prevalence of the die-back diseases, which may be reme- 

^MtJNCH, E.: Untersuchungen iiber Immunitat und Krankheitsempfanglich- 
keit der Holzpflanzen. Naturwiss. Zeitsch. f. Forst. und Landw., 7: 54-75, 87- 
114, 129-160, 1909; Appel, O.: Phytopathology & Scientific Botany, loc. cit. 



GENERAL CONSIDERATION OF PLANT DISEASES 251 

died by changing the system of irrigation. The land should be irri- 
gated at the time when the trees contain small amounts of water and 
much air, so as to prevent an excessive decrease of water in the tissues. 

The condition of the humus has a rather remarkable influence on 
the growth of plants. Ericaceous plants, such as the trailing arbutus 
{EpigcEa repens), wintergreen {Gaultheria procumbens), bearberry 
(Arctostaphylos iiva-iirsi), blueberry {Vaccinium corymhosum) flourish 
in an acid humus and if the attempt is made to grow such plants 
under other conditions, they languish and die. Other species like In- 
dian turnip {Ariscema triphylla), blood root (Sanguinaria canadensis), 
rue anemone {Anemonella thalidroides) grow best in a leaf- mould humus 
which is neutral or slightly alkaline. Reverse the reaction of the soils 
about these plants and they gradually die. 

The presence of an impervious hard pan below the surface soil is 
a condition which prevents the normal development of trees, as I have 
shown in my book on the "Pine Barren Vegetation of New Jersey," 
where in the region known as the Plains, the pitch-pine trees are kept 
dwarf owing to an impervious subsoil layer. There the trees flourish 
for a number of years, then begin to suffer until unable to penetrate the 
deeper layers of the soil, they finally succumb to be replaced by younger 
trees which meet the same fate. 

Climatic and Meteorologic Factors. — The most important 
climatic factors, which may be looked upon as in any way related to 
disease production, are light, heat, precipitation (rain, dew, frost, snow, 
hail and ice) wind and electricity (lightning, etc.). 

Light is essential for the life functions of all green plants. Carbon 
dioxide and water are united by the energy of sunlight to form starch. 
The synthesis takes place in the chloroplast, starch being formed as 
the first visible product. Ordinary sunlight of a bright, clear day may 
under certain conditions of plant growth be too intense and it acts 
prejudicially. The writer has frequently noted, that garden plants 
suffer, if after a wet, cloudy spell during the rapid period of growth, 
they are exposed to a bright sun without protection. It takes a few 
days of bright light to sun-harden the plants. Trees, especially with 
a smooth bark, which have grown in a very dense wood, and then 
suddenly isolated in later life, suffer from scorching of the cortex. 
They are sunburned. Plants grown in greenhouses, which have been 
painted with whitewash to reduce the intensity of the rays of light, have 



282 GENERAL PLANT PATHOLOGY 

their leaves burned if part of the whitewash is removed. The light 
passes through the opening thus made and the leaves on which it is 
concentrated are scorched. 

Several diseases of plants are caused by too brilliant sunlight. Such 
are sunscald, sunscorch and bronzing.^ Sunscald may follow as a 
result of too intensive sunlight, as, for example, when certain fruit trees 
are stripped of their foliage in summer, such as sometimes results from 
the ravages of the gypsy moth. In such instances the new unripened 
wood sunscalds badly. Sometimes it is associated with severe and 
abrupt changes in temperature on non-ripened wood. "Sunscorch" 
is a term applied to the burning of foliage in summer during periods 
when the soil is dry, and is also common to evergreens during warm 
wiildy days in spring before the frost is out of the ground. Any 
defects in the root system which prevent root absorption may cause 
sunscorch. "Bronzing" of leaves is a form of sun scorch characterized 
by the occurrence of a reddish-brown or bronze color of the leaf. It is 
caused by a lack of soil moisture, or defective root absorption during 
dry, hot periods. 

Too much shade is also detrimental to plants, as is seen under the 
dense canopy of beech trees on a lawn, where nothing will grow, not 
even a blade of grass. The grasses, etc., die of inanition. The condi- 
tion known as etiolation originates where a plant is grown in the dark, 
or in subdued sunlight. Growth in darkness leads to important modi- 
fications in the general habit and structure of a plant. If we take a 
potato plant and raise it in the dark, we find the etiolated shoot has 
a white stem and leaves which are at first pinkish, and subsequently 
pale yellow, and the absence of chlorophyll is noteworthy. The inter- 
nodes are long and slender and the leaves are small compared with the 
green plant and there are corresponding anatomic differences. Morn- 
ing glories raised in greenhouses in the winter do not twine. They 
grow from four to five inches tall and have only one to two flowers. 

Heat as a factor in the growth of plants is well known. Each plant 
has its minimum, maximum and optimum degree of heat. The dis- 
tribution of plants over the larger stretches of the earth's surface is 
associated with the amount of heat that the different plants receive. 
The absence of heat, where the plant is exposed to a temperature below 

1 Stone, George E.: Injury to Vegetation Resulting from Climatic Conditions. 
Monthly Weather Review, 44: 569-570, October, 1916. 



GENERAL CONSIDERATION OF PLANT DISEASES 283 

freezing, is noteworthy. The death of cells rich in water, when exposed 
to low temperatures, seems to depend upon the conversion of the water 
extruded into the intercellular spaces into ice. The parenchymatous 
tissues are ruptured and crystals of ice are formed. The water, there- 
fore, which is in the cell reaches the surface and the cell sap diminishes 
in amount and there may be chemic changes in the cell as a result of 
freezing, for in some cases .the leaves assume a leathery brown color. 
Long exposure to cold may lead to the actual disorganization of the 
protoplasm. It, however, does not always follow that the formation 
of ice in the intercellular spaces necessarily involves death. Slow 
thawing may be followed by a return of the water to the cells until 
the normal equilibrium is restored and the cells continue to live. A 
rapid thawing, however, causes death of the cells, because the water is 
not reabsorbed. Frost-killed twigs and branches are more susceptible 
to the entrance of saprophytic fungi such as species of Nectria, Dasy- 
scypha, and Valsa. The exposure of roots during a snowless winter 
may lead to their disturbance by freezing. The anatomic changes 
induced by freezing are frost blisters, such as appear on the leaves of 
fruit trees and cereals, and frost cracks, which may ultimately heal 
over, producing an external ridge or enlargement. The fruit-grower 
can distinguish four kinds of winter injury to his trees. First, the 
frosting of the blossoms after they begin to open; second, the freezing 
of the buds in winter; third, the freezing of the twigs and branches; 
fourth, root freezing. It may happen that early in the spring the 
peach trees come into bloom. Then on a cold cloudless night with no 
wind the temperature sinks below freezing and the partially open 
flower buds are nipped by the frost. About twenty years ago the 
upper Mississippi Valley was visited by an unusual cold wave. The 
frost penetrated to great depths and the cold was so intense that the 
tree roots were actually frozen in the soil.^ 

The formation of ice fringes upon plants has been investigated 
exhaustively by Coblentz,- with the dittany, Cunila mariana. He 

* Consult Waugh, Frank A.: Jack Frost's Tricks. The Country Gentleman, 
Feb. 6, 1915, p. 213. Wilson, Wilford M.: Frosts in New York. Bull. 316, 
Cornell University Agri. Exper. Stat., June, 191 2. Chandler, W.H.: The Kill- 
ing of Plant Tissue by Low Temperatures. Research Bull. 8, Coll. of Agric, 
Univ. of Mo., Dec, 1913. 

2 Coblentz, Wm. W. : The Exudation of Ice from Stems of Plants. Monthly 
Weather Review, 42: 490-499, August, 1914. 



284 GENERAL PLANT PATHOLOGY 

found that the ice fringes are formed when the temperature falls to 
freezing. They are formed on the outer surface of the plant. The 
growth of the ice fringe ceases when the ground is frozen to a depth of 
2 to 3 cm. and when the moisture in the stem is frozen. The dimen- 
sions of the fringe depend upon the rate of evaporation of water from 
the stem up which it rises by capillary action and upon the amount 
of moisture in the ground. Clouds and fogs in some regions have an 
important effect on vegetation.^ The two forms of foliage leaves on 
the branches of the redwoods of California are conditioned upon the 
height of the fogs which drift in from the Pacific Ocean. The leaves 
on the fog-exposed branches are flat and divergent, while those on the 
sun-exposed branches above the fog level are scale-like and appressed. 
The London fogs work detrimentally to outdoor and greenhouse plants, 
and in Egypt, the cotton capsules long exposed to fog are more in- 
fested with black moulds. Dew, which lodges on the margins of leaves, 
is responsible for the entrance of fungi by their spores lodging in the 
dewdrops and germinating there. 

The weight of snow and ice breaks off the limbs of trees, breaks down 
herbaceous plants, and this opens up the way for the entrance of 
various parasitic fungi. Ice or sleet storms are especially severe at times 
to trees. The year 1902 was noted for two exceptionally destructive 
ice storms which visited the Philadelphia region. One of these storms 
occurred on Friday, Feb. 21, and the other on Saturday, Dec. 13.^ The 
storm of Feb. 21 was accompanied by high winds and did an irreparable 
damage to the fruit, forest and shade trees. Meteorologically speaking, 
regions of strongly variable temperature are subject to occasional 
winter storms in which the precipitation occurring as rain, freezes as 
soon as it touches any solid body, such as the branches of trees, telegraph 
wires or the ground. This happens when the ground and the lower 
air have been made excessively cold during a spell of clear anticyclonic 
weather, when a moist upper current in advance of an approaching 
cyclone brings clouds and rain. All our meteorologists prefer to call 
such storms ice storms; locally near Philadelphia they are denominated 
sleet storms. The weight of ice which such limbs carry is astounding. 

1 Weiss, F. E., Imms, A. D., Robinson, W.: Plants in Health and Disease, 
1916; 54-56. 

" Harshberger, John W. : Relation of Ice Storms to Trees. Contrib. Bot. 
Lab. Univ. of Penna., II: 345-349, 1904. 



GENERAL CONSIDERATION OF PLANT DISEASES 



285 



The author found the weight of a branch of Liriodendron tuUpiJera with 
ice upon it to be 50 grams, without ice 9 grams; so that the ice weighed 
41 grams, giving a ratio of i : 4.5. Juniperus virginiana with its ice 
load weighed 310 grams, without ice 13 grams, making the weight of ice 
297, a ratio of i : 23. Beginning with Dec. 5, 1914, a combination 
rain, snow and ice storm swept across the Eastern States doing much 









10 



12 



13 



'^ H@ '5® '^® 



17 



□Z2ZZ2 




Fig. 113. — Sectional view of twigs and leaves of various plants showing load of 
ice carried during the ice storm of Feb. 12 and 13, 1916. i, Acer plalanoides; 2, 
blade of grass; 3, Chionanthiis virginicus; 4, Diervilla florida; 5, Forsythia suspensa; 
6, Liguslrum vulgare; 7, Liriodendron lulipifera; 8, Platanus orientalis; 9, Populus 
alba; 10, Populus delloides; 11, Quercus paluslris; 12, Syringa vulgaris; 13, Tilia 
americana; 14, Tecotna radicans; 15, xanthoceras sorbifolia; 16, Spiraea Thunbergii; 
17, leaf of Rhododendron maximum; 18, icicle on tip of Rhododendron maxifnum, 
leaf hanging down. 

local damage^ and again on Friday, Dec. 31, a severe ice storm visited 
the mountain region of Pennsylvania contiguous to the Juniata Valley 
and Susquehanna River. During the afternoon of Saturday, Feb. 12, 
191 6, a cold rain began which continued well into the night, coating the 
pavements, streets, and trees with hard ice. On Sunday morning, 
Feb. 13, men, boys and girls took advantage of the icy streets to skate 
1 Illick, J. S.: A Destructive Snow and Tee Storm. Forest Leaves, xv: 103- 
107, Fehriiari', tqi6. 



286 



GENERAL PLANT TATHOLOGY 



upon them and this unusual sight was stopped by a snow storm, which 
followed on Sunday morning. The trees were loaded to the breaking 
point. During the continuance of the storm, small branches were 
taken oflf thirteen trees and shrubs and a blade of grass growing in West 
Philadelphia, and the thickness of ice upon them measured with a 
pair of compasses. The accompanying figures drawn life size show the 
relative thickness of the load of ice borne by the twigs, whose thickness 
is shown in the drawings (Fig. 113). 




Fk, Mi 

water ni-ai the builacc 
L. I., July. 1915. 



t liii I h)nt\ iiDii I h tiiui ]iIl ntifully supiilicd with ground 
dcprcbbiuu ot the glacial uutwash plain at Westbury, 



The fall of hail stones may, if they are large enough, cause the 
decortication of twigs, or the abrasion of other plant parts, thus per- 
mitting the entrance of destructive bacteria and fungi to the interior 
of the plants. 

Wind is an active agent in the breaking off of buds and limbs and 
the formation of dangerous wounds. In such situations, as high moun- 
tains, sand dunes and rocky shores, where trees are exposed to the 
forcible action of the wind, they assume a windswept, bisected, or 
prostrate form, which is characteristic and picturesque (Fig. 16). 



GENERAL CONSIDERATION OF PLANT DISEASES 287 




Fig. 115. — Unhappy vase-shapei.l white elm, I'ini:, ,, ', . , <,..>i. luo yards south 
of a happy larger elm both growing on the outwashed plain, Westbury, L. I., July, 
1915- 




Fig. 116. — Wind-swept white poplar, Populus alba, Nantucket, Mass., August, 1915. 



288 GENERAL PLANT PATHOLOGY 

Strong winds increase the amount of transpiration, so that fre- 
quently we find there is a balance established between the absorbing 
root system and the transpiring leaf system, so that the amount of 
foliage is determined accordingly. If the amount of water lost by 
transpiration exceeds the amount absorbed by the roots the plant 
usually succumbs. Happy trees are those in which the amount of 
water available exceeds the amount transpired, while unhappy trees 
are suffering physiologic drought through the action of the wind in 
moving water faster than it can be supplied (Figs. 114, 115, 116). 
Such trees are seen in planted specimens in Long Island, Nantucket 
and along our seacoasts. With tornadic winds, trees are uprooted in 
general and irreparable damage is done. 

The effect of lightning is a marked one, as a determining factor in 
disease. Recently Jones and Gilbert^ have published a paper on the 
lightning injury to potato and cotton plants. One case occurred in a 
field at Monetta, S. C. in the summer of 1913. The cotton plants 
were fully grown and after a severe electric storm on Aug. 3, all the 
cotton plants were killed over an area three rods in diameter. The 
leaves wilted, died and blackened, but remained attached to the plants. 
The most pronounced effect, however, was on the stem and root system. 
Other cases are cited of a similar nature in Europe and America. 

The action of lightning on trees is variable. The tree may be 
scorched, it may be stripped of its leaves, it may be cleft longitudinally, 
or, more rarely, severed horizontally. Sometimes the bark is stripped 
from only one side, occasionally without a trace of burning: at other 
times, it may be riddled, as by worms, with a multitude of Httle holes. 
The lightning furrows may be single, double, oblique or spiral. If the 
tree is inflammable a fire may be started. Such tall trees, as the big 
trees of California, have been struck repeatedly by lightning and their 
leaders broken and their tops stunted as a consequence. From early 
times, there has been a current belief that certain trees attract the light- 
ning, that others are not struck. The elder Pliny beheved that "Light- 

^ Jones, L. R. and Gilbert, W. W. : Lightning Injury to Potato and Cotton 
Plants. Phytopathology, 5 : 94-101, with plate, April, 1915; Jones, L. R.: Light- 
ning Injury to Kale. Phytopathology, 7: 140-142 with i fig., Apr., 1917;, 
Stone, George E.: Electrical Injuries to Trees. Bull. 156, Mass. Agric. Exper. 
Stat., Oct., 1914. 



GENERAL CONSIDERATION OF PLANT DISEASES 289 

ning never strikes the laurel.'' In certain parts of the United States, 
it is held that the beech tree is never struck. 

"Avoid the oak, flee from the spruce, but seek the beech," yet in 
the Garden Magazine for January, 19 16, is given a photograph and an 
account of a fine beech tree which was struck by lightning in Pennsyl- 
vania about the middle of June. Plummer^ sums up his investigations 
on the relation of lightning and trees, as follows: 

1. Trees are the objects most often struck by lightning because: 
{a) they are the most numerous of all objects; (b) as a part of the ground, 
they extend upward and shorten the distance to a cloud; (c) their 
spreading branches in the air and spreading roots in the ground present 
the ideal form for conducting an electrical discharge to the earth. 

2. Any kind of tree is likely to be struck by lightning. 

3. The greatest number struck in any locality will be of the domin- 
ant species. 

4. The likehhood of a tree being struck by lightning is increased: 
(a) if it is taller than surrounding trees; (b) if it is isolated; (c) if it is 
upon high ground; (d) if it is well (deeply) rooted; {e) if it is the best 
conductor at the moment of the flash; that is, if temporary conditions, 
such as being wet by rain, transform it for the time from a poor conduc- 
tor to a good one. 

5. Lightning may bring about a forest fire by igniting the tree itself, 
or the humus at its base. Most forest fires caused by Ughtning proba- 
bly start in the humus. 

Experiments on the electric conductivity of various woods shows 
that this conductivity depends upon the water content of the wood. 
When absolutely dry none of the specimens showed conductivity, but 
the resistance of all was practically infinity. 

Effect of Smoke, Soot, Gases and Smelter Fumes on Plants. — The 
smoke, which is destructive to vegetation under our modern conditions, 
is derived from four sources of supply: (i) smoke from manufacturing 
plants, or from large buildings; (2) smoke from special concerns, such 
as the electric power plants of electric trolley lines; (3) smoke from rail- 
road locomotives; (4) smoke from the chimneys of dwelling houses. 
Smoke belts have been drawn by students of the problem to determine 
the area influenced by the smoke. From a survey made for the City 

^Plummer, Fred G.: Lightning in ReUition to Forest Fires. BulL in, U. S- 
Forest Service, 191 2. 
19 



290 GENERAL PLANT PATHOLOGY 

of Des Moines, Iowa, by A. L. Bakke,^ it. has been found that conifers 
are more susceptible than deciduous trees. The direct injury is seen 
in the deposit of the tarry matters of the smoke in the stomata of 
nearby plants; leaves and leaflets are shed, or assume abnormal shapes, 
and the formation of foodstuffs is hindered. The sulphur dioxide and 
acetylene as constituents of smoke act toxically upon the plant. The 
work which has been done in the United States may be summed up as 
follows: Burkhart states that injury from gases is the result of the 
chemical constituent of the smoke and is not due to the clogging of the 
stomata. The investigation of J. K. Haywood^ in the vicinity of 
the famous smelter at Anaconda, Mont., is of importance. He finds 
that trees are injured at a considerable distance; that very small 
amounts of SO2 are toxic to plant growth; that water used for irrigation 
purposes often has sufficient copper in it to be toxic to plant growth 
and that certain trees, as the juniper, are more resistant than others.^ 
Officials of the Forest Service are watching with interest the develop- 
ments in the matter of the fumes from copper smelters in the southern 
Appalachian Mountains. The service has been interested for years, 
but since the acquirement of land in that section under the Weeks law 
for forestry and watershed protection purposes, it has been felt that 
the destruction of forests by the action of the fumes should be stopped. 
W. L. Hall, forest supervisor of the seventh forest district, has 
recently submitted to the bureau a report upon the subject. It seems 
that one or more of the purchase areas established in the southern 
Appalachians are endangered by the fumes, which are of a sulphuric 
nature. 

iBakke, a. L.: The Effect of City Smoke on Vegetation: Bull. 145, Agric. 
Exper. Stat. Iowa State Coll. Agric. & Mech. Arts., October, 1913; The Effect 
of Smoke and Gases on Vegetation. Proc. Iowa Acad. Sci., xx: 169-187, with 
bibliography; also Anderson, Paul J.: The Effect of Dust from Cement Mills 
in the Setting of Fruit. The Plant World, 17: 57-68, March, 1914. 

2 Die Beschadigung der Vegetation durch Rauch. Handbuch zur Erkennung 
und Beurteilung von Rauchschaden von Professor Dr. E. Haselhofe, Vorsteher 
der landwirtschaftlichen Versuchsstation in Marburg i. H., und Professor Dr. G. 
LiNDAu, Privatdozent der Botanik und Kustos am Kgl. Botanischen Garten in 
Dahlem. Mit 27 Textabb. 

3 Haywood, J. K.: Bull. 89, Bureau of Chem., U. S. Dept. Agric, 1905; In- 
jury to Vegetation and Animal Life by Smelter Wastes. Bull. 113 revised, Bureau 
of Chem., U. S. Dept. Agric, 1910. 

'' The Southern Lumberman, xxix: 27, Nov. 6, 1915. 



GENERAL CONSIDERATION OF PLANT DISEASES 29T 

The fumes are apt to destroy any vegetation within a radius of 
several miles of the southern copper smelters. They are also working 
destruction in the forests of Montana, California and other states. The 
action of the fumes is peculiar and variable. Some trees succumb 
quickly to their deadly effects, notably white pine. Other trees are 
more resistant, including spruce, it is said. Nor does the gas act uni- 
formly. Its effects vary with topographic conditions. The fumes 
will travel long distances up a canyon or narrow valley, destroying the 
woods in it, but leaving trees uninjured on either side. Again, it is 
said, the sulphur fumes collect in globular form something like soap 
bubbles, and drift away, doing no damage until the globular mass dis- 
perses, sometimes at quite a distance. To a greater or less extent, 
forests at a distance of several miles from copper smelters may be 
damaged by the fumes. 

It is admitted that the fumes can be controlled by condensation or 
consumption, but the commercial practicability of the process is the 
pending question. The fumes can be and are to a certain extent con- 
verted into sulphuric acid, but the smelter people claim that the market 
for this product is Hmited, and that it does not pay to produce more than 
a certain quantity of it, as an oversupply sends the price down, which 
would make it not worth while to control the fumes further. 

Just now considerable trouble is being experienced in Tennessee 
and Georgia on account of the sulphur fumes from copper plants. 
In 1905 the State of Georgia took action against these companies, 
alleging that they permitted a discharge of gases, which destroyed 
vegetation, including forest trees, in that state. The companies were 
forced to install plants to utiUze a considerable percentage of the sul- 
phuric acid gas. These plants, however, have been unable to utilize 
a sufficient quantity of the gas, and last spring the supreme court de- 
cided to have a special expert ascertain the amount of gas released, 
and the amount which ought to be utilized in order to make the 
fumes harmless. 

The time is close when the pathologist will have to take up this 
question of fume damage, since large sections of the Cherokee area are 
subject to such damage, and it is reported that the injury has extended 
to the Georgia area. 

The injurious effect of illuminating gas and ethylene upon flowering 
carnations has been investigated by Crocker and Knight.^ The best 

1 Crocker and Knight: Botanical Gazette, 46: 256-276, 1906. 



292 GENERAL PLANT PATHOLOGY 

work in Italy has been done by Brizi,in England by Crowther and Rus- 
ton.^ Recently in America J. F. Clevenger has published a bulletin 
(No. 7), on "Smoke Investigation" for the Mellon Institute of Indus- 
trial Research and School of Specific Industries, University of Pitts- 
burgh, 19 1 3, with plates showing the effect of the smoke on the struc- 
ture of the woody specimens examined by him. 

Illuminating gas absorbed by the soil from nearby gas pipes is 
injurious to trees and has frequently killed them outright, as instance 
a group of street trees in Merchantville, N. J., a few years ago, which 
were killed in this way, and for which the owner, Edwin C. Nevin, 
received damages from the gas company for $1500, as a result of a 
successful lawsuit. All the ordinary gases used for lighting and 
heating are injurious and act much in the same way. Such are water 
gas, coal gas, gasoline, acetylene and others. The first effects of gas 
poisoning, may be seen in the foliage. The leaves turn yellow and in 
some cases drop off, while the leaves of other trees fall while still green. 
The water containing the gas in solution passes into the stem and the 
wood and the cambial portion becomes abnormal. The underlying 
tissues, cortex, bast and cambium die. Soon various species of fungi 
gain access to the tree and cause its decay. With the Carolina poplar 
especially, the bark, cortex, etc., on the trunk towards the source of 
absorption showed three or four vertical cracks, or lesions, one-half to 
two and a half feet long. The bark on the sides of these cracks bulged 
out considerably, and an investigation showed a thix:k layer of soft 
parenchymatous tissue extending to the wood and derived from the 
cambium zone. Later this tissue turned brown, disintegrated and 
became slimy in appearance, the . sUme exuding from the cracks. 
Illuminating gas dissolved in water in which willow cuttings were kept 
stimulated the opening of the foliage buds several days earlier than plants 
grown in water not charged with the gas. Stone^ found that the effect 
of gas on lenticels was to increase their size, especially under water 
charged with the gas. This appears to be a general response on the 
part of the plant tissue to a demand for oxygen. 

That the trees, shrubs and flowering plants in our large cities and 

1 Journal of Agricultural Science, 4: 25, 1911. 

2 Stone, G. E.: Effects of Illuminating Gas on Vegetation; 2sth Annual Rep. 
Mass. Agric. Exper. Stat., January, 1913; Shade Trees, Characteristics, Adapta- 
tion, Diseases and Care. Bull. 170, Mass. Agric. Exper. Stat., Sept., 1916, p. 220. 



GENERAL CONSlDERyVTION OF PLANT DISEASES 293 

in the country along our trunk-line railroads are subjected to conditions 
which cause unhealthy growth and disease has been proven abundantly. 
Large factories, power plants and railroad locomotives are pouring out 
volumes of smoke, which alone is highly injurious, but in addition the 
acid which is formed in the combustion of coal, when dissolved in rain 
water, has injurious effect upon fohage and other plant parts. Its 
action is seen in the corrosion of tin roofs, rain pipes and ornamental 
iron work about city houses. 

The following note is of interest to the plant pathologist and plant 
physiologist.^ During the night of Sept, 19, 1913, a light rain fell, 
followed by a fine drizzle in the early morning of Sept. 20. The wide- 
open campanulate flowers of the common morning glory (Ipomcea 
purpurea Roth), growing on a lot in West Philadelphia, four or five 
blocks from the Pennsylvania Railroad, had their usual quota of rain- 
drops studded over the upper, inner surface of the purple corollas. 
Wherever the drops touched the surface of the corolla, the purple 
color was changed to a pinkish red, and in the process of evaporation 
of the raindrops the acid of the drops was concentrated, so that after 
the complete disappearance of the drops a brown spot was left in the 
center of the pinkish red circles of discoloration. The explanation of 
the alteration of color is found in the change of the sap of the corolla 
cells, where touched by the acid raindrops, from an alkaline to an acid 
reaction. A similar change can be induced in blue violet petals by 
bruising them slightly and placing them in an acid liquid. The petals 
change, hke blue alkahne litmus paper, from blue to red, and this re- 
action with violet petals has proved useful in the physiologic laboratory 
in the absence of litmus paper. In nature a reverse change, which 
illustrates the same chemic principle, takes place in many flowers of 
plants belonging to the family Boraginaceae. For example, in 
Symphytum and Mertensia, the red flower buds, the cells of which have 
an acid cell sap, gradually change to blue as the flowers open. That 
this is a chemic change is proved by treating the red buds with an 
alkaline fluid and the blue flowers with an acid one. 

Similar spotting, but less clearly discernible and demonstrable, as 
the delicate reaction with morning-glory flowers, undoubtedly occurs 
on leaves and fruits, and the suggestion is made here, that such spots 

1 Harshberger, John W. : The Acid Spotting of Morning Glories by City Rain. 
Science, new ser., xxxviii: 548, Oct. 17, 1913. 



294 GENERAL PLANT PATHOLOGY 

caused by the acidity of raindrops serve repeatedly as the points of 
entry of parasitic fungi, for there are many leaf spots and fruit spots 
that show concentric rings of diseased tissue in the earliest lesions pro- 
duced. A fungus, which is stimulated to growth by an acid condition 
of the cell sap, would find ideal conditions for the commencement of 
growth by entering areas influenced by acid raindrops. 

Traumatism. — Traumatism, or mechanic injury, may be of various 
sorts and the effects are dependent upon the form and severity of the 
injury. Mechanic injury to the plant usually takes the form of wounds, 
which may be divided into natural and artificial. Natural wounds are 
those which are produced on plants living in a state of nature, or in a 
cultivated state in which other natural agents are concerned in their 
production, man's activity not being considered. Insects and worms 
may make burrows in the organs of plants. For example, bark boring 
is accomplished by species of beetles, so also are tunnels through the bark 
and the wood. Pith flecks are minute brown specks, or patches, found 
in the wood layers of trees. They consist of holes formed by boring 
insects filled with dead parenchyma cells, or dead empty cells filled 
with fungous material. Eroded and skeleton leaves, and shot-holes 
in the leaf tissue are directly traceable to the work of cutting insects. 
Frost cracks are longitudinal wounds produced by the rending action 
of the frost on the bark and wood of the trees. Sometimes this takes 
place with a loud report. The attempt on the part of the plant to 
heal the crack generally produces a frost ridge. Rents made by light- 
ning also occur. Strangulations are lesions formed by woody vines, by 
telegraph wires, or the like pressing on the outer surface of stems which 
grow about the compressing object and create additional pressure, so 
that the compressed tissue dies. Callus forms above the wounded 
areas formed by compression. Large hailstones sometimes produce 
bruises on the bark of young trees, as also the bombs shot out of vol- 
canoes. The abrasion of a tree by the branch of a neighboring tree 
rubbing against it or the cutting of large lateral roots in laying curb- 
stones must be classed as wound phenomena. Wounds are also 
formed by the teeth and horns of various mammals. Rodents, such 
as mice, rats, beavers and squirrels, are responsible for wounds pro- 
duced by gnawing with their chisel-shaped incisors. Bark is rubbed 
oft", or scratched by the horns and antlers of animals of the cow and 
deer tribes. Wounds are formed by the breaking off of branches 



GENERAL CONSIDERATION OF PLANT DISEASES 295 

under the tearing action of the wind, or by the breaking action of the 
weight of the ice and the snow of winter. The repair of wounds 
will be discussed with the consideration of the pathologic anatomy 
of plants, which will form a separate chapter of this treatise. 

Artificial wounds are due to the influence of man. The ploughing, 
discing, harrowing and cultivation of the soil frequently abrade roots, 
break them off, or seriously wound them. Limbs are broken off and 
bark removed by farm implements. Knife and axe wounds are easily 
recognized by their sharp character, where the cut may have been 
made vertically, obliquely, or horizontally. The stripping off of 
pieces of bark opens up the inner tissues of the stem to the attack of 
the agents of disintegration and decay. The removal of twigs and 
branches in the ordinary operations of pruning opens up wounds, some- 
times of a gaping character. The ringing, girdling, or scarification 
of trees for various purposes, if not properly performed, opens up 
wounds, so do nails, or spikes driven into the tree for various purposes 
and the placing of electric cables and telegraph wires along our streets 
and roads results in the removal of tree tops. The habit of cutting 
initial letters and monograms in smooth-barked trees, such as the 
beech, or the removal of sheets of birch bark, opens up wounds of vari- 
ous menace to the health of the tree. Injuries due to man-created 
environment may be of a thousand and one kinds too numerous for 
even a brief mention. 

Animate Agents of Disease. — These may be divided into two 
groups, namely, animal and plant. Many animals are responsible for 
the production of wounds and the destruction of plant parts. Man, 
cattle, herbivorous animals, rodents (mice, rats, squirrels, rabbits), and 
birds do great injury to plants by their horns, teeth, claws and beaks 
(woodpeckers). Among the invertebrates are to be included the in- 
sects, mites and worms. Certain nematode worms attack the roots of 
a large variety of plants and produce galls of characteristic form and 
appearance. Phylloxera, an hemipterous insect, winters on the roots 
of the grape, mostly as a young wingless form. Wingless individuals 
then abandon the roots and crawl up the stems to the leaves, where they 
form galls. Formerly introduced into Europe, it was very destructive 
to European grape vines until it was found that it could be controlled 
by grafting the European vine on the roots of American varieties. 
Insects injurious to plants may be roughly divided into two groups: 



296 GENERAL PLANT PATHOLOGY 

those with mandibulate, or bithig mouth parts, and those with hausti- 
late, or sucking mouth parts. The first group includes the insects 
that bore into wood, those that bite off the leaf surface (Fig. in) and 
thus skeletonize leaves and those which tear or bite pieces out of leaves 
and other plant parts (Fig. in). The sucking insects include those 
like the bugs, aphids, or plant lice, and scale insects (Fig. 112), which 
cannot be destroyed by stomach poisons. These latter insects by suck- 
ing the plant juices do irreparable damage to all kinds of fruit and 
shade trees, and reduce materially the yield of agricultural and 
horticultural crops. 

Of the mites, the most destructive is the red spider Tetranychus 
niytilaspidis. The red spider is probably identic with the insect 
known throughout Florida as the Purple Mite. It is quite a small 
insect, yet distinctly visible to the naked eye. They appear during 
summer in great numbers and damage the oranges by causing the 
fruit to drop and injure the foliage leaves so that they cannot perform 
their functions properly. The leaves become spotted and lose their 
glossy green color. The males and females are protected by stiff hairs 
and their color is purplish, or reddish-purple in the old insects, but of a 
lighter red when young. 

Animal galls are of various kinds. Those due to insects are charac- 
teristic and will be described, when the pathologic anatomy of plants 
is considered in detail. 

The field of Economic Entomology is a special one and there are 
bulky treatises dealing with various phases of it. A useful book, and 
written in an easy style is one by John B. Smith, late Entomologist of 
the New Jersey Agricultural Experiment Station, and is entitled 
"Economic Entomology for the Farmer and Fruit Grower." etc. 
Although published in 1896, it is still a useful book. A few American 
classics on the subject may be mentioned, as follows: 

Crosby, C. R. and Slingerland, M. V.: Manual of Fruit Insects, 

1915- 

Forbes, S. A.: Several Reports of the State Entomologist on the 
Noxious and Beneficial Insects of the State of Illinois. 

Harris, T. W.: Insects Injurious to Vegetation (several editions). 

Insect Life, seven volumes (a mine of information on American 
economic entomology). 

Packard, Alpheus S.: Insects Injurious to Forest and Shade 



GENERAL CONSIDERATION OF PLANT DISEASES 297 

Trees. Fifth Report of the United States Entomological Commission, 
1890. 

Riley, C. V.: Several Reports on the Noxious, Beneficial and other 
Insects of the State of Missouri. 

Saunders, Willi.^m: Insects Injurious to Fruits (several editions). 

United States Bureau of Entomology: Popular and Technical 
Bulletins on Insects. 



CHAPTER XXIV 

PLANTS AS DISEASE PRODUCERS, EPHIPHYTOTISM, 
PROPHYLAXIS 

Vegetal Agents of Disease. — The plants which are known to 
be injurious to other plants fall naturally into two large groups, namely, 
the Phanerogamic and the Cryptogamic. The latter includes injurious 
algae, slime moulds, bacteria and fungi. 

The phanerogamic parasites belong to four families of plants. 
Their morphology and physiology is fairly well known, so that in their 
discussion, we are entering well-trodden fields of investigation. 

The flowering plants, which lead a partially or wholly dependent 
life upon a host plant, may be considered as belonging to two distinct 
groups: the green parasites and the chlorophylless parasites. The 
plants of the first group illustrate by gradations how the conditions of 
life of the second group have arisen. The seeds of the first series of 
green parasites begin their growth in the soil and there develop into 
seedlings with cotyledons and root system, without any connection 
with a host plant. The root branches supplied with suckers then 
become attached to the roots or underground stems of other plants. 
About one hundred plants of the sandalwood family, Santalace^, 
belong to this series, including the true sandalwood, Santalum album 
of India, where its roots live attached to the roots of a species of Acacia 
leucophcBa and Pride of India, Melia azidarachta^. 

The bastard toad-flax of Europe, Thesium alpinum, is another 
member of this family. It develops relatively large suckers, which 
become attached to the roots of other plants. These suckers are con- 
stricted near their point of insertion. The swollen part spreads itself 
over the root of the host as a plastic mass, while the central cores per- 
forate the root and grow into the wood of the host where they spread 
out. Comandra umbellata is a santalaceous parasite found in the pine- 

" Wilson, C. C: Sandalwood. Indian Forester, xli: 248, August, 1915. 
298 



PLANTS AS DISEASE PRODUCERS 299 

barren region of New Jersey. The family Scrophulariace^ includes 
a number of these root parasites. Such are the eyebright {Euphra- 
sia), yellow-rattle {Rhinanthus), cow- wheat (Melampyrum), lousewort 
(Pedicularis) and others. The suckers of the yellow-rattle are of 
considerable size : their margins are swollen and they spread around the 
roots of the hosts. Those of the cow-wheat resemble in general those 
of the yellow-rattle. In America species of Agalinis (old genus Gerardia 
in part) are known to have parasitic attachments to the roots of various 
plants. This plant is a member of the family Rhinanthacece (Scroph- 
ULARiACE^, tribe Rhinanthae). 

The second series comprises the chlorophylless root parasites, such 
as Lathrcea squamaria, the toothwort. The young seedling lives at 
first upon the reserve substances of its seed, sending out roots in all 
directions. These finally fasten to the roots of ash, hornbeam or 
poplar, by means of a sticky sucker, which develops a central core 
that penetrates into the roots of its host. Colorless shoots covered 
with whitish scale leaves are formed and the flowering shoot which 
develops above ground has a purphsh hue. 

The third series of parasitic flowering plants includes those of the 
families Orobanchace^, Balanophorace^ and Hydnorace^. One 
genus, Orobanche, the broom-rape genus, is sufficiently common to merit 
attention (Fig. 117). The embryo of Orobanche shows no trace of root 
and stem and is without cotyledons. It is a spiral filament of delicate 
cells feeding on the stored reserve food. In its downward growth, its tip 
traces a spiral line until it finds the roots of a congenial host, when it 
not only adheres firmly to a root, but swells in such a way as to assume 
a flask-shaped appearance. The thickened part becomes nodulated 
and papillose and some of the papillae form conic pegs, which penetrate 
into the root of the host until the vessels of the parasitic attachment 
of the broom rape reach the vessels of the host. A bud is formed at 
the point of union between host and parasite and a strong thick flower- 
bearing stem grows above ground. Closely and intimately associated 
with a host, such as a clover plant, the broom-rape does considerable 
damage. Conopholis americana ,(Fig. 118) and C. mexicana live as 
parasites on oak roots, developing large swelhngs out of which the 
flowering shoots grow. 

The writer collected Conopholis mexicana in 1896 on the roots of 
an oak, Quercus reticulata, on the mountains at Eslava (10,000 feet) 



300 



GENERAL PLANT PATHOLOGY 




Fig. 117. — Broom-i-apu (Orolnniche minor) upon greenhouse geranium. 
Halslcd, B. D.. Rep. N. J. Agric. Exper. Slat., 1905.) 



{After 



PLANTS AS DISEASE PRODUCERS 



301 



above the Valley of Mexico. Cf. Wilson, Lucy L. W., Observations 
on Conopholis americana. Cont. Bot.-Lab., Univ. of Pa., II: 3-19. 

The fourth series of phanerogamic parasites comprises plants of 
the family Rafflesiace^, to which a number of genera belong. Raf- 
Hesia is a genus confined to the islands off southeastern Asia, Java, 
Borneo, Sumatra and Philippines. The whole plant is reduced to a 




Fig. 118. — Cancer-root, Conopholis americana of the broom-rope family, Oroban- 
chea; parasitic on roots of other plants. {From Gager, after Elsie M. Kiltredge.) 



gigantic ill-smeUing flower, one meter across, with parasitic attach- 
ments suggesting fungous hyphae, which penetrate the roots of vines 
of the genus Cissiis. Brugmansia and Cytinus are two other genera 
of this family. Cytinus hypocistus lives on the roots of shrubs of the 
genus Cistus in Mediterranean Europe. 

The fifth series of parasitic phanerogams includes epiphytes of 
bushy habit belonging to the family Loranthace^. The genera 



302 



GENERAL PLANT PATHOLOGY 




Fig. 119. — Distorted branch of mulberry caused by mistletoe {Phoradendron 
flavescens), Austin, Texas. {After York. H. H., Bull. 120. Univ. of Tex., pi. ix, 
March 15, 1909O 



PLANTS AS DISEASE PRODUCERS 303 

Loranthns, Phoradendron and Viscum include the well-known mistletoes. 
The American mistletoe, Phoradendron flavescens (Fig. 119), extends 
from southern New Jersey, Maryland, Ohio, Indiana and Missouri 
to Texas. It is a slow-growing green parasite, which on account of its 
chlorophyll is not entirely dependent upon its host for its carbohydrates 
(Figs. 1 20 and 121). It is essentially a water parasite, and consequently, 
its parasitic roots or sinkers grow into the woody cylinder of its host, 




Fig. 120. — Cross-section of a live oak branch showing five stems of mistletoe 
parasitic upon it. Note sinkers on parasitic roots penetrating into oakwood. {From 
Gager.) 



where they spread out circumferentially (Figs. 120 and 121). The 
white berries, which are sticky, are carried by birds as the sticky 
mass containing the seeds adheres to the bill and is only removed 
by rubbing the beak against the bark of a tree, for example. 
Mistletoe does not kill the trees directly, but it often causes them to 
become very much dwarfed and their branches distorted greatly. 



304 



GENERAL PLANT PATHOLOGY 



Parts of trees, however, may be killed. ^ The larch mistletoe, Razou- 
mofskya Douglasii laricis, is one which lives on the western larch in 
Idaho and Oregon and in the open places interferes seriously with the 
development of some of the more valuable timber trees. 

The sixth series includes the climbing parasites, which are destitute 




Fig. 121. — Sectional view, partly diagrammatic, of a branch infected with 
mistletoe, showing relation of parasite and host, a, branch of host tree; b, mistletoe; 
c, primary sucker; d, sucker from cortical root; e f, cortex; g, cambium; h, wood 
of branch. (After Bray, W. L., Bull. i66, U.S. Bureau of Plant Industry, Feb. 2, 1910.) 



1 The student should consult the following for more detailed information about 
mistletoe. Sorauer, Dr. Paul: Handbuch der Pflanzenkrankheiten (2d edition, 
1886, ii: 25-32; Peirce, George J.: The Dissemination and Germmationoi Arceidho- 
lium occidentalis. Annals of Botany, xix:99-ii3, January, 1905; York, Harlan H.: 
The Anatomy and some of the Biological Aspects of the American Mistletoe. 
Bull. Univ. of Texas, Scientific Series 13, March 15, 1909; Meinecke, E. P.: Parasit- 
ism of Phoradendron juniperinum, Proc. Soc. Amer. Foresters, vii: 35-41, March, 
1912; Mistletoe Pest in the Southwest, Bull. 166, Bureau of Plant Industry; 
Weir, James R.: Larch Mistletoe, do. Bull. 317. 



PLANTS AS DISEASE PRODUCERS 



305 



of chlorophyll and whose seeds sprout in the soil and send up a filiform 
stem which brings itself by its movements into contact with some 
host plant, which is penetrated by parasitic roots which enter, as 
far as the bast region and extract elaborated food. When estabhshed 
on the host the parasite severs its soil connection. Leaves- have been 




Fig. 122. — Dodder (Cuscuta) in flower and parasitic on a golden rod, Solidago ultni- 
folia. {From Gager, after Elsie M. KlUredge.) 



reduced to a few scales located near the clusters of small flowers and the 
twining stem assumes a yellow, or orange-yellow color. The dodder, 
Cuscuta (Figs. 122 and 123), belonging to the bindweed family, is 
illustrative of these parasites. 

Related in habit are species of the genus Cassytha. Most of the 
species of Cassytha inhabit Australia, but some are found in New 
Zealand, Borneo, Java, Ceylon, the Philippines, the Moluccas, South 



3o6 



GENERAL PLANT PATHOLOGY 



Africa, the West Indies and Florida. In Florida/ Cassytha filiformis 
is abundant on the dunes and in the rosemary scrub, where it spins its 
yellow, or reddish-orange stems from bush to bush. 

Fungous Organisms as the Cause of Disease.— The first part 
of this book dealt with the morphology, physiology, and taxonomy, of 




Fig. 123. — Photomicrograph of the section of a dicotyledonous host plant para- 
sitized by dodder, Cuscula sp. At D and Z>' note haustoria entering host plant as 
far as the bast region of the stem. (After Gager). 



the slime moulds, bacteria and true fungi. General reference was made 
to the diseases induced by them and in the third part will be given an 

1 Harshberger, John W. : The Vegetation of South Florida. Trans. Wagner 
Free Inst, of Science, vii, part 3, October, 1914; 86; Cf. Boewig, Harriet: The 
Histology and Development of Cassytha filiformis. Cont. Bot. Lab., Univ. of 
Penna., ii: 399-416, 1904. 



PLANTS AS DISEASE PRODUCERS 307 

account of the fungi which cause specific diseases. It remains for this 
discussion to consider fungi as the causes of diseases in general. Fungi, 
using the word in the broadest sense to include the bacteria and slime 
moulds, are responsible for an extraordinary number of diseases. The 
entrance of the organism into another is known as infection. Nothing 
like the infection of animals where the microbe, or its poison, circulates 
in the blood, and finds lodgment in most of the organs is found with 
plants. Infection follows, when a fungous spore germinates and pro- 
duces an infecting hyphae, which grows into the cells^ or between the 
cells of the host, it may be reaching to the ends of the plant. As disease 
is induced by parasitic fungi, the parasite which enters the host and 
spreads through it must absorb and utiHze the plastic and other sub- 
stances of the plant, which is parasitized. Thus, we can divide the 
endophytic hyphae into the intercellular hyphse such as we find in the 
oomycetous fungi and Puccinia simplex. With such hyphae ^he 
protoplasmic and other contents of cells are utilized by the formation 
of haustoria of different forms and kinds, which penetrate the interior 
of the cells. The second kind are the intracellular hyphae, which as in 
the disease of the plane tree, Gnomonia veneta, grow lengthwise and 
crosswise from cell to cell. 

The growth of the hyphae between and through the host cells is 
accompanied by the formation of soluble ferments. These dissolve the 
substance of the cell walls of cellulose, or woody walls with lignin and 
pigment deposits. The hyphae live on the products of solution.^ 
Hence timber may be damaged in two ways: by the formation of minute 
pores and apertures through it ; or by a solution of the cell- wall materials. 
The wood loses in strength and in weight and becomes "rotten." 
This rotten condition, however, is reached in a multiplicity of ways, for 
every parasitic fungus that lives in the wood of growing trees destroys 
the wood in a manner peculiar to itself. Starch grains are decomposed 
also in the cells, likewise crystals and tannin, for by the disappearance 
of the latter, the smell of sound wood is lost. Hartig has described 
the several methods in his ''Text-book on the Diseases of Trees." 

Then too, we have the epiphytic fungi which live on the surface 

^ Sometimes the h3^hae grow toward and surround the nucleus as the nucleus 
exerts a chemotactic influence. Such hyphae may be termed nucleotropic as in 
Puccinia adoxce. 

^ Consult Smith, Erwin F.: Bacteria in Relation to Plant Diseases, ii: 76-89. 



3o8 GENERAL PLANT PATHOLOGY 

of the host, as with the common mildews, and send short haustoria 
into the epidermal cells of the host on which they grow. Some fungi 
have mycelial hyphae that grow in both ways, intracellularly and inter- 
cellularly. Others, as a number of wood-destroying fungi, grow down 
through the tissue of the host and ultimately kill it. Apical growth 
is shown by some. The haustoria, as they enter a cell, may flatten out 
against the cell wall, as in Piptocephalis. Such flattenings are known 
as appressoria. The haustorium, which enters a cell, may become 
branched, or dendritic, it may enlarge into a haustorial knob, or re- 
main as an haustorial tube. Internal sclerotia are formed sometimes 
in certain parasitic fungi. These are consolidated or hardened masses 
of hyphae, which are associated with a resting period. 

Ordinarily when a spore falls on the surface of the plant, it produces 
a germ tube, which by the action of a secreted ferment bores its way 
through the epidermal cell walls and thus enters the host. Sometimes 
it penetrates the cuticle, grows between it and the cell wall and grows 
down between the membranes of the cells, as in Botrytis parasitica. 
Occasionally, but not commonly, it enters through the stomata, or 
sometimes through nectaries and stigmatic surfaces. However, there 
are certain bacteria, such as those which cause the black rot of the 
cabbage, which fall upon the drops of water excreted by water stomata 
and by following the water back into the plant infect the cabbage 
leaves. A cork layer is protection against infection. Fungi, however, 
gain access to the interior of the plant in a variety of ways. Some 
years ago^ the writer considered the way in which fungi enter living 
trees and a restatement of the facts presented in that paper is 
apropos. 

Occasionally the planted seed contains a dormant fungus (but not 
as a mycoplasm in Eriksson's sense), which begins its growth, as soon 
as the seedling plant emerges. The oat- or wheat-smut spores are 
produced in the grain and consequently infect the cereal plant when 
it is small, and at or near the surface of the ground. In other cases the 
fungus penetrates the underground parts or the twigs of trees. Fungi 
gain entrance to plants, through injuries caused by mechanic, meteoro- 
logic, chemic, or other agents. Mechanic injuries are due to man, 
animals, or other causes, such as the weight of snow, the rubbing of 

1 Harshberger, John W.: How Fungi Gain Entrance to Living Trees. Forest 
Leaves, viii: 88-90, December, 1901. 



PLANTS AS DISEASE PKODUCERS 



309 



two branches together. Squirrels in search of food bite off the twigs 
of trees. Deer and moose browse upon the tender branches and bark 
of various trees, the moose especially upon Acer pennsylvanicum and 
Sorbus americana. Grizzly bears rub their backs against the bark of 
trees and sometimes in this way decorticate them. Rodents peel off 
the outer protective layers of roots as food, or as material with which to 
line their burrows. The mycelia of Rhizocionia, or the oak-root fungus. 




Fig. 124. — Street tree injured by use as a hitching post. ( I//1 
Conn. Agi-ic. Expcr. Stal., pi. iii, igou ) 



\V. C, Rep. 



RoseUinia quercina, which live in the soil, penetrate into roots through 
wounds produced by field mice and gophers. The honey agaric, 
Armillaria niellea, forms strands of hyphae known as rhizomorphs, 
which grow through the soil and find an easy entrance into roots 
decorticated by rodents. Beavers are active agents in cutting down 
trees and removing the bark therefrom. Woodpeckers drill holes into 
trees and in their case it has been definitely proved that they carry the 
viable summer spores of the chestnut-bHgtht fungus, Endothio para- 



3IO 



GENERAL PLANT PATHOLOGY 



sitica, a single downy woodpecker carrying 757,074 spores.^ Wood- 
boring insects (Family Scolytid^) of the genera Dendroctonus, 
Scolytus, Tomicus are responsible agents in the destruction of trees 
opening up holes through which fungi may gain entrance. Horses 
do considerable damage to trees by stripping off the bark with their 
teeth, and street trees cannot be too 
soon or too carefully protected from 
such ravages, for a tuHp tree planted in 
the afternoon in front of the house of 
the writer in West Philadelphia had a 
strip of its bark removed by the curb- 
stone horse of a delivery wagon before 
nightfall of the same day (Fig. 124). 

Telegraph wires stretched in every 
direction rub against the trunks and 
limbs of trees, and do mechanic injury 
in this way, but, if the insulation is 
rubbed off the tree may be badly burned, 
or even set on fire by the electric cur- 
rent, especially on rainy days when 
there is a direct grounding of the cur- 
rent through the water running down 
the crevices of the bark. Many trees 
in our cities are planted too close to the 
curb and the wheels of passing wagons 
tear off pieces of bark (Fig. 141). 
Farmers in plowing, hoeing, mowing 
and cultivating the soil injure the 
roots and stems of cultivated plants 
and open the way for the entrance of destructive fungi. The blazing 
of trees by surveyors, the careless system of lumbering, careless trans- 
planting of young trees, are fruitful sources of injury to trees. Careless 
pruning (Figs. 125 and 126) of trees by inexperienced men, such as was 
prevalent in Philadelphia before the Park Commission undertook to 
properly care for the trees, caused the death of many fine shade trees. 




Fig. 125. — Decay following un- 
skillful pruning. {Slurgis, W. C. 
Rep. Conn. Agric. Ex per. Stat., pi 
Hi, 1900.) 



1 Heald, F. D. and Studhalter, R. A.: Preliminary Note on Birds as Carriers 
of the Chestnut Blight Fungus. Science, new ser., xxxviii: 278-280, Aug. 22, 1913. 



PLANTS AS DISEASE PRODUCERS 



311 



Stubs were left which never healed over and through the exposed sur- 
face the fungi of wood decay gained easy access. 

The injuries produced by meteorologic causes are important. 
Entire forests have been levelled by tornadoes. Cracks are produced 
by wind action. Lightning opens a way by cracks to the interior. 
Snow and ice snap off large limbs and hail stones bruise the bark and 
leaves of trees so that fungi can readily enter. Chemic substances are 
rather exceptional destructive agents to which reference has been called 




26. — Black walnut, Juglans nigra. Cold Spring Harbor, L. I. Note large 
open-branch stub (July, 1914). 



in a previous page. Besides these agents, it occasionally happens, that 
fungi enter healthy plants through diseased grafts which are inserted. 
Robert Hartig mentions such a graft union of diseased and healthy 
roots in the case of the red-rot fungus, Trameies radiciperda. Here 
contact of the diseased root containing the fungus with the sound one 
of a neighboring tree and the partial natural graft union of these two 
roots explains how such infection occurs. An enumeration of the 
way in which fungi can gain entrance to plants follows: 



312 



GENERAL PLANT PATHOLOGY 



Infection by natural 
growth of the fungus 



A. By means of spores, or h>i)luc, into stoinata and 
water stomata. 

B. By rerment action of a fungus on the epidermis of 
the host. 

f By developing from a dormant state in the seed into 
[ an active state in the seedling. 

[ Beasts 
I. Mechanic injuries ) Man 



Infection through 



induced by 



II. Meteorologic in- 
juries induced by 



III. Chemic injuries 
induced by 



Fall of fruit 

Combined weight action of fruit 

Wind 

Snow 

Ice 

Hail 

Lightning 

Sun 

Frost 

Factory gases 

Sewer gases 

Locomotive gases 

Chemicals at roots. 

Alkali soils 

Gases and chemicals in geysers, etc. 



IV. Non-classifiable 
injuries induced by 



Natural grafting and budding 



Incubation.^ — The period of incubation is the time between ex- 
posure to the cause of the disease and the first appearance of the symp- 
toms, or physical signs of the disease. This period in plants is quite as 
variable as in animals, and it is dependent on the nature of the organ- 
ism, whether it is virulent, or its virulency attenuated, on its food re- 
quirements, on its temperature requirements, the volume of infectious 
material, the stage of development, or age of the host plant, the amount 
of water and air in the invaded tissues, and individual or varietal re- 
sistance. The period of incubation may be as short as a few hours, 
or as long as three to four weeks. Presumably on seedling tissues the 
period of incubation of the damping-off fungus, Pythium de Baryanum, 
is only a few hours. Experiments performed by Erwin F. Smith^ 
1 Smith, Erwin F.: Bacteria in Relation to Plant Diseases, ii: 66. 



PLANTS AS DISEASE PRODUCERS 



313 



with Bacillus trachciphUus and young cucumbers where the organ- 
ism was inoculated from young cultures, and on susceptible plants by 
needle-pricks, showed that signs of disease rarely appeared in less than 
three to four days, and that signs of wilt and change of color usually 
were visible in five to seven days. In the case of the white pine bhster 
rust, Cronartium ribicola, the period of incubation in the pine is from 
one to six years. 

Duration of Disease. — The resistance of plants to disease is various 
even after the fungus has obtained an entrance into the tissue of the 




Fig. 127. — Chestnut, Caslanea denlaia, killed by blight fungus, lindolhia payascaili, 
Cold Spriiig Harbor, L. I., July, 1914. 

host. In the case of large trees like the white oak, a number of years 
may elapse before the tree finally succumbs to such fungi, as Fomes 
{Poly poms) applanatus. A chestnut tree, a few miles outside of 
Philadelphia resisted the chestnut-blight disease for over four years 
from the time of first infection before it finally succumbed. Smith 
{loc. cit.) describes how a good-sized potato tuber was half rotted in 
five days at ordinary autumn temperatures when inoculated with 
Bacillus phytophthorus by means of a few needle-pricks. 



314 GENERAL PLANT PATHOLOGY 

The final outcome of the disease may be a complete destruction of 
the host (Fig. 127), or its complete recovery. The simplest cases are leaf 
spots, or fruit spots, which are removed from the plant when the leaves 
and fruits fall without in any way jeopardizing the general health of the 
plant. Sometimes the plant recovers from bacterial, or fungal diseases, 
but such recovery does not protect the plant from subsequent attacks 
of the same disease, as is the case with some diseases of animals. Old 
and slow-growing cabbages are rather resistant to Pseudomonas cam- 
pestris while young and rapidly growing plants are apt to be destroyed. 
Vaccination of plants to ward off diseases has never been successful, 
and it is doubtful whether this means of protection is available for 
plants. It is, however, a wholly unworked field. Some experiments 
which Smith, Townsend and Brown performed in 1908 and 1909 seem 
to show that after Paris daisies have been inoculated several times with 
Pseudomonas tumefaciens with the production of tumors, that subse- 
quent inoculations with cultures of the same virulence are without 
effect, but owing to the possibility that the results were due to loss of 
virulence, the experiments were inconclusive. For the student, who 
may be interested in pursuing this line of important research work 
further, the following bibliography is here given, taken from Smith. 

Shattock, Samuel G.: The Healing of Incisions in Vegetable Tissues. Journ. 

Path, and Bact. Edinburgh and London, v: 39-58, 1898. 
HiLTNER, L. and Stormer, K.: Neue Untersuchungen iiber die WurzelknoUchen 

der Legurainosen und deren Erreger. Arb. a.d. Biologischen Abt. fur Land- 

und Forstwirthschaft am Kaiser. Gesundheitsamte iii, heft 3: 151, 1903. 
Brullowa, J. P.: Ueber den Selbstschutz der Pflanzenzelle gegen Pilzinfektion. 

Jahrb. f. Pflz. Krh. K. Bot. Garten Petersb., Nr. 4, 1907. 
Alten, H. von: Zur Thyllenfrage. Callusartige Wucherungen in verlezten 

Blattstielen von Nuphar luteum. Bot. Ztg., 68, part ii: 89-95, 1910. 
Smith, Erwin F.: Bacteria in Relation to Plant Diseases, ii: 93-94, 1914. 

DISSEMINATION OF FUNGI 

Fungi are usually reproduced by spores, which are minute and light 
and easily carried about by various agents, such as on seeds, by the wind, 
by water, by insects, by other animals, by agricultural and commer- 
cial practices and by railroads, cars and other vehicles. The black-leg, 
or Phoma wilt of cabbage of recent introduction, was introduced from 
Europe undoubtedly with imported seed, and as we have seen various 



PLANTS AS DISEASE PRODUCERS 315 

smuts are carried by the single fruits of various grains. In the aecial 
stage of the cedar-apple fungus, Gymno sporangium juniperi-virginiance, 
the spores are set free during dry weather at a time when they are most 
likely to be wind-carried.^ The spores of the water molds are carried 
by currents of water and those of the cranberry gall due to Synchy- 
trium vaccinii. The motile zoospores of the damping-off fungus need 
water for their dissemination. The spores developed during the 
Sphacelia stage of the ergot fungus on rye are carried by insects. The 
formation of the conidiospores is accompanied by a sweet substance, 
the so-called honey-dew, which is much relished. Birds, especially 
woodpeckers, disseminate the spores of the chestnut-blight fungus, 
Endothia parasitica, and in a great many different ways man is active. 

EPIPHYTOTISMS (EPIDEMICS) 

When a plant disease becomes virulent, rampant and aggressive, 
spreading rapidly from place to place, it is said to be epiphytotic 
(epidemic). A number of such epiphytotisms (epidemics) have oc- 
curred and the destruction due to some particular plant disease has 
been enormous. The potato crop in the British Isles during the 
summer of 1845, owing to a high temperature and abundant rains, 
suffered entire destruction in the short space of a fortnight. This was 
due to the ravages of Phytophthora infestans, an oomycetous fungus, 
whose spores in wet weather produce numerous infecting motile 
zoospores. The destruction of the potato crop led to the repeal of the 
corn laws of England, and as a sequence, the inauguration of a free trade 
policy. The Irish famine was the direct result and thousands of the 
natives of the Emerald Isle emigrated to America. With respect to the 
disease known as peach yellows Dr. Erwin E. Smith writing in 1891^ 
says: "Formerly this disease was confined to a small district on the At- 
lantic Coast, but during the last twenty years it has invaded distant 
regions hitherto free, and has entirely ruined the peach industry over 
very considerable areas. Within ten years the disease has taken fresh 

1 Heald, V. D.: The Disseminations of Fungi Causing Disease. Trans. 
American Microscopical Society, xxxiii: 5-29, June, 1913. 

2 Smith, Erwin F. : Additional Evidence on the Communicability of Peach 
Yellows and Peach Rosette, Bull, i, Div. of Vegetable Pathology, U. S. Dept. 
Agric, 1891. 



3l6 GENERAL PLANT PATHOLOGY 

very strong hold upon the orchards in the Delaware and Chesapeake and 
region, the north portion of the peninsula, and has destroyed thousands 
and thousands of trees, rendering a great industry unprofitable and 
precarious." The recent spread and virulency of the chestnut-blight 
fungus, Endothia parasitica, from the neighborhood of New York City, 
where it was probably first introduced, is so recent and fresh in the 
minds of the public, that an extended account of the epiphytotism 
(epidemic) need hardly be made here. The disease has practically 
destroyed the native chestnut trees of the forested areas of the east- 
ern states east of a line running northeast and southwest through 
the central part of Pennsylvania . There have been a few sporadic cases 
west of that line removed through the heroic efforts of the men em- 
ployed by the Pennsylvania Chestnut Blight Commission, who with a 
big appropriation of state money tried to find a way of heading off the 
disease and finally controlling it but without success. Introduced in all 
probability from China, where it has been found recently, the ravages 
of this disease have been without precedent. 

As to the epiphytotic diseases of plants due to animals, we have a 
number of instructive illustrations. The account of the introduction, 
spread and final control of the cottony cushion scale forms one of the 
most interesting chapters in the history of American phytopathology. 
Having been introduced from Australia to California in 1868, it 
spread so rapidly during the next twenty years that its ravages proved 
a very serious menace to the citrus industry of the southern part of 
California. The Australian ladybird beetle, which was introduced 
into California from Australia in 1889 for the purpose of controlling 
this scale, was so successful, that except for occasional outbreaks it 
ceased to be considered a serious citrus pest. 

All of these epiphytotisms (epidemics) and others that might be 
cited have been possible in all probability because the climatic condi- 
tions of temperature, moisture, rainfall, wind and soil conditions have 
been favorable during the period of most active virulency, when the 
diseases became firmly established. As an important contributing 
cause may be considered the unhealthy, abnormal, or susceptible condi- 
tion of the host plant owing to the methods of cultivation which have 
reduced the disease-resisting capacity of the plant. In the case of 
the chestnut, the restoration of the trees by sprouting from the stump 
was undoubtedly one of the contributing causes of the rapid spread of 



PLANTS AS DISEASE PRODUCERS 317 

the disease. Altogether, these epiphytotisms (epidemics) result either 
when the conditions are favorable for the spread of the parasites, or 
when the general tone and health of the plant has been lowered by 
improper methods of handling, so that its disease-resisting capacity 
has been reduced. Recognizing the possibility of the introduction of 
other virulent fungous, or animal diseases, a stricter quarantine has 
been instituted by both the individual state and national governments 
with a careful inspection of nursery stock designed for shipment from 
place to place. 

PROPHYLAXIS 

Prophylaxis may be defined as the means taken to prevent disease. 
It includes a consideration of the methods of protecting plants from 
disease, of preventing the spread of disease, and of the methods of 
breeding by which the disease resistance of plants is increased until in 
some cases absolute immunity is reached and the plant is made proof 
against disease. Some diseases are preventible by the observance of 
proper care in the cultivation of plants,^ and by habits of cleanliness, 
when no refuse which might harbor insect or fungous disease is per- 
mitted to remain, but is either destroyed, or rendered innocuous. 
For example, vegetable and agricultural crops should be rotated, so 
that the same crop would not follow upon the same piece of soil where 
the animal or fungous parasite may be lurking. Neither should the 
farmer attempt to cultivate certain crops in acid soils, or in low situa- 
tions subject to frost action. Nor should seeds be placed in beds rife 
with the spores of the damping-off fungus, Pythium de Baryamim. By 
proper care on the part of the grower diseased plants should not be 
sent away from an infected locality, and vice versa, he should be careful 
about the introduction of nursery stock and plants from other localities 
without a careful inspection. The national and state quarantine 
regulations are designed to help the grower in these respects, and he can 
refuse to purchase new plants without they are accompanied by a 
certificate setting forth that these plants are free from animal and 
fungous diseases. Orton- in two suggestive papers, has shown that 

^ BoLLEY, H. L. : Cereal Cropping: Sanitation, a New Basis for Crop Rotation, 
Manuring Tillage and Seed Selection. Science, xxxvii: 249-250, Aug. 22, 1913. 

^ Orton, W. A.: International Phytopathology and Quarantine Regulation, 
Phytopathology, 3: 143-151, June, 1913. The Biological Basis of International 
Phytopathology, Phytopathology, 3: 325-333, February, 1914. 



3l8 GENERAL PLANT PATHOLOGY 

this problem is not only of national, but of international and inter- 
continental importance. These papers should be read by every 
serious-minded student. 

Plant protection may be secured by the use of spraying materials.^ 
The principal rules to be observed in their use are: (i) the poison em- 
ployed must be sufficiently strong or concentrated to kill the parasite, 
but not sufficiently powerful to injure the host; (2) it must be applied at 
the right time, as suggested by a knowledge of the life history of the 
fungus, or insect in question. Such sprays may, therefore, be divided 
into two kinds, viz., insecticides and fungicides. Applications of these 
to healthy plants serve to protect the plant from the attacks of its 
fungous and insect enemies. Vast possibilities of controlling disease 
have been opened up by the treatment of seeds with hot water and other 
substances before the seeds are planted. 

iMcCuE, C. A.: Plant Protection. Bull. 97, Del. Coll. Agric. Exper. Stat. 
June IS, 1912; Rees, Charles C. and Macfarlane, Wallace: A Bibliography of 
Recent Literature Concerning Plant Disease Prevention. Univ. of 111.: Agric. 
Exper. Stat., Circular 183, May, 1915. 



CHAPTER XXV 
PRACTICAL TREE SURGERY^ 

The object of tree surgery is to repair the damage done to trees by 
the various causes previously described (page 274). The principles 
involved in all such remedial work are the removal of all decayed, dis- 
eased, or injured wood and bark, the cauterization, sterilization, and 
waterproofing of the cleaned, or cut, surfaces, and the putting of the 
tree in a condition for rapid healing. Such treatment should be 
watched from year to year, so that any defects will receive immediate 
attention. 

As the work requires the apphcation of scientific principles, no 
ignorant laborers should be employed. The men who act as tree sur- 
geons should have some knowledge of the structure of trees, their 
physiology and their habits of growth. A knowledge of the general 
principles of horticultural practice would not come in amiss, such as 
the tenets of grafting and pruning. Such workmen would be still 
better prepared, if acquainted with the structure, growth and life 
histories of the common destructive fungi and insects. If a town or 
municipality is unable to obtain such skilled labor, then the appoint- 
ment of a superintendent, or town forester, who is acquainted with such 
matters, should be made. Such a man should know the right thing 
to be done and all the details of the work. 

Preventive Measures. — As means Oi" preventing injuries to trees, 
various things may be done. The placing of an open tree box or fence 
of iron, or wire netting, is important, because it protects the tree from 
the gnawing of horses and the rubbing action of passing vehicles, or the 
viciousness of street arabs. Proper attention to the insulation of 
telephone, telegraph and electric wires will prevent a lot of damage to 
shade trees. Electric linemen, unless properly supervised, have no 

' A detailed account of practical tree surgery by J. Franklin Collins will be found 
in the Yearbook of the United States Department of Agriculture, 1913; also con- 
sult Stone, George E.: Shade Trees, Characteristics, Adaptation, Diseases and 
Cure, Bull. 170 Mass. Agric. Exper. Stat., Sept., 191 6. 

319 



320 



GENERAL PLANT PATHOLOGY 



regard for shade trees, as they look upon them as obstacles to the 
prosecution of their work. Improper pruning, when large stubs are 






Jl 


IFI 


^ 


Ci 


" '-"^4 


/'^ 




^^E 


r^ m 




^Hy 


^ ' m 




^^1 


M 




md 


f 



Fig. 128. — Properly treated area left 
by branch removal. Scar beginning to 
heal over by callus growth. (After 
Collins, F. L., U. S. Yearbook Dept. 
Agric, 1913-) 



Fig. 129. — Properly treatcil branch 
scar' about three-quarters healed over. 
(After Collins, F. L., Yearbook U. S. 
Dept. Agric, 1913) 



left, is another source of danger to the tree, which with proper knowledge 

can be safeguarded. There are a 

thousand and one details which, if 
neglected, will work injury to the 
planted trees. 

Character of the Work. — Tree sur- 
gery consists in the removal of de- 
cayed or dead limbs from trees, the 
cutting ofif of stubs left by improper 
methods of pruning, and the treat- 
ment of scars, holes and cavities, so as 
to prevent decay and secure proper 
healing (Figs. 128, 129, 130). The 
removal of branches from trees should 
be done in such a way as to prevent 
injury to the surrounding bark and 
cambium or active layer of growth. 
For this purpose, a saw, or gouge, a chisel, a mallet and a strong 
knife are essential. Where the branches are high above the ground, 




Fig. 130. — Cross-section of 7- 
year old blaze on a quaking aspen 
nearly healed over. (After Collins, 
F. L., Yearbook U. S. Dept. Agric. 
1913-) 



PRACTICAL TREE SURGERY 32 1 

a rope and ladder are needed. The cuts should be made close to the 
main tree trunk, so as to reduce the surface exposed to the action of 
the elements. Cut surfaces should be cauterized and water-proofed. 
The best antiseptic dressings are some of the creosotes, which destroy 
and prevent the growth of wood-destroying fungi, because it penetrates 
the wood better than a watery antiseptic. The antiseptic treatment 
with creosote should be followed by painting the scar with coal-tar. 
Lead paint is sometimes more available. It is useful, but not as 
satisfactory, as a heavy coat of coal-tar. 

Cavity Treatment. — The removal of all decayed and diseased parts 
of the tree should be accomplished first by the use of gouges, chisels and 
scraping tools. The use of the chisels is assisted by a wooden mallet. 
These cutting instruments should have keen edges for the cambium 
may be injured by dull tools. After properly clearing away all decayed 
material, the freshly cut surfaces should be treated with creosote and 
heavy coal-tar which should coat the surface of the sound and healthy 
exposed surfaces of the wood. The excavation should be so made as 
to provide drainage at the bottom of the cavity, but the undercutting 
should be done in such a way as to hold the filling material. Before 
the filling material is added to the cavity, it may be necessary to place 
one or more bolts in position to hold the tree shell firmly together. 
Iron rods and wire netting are also sometimes placed in the hollow to 
help reinforce the concrete, or cement, when it is mixed and ready 
for use. The tree surgeon learns by experience the best methods of 
procedure in the use of bolts, wire netting and the placing of the filling 
substance. 

Mixing and Placing the Cement. — A good grade of Portland cement 
and clean, sharp sand free from loam (i part of cement to 3 or less of 
sand) should be used. The mixing can be done in a mortar bin, a 
wheelbarrow, a pail, or in any other available receptacle. A mason's 
flat trowel and an ordinary garden trowel with a curved blade will be 
found convenient in placing the cement. A tamping stick, one or two 
inches thick and one to three feet long, according to the size of the cavity, 
will be needed, also some rocks to help fill the cavity and a pail of 
water. As the cement begins to harden, the surface should be carefully 
smoothed, so that it conforms with the general contour of the tree trunk. 
Sometimes cloth, or wire dams are used. These are stretched across 
the opening and a more liquid cement is poured into the space behind 



322 



GENERAL PLANT PATHOLOGY 




Fig. 131. — Cement cavity fillings, showing different types and successive stages. 
I, A large cavity in an elm filled with cement blocks separated by layers of tarred 
paper; a patented process. 2, An excavated cavity ready for treating and filling. 
3, The cavity shown in 2, which has been nailed and partly filled with cement. The 
ends of the rods for reinforcing the concrete are sprung into shallow holes in the wood. 
The wire dam is sometimes allowed to remain embedded in the cement, though it 
is usually removed as soon as the cement has partially set. 4, A later stage of the 
work shown in 3. The height of the wire dam has been increased. 5, The same 
cavity shown in 2, 3, and 4, several days after the filling was completed. (After 
Collins, F. L., U. S. Yearbook Dept. Agric, 1913.) 



PRACTICAL TREE SURGERY 323 

the dam which is removed when the fiUing has hardened. Asphalt and 
asphalt mixtures promise much for the future, when the proper methods 
of applying liquid asphalt have been discovered (Fig. 131). 

Defects in cement work are due to the use of cheap materials, 
carelessness in the mixing of the cement, splitting of the tree by the 
action of intense cold, dislodgment of the cement by the swaying action 
of the wind. Cracks appear in the cement, if the wood of the tree 
contracts away from the Ming, or by the spread of the decayed tissue 
behind the cement work due to lack of care in excavating rotten wood 
prior to the filling operation. These defects may cause lots of trouble. 

Metal-covered Cavities. — Sheet tin, zinc and iron have been used 
extensively to cover cavities. These coverings often serve to exclude 
rain, fungous organisms and destructive insects for some time. If not 
properly applied, such tin-covered cavities are a greater menace to the 
tree than open cavities. If such covers are used at all, the excavated 
cavity should be thoroughly sterilized and waterproofed. The metal 
is nailed fast with a light hammer and its center should be allowed 
to curve outward, so as to conform to the general shape of the tree 
trunk. The tacked edges should be as nearly air-tight and water- 
proof as it is possible to make them, and this can be assisted by paint- 
ing the surface of the tin. Sometimes fumigation of the cavity is 
resorted to as an added precautionary measure. 

Where the tree is not of sufficient value to fill with cement, an open 
cleaned cavity may be left after cauterization of the cleaned wood 
surface and waterproofing. A layer of burned wood is sometimes a 
sufficient protective covering, if the burning is accompHshed by one 
of the blow lamps, such as painters use for stripping the paint off 
woodwork. 

Guying. — Closely associated with the work of tree surgery proper, 
and often an indispensable adjunct is the guying of limbs to prevent 
the spHtting of the crotches, or to check further splitting. Experience 
demonstrates the best methods of applying the hook bolts, chains or 
other braces to the trees to be treated. This varies so widely in dif- 
ferent trees that it is impossible to give specific directions for this 
kind of work. 

In conclusion, it should be stated that tree surgery can be under- 
taken safely at almost any season of the year, especially well when the 
sap is not flowing actively, and the weather is not too cold, to freeze 



324 GENERAL PLANT PATHOLOGY 

the cement, and destroy such expensive filling work. Most ornamental 
and shade trees having only a few dead limbs are unquestionably worth 
attention. Others which have many dead limbs, or numerous decayed 
areas may not be worth the expense. Trees of large size, rare trees, 
historic trees and trees which fill a peculiar place in the landscape are 
probably worth saving by the most expensive methods of tree surgery, 
if necessary. Another phase of tree surgery is the commercial side, 
where ignorant men and tree fakers have undertaken to make a business 
of pruning and treating trees. The sad appearance of excessively 
pruned trees in all of our large American cities are living spectacles of 
the zeal of such men, who should be driven out of the business, as they 
have in Philadelphia by the municipal authorities undertaking to do 
the work by the employment of skilled tree surgeons. 

Bailey, L. H.: The Pruning Book. The Macmillan Co., New York, 1907. 
Blakeslee, Albert F. and Jarvis, Chester Deacon: Trees in Winter. Their 

Study Planting Care and Identification. The Macmillan Co., New York, 1913. 
Collins, J. Franklin: Practical Tree Surgery. Yearbook of the United States 

Department of Agriculture, 1913: 163-190. 
Gaskili, Alfred: The Planting and Care of Shade Trees. 

Forest Park Reservation Commission of New Jersey, 19 1 2, with papers on Insects 

Injurious to Shade Trees by John B. Smith and Diseases of Shade and Forest 

Trees by Mel T. Cook. 
Start, E. A. Stone, G. E., and Fernald, H. T.: Shade Trees. Bull. 125, Mass. 

Agric. Exper. Sta., Oct. i, 1908. 

It has been a matter of general knowledge that a disease may be 
controlled by a change in the time of planting, for with smuts the very 
different climatic conditions prevailing at the time of the various 
sowings have influenced the rate of infection. Early sowing of winter 
wheat has been found beneficial in the reduction of the amount of 
stinking smut, for wheat sown early in October showed no sign of infec- 
tion, while plants sown at the end of October were much attacked 
(about 60 per cent.) by the smut. By experiment as a problem in 
prophylaxis this matter of sowing as a means of controlling disease 
should be established for all of our important cultivated crops. 

Then too, a study of the cells and tissues which protect plants 
against the entrance of insects and fungi is a matter of prophylactic 
interest. The formation of cork, of bark, of callus, of how in response 
to the attack of fungi, the multiplication of protecting, or outer cells, 
is accomplished, should receive the attention of the student of phyto- 



PRACTICAL TREE SURGERY 325 

pathology. The presence of tannin and other protective chemical 
substances in the plant may explain immunity or non-immunity.^ 

Disease resistance and disease susceptibility are understood imper- 
fectly. The determination of the cause of the inherent differences in 
the tendency of this or that variety to suffer from disease is a matter 
of great importance. Breeding for disease resistance is a promising 
field of research. 2 Something has been accomplished along this line, 
but the amount which we do not know vastly exceeds the knowledge 
which we now possess. Rustproof varieties of wheat have been ob- 
tained. At the Ohio Experiment Station by selection of hills of 
potatoes that withstood attacks of the early blight fungus and planting 
tubers therefrom with subsequent repetition of this line of work, early 
blight resistant strains were secured. Progress has been made with 
cotton resistant to wilt and with musk melons resistant to leaf blight. 

Recently Jones and Oilman^, Wisconsin, have undertaken to con- 
trol the disease known as yellows caused by the parasitic soil fungus, 
Fusarium conglutinans, by breeding cabbage plants that show disease 
resistance. By repeated selection of the occasional sound heads in 
fields of diseased cabbages, strains of winter cabbage of the Hollander 
type have been secured which have proved in a high degree resistant 
against the attacks of Fusarium. The chances for research along these 
lines are practically unlimited and full of promise for the future of 
agriculture and horticulture. 

1 Cook, Mel T. and Taubenhaus, J. J. : The Relation of Parasitic Fungi to 
the Contents of the Cells of the Host Plants, (i. The Toxicity of the Tannins) 
Bull. 91, Del. Agric. Exper. Stat., February, 1911. 

2 Orton, W. a. : The Development of Farm Crops resistant to Disease. Year- 
book of the United States Department of Agriculture, 1908: 453-464. 

3 Jones, L. R. and Oilman, J. C. : The Control of Cabbage Yellows through 
Disease Resistance. Research Bull. 38, Agric. Exper. Stat. Univ. Wis., December, 
1915; Norton, J. B.: Methods used in Breeding Asparagus for Rust Resistance, 
U. S. Bureau of Plant Industry, Bull. 263, 1913. 



CHAPTER XXVI 
INTERNAL CAUSES OF DISEASE 

During recent years attention has been called to diseases which are 
evidently due to the action of an enzyme, or ferment in the plant, 
which renews itself perhaps as a catalytic agent in the tissues of the 
host. As it is filterable through a Berkefeld filter, it may be a soluble 
enzyme pure and simple, or it may be one of the extremely minute, 
ultra-microscopic organisms to which attention has been called recently. 
All the evidence seems to point to its enzymatic nature. Such diseases 
are caused by the excessive activity of the oxidase and peroxidase 
enzymes in the plant and the loss of function of catalase, another en- 
zyme, which carries off some of the residual products of the others 
mentioned. Such diseases due to a Contagiimi viviim fluidum affect a 
number of plants, notably the tobacco, and all of these diseases seem 
to be more or less related, as to their nature and origin. Recently 
Kiister in the second edition of his "Pathological Plant Anatomy" 
(191 6) has grouped many of the enzyme-produced conditions under 
the head of "Panaschiering." He distinguishes several types. The 
first is when the green parts contract sharply under the pale parts. 
Under this head he considers: (a) marginal panaschiering, when such 
terms as "albo-marginatis" would be applicable, as in such cultivated 
plants as Pelargonium zonale, Hedera helix and Weigelia rosea, (b) 
In sectional panaschiering, the white and the green colors are dis- 
tributed sectionally over leaves and stems, as in Chamaecyparis pisi- 
fera plumosa argentea. (c) He distinguishes marbled and pulverulent 
panaschiering. His second group includes cases where the border 
between green and pale parts is not sharply marked and this group 
includes {a) Zebra-panaschiering, as in the banded leaves of Etdalia, 
and (b) flecked panaschiering, where white specks are distributed over 
a green background and blend with it. It is clear that "Mosaic," 
"Brindle," "Calico" or "Mottle Top" of tobacco is a physiologic, 
not a fungous or bacterial disease. 

326 



INTERNAL CAUSES OF DISEASE 327 

It is infectious, and to a certain extent contagious. As calico is an 
important disease of tobacco and tomato a description of it in these 
plants will serve to show what enzyme diseases are like in general. 
The leaves present a mottled appearance, being divided into smaller, or 
larger, areas of light-green and dark-green patches. In the tomato, the 
light-green areas become yellowish, as the disease progresses, and in 
very badly affected plants become finally purplish-red in color. The 
leaves are much distorted, stiff, and badly curled. It attacks other 
plants, notably the poke weed. Phytolacca decandra, ragweed, Am- 
brosia artemisicBfolia, Jamestown weed. Datura stramonium. It is 
probable that peach "yellows," aster "yellows" are more or less similar 
to the true "mosaic." Calico is primarily a disease of the green color- 
ing matter (chlorophyll) of the infected plants; hence it disturbs the 
normal nutrition of the plant. To this destruction of the chlorophyll 
the name of chlorosis has been given and calico is, therefore, a state of 
chlorosis. The contagious nature of calico is shown by experiments 
which prove that it can be communicated at least in some cases by 
mere contact of calicoed plants with the healthy. Juice on the hands 
from calicoed plants when handling disease-free plants will spread the 
disease in nearly all cases, and this infection is due to the chlorotic juice 
on the hands of the experimenter. Chlorosis, or calico, usually takes 
ten to fourteen days to make its appearance after infection and a plant 
once infected remains permanently so, and all new growth usually 
becomes calicoed. Calico, or mosaic, can be transferred to other species 
and varities of Nicotiana than the common N. iabacum, also to potato, 
egg plant, peppers, petunia, etc. The dried leaves of calicoed tobacco 
retain their power of infection for at least a year or two, to some degree, 
but if wetted they lose this power. The virus, if it is permissible to 
use this word, can be apparently extracted from calicoed leaves by 
ether, chloroform and alcohol without destroying its infectious qualities. 
Bunzel has measured the oxidase content of plant juices, because of the 
importance of oxidase in chlorotic diseases of plants, in their causal 
relationship to color production in plants, their importance in the dark- 
ening of tea and in the production of the smooth, black and hard 
lacquer of the Japanese, from the white, fluid, soft secretion of the 
lacquer tree, Rhus vernicifera. The literature on oxidizing enzymes 
is a copious one. The following papers and books can be consulted, 
as well as the bibliography which each includes: 



328 GENERAL PLANT PATHOLOGY 

BuNZEL, Herbert H. : The Measurement of the Oxidase Content of Plant Juices. 

Bull. 238, Bureau of Plant Industry, U. S. Dept. Agric., 191 2. 
Chapman, G. H. : Mosaic and Allied Diseases with Especial Reference to Tobacco 

and Tomato. 2sth Annual Report Mass. Agric. Exper. Stat., 1913: 94-104. 
Clinton, G. P.: Chlorosis of Plants with Special Reference to Calico of Tobacco. 

Report Conn. Agric. Exper. Stat., New Hav^en, 1914: 357-424, with 8 plates. 
Kastle, J. H. : The Oxidases and other Oxygen Catalysts concerned in Biological 

Oxidations. Bull. 59, U. S. Hygienic Lab., 1910. 
Klebahn, Professor Dr. H.: Grundziige der Allgemeinen Phytopathologie, 

191 2: 124-127. 
Woods, Albert F.: Observations on the Mosaic Disease of Tobacco. Bull. 18, 

Bureau of Plant Industry, U. S. Dept. Agric, 1902. 

Nutritive disturbances may also be included as internal causes of 
disease. If for any reason, such as the inability of the living cells of 
the root to take up water through a change in the osmotic power of the 
protoplasmic membrane of the root hair cells, the leaves above owing 
to active transpiration cannot secure sufficient quantities of water 
and the whole plant wilts. A disturbance in the formation of starch 
in the chloroplast results in a deficiency of the plastic carbohydrates, 
and the active cells of the cambium during this period of starvation 
form less wood and, therefore, fewer conducting vessels. This reacts 
on the tissues everywhere in the plant by reducing the available water 
and food and, therefore, the plant is dwarfed and perhaps sickly. 
Intumescences are trichomatous outgrowths not associated with 
insects or fungi which are due to some disturbance of the balance 
between transpiration and assimilation. 

Mutations which result in the sterility of an annual species would 
lead to the extinction of the plant with such non-seed production. 
(Enothera albida is a pale-green, rather brittle and very delicate form 
with narrow leaves; never attaining anything like the height of (E. 
Lamarckiana. It bears pale flowers and weak fruits which contain 
little seed. It appears every year in most of de Vries's cultures in 
larger or smaller numbers. The plants are so weak that de Vries 
imagined them to be diseased,^ and after much difficulty he secured 
seeds from them. Enough has been given on these points to show that 
mutations may be along the line of plants constitutionally weak. 
The absence of amygdalin and prussic acid in the Sweet Almond 
may make such a form more susceptible to disease, as also the absence 
of quinine from cinchona trees kept in European hot houses. 

^DE Vries, Hugo: The Mutation Theory (English edition), I: 229, 1909. 



internal causes of disease 329 

Malformations and Monstrosities 

Hugo de Vries has shown that malformations and monstrosities 
do not arise as a result of variations, but may be looked upon as muta- 
tions. His tricotylous, hemisyncotylous, syncotylous, and amphi- 
syncotylous races are proof of this statement. Fasciation in its 
simplest form consists of a flat, ribbon-like expansion of stem, 
branch, flower clusters, flowers and fruits which may be cylindric 
below, but flattened above. This is one of the most common of all 
malformations and by numerous experimental cultures the fasciation 
has been found to be heritable. Spirally twisted plants are more 
striking malformations than fasciations. Valeriana officinalis is 
one of the best-known examples displaying spiral torsion. It is also 
displayed in a teasle. Dipsacus silvestris torsus, twisted sweet william, 
Dianthiis barbatus, dark-eyed Viscaria, Viscaria oculata. Such mal- 
formations de Vries has shown to be truly heritable. (Pleiphylly is 
that condition where two or more leaves arise in place of a single one.} 
Such we find in the ever-sporting races of clovers, where four, five, 
six, seven, or even eight leaves appear instead of the normal three. 
The presence of three leaves in a whorl, or of three cotyledons, as above 
noted, is called polyphylly. Shull has shown that the ascidial 
leaflets of the white ash, Fraxinus americanus, are heritable. Pistil- 
lody is demonstrated in the appearance of imperfect pistils in place of 
stamens, as in the poppy. When colored flower parts become green, 
this condition is known as antholysis, or chloranthy, and is illustrated 
in green roses and green dahlias. This condition and petalody and 
sepalody are transmitted. Peloria, where a normally zygomorphic 
flower, as in the toad-flax, Linaria vulgaris, is transformed into a regular 
flower with five spurred petals instead of one spurred petal, is 
another example of monstrosities which are heritable. 

The history of Cytisus Adami which originated as a graft hybrid 
is of interest in connection with the study of Chimaeras. Hybrids that 
arise by vegetative reproduction, where scion and stock are mutually 
affected, are known as graft hybrids. The origin of Cytisus Adami 
seems to have been as follows: a shoot of Cytisus purpureus was 
grafted on a stock of Cytisus laburnum; from this were produced many 
shoots, one of which grew vigorously, and developed larger leaves 
than those of C. purpurcus and from this shoot plants were propagated 



330 GENERAL PLANT PATHOLOGY 

constituting Cytisus Adami. It was found, that on flowering, this 
form had dingy red flowers. Winkler believes that graft hybrids and 
chimaeras are the result of the process by which cells of two distinct 
kinds or species are united vegetatively instead of by sexual methods, 
and that this serves as the point of departure for an organism which in 
a single growth shows bound together the peculiarities of both species. 
Hence, a graft hybrid is a complex chimgera. Baur thinks that the 
union between CratcBgus and Mespilus {Crafa gomes pilus) is a periclinal 
chimgera, and refers this and the graft hybrid to the development of a 
mixed vegetation point, where the periclinal chimaera originates in 
the development of an apical region with a periclinal arrangement 
of cells. ^ 

Branches of shrubs and trees originate as mutants with a dififerent 
combination of characters than the rest of the shrub, or trees. Such 
mutants probably arise in the change of some single cell. The shoot 
which arises from tissue formed by mutating cells develops into 
something new which is called a bud variation, or sport variety. If 
the shoot arises from the mutating cells alone, then the resulting 
shoot will consist only of the new cells an^ the sport can be propagated 
true without any reversion. If the tissue which gives rise to the shoot 
combines both old and new cells, then there arises a mixed branch, 
which is known as a "sectorial chimaera." Citrus treess how such 
"sectorial chimaeras" not infrequently when a Valencia orange tree 
bears typical Valencia oranges and a small rough and worthless muta- 
tion. A twig here and there produces oranges in which certain sectors 
of the fruits show mutant tissue," forming what may be called mixed 
oranges. These have probably arisen because the mutant tissue is 
scattered or mixed with the tissue of the original form thus constituting 
a "hyper chimaera." 

"Mutations often occur in the cells which begin the formation of 
the minute ovaries in the blossom buds. As the ovary grows in size, 
the mutation appears as a sector of the fruit which differs in color, 
ripening season, or thickness of skin from the rest of the fruit. Such 
curious fruits have been called spontaneous chimaeras" (Coit). 

1 Winkler, H.: Ueber Pfropfbastarde und Pflanzliche Chimaren. Ber. 
Deutsch. Bot. Gesellsch., 25: 568-576, 1907; Baur, E.: Pfropfbastarde, Periklinal 
chimaren und Hyperchimaren, Do., 27: 603-605, 1909. 

2 Coit, J. Eliot: Citrus Fruits, 1915: 121-122. 



CHAPTER XXVII 
CLASSIFICATION OF PLANT ABNORMALITIES 

The older botanists prior to the pubHcation of the important work 
of Maxwell T. Masters in 1869 gave little attention to abnormalities in 
plants. Linnaeus treated of them to some extent in his ''Philosophia," 
but it is mainly to Augustin Pyramus de Candolle that the credit is 
due of calling attention to the importance of vegetable teratology, as 
throwing light upon normal structure and functions. Until the epoch- 
making work of de Vries on plant mutations drew attention to the 
absolute necessity of experimental methods in the study of normal and 
teratologic plants, the field of vegetable teratology was the concern of 
the plant morphologist and the different abnormalities were studied by 
comparative morphologic methods. Hugo de Vries and several of 
his co-workers pointed out that many abnormal forms are heritable and 
this suggested that the line of approach in their study was through 
experiments in breeding these forms to discover their origin and 
true character. This has been done with a few forms, but the whole 
field should be worked by some competent geneticist, who would devote 
his life to the undertaking. Without further discussion, it has been 
thought advisable to put in a form accessible to American college 
students, a glossary of the more important terms used in teratology. 
With the exception of a few additions the terms given in first volume 
of " Pflanzen-Teratologie" (1890) by Dr. 0. Penzig are here translated 
from the original, as serving as an outline of teratology for American 
students. 

Abortion (Masters and English authors; Abortus, German Avortion 
or Avortement, French)— Stunting of an organ, that is the exceptionally 
small formation of the same, whereby the form remains unchanged. 
The German and French authors use the same expression very fre- 
quently for the cases where a certain organ is entirely suppressed and 
does not make an appearance. 

Acaiilosy. — Acaulosia is the diminution in the size of the stem, for 
absolute suppression of the stem, as the terms acaulescent and 

331 



332 GENERAL PLANT PATHOLOGY 

acaulosia would signify, is an impossibility in a typic plant. The term 
is purely a relative one. 

Acheilary (Ch. Morren). — The suppression of the labellum in such 
flowers as the Orchidace^. 

Adesmy (Ch. Morren). — Congenital separation of organs which 
are normally united together, therefore, often included as atavism. 
Morren distinguishes between homologous adesmy as the separation 
of members of one whorl and heterologous adesmy the separation of the 
members of one whorl from those of another. 

Adenopetaly. — Formation of a nectary in a former nectarless petal. 

Adhesion.^ — Normally used for the union of parts of different whorls 
in the flower, for example, the union of a sepal with a petal, or of a 
stamen with a carpel, and also for fusion in general (of a branch with 
the main axis, of a leaf with a branch, etc.). 

Adherence (Moquin-Tandon). — Fusion of organs which normally 
are separate. 

Anaeretic (Schimper, 1854).^ — Vnder foli alio anceretka, C. Schimper 
obviously understood the abnormal arrangement of leaves on an axis 
in a single row, a condition sometimes produced by a torsion, or twisting 
of the axis. 

Antherophylly (Ch. Morren).- — Formation of anthers upon leaf 
blades. 

Anthesmolysis (Engelmann). — Central or lateral metamorphosis 
of an inflorescence, especiafly of heads as in the Dispaceae and 
Compositse. 

Antholysis (Spenner in Flor. Friburg). — A solution of flowers, 
particularly applied to the condition in which the axis becomes elongated 
and the flower whorls separated from each other. 

Aphylly.^ — The condition of the plant in which leaves are suppressed. 

Apilary (Ch. Morren). — Suppression of the upper lip in normally 
bilabiate flowers, as in Calceolaria. 

Apogamy.- — Vegetative reproduction of plant individuals instead 
of by the usual method with sex organs, especially used with reference 
to ferns where the antheridia and archegonia are suppressed or not 
functional, the young plant arising directly from the prothallium. If 
is also used for the non-sexual formation of embryos in the embryo sac 
of the phanerogams. 

Apophysis. — Vegetative, central proliferation of an inflorescence. 



CLASSIFICATION OF PLANT ABNORMALITIES ^^^ 

Apostasis. — The monstrous disunion of parts normally united as 
in the elongation of a flower axis, as a result of which the whorls are 
transformed into spirals. One, however, uses the term for the sepa- 
ration of single floral phyllomes, for example single sepals from the 
calycine whorl. 

Atrophy. — Wasting away; degeneration of organs; abortion. 

Autophyllogeny (Ch. Morren). — The budding of one leaf from 
another, as from the midrib. 

Balance Organic (Moquin-Tandon).^One uses this expression for 
cases that by atrophy of single organs of a plant is compensated by 
hypertrophy of others. 

Biastrepsis (C. Schimper). — This is analogous to the torsion, or 
twisting of other authors. 

Blastomany (A, Braun). — Abnormal tendency of single plant 
individuals to develop an unusual number of leaf buds (axillary or 
adventitious). 

Calycanthemy (Masters). — Transformation of sepals to petaloid 
structure. 

Calyphyomy (Ch. Morren). — Adhesion of one or all of the sepals to 
the back of the petals. 

Cenanthy (Ch. Morren).- — Kevds = empty + avdos = flower: Abor- 
tion, or suppression of the stamens and pistils of a flower, leaving the 
perianth empty. 

Ceratomany. — Abnormal formation of horn-like, or hooded, fre- 
quently nectariferous structures in a flower. Clos has employed the 
same term for the increase in the spurs in many families (Orchidace^) . 

Chellomany (Ch. Morren). — The doubling of the lip, or labellum, 
in orchids, as in Orchis morio. 

Chloranthy. — The transformation, or change of all or most of the 
floral parts into leaf-like green parts; frondescence. 

Chorisis. — The separation of a leaf or phylloid part into more than 
one; dedoublement, doubling. 

Cladomany. — An abnormally richly branched plant. 

Cohesion. — A union between the members of one and the same 
whorl (particularly in flowers), or between the parts of a composite 
organ. 

Coryphylly. — An abnormality in which a leaf ends the axis. This 
leaf is sometimes colored. 



334 



GENERAL PLANT PATHOLOGY 



Crateria.^ — C. Schimper uses this term for a leaf blade which de- 
velops ascidia, as the ascidial white ash discovered by George H. Shull. 

Cyclochorisis (Fermond). — Division of an axial organ in two direc- 
tions, so that in place of a simple axis there arise whole clusters of 
secondary axes. 

Dedoublement (chorisis, doubling) .^ — Congenital division of an 
organ in which several parts arise out of a single primordium. Lateral 
and serial dedoublement are distinguishable. 




Fig. 132. — Twin cherries due to dialysis, or disjunction, of the pistil of the flower 
into two carpels, each of which matures into perfect drupe joined at the base with 
its fellow. Philadelphia Market, May 25, 1916. 

Deformation.^ — A malformation, or alteration from the normal 
kind. A general expression for the irregular formation of an organ, 
or a complex of organs. 

Degeneration (Masters) .^ — Stunted formation of an organ with 
which changes of form are associated. An alteration for the worse. 

Dialysis (Ch. Morren, Masters). — The separation of parts normally 
in one, especially parts of the same whorl. Scarcely distinguishable 
from adesmy (Fig. 132). 

Diaphysis (Engelmann).— A central proliferation of flowers. If 
the flower axis elongated beyond the carpels bears another flower, we 



CLASSIFICATION OF PLANT ABNORMALITIES 335 

speak of Diaphysis floriparous; if leafy shoots arise, it is Diaphysis 
frondiparons; if a cluster of flowers, it is known as Diaphysis 
racemiparous. 

Diplasy (Fermond). — The division of an axial organ into two 
parts. 

Diremption.^ — The occasional separation, or displacement of leaves. 

Diruption. — A term used by Germain de St. Pierre for different 
appearances (division of leaves, axes, fasciation). 

Discentration (C. Schimper).^ — A term applied to fasciation of an 
axial organ, but used occasionally for the multiple division of a 
phyllome. 

Displacement (Masters). — The abnormal position of a plant organ. 

Distrophy (Re). — The dissimilar formation of the homologous 
organs of a plant. 

Divulsion (St. Germain de Pierre).- — See diruption. 

Ecblastesis (Engelmann).^ — ^Lateral proliferation, that is bud for- 
mation in the axils of flower parts (sepals, petals, stamens or carpels). 
There can be distinguished floriparous, frondiparous and racemiparous 
kinds of ecblastesis. 

Enation.^ — The formation of excrescences of different kinds on the 
upper surface of other organs. We find scales projecting from petals, 
small lamina on foliage, leaves, etc. 

Epanody (Ch. Morren). — Abnormal reversion of an organ to a 
simpler form than it normally shows. 

Epipedochorisis (Fermond).- — A manifold division of an axial 
organ in one plane. Frequently not distinguishable from fasciation. 

Epistrophy (Ch. Morren). — A reversion of an apparently constant 
monstrosity to the normal form of single organs, for example, the 
development of branches with normal leaves in place of those with cleft 
leaves. 

Etiolated. — Blanched, or lengthened abnormally by the absence of 
light. 

Expansivity .^ — A term used by Germain de St. Pierre with a similar 
sense to Diruption and Divulsion. 

Fasciation (Olaus Borrich, i67i).^A flat band-like, or ribbon-like 
expansion of a normal cylindric axis, or stem, associated with departure 
from the normal leaf position. If flowers are developed they are 
generally altered in structure (Fig. 133). 



336 



GENERAL PLANT PATHOLOGY 



Fission. — A division of a normally simple organ. 

Frondescence.^ — The prolifer- 
ation of a normally reduced petal 
to a foliage leaf with lamina. 

Gamomery (Engelmann). — 
The condition in which the 
normally distinct petals are 
united into a gamopetalous 
corolla. 

Gemmiparity. — The condtion 
of leaves which develop adventi- 
tious buds. 

Gymnaxony (Ch. Morren).— 
The condition in which the 
placenta protrudes through the 
ovary of the flower. 

Gynophylly (Ch. Morren). — 
The transformation of a carpel 
into a foliage leaf. Phyllomor- 
phy of the ovary. 

Hemitery. — An abnormality 
of elementary organs, or of axial 
appendages. 

Heterogamy (Masters). — An 
alteration in the position of the 
sexual organs. 

Heteromorphy (Masters). — 
Irregular formation of an organ. 

Heterotaxy. — This term is 
used by Masters for the cases in 
which a new organ, or structure, 
appears in unusual places, as leaf 
buds and flower buds on a root. 
Later authors (Freyhold) use the 
word in an entirely different sense 
for the inversion of the floral plan. 

Homotypy. — The develop- 
ment of an organ, or of any 
structure in the same place, where normally another one originates. 




Fig. 133. — Fasciated stem and fruits o^ 
the poppy {Papaver). {Drawing by Alice M- 
Russell.) 



CLASSIFICATION OF PLANT ABNORMALITIES 337 

Hypertrophy. — An abnormal largeness, strong formations of any 
plant part. 

Idiotery. — A monstrosity by which a plant departs from the normal 
type and from all of its related forms. 

Lepyrophylly (Ch. Morren). — The transformation of the integu- 
ments of the ovule into scales, or leaves. 

Meiophylly. — The diminution in the number of leaves in a whorl, as 
compared with those of the preceding whorl. 

Meiotaxy.— The suppression of entire whorls. 

Metamorphosis. — The transformation of an organ into another one, 
that is morphologically equivalent to it, but it may be has a wholly 
different appearance and other functions. 

Metaphery (Ch. Morren) .^ — The displacement of organs, as when 
alternate become opposite. 

Metastasis (Moquin-Tandon). — The shifting of an organ to some 
unusual position. 

Mischomany (Ch. Morren). — An increase in the number of pedicels 
or the branching of the inflorescence, as in Muscari comosum. 

Monosy (Ch. Morren). — Separation of floral parts from one another 
with which they normally are in Cohesion, or Adhesion. The abnormal 
isolation of parts due to a desmy or dialysis. 

Multiplication. — The division of an order into many homologous 
parts. 

Oolysis. — A greening (viridescence) which shows conspicuously 
in the carpels and ovules of the flowers. 

Peloria (Linnaeus). — The radial (actinomorphic) regular formation 
of a normal zygomorphic (irregular) flower. 

Periphyllogeny (Weinmann). — The formation of numerous leaflets 
about the border of a leaf blade. 

Permutation (De CandoUe). — An enlargement of the floral envelopes 
with corresponding abortion of the sexual organs. 

Petalody. — The metamorphosis of stamens, or other organs into 
petals with their usual form, color and consistence. 

Petalomania. — An abnormal multiplication of petals. 

Phyllocally (Lemaire). — The budding of new leaflets on the surface 
of foliage leaves. 

Phyllody (Masters). — The appearance of foliage leaves in place of 
floral ones. 



338 GENERAL PLANT PATHOLOGY 

Phyllomania. — An abnormal production of green leaves. 

Pistillody — The transformation of floral parts into carpels. 

Pleiomorphy (Masters). — An abnormal or excessive development. 

Pleiophylly (Masters) .^ — The appearance of many leaves in place of 
a single part. 

Pleiotaxy (Masters). — The increase in the number of whorls in a 
flower. 

Plesiasmy (Fermond). — An abnormal shortening of the stem inter- 
nodes, so that the leaves are arranged closely together. 

Pollaplasy (Fermond). — The division of a theoretic simple organ 
into many analogous structures. 

Polyclady. — An unusual development of branches and twigs. 

Polyphylly. — The abnormal increase in the number of parts of the 
floral whorls. 

Prolification. — This term is used with a number of different 
meanings. One is the central, or lateral, outgrowth from a flower, or 
an inflorescence. The different kinds are designated as median, axil- 
lary, extrafloral, while each kind is again divided into foliar and floral, 
depending upon the nature of the adventitious bud. The axillary 
prolification is known as echlastesis (Engelmann) and the median as 
diaphysis. 

Rachitism (Touchy). — Hypertrophy of the floral envelopes, as in 

JUNCACE.E, CyPERACE^, GrAMINACE.E. 

Recrudescence.- — The production of a leafy, or flowering, shoot from 
an axis of inflorescence after the formation of ripe fruit on that axis, 

Rhizocallesy (Ch. Morren). — The union of two plants of the same 
species solely by their roots. 

Salpinganthy (Ch. Morren).— The transformation of ligulate or 
ray florets of Compositae into conspicuous tubular florets. 

Scyphogeny (Ch. Morren). — The formation of ascidia from leaf 
blades. 

Sepalody.^The transformation of petals into sepals, or sepaloid 
parts. 

Solenoidy. (Ch Morren). — The metamorphosis of stamens into 
tubular structures. 

Solution (Masters) .^ — Abnormal separation of the members .of a 
whorl from those of another (similar to the Adesmia heterologous of 
Morren). 



CLASSIFICATION OF PLANT ABNORMALITIES 339 

Sphaerochorisis (Fermond). — Multiple division of an axis in all 
directions producing a witches'-broom-like arrangement of branches. 

Speiranthy (Ch. Morren). — The anomalous condition in which the 
flowers develop into a twisted form. 

Spiroism (Ch. Morren).— An elongated snail-like development of 
an organ. 

Staminody. — The transformation of a petal into a stamen. 

Stasimorphy (Masters). — The arrest in the development of an 
organ, or an organ complex, and the stoppage of development at a lower 
stage. 

Stesomy (Ch. Morren). — A term with similar usage to stasimorphy. 

Strophomany (Schimper).^ — A term used in the same sense as 
biastrepsis for twisting, or torsion. 

Suppression. — The complete abortion of an organ. 

Synandry.^ — The abnormal union of stamens. 

Synanthy.^ — Lateral union of two or more flowers. This condition 
can arise in a number of ways; for example, by the approach and fusion 
of two floral fundaments, or through the partial forking of a receptacle, 
or through floriparous.ecblastesis, etc. 

Synanthody. — ^Lateral union of two floral buds on the same stalk, 
or on two pedunfles which have become fasciated. 

Syncarpy.- — ^Lateral fusion of two or more fruits. This condition 
is the natural result of synanthy. 

Synophthy (Ch. Morren). — The union of two leaf buds, or foliage 
shoots with each other. 

Sjmspermy.^ — The fusion of several seeds. 

Taxitery (Gubler). — A modification which is so slight that it admits 
of comparison with the normal form. Contrast Idiotery. 

Torsion. — A spiral twisting, or bending, or parts or organs. 

Triplasy (Fermond). — The separation of an organ into three analo- 
gous structures. Trifurcation. 

Virescence. — The abnormal development of flowers in which all 
organs are colored green and more or less wholly transformed to small 
foliage leaves. If the metamorphosis is complete, there result foliage 
leaves with distinct lamina and this condition is known as frondescence. 

In concluding this glossary of teratologic terms, it might be well 
to add that a recent work on plant teratology has appeared. It is 
designed to bring our knowledge up to date. The first volume of 



340 GENERAL PLANT PATHOLOGY 

Worsdell's^ "Principles of Plant Teratology" includes a consideration 
of the fungi and bryophytes as non-vascular plants and with vascular 
plants he goes as far as a consideration of the teratology of roots, stems, 
leaves and flowers. It is issued by the Ray Society, as was that of 
Maxwell T. Masters in 1869. 

^ WoRSDELL, Wilson Crosfield: The Principles of Plant Teratology, vol. i., 
London, printed for the Ray Society, 1915; vol. ii, 1916. 



CHAPTER XXVHI 
SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 

The preceding pages have dealt with the causes of plant diseases, 
that is their etiology. It remains to discuss the symptoms of disease 
as that is a very important matter in deciding as to the nature of the 
disease, and the harm that the various diseases may do to our agri- 
cultural crops. It is easy to determine that there is something wrong 
with the plant, because such well-known symptoms as withering, 
as yellowing, as abnormal growth are evidences of it, but it is quite 
another thing to decide as to the specific nature of the disease, its cause 
and probable amelioration. Even to the trained plant pathologist, it 
is not an easy problem to decide what the trouble is. It requires some- 
times two or three years of research work with all the refined methods 
of modern science to reach a satisfactory conclusion, and at times even 
then the solution is baffling. To call a pathologist, or a botanist, an 
ignoramus, because he cannot by a study of the symptoms name the dis- 
ease, is unworthy of people who claim to be cultured, and yet it fre- 
quently happens that the farmer's opinion of the book scientist is based 
upon just such a flimsy pretext. General conclusions are reached in 
this field of inquiry, just as in other fields, by the process of exclusion. 
The pathologist puts questions to himself about the plant and gradually 
he eliminates the impossible conditions, gradually narrowing himself 
down to a few possibilities. For example, he might ask himself 
whether the cause of the disease is external or internal. If external, 
then whether it is due to climate, to animals, or plant parasites. If 
plant parasites are concerned, then are they flowering plants or fungi. 
We will suppose that he finds that the disease is of fungal origin. Then 
with the cultural means at his disposal, the fungus must be obtained 
in pure culture, and its pathogenicity tried out upon healthy individuals 
corresponding racially, or specifically, with the diseased ones. If the 
inoculation of the healthy host is successful, then the recovery of the 
fungus from the tissues for comparative cultural study will follow. 

341 



342 GENERAL PLANT PATHOLOGY 

Knowing the specific fungal organism, a great stride has been made 
toward a comprehensive knowledge of the disease. 

The plant pathologist, who would be successful in his profession, 
must be acquainted with the normal, or healthy, conditions of plants, 
or how can he study the unhealthy states? Any departure from the 
healthy state is indicated by a certain behavior of the plant, or reac- 
tion to the causes of disease and certain peculiarities of structure, form 
and color are also manifested. An investigation of these character- 
istics of disease concerns symptomatology. The most common symp- 
toms of plant diseases may be classified according to the outline pre- 
sented by Heald in Bulletin 135 of the University of Texas, Nov. 15, 
1909, entitled "Symptoms of Diseases in Plants." 

1. Discoloration or change of color from the normal. 

(a) Pallor. Yellowish or white instead of the normal green. 

(b) Colored spots or areas on leaves or stems. 
Whitish or gray: mildews; white rusts, etc. 
Yellow: many leaf spots. 

Red or orange: rusts, leaf spots, etc. 
Brown: many leaf spots. 
Black: black rust, tar spots, etc. 
Variegated: leaf spots, etc. 

2. Shot-hole: perforation of leaves. 

3. Wilting: "damping-off," "wilt," etc. 

4. Necrosis: death of parts, as leaves, twigs, stems, etc. 

5. Reduction in size: dwarfing or atrophy. 

6. Increase in size: hypertrophy. 

7. Replacement of organs by a new structure. 

8. Mummification. 

9. Change of position. 

10. Destruction of organs. 

1 1 . Excrescences and malformations. 

Galls: pustules, tumors, corky outgrowths, crown galls, etc. 
Cankers: malformations in the bark generally resulting in an open 

wound. 
Punks or conchs and other fruits of fleshy fungi. . 
Witches' brooms. 
Rosettes and hairy root. 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 343 

12. Exudations. 
Slime flux. 

Gummosis: especially for stone fruits. 
Resinosis: especially for coniferous trees. 

13. Rotting: 

Dry rot and soft rot: "the gangrene" of plant tissue. 

Root rots: alfalfa, cotton, beets, cherry, etc., generally woody or 
fleshy roots. 

Stem or trunk: dry rot of trees; rot of modified stems like rhi- 
zomes, bulbs, or tubers. > 

Buds. 

Fruits: fleshy fruits of various kinds. 

It will be profitable to discuss the symptoms of disease under the 
above heads. 

I. Discolor ations. — ^The unnatural, or false color which plants 
assume under diseased conditions may be included under the head of 
discolorations. Sometimes, as in woods, the discoloration may appear 
as a stain. AbnormaUty of color usua|y accompanies other symptoms 
of plant disease. Pallor, or chlorosis, v^ere the plant assumes a yellow- 
ish to white, or sickly-pale hue, is due to a number of causes. Promi- 
nently, one form is due to the absence of light, whereby the plant be- 
comes etiolated, or suffers etiolation. It is considered that the laying of 
wheat and other cereals is one form of this etiolation where, through 
lack of carbohydrates, the cellulose which forms the strengthening of the 
cell wall does not form properly.;;,' Sometimes the gardener induces 
etiolation in his celery, endive and asparagus plants, where the blanch- 
ing is secured by covering such plants with soil. True chlorosis is due 
to an enzyme which destroys the chlorophyll pigment of the chloroplasts 
which are fully developed. Icterus is the condition where the organs 
are only yellow; chlorosis, where they are white, such as in the mosaic, 
or calico disease of plants formerly described. Yellowing may be in- 
duced experimentally by an excess of carbon dioxide, in fact yellowing 
accompanies wilting, the attack of wire worms, the presence of poisons, 
or acid gases. 

Variegation and albinism may be apparently normal conditions of 
some varieties of plants, for gardeners and horticulturists grow such 
plants by preference for decorative uses. This variegation, or albinism, 



344 



GENERAL PLANT PATHOLOGY 



is induced in all probability by the presence of oxidizing enzymes in 
patches of cells where the chlorophyll pigment is destroyed and not in 
other adjoining areas. 

The formation of spots on leaves (Fig. 134), stems, flowers, or fruits is 
due to a variety of causes. The grayish or whitish spots on the under 
surface of grape leaves are due to mildews, on the stems of cruciferous 
plants to white rusts and on the leaves of the parsnip are found white 
spots due to a fungus, Cercospordla. Grayish spots on the prickly pear 




Fig. 134. — Apple leaves showing leaf spots produced by natural infection with 
Sphaeropsis malorum. {After Scott, W. M., and Rorer, J. B., Bull. 121, U. S. Bureau 
of Plant Industry, 1908.) 

and on the leaves of the box trees are occasioned by a disease known as 
anthracnose. Many leaf spots are yellow as in violets, oaks, cucumbers 
and melons. The red or orange spots on plants usually suggest the 
presence of rusts as on wheat, rye, alfalfa and a host of other cultivated 
and wild plants. The so-called tar spots of the maple leaves are bla'gk 
in color and such discolorations of the leaf surface are traceable to the 
attack of a fungus, Rhytisma acerinum. Apples are frequently marked 
by fly specks which are usually clustered as small circular black spots.. 
A fungus is the causal agent. 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 



345 



2. Shot-holes (Fig. 135). — The perforations of leaves and the forma- 
tion of what are called shot-holes illustrate another form of fungous 
attack, where circular patches of dead tissue killed by the fungus drop 
out leaving a hole. The Enghsh morello cherry trees in some sections 
of our country have been killed during the past few years by this " shot- 




FlG. 135. — Shot-hole disease of the plum due to Cylindrosporium 

Heald, F. D., Bull. 135 {Sci. Ser. 14), Univ. of Tex., Nov. 15, 1909.) 



{.After 



hole" disease. When the funguses belonging to the genera Cercospora 
and Phyllostida attack the leaves of Virginia creeper perforations may 
be formed. 

3. Wilting. — Wilting in general is due to the lack of sufficient water 
to supply that lost by transpiration, for wherever the amount of water 



346 GENERAL PLANT PATHOLOGY 

transpired exceeds that absorbed by the roots wilting occurs. Wilting 
may result, if the normal ascent of the sap is interfered with by the 
growth of fungi into the water-conducting tissues, the entrance of bac- 
teria into the woody vessels of the plant, whereby they are literally 
plugged with such organisms, or some injury which cuts off the ascend- 
ing current of water. Damping-off is a form of- wilt in which an oomy- 
cetous fungus enters the collar of seedling plants, or where a Rhizoctonia 
species invests the roots of the growing plants and interferes with the 
regular water absorptive processes. 

4. iVecro5M.— Necrosis is the mortification, or death, of the tissues. 
The term is usually applied to the death, or loss of vitality, of one part of 
a plant, while the other parts remain alive. When the fungus, Fusa- 
rium trichothecoides , is inoculated into Green Mountain potato tubers, 
in about three weeks' time it will be found that a portion of the tuber, 
usually the central part directly beneath the point of inoculation, has 
undergone necrosis. The surface of the potato tuber becomes sunken 
through the death and collapse of the starch containing cells and the 
lesions may involve half of the tuber. The black rot of the navel 
orange is due to a fungus, AUernaria citri, which gains entrance to the 
fruit through slight imperfections about the navel end. A black 
decayed area is found under the skin. This decay does not spread im- 
mediately through the entire fruit, but remains for weeks- as a small 
black necrotic area with a mass of the fungus present. The decayed tis- 
sue does not always extend to the surface, but remains beneath the skin. 
Necrosis often follows the action of frost in killing the cortex cells of 
fruit trees in patches with a blackening of the tissues. Fire bhght may 
be the cause of necrosis, for the cambium which is killed dries up in 
black patches. 

5. Dwarfing. — A reduction in the size of a plant is very often asso- 
ciated with disease. This may be true of the whole plant, or some 
particular organ only may be dwarfed. Apples are frequently reduced 
in size by the attack of the scab fungus, sometimes not reaching one- 
fourth the size, and the same is true of apples affected by the cedar rust. 
Dwarfing of the whole plant may be a symptom of malnutrition. It 
may be evidence of a poor soil, or the repeated maiming, or nipping off of 
the buds by cattle, or purposely by man, as is the case with the minia- 
ture trees of the Japanese. Dwarfing, or nanism, may be the result 
of climate, as is the normal case with alpine plants. Prostrate forms of 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 



347 



trees of great age are formed by the action of the dimate of high 
mountains, or by growth in porous sand on exposed sea dunes. Atro- 
phy, or the non-formation of parts, or organs, is a phase of dwarfing. 
It is seen in the dwindling of organs in size, as the result of various 
causes, such as the attack of fungi. The carpels of Anemone are 
atrophied in plants infested by Mcidium and the whole flower is sup- 
pressed when the cherry is attacked by Ex- 
oasciis cerasi. Exoascus pruni is responsible 
for the absence of the stone in plum fruits, etc. 

6. Hypertrophy. — The undue excessive de- 
velopment of a plant part is a symptom of a 
diseased condition of that part. The bladder 
plums formed in the plum pocket disease are 
good illustrations of hypertrophied tissues, as 
the replacement of the rye ovary by the ergot 
sclerotium, following the entrance of the spores 
of Clamceps purpurea. The attack of Gym- 
nosporangium biseptatum (Fig. 136) results in 
the massive enlargement of the stem of the 
white cedar. A rust fungus is responsible for 
the increase in size of the twigs and petioles of 
our common ash and elder. 

7. Replacement: — ^A new structure takes 
the place of organs. 

8. M ummifi cation. — The drying and 
wrinkling of fruits and other plant parts 
where the general shape of the part is pre- 
served, but in a reduced size, is an evidence 
of the unhealthy condition of that organ, or 
part. The attack of the black-rot fungus, 
Sphceropsis malorum, brings about a slow desiccation of the fruit which 
may remain hanging on the tree over winter and in a shriveled condi- 
tion. Frequently, the mummies produce a crop of spores, which spread 
the disease. 

9. Alteration of Position. — The change of position of an organ from 
its normal one'is a sure symptom of disease, usually the attack of some 
fungous parasite. The normal position of the leaves of the house leek, 
Sempervivum tectorum, is that of a rosette with the spirally arranged 




Fig. 136. — Swelling of 
main stem of white cedar 
caused by Gymnosporangium 
biseptatum. (After Harsh- 
berger, Proc. Acad. Nat. Set., 
Phila., May, 1902.) 



348 GENERAL PLANT PATHOLOGY 

leaves approximately horizontal. When attacked by a rust fungus, 
Endophyllum sempervivi (Fig. 137), the diseased leaves grow erect. 
The same is true with our native American hepatica, Hepatica triloba. 
Infrequently, it is attacked by a rust fungus in the aecial condition, 
Tranzschelia punctata, so that (Fig. 138), the rusted leaves develop a 
larger, stiffer petiole, stand erect .with a smaller, stifYer leaf blade on 
which the aecia are found. The common garden purslane Portiilaca 
oleracea, usually grows in a prostrate position, but when attacked by 
the white rust, Cystopus (Albugo) portulacce, many of the diseased 
branches become erect or ascending. The stems of Vaccinium vitis- 
idcBa become erect the second year after infection by Melampsora 
Goeppertiana. 




Fig. 137. — Two plants of house-leek, Sempervivum. Left one affected by Endo- 
phyllum sempervivi. Right one, a healthy plant. {After Grove, W. B.: The Brilish 
Rusl Fungi, 1913: 54. 

10. Destruction of Organs. — The destruction of plant organs by the 
attack of fungi is well illustrated by the cereal smuts, which attack the 
flower parts reducing them to a black powdery mass of spores, which are 
carried away, leaving nothing but the bare axis on which the flowers 
were originally situated. 

11. Excrescences and Malformations. — These will be treated of in 
detail in another chapter. Here it may be said that galls, pustules, 
tumors, corky outgrowths, crown galls, cankers, burls, or knauers, 
(Fig. 139) witches' brooms (Fig. 140), etc., are evidences of diseased 
conditions. The nature of these excrescences and malformations can- 
not be discussed here, but it may be said that they are specific and 
usually associated with the attack of some fungus, as for example the 
plum knot due to Plowrightia morbosa, the cedar apples formed on the 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 349 




Fig. 138. — Hepatica triloba parasitized by a rust fungus, Tranzschelia punctata, 
which causes some of the leaves to stiffen and grow erect. Left figure shows ascia, 
April 29, 1915. 



35° 



GENERAL PLANT PATHOLOGY 



red cedar by Gymnosporangimn juniperi-virginiatKE. The crown galls, 
or possible vegetal caricers, are another illustration of such excres- 
cences, while malformations are represented by peach leaf curl and 
the witches' brooms on trees. 

12. Exudations. — The formation of slimy substances, which flow 
from trees and plants, the diseased conditions known as bacteriosis, 
gummosis^ and resinosis, illustrate the character of the exudations from 




Fig. 139. 



-Burl, or enlarged base of an oak tree in the forest on Gardiner's Island, 
New York, July 17, 1915. 



plants under abnormal conditions. The production of clear amber- 
colored secretions, which accumulate on the surface of the diseased parts, 
is known as gummosis and is seen in cherries, apricots, almonds and 
many other trees. It follows wounds or the attack of fungi. The 
same condition in coniferous trees is known as resinosis and in a few 
trees it is of economic interest because, as in the spruce, the exudation of 

1 Wolf, Frederick A.: Gummosis. The Plant World, 15: 49-59, March, 191 2. 
Butler, O.: A Study on Gummosis of Prmiits and Citrus. Annals of Botany, 
25: 107-153, 1910- 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 35 1 




Fig. 140. — Branch-knot or witches'-broom of the Hackberry ,(C>//J5 occidentalis) . 
{After Kellerman, W. A., Mycological Bulletin, Nos. 61-72, July, 1906. 



352 



GENERAL PLANT PATHOLOGY 



gum rosin known as ''spruce gum" is collected and sold at from two 
dollars to two dollars and fifty cents a pound. ^ Where due to the attack 
of bacteria it is called bacteriosis. Tumescence is the over-turgescence 
of plant tissues due to the excess of water. It sometimes indicates 
pathologic changes and was formerly called (edema, or dropsy. Flux 
is another name applied to the issuance of fluids from wounds in trees, 
while slime flux issuing from wounds may be frothy, owing to the fer- 
mentative activity of yeasts and other fungi, which live in such slimes. 
Manna flux is found in such trees as the manna ash and species of 
tamarisk. Cuckoo spit is a frothy material found on grasses and 



■ g 






'1 




"M 


1 




1 


1 


'"'i 


P 




7 


1 



Fig. 141. — Crown gall with hairy root on nursery stock of Northern Spy apple. 
- {From Marshall after Paddock.) 

other plants in which green sucking insects live. Honey-dew is the 
excretion of plant lice, or aphides, and its presence encourages the 
growth of fungi {Meliola, Scorias). 

13. Rotting. — Rottenness of plant parts is the state of decomposition 
putrefaction, or decay usually associated with the formation of 
malodorous, or putrid substances. Several kinds of rots are dis- 
tinguished as dry rot, soft rot, black rot and gangrene. Usually such 
rot or gangrene is due to the presence of some bacterial, or fungous 
organism, which brings about the decomposition of the parts attacked. 
The decay may be slow, or rapid. Sometimes the rot is associated with 
the production of bitter substances, as in the bitter rot of apples. 
^ Record, Samuel J. : Harvesting the Spruce-gum Crop. Tlie Country Gentle- 
man, Feb. 26, 1916, p. 475. 



SYMPTOMS OF DISEASE (SYMPTOMATOLOGY) 353 

The wet rot of potatoes is probably due to putrefactive bacteria. The 
tissues become soft, then mushy, and finally become a liquid mass with 
a vile smell. 

BIBLIOGRAPHY OF PLANT DISEASES IN GENERAL 

Heald, Frederick D.: Symptoms of Disease in Plants. Bull. 135, University of 

Texas, Nov. 15, 1909. 
Klebahn, Prof. Dr. H.: Grundziige der allgemeinen Phytopathologie. Berlin 

Gebriider Borntraeger, 191 2. 
KtJSTER, Dr. Ern.st: Pathologische Pflanzenanatomie. Gustav Fischer in Jena, 

1903, Zweite Auflage, 1916. 
KtJSTER, Dr. Ernst: Pathological Plant Anatomy. Authorized translation by 

Frances Dorrance, 1913-1915. 
Smith, John B.: Economic Entomology for the Farmer and Fruit Grower, and for 

Use as a Text-book in Agricultural Schools and Colleges, J. B. Lippincott Co., 

1896. 
Stengel, Alfred: A Text-book of Pathology, W. B. Saunders Co., Philadelphia, 

1906. 
Ward, H. Marshall: Disease in Plants, Macmillan Co., & 1901. 



23 



CHAPTER XXIX 
PATHOLOGIC PLANT ANATOMY 

With the multiplicity of higher plant forms, in which the same end 
is attained in a diversity of ways, the terms normal and abnormal 
become in one sense merely relative terms for what apparently is the 
normal method of procedure in one group of plants, may be decidedly 
different, or abnormal, in other uncommon groups. The words normal 
and abnormal are, therefore, variable terms, but useful ones. Speci- 
fically, when we use the word abnormal, we mean the departure, or 
deviation, from the normal (average) structure or function of the mem- 
bers of any group selected for investigation. Pathologic plant anatomy, 
therefore, has to deal with abnormal, but not necessarily diseased 
organs, and yet a study of diseased tissues is an important subject of 
investigation for the plant pathologist. 

The material which forms the substance of our inquiry naturally 
falls into two principal groups. 

1. The differentiation, number or size of the cells of pathologic 
tissues remain more or less below the normal, so that the tissues in one 
or more ways remain in a stage of incomplete development. The term 
Hypoplasia designates those abnormal processes of formation, which 
compared with the corresponding normal processes of development 
appear retarded as it were and prematurely. 

2. The pathologic cells and tissues exceed the conditions of differen- 
tiation and growth characteristic of normal plants, so that a treatment 
of such necessitates a consideration of several independent groups. 

(a) The abnormal cells differ from the normal ones only in their 
internal structure (contents, mechanics, etc.) and for the processes of 
differentiation by which the tissue cells supplement their normal 
qualities, or exchange them for new ones, the term Metaplasia is 
used. 

(6) The increase in size of abnormal cells over normal ones is 
termed Hypertrophy (v-rrep = over, excessive; rpepoi = to nourish), 
and it is not important fundamentally whether the histologic structure 

354 



PATHOLOGIC PLANT ANATOMY 355 

of the cells concerned remains similar to that of the normal ones, or is 
altered in some way. 

(c) The increase of a part by an increase in the number of its indi- 
vidual structural elements is known as Hyperplasia (wep = over, 
excessive; TrXoo-ts = formation, structure), and this depends on cell 
division following cell growth. A large number of abnormal formations 
arise through hyperplasia and the histology of the newly formed tissues 
is exceedingly varied. 

3. The processes of Restitution consist in the restoration of 
structures, which resemble those lost in injuries and mutilations of the 
plant body. Although the tissues thus formed are like the normal 
ones yet their formation following injuries, or mutilations, comes within 
the realm of pathologic anatomy. 

Hence we shall treat of morbid anatomy under the five heads 
suggested in the above considerations. Naturally the material for 
our investigation and treatment arranges itself into five chapters, on 
"Restitution," "Hypoplasia," "Metaplasia," "Hypertrophy" and 
"Hyperplasia." 

RESTITUTION 

Following a wound or other injury or the removal of a plant part, 
the organs are stimulated to renew the lost part, or to repair the damage 
to the cells or tissues. The regeneration of lost or injured plant cells, 
tissues, or organs, is called specifically in pathologic plant anatomy 
restitution, wHile the word regeneration, although implying restitution 
(L. restitutio (-n), < restitutus, pp. of restituo, restore, < re-, again, + 
statuo, set up, < sto, stand), is used in a somewhat different sense. 

The process of restitution, it is conceivable, includes a number of 
distinct operations.^ The newly formed parts are formed at the place 
of amputation and are like the lost portion (as the regeneration of root 
tips) or the newly formed parts, which resemble the lost ones, are not 
produced at the injured place, but some distance away from it, or the 
new parts arise on the cut surface, but are unlike the lost part (hetero- 
morphosis), and finally the new parts do not resemble the lost ones, nor 
do they arise at the surface of the amputation. 

It will be profitable to discuss the two most important forms of 

* Consult Studien iiber die Regeneration v. Professor Dr. B. N^mec. Mit 18 
Textabb. 



356 GENERAL PLANT PATHOLOGY 

restitution, viz., that of the cell and that of the tissues. The experi- 
ments of Tittman have shown that the waxy cuticle of the castor-oil 
plant, Ricinus communis, may be restored after removal. Exposure 
of the protoplast results in many cases in the formation of a new cell 
membrane, as is illustrated in some of the large-celled algae belonging to 
the Siphoned. Frequently, it is possible to demonstrate the restitu- 
tion of the cell membrane by the process of plasmolysis in which the 
protoplasm is made to retreat from the cell wall. The time varies for 
its formation under conditions of plasmolysis. In Conferva, it takes 
place in one to two days, in Zygnema in three to four days. When the 
root hairs of dicotyledonous plants are plasmolyzed new membranes 
are formed about the protoplast. 

Wounded siphonaceous algal cells {Caulerpa, Valonia, Vaucheria), 
where the cell wall has been injured, are capable of restoring the cell 
wall. Some fungi show such restitution also, while the injured cells 
of the higher plants lack this power. A few exceptions are known where 
nettle hairs of Urtica dioica may imperfectly replace the broken-off tip. 
Pricking the turgid cell of Valonia utricularis, as I have done with 
fresh specimens in Bermuda, is followed by the escape of a liquid jet 
and later the opening is closed by a gall-like, protoplasmic, chloro- 
phylless plug. 

It has been demonstrated that the important cell wall can be regen- 
erated on fragments of protoplasm provided the influence of the nucleus 
is felt in such formation. Klebs has shown that, with the removal of 
the nucleus from the cell, that cell has lost all its power to produce new 
cell walls, but a distant nucleus may extend its wall-forming influence, 
when removed several millimeters away in an adjoining cell. 

In the restitution of tissues, we will consider those cases in which the 
injured cells remain unhealed, but in which the uninjured neighboring 
cells bring about the restitution. The removal of the rhizoidal hairs 
on the thallus of Marchantia is followed by the appearance of other 
hairs in a few days, which may grow out through the cavity of the 
mutilated one as described so carefully by King. The mutilated 
tip, or growing point, of many multicellular algae is replaced by the 
development of the uppermost intact cell. Brefeld found in the 
sclerotia of Coprinus stercorarius the inner cells are able to regenerate 
the outer black cuticularized coat, if that is removed. 

The number of cases of tissue restitution known in the higher plants 



PATHOLOGIC PLANT ANATOMY 357 

are few. The peridium, or secondary tegumentary tissue of stem or 
root, is easily regenerated, as is seen in the formation of new cork layers 
in the cork oak after the removal of older ones. The epidermis is not 
always replaced but Massart found that removal of the epidermis of 
Lysimachia vulgaris resulted in the regeneration of a new hair-bearing 
epidermis. The regeneration of the vascular bundles has been studied 
in monocotyledonous plants and in dicotyledons. The regeneration 
of roots in monocotyledons consists in the replacement of epidermis, 
phloem and xylem. In dicotyledons before the wood and bast are 
replaced there is a regeneration of the endodermis, so that the restora- 
tion of central cylinders, that have been destroyed, is not unusual. 

HYPOPLASIA 

The condition of hypoplasia in plants is one of arrested develop- 
ments. The organism, or one of its parts, does not reach normal devel- 
opment, but that development is arrested, or stopped prematurely. 
Hypoplasia is, therefore, defective development. The plant morpholo- 
gists and plant anatomists are chiefly concerned with the problems 
of arrested development and recently awakened interest has been 
taken in its study, because it has been found that the interpretation of 
certain phenomena is subject to experimental treatment, and hence, 
there has arisen a coterie of experimental plant morphologists. Such 
investigators have found that the processes of growth and differentia- 
tion are not always equally arrested, which are associated in time and 
place in the normal course of development. For example, leaves differ 
from the normal by their small size. They may be retarded in their 
form, as the narrow leaves of Sagittaria produced under water, or the 
form may remain entirely undeveloped. We will treat of hypoplasia as 
to the number of cells, as to the size of the cells, as to the differentiation 
of the cells and the tissues. 

A. Number of Cells. — It has been found in a study of the dwarf 
forms of plants such as occur on high mountain tops that the condition 
of nanism is not so much due to a decrease in the size of the cells over 
those of the normal plant, but is chiefly conditioned on a reduction in the 
number of cells. The internodes of plants may be shortened, the size 
of the leaf blade may be reduced, the thickness in the leaf may be re- 
duced, and this reduction in size is usually associated with a loss in the 



358 • GENERAL PLANT PATHOLOGY 

number of cells, as for example, the omission of one of the palisade 
layers of the leaf. External factors are important in determining the 
structure of the leaf tissue, for the leaf more than any other plant 
organ is an index of the influence of climate. This fact is empha- 
sized by a work entirely devoted to this subject and given the 
appropriate title of "Phyllobiologie." There is a marked difference 
in the thickness of beech leaves, for example, which have developed 
under different environmental conditions, as I have proved satisfacto- 
rily by the use of calipers and microscopic measurements, which show 
an accurate coincidence. The thickness, or thinness, of such a leaf de- 
pends essentially on the number of rows of cells. The thickest leaves 
with the largest number of palisade layers which I have studied, grew 
in the bright sunlight in exposed places along the edge of a salt marsh 
at Cold Spring Harbor, Long Island. Sun leaves back from the influ- 
ence of salt water were thinner and broader, while those, growing in 
the dense shade of the forest in an inland situation near Philadelphia 
were the broadest and thinnest of all. Not only was the mesophyll 
modified in these leaves, but a marked difference was found in the shape 
of the epidermal cells in the sun and shade leaves. 

The number of cells which arise from the cambial layer suffers a 
marked diminution in trees which grow under unfavorable climatic life 
conditions. Drought, strong winds, pressure, unfavorable light and 
nutrition are disturbing factors. Growth activity of the cambium may 
cease entirely, if these factors become too intensive. Huntington has 
proved abundantly by his study of yellow pines of New Mexico and 
the big trees of California that climatic cycles of wet and arid conditions 
in the past history of North America can be determined from a study of 
the size and character of the annual rings due to the cambial activity of 
those trees, and he has plotted curves showing this relationship for a 
period approximately 3500 years in the case of the big tree. Sequoia 
gigantea} 

B. Size of Cells. — The size of ceUs must be considered also in dis- 
cussing the phenomena of hypoplasia. Abnormally small cells may 
be produced in different ways: A fresh division of the cells may take 
place before the cells have reached the average size which they as- 
sume under normal conditions. Klebs recites a case where he culti- 

1 Huntington Ellsworth: The Climatic Factor. Publ. 192, Carnegie Institu- 
tion of Washington, 1914: 153. 



PATHOLOGIC PLANT ANATOMY 359 

vated Euaslrum verrucosum, a desmidiaceous alga, in lo per cent, cane 
sugar. The daughter cells formed by a previous division of those 
cells divided again before they had attained their normal size. The 
conditions in the higher plants where hypoplasia is shown by the 
production of abnormally small cells are such that the period of elon- 
gation, which normally follows the last cell division, does not take 
place, or is stopped part way. Abnormally narrow tracheal tubes are 
found in dwarfs, in etiolated and poorly nourished plants, or in in- 
dividuals infected by fungi, or gall-producing animals. Disturbances 
in nutrition reduce the size of the wood elements produced by cambial 
activity. 

In the study of the differentiation of cells and tissues, those cases 
should be considered first which concern the individual cells, where the 
formative process may stop prematurely. An investigation of Udotea 
Desfontainii shows the arresting action of unfavorable life conditions 
upon the development of the cell form. The leaf-like part of this alga 
is composed of elongated sacs, which run lengthwise and parallel, with 
numerous side branches of limited growth, which interlock to give 
the thallus its characteristic firmness. If artificially cultivated, the 
parallel sacs show undiminished growth activity, but the side branches 
no longer show limited growth, but unlimited, and the thallus loses its 
wonted form. 

Arrestment of the development of the cell wall is indicated in the par- 
tial, or entire cessation of the secondary growth in thickness, and as a 
result, the elements normally thick-walled have walls of only moder- 
ate thickness. Weak, or insufficient, transpiration acts pari passu in a 
poor development of the cuticle of epidermal cells. Dwarfed plants 
frequently show weakly developed cell membranes, as a sign of disturb- 
ances in the nutritive processes. Chemic changes may be associated 
with hypoplasia. Lignification is rarely excluded in the formation 
under disturbing influences of the woody elements of plants. The cells 
of the medullary parenchyma in thorns {CratcBgus) remain unhgnified, 
when infected with a rust fungus, Roestelia. Finally, the formation of 
cross walls may remain incomplete, thus giving rise to chambers, 
sometimes communicating with each other. 

Hypoplasia, as it affects the cell contents, may be seen in the 
reduction in the number of chloroplasts in variegated leaves, in plants 
with pale-green leaves and in plants which grow in places saturated with 



360 GENERAL PLANT PATHOLOGY 

vapor. The individual chlorophyll grains may not attain their normal 
size, remaining small. The formation of chlorophyll presupposes a cer- 
tain temperature, the action of light, the presence of iron and certain 
organic food materials. Low temperature may reduce chlorophyll for- 
mation, as is seen in grain seedlings and bulbous outgrowths or with 
yellowish color grown under a low temperature. Deficiency of light and 
iron causes etiolation, more especially chlorosis, or icterus in the absence 
of normal pigment due to the lack of iron, while in vines unable to 
absorb iron chlorosis may take place with abundance of iron in the soil. 
Sometimes it happens, on the other hand, following the attacks of an 
insect that ripening lemons remain green-flecked. This condition 
is due to arrested development of the chloroplasts, which normally 
would be transformed to yellow chromatophores. 

Light also seems to influence the development of the red pigment, 
anthocyanin, as is especially noticeable in varieties of Coleus, while 
other parts, such as rhizomes, bulbs and roots, which remain under- 
ground, are richly provided with anthocyanin. Chromogenic bacteria 
may lose the power of producing pigment, as is illustrated by Micro- 
coccus prodigiosus grown at the high temperature of 4o°C. A.F.W. 
Schimper and other botanists have shown that the formation and dis- 
tribution of crystals of calcium 'oxalate in plants is to a large extent 
dependent on external factors. Shade leaves contain fewer crystals 
than sun leaves and plants grown in moist air, or without light, are also 
poor in these crystals. 

C. Tissue Differentiation. — The arrestment of tissue differentiation 
can be illustrated in simple algae where the cells are united into colo- 
nies. When the green alga, Scenedesmus caudatus, the end cells of 
which have gelatinous horns, is subjected to abnormal life conditions 
the horns do not form. In the consideration of tissues of multicel- 
lular growths it may be said that there is no organ in which homo- 
plasia may not appear. Examples have been found in the hepatic and 
true mosses. 

The best illustrations of the developmental arrest of tissues are 
found among the flowering plants, where as one case the guard cells of 
the stomata may be arrested by a lowered transpiration and weak illumi- 
nation. Stapf in his experiments with the potato, Solanum tuberosum, 
showed that under normal conditions there was one stoma for every 
forty-six epidermal cells, and in specimens matured by him in gaslight, 



PATHOLOGIC PLANT ANATOMY 



36] 



there was a pair of guard cells for every 204 epidermal cells. The for- 
mation of the hairs on the edge of the ocrea of Folygonum amphibium 
is entirely suppressed in the form natans, which is grown under water, 
while they are present in the form terrestre. The modification of the 
mesophyll tissue in homoplasia is .due to the character of the environ- 
ment. Plants cultivated in places saturated with moisture, or after 
infection by fungi or animals, show a homogeneous development of 
the mesophyll. 

In homoplasia, the vascular bundles decrease in number, the 
mechanic tissue degenerates and the collenchyma sometimes does not 




A B 

Fig. 142. — .4, Cross-section of a normal thalloid shoot of Lunularia. {After 
Nestler, Die natiirlichen Pflanzenfamilien 1. 3, p. 17.) B, Cross-section of a thalloid 
shoot grown in the absence of light. {After Beauverie in Ktister Pathologische PJlanzen 
Anatomie, 1903: 42.) 

form. Thouvenin by the use of mechanic pressure retarded the 
development of the woody tissues in the stem of Zinnia. The stems of 
Cardamine grown under water develop no mechanic tissue. The 
length of the vascular bundles is less in plants grown in moist places 
over plants which transpire strongly. Stahl found in his study of the 
leaves of Lactuca scariola, that the mesophyll consists of palisade cells 
throughout in the vertical leaves and in horizontal leaves lighted from 
above of palisade cells only on the upper side of the leaf. If we call 
upon homoplasia to explain the formation of shade leaves (Fig. 142), as 



362 GENERAL PLANT PATHOLOGY 

the unavoidable product of some arresting factor, then the structure of 
shade leaves and those from alpine habitats, as well, as those placed under 
water and which have a shade leaf structure, lose their remarkable char- 
acter. Taking into consideration all of the experiments which have been 
performed, it may be stated in concluding this chapter, that all of the 
described hypoplasias may ' be traced back to scanty nourishment. 
We are probably correct in assuming that there is poor nutrition in 
plants grown in distilled water, in the dark, in an atmosphere deprived 
of its carbon dioxide in moist places, or under water. Insufficient 
nourishment leads to an arrestment of differentiation and this becomes 
evident in a number of ways. 

Metaplasia 

Metaplasia has been defined as the progressive change of any cell, 
which is not connected with cell division and cell growth. The empha- 
sis in this definition is upon the word progressive in contradistinction to 
the word regressive. Metaplasia is less important in the histology of 
plants than it is in animal histology. Changes of a metaplastic kind 
are produced in the cells of plants, especially in the production of new 
cell contents, or of the cell wall by increase in thickness. 

Cell Contents. — Frequently, it happens with tubers, bulbs, rhizomes 
and roots of many plants that they develop a green color in place of 
their normal chlorophylless character. Potato tubers kept in a damp, 
warm, sunny place sometimes develop a green color and become 
poisonous through the formation of metaplastic solanin. Bonnier 
found that the tissues of his experimental plants exposed to strong arc 
lights turned green even to the pith. Likewise red pigment dissolved 
in cell sap may appear as a metaplastic change. For example, the nor- 
mally green pitchers of Sarracenia purpurea become purplish green when 
the plant is grown in intense sunlight. Such is also true in the heather, 
Calluna vulgaris, Azolla, many succulents as Opuntia and Sedum. In- 
jury to plant parts may be followed by the development of a red color. 
The normal color of the leaves of Saxifraga Ugulata are green, but if leaves 
are cut through the midrib, a red coloration developed along the edges 
of the wound. Parasitic fungi may cause a local reddening of the cells 
affected as in certain fruit and leaves spot diseases. The metaplastic 
formation of coloring matters appears in the so-called graft hybrids. 



PATHOLOGIC PLANT ANATOMY 363 

The excessive formation of starch in the leaves of such plants as the 
buckwheat, Polygonum fagopyrum, when insufficiently supplied with 
chlorine is a case in point, as also the unfavorable nutrition occasioned 
by potassium salts, while Schimper succeeded in getting the same ac- 
cumulation of starch in unusual amounts in the leaves of Tradescantia 
selloi by cultivation in nutrient solutions free from calcium. 

Cell Membranes. — The metaplastic modifications of cell walls may 
be considered under two heads. The first condition is found where 
bordered pits are formed, as in such orchids as Cymbidium ensifolium, 
LcBlia anceps and Epidendrum ciliare, whose leaves have been scarred. 
The second modification is seen where the cell walls have been thick- 
ened abnormally by cellulose knobs, or thickenings. Such cellulose 
deposits occur about calcium oxalate crystals, oil drops, as in Piper- 
ace^, Laurace^ and about the hyphae of fungi which penetrate cells, 
the hyphae along with certain cytoplasmic inclusions being surrounded 
by the cellulose sheath bridging the space of the cell. Wortmann has 
found heavy wall thickenings in the epidermis and bark of beans and 
other twining plants, if they are prevented from carrying out their 
reaction curvatures, while Kiister noticed the lignification of the cell 
walls in the leaves of Juglans under the influence of certain plant lice. 



CHAPTER XXX 

PATHOLOGIC PLANT ANATOMY (CONTINUED) 

HYPERTROPHY 

The plant pathologist applies the word hypertrophy to an abnormal 
process of growth in which the individual cells are larger than the nor- 
mal, or when whole tissues become enlarged, or distended. Cell 
division is left out of account as a means of the formation of hyper- 
trophied cells, or tissues. The cells which are enlarged may be derived 
from the meristematic elements, which have continued their growth to 
the enlarged size, or cells continue their growth longer and more in- 
tensively, or cells of permanent tissue are concerned, which take up 
anew the process of growth in size. The cell may enlarge in all of its 
dimensions, so that the original shape of the cell is maintained, or it may 
enlarge in one or two directions, when the original shape is no longer 
kept. If the enlargement is in two directions the cell will be distorted, if 
in one direction it will grow abnormally long. The extent of the en- 
largement and its direction will be determined by the character of the 
surrounding cells, or their absence. An hypertrophied cell may be 
surrounded by cells incapable of distention, hence its enlargement will 
be limited to the size of the available free space. Kiister distinguished 
two kinds of hypertrophy, cataplastic and prosoplastic. Cataplastic 
hypertrophy is an abnormal increase in the volume of cells associated 
with degenerative atrophy of their living contents, for the functional 
decline of the cell has been termed by Beneke, cataplasia. Prosoplastic 
hypertrophy involves new anatomic characteristics and functional 
activities, for the cells store up fats, proteins and starches, or develop 
chlorophyll, or red coloring matter. The involution forms of Bacillus 
radicicola, which forms the leguminous root tubercles, and those of 
the crown-gall organism, Pseudomonas turn efac tens, are examples of 
simple hypertrophied cells (Fig. 143). With these preliminary remarks 
it is important to illustrate the different kinds of hypertrophy which 
have been described by plant pathologists. The most simple cases are 
those in which the meristematic cells capable of division have grown to 

364 



PATHOLOGIC PLANT ANATOMY 



365 



an abnormal size by the omission of cell division. Under the influence 
of a fungous parasite, Chytridium sphac ell arum, the apical cells of the 
lateral branches of an alga, Cladostephus spongiosus, stop dividing and 
enlarge into club-shaped swellings at their upper end. If specimens of 
Padina pavonia, a siphonaceous alga, be inverted and are exposed to 





• / / V *' 

V B 


^ > C 


»• 'A *^ D 







Fig. 143. — Drawings of rods and involution forms of Pseiidotnonas lumefaciens 
from young tumors. A, B, Daisy on daisy; C, D, hop on red table beet; E, F, hop 
on sugar beet. (After Smith, Brown, McCulloch, Bull. 255, U. S. Bureau of Plant 
Industry, 1912.) 

light, their spiral edges uncoil and the cells of the apex enlarge into 
vesicular form. The hyphae of the sterile mycelium of Rozites 
gongylophora found in the fungous gardens of the tugging-ant, Atta, 
show regular ball-like swellings on the ends of the hyphae. These 
united into thick groups form the kohl-rabi growths which serve the 
ants as food. 



366 GENERAL PLANT PATHOLOGY 

Etiolated plants afford interesting examples of hypertrophy, for 
in the absence of light the internodes of the stems and the petioles 
of the leaves become inordinately long. If this follows cell divisions, 
then it is a hyperplastic phenomena, but where it is due to the abnormal 
lengthening of existing cells, it is a simple case of hypertrophy. Kiister 
found in the etiolated peduncles of Tulipa Gesneriana, that the cells 
were from a third to a half longer than the normal ones. Longer cells 
than usual are produced in plants grown experimentally in moist air. 

Hyperhydric tissues are abnormal and are formed by an excess of 
water within the plant. They constitute a homogeneous group from 
a causative (etiologic) point of view. As examples may be cited 
the spongy white masses of cells which appear in the lenticels of the 
twigs of alder, poplar, willow when such twigs are placed in water. 
The individual cells of this porous tissue are chlorophylless, have a thin 
layer of cytoplasm and a clear abundant cell sap. Such water lenticels 
were compared by Schenck with typic aerenchyma found on numerous 
water plants. Such lenticel excrescences arise from normal lenticels 
by the enlargement of the phelloderm cells and in some cases the bark 
cells lying under the lenticel hypertrophy. Von Tubeuf and Devaux 
give extensive lists of the plants which produce hypertrophied lenticels.^ 

Bark excrescences form another kind of hypertrophied tissue. 
They have been produced experimentally on the bark of the red currant, 
Rihes aureum (Fig. 144). In such boss-like excrescences the paren- 
chyma cells of the bark grow out into long sac-like cells of different 
form and size by growth in a radial direction. Not only the cells of 
the outermost bark layers take part, but all the elements down to the 
wood take part in the abnormal growth and have become completely 
or nearly colorless. The firm connection between bark cells is lost and 
they are separated from each other by large intercellular spaces. 
Sorauer kept cuttings of shoots of Ribes aureum several years old in a 
vessel of water and in moist air. At the end of four weeks extensive 
excrescences were formed. 

Intumescences are small pustules, which are formed only in limited 
areas, and their formation follows the same processes of growth as in 
the case of bark excrescences. They are known in the branches of 
Acacia pendula, Eucalyptus rostratus, Lavatera trimestris and Malope 

^ KtJSTER, Dr. Ernst: Pathological Plant Anatomy, authorized translation by 
Frances Dorrance, 1913: 74-75. 



PATHOLOGIC PLANT ANATOMY 



367 



grandiflora. They are formed on the side of the branches exposed to 
the sun and the bark cells are elongated in a radial direction, finally 
breaking through the epidermis as spongy masses of cells. Leaves 
also produce intumescences. Originating in the mesophyll cells, they 




Fig. 144. — Cross-section of a part of a strongly hypertrophied bark of Ribes 
aureuni. K, Cork; P, periderm; H, abnormally elongated bark cells. {Kiisler, 
Pathologische Pflanzenanatomie, 1903: 80.) 

appear as greenish or whitish pustules of varying size and beneath the 
cells lose their chlorophyll content. Cataplastic hypertrophy explains 
the origin of some intumescences. For example, the lower cells of the 
several-layered epidermis of Ficus elastica are pressed together by the 



368 GENERAL PLANT PATHOLOGY 

growth of the mesophyll cells and the space originally occupied by the 
former is finally filled with the cells of the mesophyll. Excess of water 
is one of the contributing causes in the formation of intumescences, 
as also treatment of plants with poisons, especially copper salts. 

Abnormal succulence, as an hypertrophy, is such where plants with 
normally thin leaves, develop thick ones in their place. Salt solutions, 
if used experimentally upon certain plants, may induce succulency. 
LeSage produced artificial succulence in the leaves of Lepidium sativum 
by abundant doses of common salt, NaCl. The mesophyll cells were 
elongated greatly. 




Fig. 145. — Cross-section through the wounded border of a cabbage leaf. The 
hypertrophied mesophyll cells are enlarged into vesicular swellings. {Kilster, Palh- 
ologische PJlanzenanatomie, 1903: 94.) 

Callous hypertrophy arises after an injury when the living cells of an 
organ enlarge without division, especially at the edge of the wound, 
where they may enlarge to many times their normal volume (Fig. 145). 
As it frequently happens that cell divisions follow an injury, it is not 
always easy to distinguish between callous hypertrophies and callous 
hyperplasias. We find callus hypertrophies among the thallophytes, 
as in Padina pavonia, and in the higher plants where the bark, wood 
parenchyma, leaves are affected. Kiister produced callous hyper- 
trophies near the upper surface of the cut by keeping one end of the 



PATHOLOGIC PLANT ANATOMY 



369 



cutting under water, the other extending into moist air. The bark 
cells were enlarged greatly, producing ball-Hke or weakly lobed forms. 
Only single cells in the bud hypertrophied and they grew out into large 
colorless vesicles. Miehe has found Tradescantia virginica a suitable 
object to produce callous hypertrophies experimentally. The destruc- 
tion of cells, or cell groups, of the epidermis causes the formation of 
empty places which are filled by the neighboring cells which close the 





Fig. 146. — Pitted vessel of black locust, 
Robinia pseudacacia, filled with enlarged 
parenchyma cells or tyloses. At a the con- 
nection between tyloses and original cell is 
seen. (Kiister, Pathologische Pflanzenanal- 
omie, 1903: 100. 



Fig. 147. — Cross-section through 
old wood of Mespilodaphne sassafras. 
The lower vessels contain .stone 
tyloses, the upper besides stone 
tyloses, contain thin-walled tyloses. 
{After Molisch in Kiister, Pathologische 
Pflanzenanatomie, 1903: 100.) 



opening. Haberlandt in his culture of isolated tissue elements obtained 
abnormally large cells which should be classed among callous hyper- 
trophies. He kept alive isolated mesophyll cells from the leaves of the 
purple dead nettle, Lamiuni purpureiim, for weeks in Knop's solution, 
or in nutrient sugars, and these cells grew perceptibly at the same time 
that a thickening of their membranes took place. The exact causative 
influence in the development of callous hypertrophies is still an open 
question. 
24 



370 GENERAL PLANT PATHOLOGY 

Tyloses^ are more or less closely packed, bladder-shaped intrusions 
derived from the parenchyma cells adjoining the cavities of water- 
conducting elements into which they project, often completely blocking 
the cavities (Fig. 146). They were first investigated by Hermine von 
Reichenbach, who noticed that the swelling is not cut ofiF from the 
parent cell by a septum. They arise frequently in association with one- 
sided bordered pits, the limiting membranes of which undergo active 
surface growth and thus push their way into the cavities of the vessels 
(Fig. 147). Several tyloses may arise from a single epidermal cell. They 
occur beneath branch scars that have been formed by a branch breaking 
off and also at the wounded end of cuttings being formed in such 
numbers, that they become flattened by mutual pressure. The cavities 
of vessels are thus filled and they probably serve, as Boehm first sug- 
gested, to plug up the cavities of the water-conducting tubes that have 
suffered mechanic injury. This explanation suffices for such special 
cases of injury, but tyloses are formed in uninjured vessels where they 
obviously do not serve to close up a wound. Haberlandt believes that 
tyloses of this last-mentioned type take some part in the process of 
conduction, by increasing the surface of contact between the vessels 
and the neighboring parenchyma cells. Kiister in his "Pathological 
Plant Anatomy" gives a detailed account of the different kinds of 
tyloses and their method of formation, which need hardly be discussed 
in a text-book for student use. Molisch gives a list of plants in which 
tyloses have been found. Sometimes tyloses fill the air chambers of 
the stomata partially or almost entirely, where the epidermal cells 
adjacent to the guard cells grow out into large unicellular bags, as in 
Tradescantia viridis. 

Gall hypertrophies are those which are produced by the effect of a 
poison formed by an attacking animal, or plant. The tissue products 
are the most diverse and a sharp distinction cannot be drawn between 
hypertrophic and hyperplastic gall tissues. Gall hypertrophies usually 
occur in the epidermal and the fundamental tissues of various plants. 
The galls of the fungi belonging to the family Chytridiace^, namely, 
those occasioned by species of Synchytrium, are very simple, for the 
entire life history of the fungous parasite is passed in a single cell of the 

1 Gerry, Eloise: Tyloses: Their Occurrence and Practical Significance in Some 
American Woods. Journal of Agricultural Research, i: 445-470, with 8 plates, 
March 25, 1914. 



PATHOLOGIC PLANT ANATOMY 37 1 

host. The zoospores of the species of Synchytrium penetrate the epi- 
dermal cells and incite these cells to active growth causing their enlarge- 
ment, as in the cells attacked by Synchytrium drabcB. Sometimes the 
infected cell grows inordinately and pushes the mesophyll cells lying 
below apart, until it projects into the underlying cells as a spheric 
pouch. If the neighboring epidermal cells are stimulated warts are 
formed. 

The second group of gall hypertrophies are certain hair-like develop- 
ments of epidermal cells due to the irritation of certain mites of the 
genus Phytoptus, which produce felt-galls, or Erineum. These erineum 
structures arise in clusters on the surface of leaves of such trees as 
maples, alders, birches, beeches, oaks, willows, limes and on herba- 
ceous plants belonging to the genera Geranium, Mentha, Salvia, etc. 
These outgrowths so resemble fungi, that Persoon was deceived into 
so believing. They are usually pale, or even white at first, and they 
turn brown aS the hair-like outgrowths die and lose their sap, but 
since the latter may be colored yellow, red or purple, the outgrowths are 
conspicuous objects on smooth leaves. The botanist Malpighi in 
1675-1679 was the first to call attention to these galls. One-celled 
erinea are the rule, but multicellular abnormal hairs are formed by the 
hypertrophies of the normal trichomes as Frank reports on Quercus 
(Bgilops. 

Gall hypertrophies, where the ground tissues of plants participate in 
their formation, are known. The roots of the Cycadace^ develop 
sacs out of their parenchyma cells, so that large intercellular spaces are 
formed in which a blue-green alga, Anabcena cycadearum, the causal 
organism, lives. Galls produced by flies and belonging to the group of 
zoocecidia may be taken as illustrations of gall hypertrophies. One is 
known as the window gall of the maple, and the other is a reddish-brown, 
bladder gall occurring on the leaves of Viburnum lantanum. 

Multinuclear giant cells may be formed in plants, if the nuclei divide 
regularly, but for some reason the formation of cross-walls becomes 
impossible. The cells are stimulated to abnormal growth forming the 
so-called giant cells. Such hypertrophies are associated with an in- 
crease of the cytoplasmic contents of the cells. Such giant cells are 
those produced by certain Nematode worms of the genus Heterodera on 
such host plants as Beta, Coleus, Daucus, Plant ago and Saccharum (Fig. 
148). Prilleux produced multinuclear giant cells in seedlings which 



372 



GENERAL PLANT PATHOLOGY 



were cultivated at an abnormally high temperature. The number of 
nuclei rarely exceeded three. 

Multinucleate cells occur in crown gall which are perhaps compar- 
able to the giant tells of the animal histologist. Cancer specialists have 
divided these into two groups, viz., foreign-body giant cells in which the 




Fig. 148.- — Cross-section of a part of a root gall of Circaa luteliana in old stage, 
numerous giant cells are seen, the nuclei of which have begun to degenerate; b, irreg- 
ularly branched nuclei out of the giant cells dividing by amitosia within anuceoli; 
C, a single multinucleate giant cell. {After Tischler in Kuster, Pathologische Pflanzen- 
anatomie, 1903: 128.) 



stimulus is some introduced foreign substance, and genuine ones in 
which no foreign bodies are visible. There is probably no real distinc- 
tion other than that those occupied by parasites are malignant and those 
induced by non-Hving granules are harmless. The cells in question in 
crown gall are not very large, but they contain several nuclei (Fig. 



PATHOLOGIC PLANT ANATOMY 



373 



149). Four nuclei in one cell is the most we have seen, but it is prob- 
able that larger numbers occur. It would seem from the studies of 
Erwin F. Smith, which, however, are incomplete, that most of the cell 
divisions in crown gall are by mitosis. Frequently, however, there 
have been found nuclei variously lobed and in process of amitotic 
division, and this is probably the way in which several nuclei are 
formed in one cell (Fig. 149). 




Fig. 149. — Nuclear division in crown gall; 1-16, cells showing amitotic (direct) 
division; 17, mitotic division in which more chromosomes have passed to one pole 
than to the other. (After Smith, Brown, McCulloch, Bull. 255, U. S. Bureau of Planl 
Industry, 1912.) 

HYPERPLASIA 



Virchow in his " Cellularpathologie " (1858: 58) defined hyper- 
plasia as all abnormal quantitative increase, produced by cell division, 
and that definition will be adopted here. It is very difficult in practice 
to distinguish without a careful study between hypertrophy and hyper- 
plasia, but in the latter abnormalities are produced by cell division, 



374 GENERAL PLANT PATHOLOGY 

while in hy})crtiophy they are not. A number of well-defined groups of 
vegetative hyperplasias may be distinguished by their etiology. Chemic 
stimulation may be the cause of some, injury the cause of others. The 
normal currents of foodstuffs may be clogged, the food may be irregu- 
larly distributed and these interferences with normal processes may 
result in proliferations and other abnormalities. Special stimuli may 
also bring about abnormal supplies of food with consequent hyperplas- 
tic tissue formation. The study of the abnormality to determine its 
kind must be based on histologic analysis. If in our histologic examina- 
tion, we discover that the abnormal tissues resemble the corresponding 
normal plant parts, we are dealing with homooplasia; if they differ from 
the normal, that is are composed of cells different from the correspond- 
ing normal ones, then we have a case of heteroplasia. 

Heteroplastic excrescences are of great interest histologically. The 
difference between normal and abnormal states is sometimes greatly 
diverse. This difference may be one of size, of tissue differentiation, of 
constitution, and it is important in our pathologic study to determine 
the nature of the differences between normal and abnormal conditions. 
Thus, when we find a less differentiated tissue produced by abnormal 
cell division without regard to the increase in the numbers of cells, we can 
speak of the degeneration of tissue formation combined with an increase 
of volume. This is known as cataplasy, and the products of the cata- 
plastic processes as cataplasms and the kind of hyperplasia illustrated 
in these abnormal changes as cataplastic hyperplasia. When, on the 
other hand, we find new histologic characteristics and functional activi- 
ties associated with hyperplasia, we speak of prosoplasy, of prosoplasms, 
and of prosoplastic hyperplasia. 

Homooplasia. — This term may be defined as abnormal tissue forma- 
tion produced by an increase of the normal elements; it has a limited 
use to abnormalities, not to increase in size of normal organs by a mere 
increase in the number of cells. We would not use the word homo- 
oplasia for the unusually large leaves which of normal form and texture 
appear on the shoots which arise from tree stumps and which have been 
studied by the writer in a number of our American forest trees, such as 
the tulip tree, Liriodendron tulipijera. Homooplasia is opposed to the 
phenomena of giant growth here mentioned. 

Localized tissue excrescences composed of the same histologic ele- 
ments and of homooplastic character are not common. Occasionally 



PATHOLOGIC PLANT ANATOMY 375 

sugar beets continue their growth to abnormal thickness by the forma- 
tion of ridge-like tissue excrescences composed of normal layers of tis- 
sues which extend longitudinally. De Vries investigated a case where 
new cariibial rings were formed outside of the latest ones of the first year 
coincident with an arrestment of activity. Hottas incased roots of 
Viciafaba in plaster casts pierced by holes. He found that by correla- 
tive growth homooplastic excrescences filled the holes. 

Some kinds of homooplasias are characterized by the fact, that only 
single tissue forms of an organ are developed unusually without the for- 
mation of local excrescences by which means the histology of the organ 
is altered. Increased demand upon a tissue may result in the formation 
of abnormally abundant tissue and to this the name of activity homo- 
oplasias has been given. Various experiments have been conducted in 
the attempt to form mechanic tissue by putting an increased mechanic 
demand upon plant tissues. The experiments of Kiister with sunflower 
stems were negative, as also those of Wiedersheim with branches of 
beech and ash, for he found no strengthening of the hard bast in his 
experiments. He proved, however, an increase of stereids in the 
strained branches of Corylns avellana. Vochting has shown that hori- 
zontal stalks of the Savoy cabbage strained at the extremity by hanging 
weights developed thickenings on the upper side of the branch. De 
Vries has described an abnormal potato tuber in which through the need 
of conduction of plastic substances the bundles of the tuber had devel- 
oped to an extent unusual to the normal plant. The wood and bast 
portions were both increased. Vochting's experiments with potato 
tubers supplement those of de Vries; for he succeeded in interpolating 
the potato tuber as an element in the potato plants grown from it and 
succeeded in getting hyperplastically developed vascular bundles. 

Correlation homooplasias result when there is a local arrestment of 
growth, and growth is started elsewhere with homooplastic changes in 
the tissues. The experiments of Boirivant and Braun have proved this 
in a number of plants. Only one case of callus homooplasia has been 
reported and it is described by Schilberszy, who succeeded in stimulat- 
ing an increase of vascular tissue in the stalks of Phaseohis mtdtiflorus 
through injury. No positive cases are known where homooplasias 
occur in the formation of galls. 

Heteroplasias. — This term of pathologic anatomy is used when 
there is a quantitative increase of an organ in which by abnormal di- 



376 GENERAL PLANT PATHOLOGY 

vision of the cells there are produced tissues, the single elements of which 
have no resemblance to normal ones. Size of cells is of relatively little 
interest in the study of these abnormalities. More important are cata- 
plasmic and prosoplasmic tissues, which are formed in heteroplasia. 
Cataplasmic tissues are those which are more simply constructed than 
the corresponding normal tissues, while prosoplasmic tissues are those in 
which we can see processes of differentiation in the formation of their 
single cells and in the distribution of their different elements, which are 
not manifest in the formation of the corresponding normal tissue. 

The material illustrating the various kinds of heteroplasia may be 
treated of under the following heads: 

1. Correlation-heteroplasms 1 

2. Calluses \ Cataplasms 
Heteroplasias 3. Wound- wood J 

4. Wound-cork 



Galls 



I . Correlation-heteroplasms 



(a) Cataplasms 

(b) Prosoplasms 



This term is applied to cases where the normal growth of any plant 
is arrested at its vegetative points by any causative factors whatsoever, 
and where under the stimulus of the unused nutritive materials some part 
of the plant develops abnormal growth and tissues. Vochting has 
studied this subject in all of its details. He found that decapitation 
of sunflower plants resulted in the production of tuber-like swellings 
on the roots and that in the aerial runners of Oxalis crassicaulis filled 
with reserve materials that removal of the apical cells and all axillary 
bud cells resulted in the formation of swellings on the leaves and 
internodes. According to Vochting, the parenchyma participates, also 
the vascular bundles, which have fewer ducts than the normal ones. 
The sieve tubes, however, are richly developed and extensive funda- 
mental tissue outgrowths are found between bast and wood. The first 
experimentally produced correlation-heteroplasms were made by Sachs. 
He cut off all the vegetative points of pumpkin plants. He found, as a 
result, that the embryonic root cells present in the stem at the right 
and left of each petiole grow out into short-stalked tubers, as large 
as marbles, in which the root cap and vegetative point are absent and 



PATHOLOGIC PLANT ANATOMY 



377 



the axillary fibrovascular cord is resolved into a circle of isolated bundles 
separated by chlorophyll-containing cells. 

2. Callus 



Callus may be defined in the widest sense of the word as all cell and 
tissue forms produced subsequent to and as a result of injury. In 
many plants and plant organs, only a metaplastic change of the cells 
was incited by the injury (callus-metaplasia); in others, the cells laid 
bare showed an abnormal growth and were changed into voluminous 
vesicles and sacs (callus-hypertrophy), or an 
increase of the normal tissue may result from 
wound stimuli (callus-homooplasia). The 
cells may be abundant after an injury owing 
to active cell division and heteroplastic tissue 
arises (callus-heteroplasia). When excres- 
cences arise, which are composed of cells very 
little differentiated and of the simplest form, 
they are called cataplasms. If produced after 
injury, they are found to differ greatly. The 
tissues produced after an injury, if resembling 
cork, are termed wound-cork, if similar to those 
of wood, they are called wound-wood and 
where we have the healing tissue composed of 
nearly homogeneous parenchyma, it is called 
simply callus. 

Callous tissue may be formed as wound 
tissue in very different plant groups. It has 
been found in the algal fungi and vascular 
cryptogams. The woody seed plants have been studied carefully as 
to the formation of callus, because of its economic importance in forestry 
and horticulture. Rose, poplar, or willow cuttings kept in moist air 
and at a proper temperature after a few days form a ring-like tissue 
excrescence from the cambium of the cut surface. This spreads out 
rapidly and finally closes over the wound. Such rolls of tissue have 
been called callus (callus, hard skin). 

Callus at least in its first stages appears in the form of a ring, some- 
times it is irregular in its formation, often being lacking in some places 




Fig. 150. — Longitudinal 
section of a callused end of 
a cutting. C, C, Callus de- 
veloped from cambium; H, 
wood; R, bark. (After 
Kiisler, p. 159.) 



378 



GENERAL PLANT PATHOLOGY 



and this is sometimes due to limitations of space relations. Sometimes 
the callus is most luxuriant, as in Cuttings of Populus pyramidalis 
(Figs. 150 and 151) and Lamium orvala (Fig. 152), which produces the 
largest callous rolls among herbaceous plants. All organs of the plant 





Fig. 151. — Cross-section of a calloused end of a 
poplar cutting. G, Vessel; M, pith ray. {After 
Krister, p. 159-) 



Fig. 153. — Stem of 
Lamium orvala with strong cal- 
lous growth^ {After Kuster.) 



are capable of producing callus, such as roots, stems and leaves, yet 
all parts of all plants do not have the capacity of forming it. Such 
growth seems to reside in the living elements of exposed tissue and the 
productive power of different kinds of tissues varies greatly. Cam- 
bium is the most active layer in the production of callus and next to 



PATHOLOGIC PLANT ANATOMY 379 

the cambium the primary and secondary bark tissues. The epidermis 
plays an unimportant role. Pith also can develop callus. 

The investigations of R. Hoffman, Kiister and Stoll go to show that 
the cambial cells when division takes place after injury are not re- 
stricted to the mode of normal division but can grow in every direction. 
It is certain, therefore, that the conditions of changed pressure are of 
importance and significance, and yet this fact alone is hardly sufl&cient 
to explain the phenomena of growth subsequent to an injury. The 
cell divisions are very regular and rapid in those woody plants which 
form callus. 

Cuttings of woody plants, such as Populus pyramidalis (Fig. 150), if 
placed in water and covered with a bell glass, so that the upper end 
extends above the water into the moist air, shows early division of the 
cambial cells near the upper wounded surface. We find these cells 
are divided by walls perpendicular to their long axis, and in a lively 
manner, by forming tangential walls, causing an abnormally intensive 
growth in thickness of the cutting near the injured place. A strong 
callus has been formed by abundant division of the cambial cells and the 
cutting assumes a club-shaped form at its upper end. The wedge, 
which is formed in this way between the wood and bast, has been termed 
by Th. Hartig the "Lohdenwedge," which might be termed more ap- 
propriately in English the healing wedge. In the formation of this 
wedge, the cambial cells have divided just as under normal conditions, 
but the relief of pressure has caused some of the outer cells to protrude 
to form the enlarged part of the wedge with the outer cells bent 
strongly. Primary bark as in Salix easily forms callus, and petioles and 
leaves often form abundant callus. 

Histologically the tissues of callus are distinguished by the slight 
differentiation of their cells. The cushions of callus in many kinds of 
cuttings are made up of the same kinds of cells and in a homogeneous 
fashion. The cells are typically nascent ones with thin cell wall, pro- 
toplasmic contents and a colorless cell sap. If the growth is slow, the 
callous cells are small and closely fitted together, but with rapid growth 
the cells are large and loosely placed with conspicuous intercellular 
spaces. Tracheids are absent from the upper cells of the cushion of 
callus, but in the lower part of the healing wedge some of the cells 
assume the tracheal character. The formation of a tegumentary layer 
is next to the development of tracheids the most interesting process of 



380 GENERAL PLANT PATHOLOGY 

differentation in the callus. The callus of poplar cuttings is favorable 
for a study of its formation. The outer cells of the wedge of healing 
are long and pouch-like, and their outer walls give the cork reaction, 
since they take up Sudan III with avidity, and at the same time are 
colored with hydrochloric acid and phloroglucin. Sooner or later, a 
cork cambium is produced in the outer cell layers of most callous for- 
mations. Massart, who first studied the nuclear phenomena in callous 
tissue, rarely found that the cells contained more than one nucleus. 
He found that direct nuclear division took place after wounding in 
Cucurbita, Ricinus and Tradescantia, while Nathansohn found mitosis 
in the callus of the divided roots of Vicia faba and both mitosis and 
amitosis in that of poplar cuttings. 

Conditions of Callous Formation 

The behavior of cuttings from different plants varies within rather 
wide limits. Some cuttings develop callus quickly, others slowly, and 
the quality of the callous tissues differs as greatly. The poplar develops 
a large amount of callus, while cuttings of elm, willow and oak form 
only a low callus ring. Organs rich in foodstuffs form callus more 
quickly than those poor in food materials. For example, the cotyle- 
dons of Phaseolus and Vicia, rich in proteins and starch, develop callus 
to an extraordinary degree. Moisture is an important factor in the 
formation of callus, for it is formed in water, but better in moist air, 
and not at all in dry air. Cuttings of poplar with both cut ends in 
moist air develop callus at both extremities, but usually there is a 
polarity shown. Cut-off petioles of the poplar form a more prolific 
callus at the basal end of the petiole than at the end nearer the leaf 
blade With stem cuttings, the callus is best developed at the basal 
end in preference to the apical. Pieces of dandelion roots, 3 cm. long, 
kept in a moist place, show most abundant callus on the upper stem 
ends and not at all, or only slowly at the apex, but in alfalfa a power- 
ful tuber-like callus is produced at the root end and feebly at the sprout 
end. So that having varied the external conditions of their formation, 
it becomes evident that internal conditions are active and these prob- 
ably depend upon inequalities in the nutritive condition of the cut 
parts and also on the direction of established sap flow. 

Loosely connected with pathologic anatomy ^re the regenerative 



PATHOLOGIC PLANT ANATOMY 38 1 

processes ivhich result in the formation of the vegetative points of roots 
and shoots following an injury. Following an injury in very many 
woody plants, there is a formation of adventitious roots and adventi- 
tious shoots which grow from vegetative points developed directly 
from the permanent tissue of the wounded plant organs, but this opera- 
tion is necessarily preceded by formation of callus and in some cases 
the new vegetative points are developed directly from the callus. 
Upon these functional operations depend the success of the horticultural 
operations of the making and establishment of cuttings of roots, stems, 
and leaves. A very large number of plants may be raised by means of 
cuttings. Soft-wooded, or herbaceous cuttings having leaves are used 
in many cases, the shoots being in a half-ripened condition, that is 
neither too young nor too old, dry and woody. Such cuttings are 
usually inserted in sandy or gritty soil, and most of the leaves are 
stripped off to check transpiration of moisture. Several leaves are 
retained, so that a certain amount of assimilation can be carried on to 
induce callus formation. 



WOUND- WOOD. 

The wood, which is formed on the surface of the exposed wood of 
the stem and on the inner surface of the detached bast, is distinguished 
from ordinary wood by its abnormal structure, and especially by the 
shortness of its cells and the absence, or scarcity of vessels. Hugo de 
Vries,^ who was the first to direct attention to this abnormality, called 
such wood, wound-wood. Such abnormal wood is distinguished from 
the normal xylem by its simple histologic character, and is to be added 
to the list of cataplasms. 

The difference between wound-wood and normal wood depends 
upon whether its formation has been brought about by cross cuts into 
the cambium, or by longitudinal wounds. In the latter, the wound- 
wood is distinguished by a wide-celled structure and by more numerous 
ducts than in normal wood, but the libriform fibers are less in evidence. 
Hugo de Vries studied Caragana arborescens and proved that the 
wound stimulus caused the formation of wound tissue 7 cm. from the 
wound itself. The nearer the cells of the cambium are to the wound 
the more cross walls are formed, so that the short-celled zone of the 

1 DE Vries, Hugo: Ueber Wundholz. Flora, 1876: 2. 



382 GENERAL PLANT PATHOLOGY 

wound-wood is produced near the place of injury, the transitional forms 
at a greater distance and then the long-celled zone, which is formed 
from undivided cells of the cambium. The daughter cells of the cam- 
bium of the short-celled zone form near the edges of the injured part, 
a wound-wood composed of polyhedric fundamental tissue cells re- 
sembling the medullary ray cells of normal wood, only a few of such ele- 
ments develop into parenchymatous tracheids. The cells of the long- 
celled zone retain the character of wood parenchyma, but between them 
narrow vascular cells united into strand-like groups are formed, while 
wood fibers and broad ducts are absent. Such formed elements have 
been termed primary wound-wood by de Vries, and later, there occurs 
the production of a secondary wound-wood in which the cells gradually 
assume a normal form. Abnormal resin ducts are formed in wound- 
wood and these ducts are often more numerous in abnormal wood than 
in the normal. 

Sometimes the wound-wood does not form definite stratified tissues. 
Occasionally tracheid-like cells are found in the callus which become 
united into ball-like groups separated from the normal wood. Wood 
fibers, which have an irregular course, have formed the gnarled wood. 

The pith may take part in the formation of wound-wood, for it is 
highly capable of producing callus, and also from the ground tissue of 
injured leaves. No definite outer form is characteristic of wound-wood. 
Frost action may kill the cambium in places, and if the dead places are 
surrounded by cushions of wound-wood, then we speak of frost canker. 
Frost cracks are filled with wound-wood, which close up the wound 
followed by the formation of a frost ridge. Such canker tissue may be 
destroyed during a frosty spell and a new attempt to form Callus results 
in the addition of new wound-wood to the old and frost cankers are 
formed. 

Sometimes without an injury, tissues resembling wound-wood are 
formed by the activity of the normal cambium, or from a newly formed 
independent cambium. Under some conditions, the parenchyma of 
the medullary rays increases at the expense of the formed elements of 
the wood, so that broadened medullary rays are formed. Fasciated 
branches frequently show such broadened medullary rays. Tuber-like 
gnarls are formed in fruit trees that have stone fruits, and also in 
beech bark and the structure of gnarls has been investigated by 
Sorauer, and the bark tubers of beech by Krick. 



PATHOLOGIC PLANT ANATOMY 383 



Wound-cork 



Injury to different plant organs such as roots, tubers, rhizomes, 
stems, leaves and inflorescences is followed by the formation of cells 
in rows and adjacent to the place of injury. The walls of these new 
cells react to sulphuric acid, chlor-iodide of zinc and Sudan III and the 
application of such reagents demonstrates the formation of cork, 
which has been termed wound-cork. It is developed generally on all 
parts of the wound, and at its edges connects directly with the normal 
membranes, thus closing the wound. The walls of wound-cork cells 
are always thin and are often folded, and the cork cells thus formed are 
larger than those of the phelloderm. A stem wounded by a knife cut 
soon heals up unless disturbed. The cut cells die, while those next 
below grow out as a result of the decreased pressure, giving rise to cork 
cells. As the opposing cushions of callus close together, this cork is 
squeezed between them and finally a shearing of the cork cells results 
as the tips of callus close together and unite. The only external sign 
of the wound is a slight ridge-like elevation beneath which are traces 
of the dead cells and the cork trapped here and there beneath the ridge. 
Normally, wound-cork closes over the broken surface of the scars 
formed in the autumn by the fall of the leaf, which is actually occasioned 
by the formation of a cork layer, which cuts off the leaf from the stem. 



CHAPTER XXI 
GALLS 

Galls may be defined as all abnormal tissues produced by the action 
of animal, or vegetal parasites. The great majority of galls arise either 
through the growth of cells alone (gall hypertrophy), or by cell division 
(gall hyperplasia). The number of galls constructed heteroplastically is 
very large, exceeding the diverse gall hypertrophies. Galls of heteroplastic 
origin occur in the most diverse kinds of plants and on all organs of these 
plants. The term gall, or cecidium (cecidia), is applied to those varia- 
tions in form which are caused by foreign organisms. In the forma- 
tion of the cecidium, an active participation of the host plant is neces- 
sary and the biologic connection between the host plant and the gall- 
producing organism must be considered. Only those cases fall within 
our purview in which abnormal tissues are produced. 

Considered biologically and etiologically galls form a well-defined 
group without, however, any one feature common to all. Even when 
considering only gall hyperplasias, we will find no common characteristics 
except that a production of heteroplastic tissue is involved in all. This 
is either extraordinarily simple histologically, showing little or no dififer- 
entiation, or there are specific differentiations which produce structures 
entirely distinct from those of normal tissues. The first kind are cata- 
plasmic galls, and the second kind prosoplasmic. Galls may be clas- 
sified as to their morphologic characteristics, as well as by their histolo- 
gic. They may be found on every part of plants, roots, stem, branches, 
leaves, flowers and fruits and plants capable of producing galls belong- 
ing to all groups of the plant kingdom. 

The following descriptive terms for galls will serve as a rough clas- 
sification of their morphologic forms. Connold^ gives an example of 
each kind. 

As to morphologic character, galls are: axillary, coalescent, con- 
glomerate, cymbiform, elongated, globose, glossy, gregarious, hirsute 

1 CoNNOLD, Edward T.: British Vegetable Galls, 1901: 24-25. 
384 



GALLS 385 

imbricate, pedunculate, pilose, pubescent, pustulate, rugose, rosaceous, 
scabious, separate, sessile, solitary, spiny, rolling and thickening of the 
leaf, upon the upper surface of the leaf, upon the under surface of the leaf, 
upon the margins of the leaf. Some cecidologists would classify galls 
by the causal animal or fungus, by the natural families of the host 
plants, according to the situation of the galls upon the plant, according 
to their modes of growth, etc. Anton Ke.rner in his "Natural History 
of Plants" (translated from the German by F. W. Oliver) divides galls 
into simple, where one plant organ is involved, and compound, where 
several plant organs are concerned in their formation. The simple 
galls he divides into (a) felt galls, (b) mantle galls and (c) sohd, or 
tubicular galls. 

Cataplasmic galls are often produced by the action of parasitic 
fungi, which invade the interior of the plant after an infection by ani- 
mals, which by their wanderings over the surface of the plant may en- 
large the field of their stimulation. Domiciled organisms are the cause 
of prosoplasms, where the extent of the field of stimulation remains the 
same under all circumstances, and is effective only in certain phases of 
the development of the host plants. 

The etiology of galls is of great interest. Malpighi in his " Anatome 
Plantarum" published in 1675-79 attributes the formation of insect 
galls to the action of a poison excreted by the gall insect. Darwin and 
Hofmeister explained galls, as the action of different kinds of poisons. 
The stimuh, which cause the formation of galls, is undoubtedly chemic, 
some unknown substances excreted by the causal parasite, excite 
the cells of the host plant to growth and cell division and to different 
kinds of differentiation. We know nothing definite about the chemic 
substance, nor have the attempts to produce artificial galls been suc- 
cessful. Traumatic stimuh, too, must come into play, for injury to the 
plant goes hand in hand with infection, for the first stage of the develop- 
ment of galls resembles callous tissue. The galls produced may be due 
to plants, phytocecidia, or to animals, zoocecidia. The fungi and a few 
flowering plants are largely responsible, while dipterous and hymenop- 
terous insects and mites are gall-producing animals. 

(a) Cataplasms. — Cataplasmic galls are those which are distin- 
guished from the normal tissue of the corresponding organs by the small 
amount of their tissue differentiation. The cell elements may often be 
abnormally large, and the union of these elements usually forms a thin- 



386 



GENERAL PLANT PATHOLOGY 




Fig 153. — Tubercles of velvet bean produced by inoculation. {After Moore, Geo. T., 
Yearbook. Depi. Agric, 1902, pi. xxxvii.) 



GALLS 



387 



walled often homogeneous parenchyma, while in other cases the cata- 
plasms are marked by the absence of any definite form, or size. Almost" 
all phytocecidia, or plant-induced galls, are cataplasmic. The swell- 
ings on the roots of various members of the CRUCiFERiE caused by the 
slime mould Plasmodiophora hrassiccB are of this nature. It is known 
as Hanbury, clubroot, finger- and- toes by the practical grower of 
plants. Root nodules, or tubercles, are produced on the roots of legu- 
minous plants by bacteria (Figs. 153, 154, 155, 156), which can utilize 







Fig. 154. — Cross-section of root tubercle of Lupinus angiislifolius containing bac- 
teria, X 46. {After Moore, Geo. T., Yearbook Dept. Agric. pi. xxxviii, 1902.) 



free atmospheric nitrogen and by their activity the leguminous plants 
secure large amounts of nitrogen. A species of Actinomyces, or ray 
fungus, is probably the cause of the mycodomatia of Myrica. Bacteria 
also cause tumors on the Pinus halepensis and Oka europcea, on the latter 
in the nature of a crown gall suggested to be somewhat like animal 
cancer (Figs. 157, 158, 159). Recently Erwin F. Smith in relation to 
the abnormal multiplication of the tissues which result in a crown- 
gall tumor, or hyperplasia, concludes that the removal of growth inhibi- 
tions is brought about by the physical action of substances liberated 



388 GENERAL PLANT PATHOLOGY 

within the tumor cells as the result of the metabolism of the im- 
prisoned bacteria iPseudomonas tumefaciens) . Growth of the tumor 
comes about not by the direct application of stimuh, but indirectly 
by the removal of various inhibitions. Under normal conditions the 
physiologic brakes are on at all times, more or less, in both plants 
and animals, and only when they are entirely or largely removed in 





■ ■■„,_ * ■• 1 ■ v. 


^■\ ' '^^m, 


BflfyiP&WSKM . f t 


%:^^m 


p^p^ 


' ,;^ . - 


■ -..^.saS&a^^. •■^ 



Fig, i,t t .o lcluu ul i ul luhu ol lubcicle of Lupinus aiigustifolius, con- 
taining bacteria, X circa 60. {AJter Moore, Geo. T., Yearbook U S. Dept. Agric, 
pi. xxxvtti, 1902 ) 

particular areas do we observe an unlimited cell proliferation result- 
ing in the hasty and peculiar growths known as neoplasms, or cancers 
(Figs. 158, 159). Various weak (dilute) poisons are known to cause 
cell proliferations in plants- — ^that is, copper salts, ammonia, salts of 
lithium, and the excretions of the larvae of gall flies, of certain nema- 
todes and of various fungi. ^ 

The true fungi (EUMYCETES), including all the important groups, 
^ Smith, Erwin F.: Mechanism of Tumor Growth in Crown gall. Journ. .Vgric. 
Res. viii: 165-186, Jan. 29, 1Q17, with 65 plates. 



GALLS 



389 



form cataplastic plant galls. Galls are due to species of Synchytrium, 
to the aecidial stage of the rusts on violets, barberries, nettles and buck- 




FiG. 156. — Longitudinal section through red clover rootlet, showing formation 
of tubercle, a, Rootjhairs; 5, normal root parenchyma; c, vascular tissue; </, infected 
areas showing infection strands; e, growing cells of tubercle. (Fig. 44, page 95, 
Schneider, Pharmaceutical Bacteriology, 1912.) 



390 



GENERAL PLANT PATHOLOGY 



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[57. — Stem tumors on an old apple tree at Mesilla Park, N. Mex. {After Hedg- 
cock, G. G., Circ. 3, U. S. Bureau of Plant Industry, May 11, 1908.) 



GALLS 



391 



thorns. Branches of Vaccinmm vitis-idcBa are enlarged by Calyptospora 
Goeppertiana and those of Juniperus and Chanicecyparis by rusts of the 
genus Gymnosporangiiim. Various species of the genus Exobasidium 
produce soft, edible galls. All such galls are mycocecidia (Fig. 84). 

Various algae, such as Cystoseira opuntioides, C. ericoides, and Ecto- 
carpus Valiantei, live parasitically and cause tissue excrescences, while 
the higher plants, especially of the family Loranthace^, produce large 
galls and the so-called wood roses on their host plants. These wood 
roses are formed by the woody tissues of the host forming a ridge-like 
growth about the clasping part of the parasite. 

The animal-produced galls known as 
zoocecidia are some of them of cattiplastic 
nature and are caused by nematode worms, 
insects and mites. The most important 
nematode worm responsible for the forma- 
tion of galls is Heterodera radicicola, which 
attacks many cultivated plants both in the 
greenhouse and in the open. The mite 
galls include the fleshy (hyperplastic) curl- 
ings of the leaf edges, shoot tips of various 
woody plants. Erineum galls, consisting of 
multicellular cones and ridges, are to be 
placed here. Dipterous insects produce 
galls with a prosoplasmatic structure, while 
the cataplasms produced by them have the 
form of fleshy curlings of the edges of the 
leaves of the host plants. Galls are produced Fig. 158. — Crown gall on 

also by the attack of bugs, aphids, or plant raspberry. {After Conn, a gri- 
1 ,, , cultural Bacteriology, -p. ^06.) 

lice, leaf wasps and gall wasps. They are 

found on roots, stems, leaves, inflorescences and fruits. Such are 

those on the roots of the grape due to Phylloxera vastatrix, etc. 

Histology of Cataplasms. — Usually aside from the slight tissue 
differentiation cataplasms are composed of abnormally large cells with 
an abundant protoplasmic content and sometimes with red cell sap, 
also a large starch content. The primary and secondary tissues are 
both involved in the formation of the galls. 

Primary Tissues. — ^Leaves, which are infected by fungi on which are 
formed mycocecidia, show an arrestment of the tissue differentiation. 




392 



GENERAL PLANT PATHOLOGY 



For example, the distinction between the pahsade and spongy paren- 
chyma is often lost, because the palisade layer is not formed as such 
and sometimes the spongy parenchyma undergoes a rich proliferation 




Fig. 159. Section uf tobaccu. Margin of infected needle wound. Tumor in 
middle part of back parenchyma; sieve tubes at x. (After Smith, Broiun, McCulloch, 
Bull. 255, U. S. Bureau of Plant Industry, 1912, pi. cl.) 

and red pigment sometimes appears. The same failure to form the regu- 
lar tissues is displayed by the zoocecidia. The vascular and mechanic 
tissues may also undergo the same reductions in cataplasm, as do the 
assimilatory tissues, so that the vascular bundles in infected parts are 



GALLS 393 

often only moderately developed. Wakker describes the disappear- 
ance of the coUenchyma in the stalks of Vaccinium vitis-idcBa infected 
with Exohasidium. Hyperplastic excrescences may be found by the 
pith as in branches of Clematis attacked by jEcidiuni Englerianum. 

Secondary Tissues. — Under this head will be considered the products 
of the cambium. The formation of galls may be due to the division of 
the living derivatives of the already-formed annual ring, or as in wound- 
wood, its own cells are used in the production of the cataplasmatic tis- 
sue. The wood and bark swellings formed by the attack of animals and 
fungi may be clustered or knob-like and resemble the frost-induced 
cankers or even the witches' brooms. 

Abnormal wood found in many woody galls is induced by many 
fungi belonging to the genera Dasyscypha, Gymnosporangium and Peri- 
dermium, by insects, and by parasitic flowering plants. A character- 
istic feature of such galls is the abnormal increase in the parenchyma, 
produced by the division of the cambial derivatives, which give rise to 
group of parenchymatous cells. Sometimes the cambial rays are 
broadened, so that extensive continuous masses of parenchymatous 
wood are produced. The same kind of tissue formation is seen in an 
examination of mycocecidia and zoocecidia. The mycocecidia may be 
illustrated by a brief consideration of the spindle-like, or ball-like, 
woody galls induced on different species of Juniperus by forms of the 
genus of rust fungi, Gymnosporangium. In the diseased wood, the 
difference between the spring and autumn wood is scarcely recognizable, 
and the parenchyma occupies a relatively broad space. The cambial 
rays in the parts of the branches infected by Gymnosporangium clavar- 
iceforme, instead of being only two to ten cells deep, are often ten to sixty 
cells deep and at least three cells broad. The woody gall of Gymnospor- 
angium juniperi-virginiancB shows still broader cambial rays, when 
viewed in tangential longitudinal section. According to the investi- 
gations of Reed and CrabilV the cedar apple gall is a modification of 
the leaf of the red cedar (Fig. i6o). The cedar leaf parenchyma makes 
up the greater portion of the cedar apple with the fungous hyphae in 
the intercellular spaces of the parenchyma cells. 

The fibro vascular system of the gall is a modified continuation of the 

1 Reed, Howard S. and Crabill, C. H.: The Cedar Rust Disease of Apples 
Caused by Gymnosporangium Junipcri-Virginiana. Technical Bull. 9, Va. Agric. 
Exper. Sta., May, 1915. 



394 



GENERAL PLANT PATHOLOGY 



fibrovascular system of the cedar leaf (Fig. i6i). From, or near the 
base of the cedar apple, where the vascular elements are much con- 
torted, arise many branches, which extend radially almost to the cortex. 
Harshberger^ has investigated the galls produced by two species of 
Gymnosporangium on the coastal white cedar, ChamcBcyparis thyoides, 

and Stewart^ has published an 
account of the anatomy of 
Gymnosporangium galls and 
Peridermium galls. 

There may be an over-pro- 
duction of the wood paren- 
chyma and the parenchymatous 
elements may divide without 
abnormal widening of the 
annual ring. The production 
of abnormal resin canals which 
are always surrounded with 
parenchyma illustrate this 
point. Hartig produced an in- 
crease of resin ducts in the dis- 
eased areas of coniferous trees 
infected by Ar miliaria mellea. 
Abnormal Bark. — Many gall 
formations exist where exten- 
sive bark excrescences are pro- 
duced whereby there is an ab- 
normal formation of paren- 
chyma. An examination of 
the galls due to species of 
Gymnosporangium shows that 
the bark and wood form excres- 
cences simultaneously. Wornle found that in weak branches of 
Juniperus communis a rust fungus, Gymnosporangium davaricBforme, 
incited the bark to' form woody parenchyma. 

1 Harshberger, John W.: Two Fungous Diseases of the White Cedar. Proc. 
Acad. Nat. Sci., Phila., 1902: 461-504, with 2 plates. 

2 Stewart, Alban: An Anatomical Study of Gymnosporangium Galls. Amer. 
Journ. Bot, ii: 402-417, October, 1915; Notes on the Anatomy of Peridermium 
Galls, do, iii: 12-22, January, 1916. 




Fig. 160. — Unopened cedar apples on red 
cedar, Juniperus virginiana. (After Jones 
and Bartholomew, Bull. 257, Agric. Exper. Stat. 
Univ. Wise, July, 1915.) 



GALLS 395 

Witches' Brooms and Stag-head. — The branches of the silver fir, the 
flowers, fruits and portions of stem of various species of plants are trans- 
formed into witches' brooms, or stag-head by the action of fungi of the 
genus Exoascus and in the silver fir by Mcidium elatinum. The shoots 




Fig. i6i. — Diagram of a longitudinal section of a cedar twig bearing a small 
cedar apple in June, a, Epidermis of cedar leaf; b, sclerenchymatous layer; c, fibro- 
vascular bundle; d, resin gland; e, parenchyma; /, parenchyma of cedar apple; g, 
fibro-vascular system of cedar apple; h, cortex. (After Reed, H. S., and Crabill, 
C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 1915.) 

are annual instead of perennial and are always sterile and branch out 

into broom-like, or antler-like forms called thunder bushes by some. 

{b) Prosoplasms.^ — Those galls are included, as prosoplasms, which 

do not have arrested tissue dififerentiations, nor in which callus tissues 



396 GENERAL PLANT PATHOLOGY 

are found, but in which new kinds of tissues are formed differing from 
the normal and in which definite proportions of form and size normal for 
the species are repeated in them. Therefore, prosoplasms display in 
their external form, something independent and well defined from the 
organs of the normal plant both internally and externally. Hyper- 
plastic tissues of this sort have been found until now only in the excres- 
cences caused by parasites and almost entirely those of the animal 
world, which produce zoocecidia. Six different orders of insects are the 
principal producers of galls and various fungi. They are as follows: 
The Acarina, or Mites of diminutive size, produce galls of simple form 
and structure. 

The Diptera, or Flies, cause many prosoplasms. The galls produced 
by the gall gnats, or gall midges, are very different in character and often 
very complicated. 

The Hemiptera, which include the aphides commonly known as 
green fly and plant lice, also produce numerous usually simple proso- 
plasms. 

The Hymenoptera, or gall-wasps, produce striking galls on account 
of their size, diversity and complexity of form external and internal. 

The Coleoptera and Lepidoptera (Heterocera) are responsible for 
relatively few galls, and if formed their structure is relatively simple. 

There are several plant-produced galls, or mycocecidia, in which 
there is a regular arrangement of certain elements such as the cells in 
which anthocyanin is formed. Ustilago Treuhii causes the production 
of canker-like excrescences on the stems of Polygonum chinense, which 
consist of spongy, parenchymatous, wood tissue. The excrescences, 
which develop from the canker swelling, are fleshy, succulent, easily 
breakable, irregularly bent, cyhndric and often longitudinally furrowed 
broadened at the top Hke the head of a snail. The fruit galls, which 
represent the part which produces the spores of the fungus, are repre- 
sented by this part of the gall. 

Histology of Galls 

Three types of abnormal cell divisions, connected with the formation 
of galls, may be distinguished, according to the direction that the di- 
vision takes. In the first type, the regular orientation of the trans- 
verse partitions cannot be recognized in young galls. In the second 
type, the cells divide usually in a plane perpendicular to the upper sur- 



GALLS 397 

face of the affected organ. The third type is where no definite direction 
of cell division may be found. 

The tissue material used in the formation of galls may be considered 
from several viewpoints. Thomas asserts that only those tissues are 
able to form galls which are attacked during development, or in other 
words permanent tissue cannot form galls and this is certainly true of 
prosoplasmatically formed galls, but with cataplasms there seem to be 
exceptions, where callus has been formed from bark parenchyma several 
years old. Definite experimental proof of the contested points cannot 
be obtained, because all attempts with experimentally producing cecidia 
have failed. It is certain, however, that many galls are produced from 
completely undifferentiated tissue, that is, from the primary meristem 
of the tips of shoots, or from callus tissue, but not from cells and tissues 
with lignified walls. It has been proved that all living cells belonging 
to the epidermis, the ground tissue, or the vascular bundle tissue, can 
under certain circumstances participate in the formation of galls. The 
fundamental tissue, or parenchyma, produces the largest mass of the 
galls, and it should be remarked in passing that the pith, bark and 
mesophyll cells often proliferate with astonishing luxuriance. If in 
leaf galls, for example, the infected part of the leaf becomes ten or twelve 
times the thickness of the normal leaf, it is in nearly all case's the meso- 
phyll which has been active, for in nearly all galls the tendency to form 
parenchyma is striking. The epidermis is concerned only occasionally 
in the formation of galls and the chlorophyll content of galls is scanty. 

The comparison of galls with animal tumors has been made but in- 
advisedly because with the exception of a diseased new formation of 
tissue being involved and in the absorption of appreciable amounts of 
foodstuffs from the fundamental tissue galls and tumors have little in 
common. Galls in contrast to tumors are developed by a typic infection 
growth. Mixed swellings occur in galls where epidermis, bark, meso- 
phyll and other tissues unite to form an homogeneous whole while no 
tumor is known, which consists of characteristic tissue zones of such 
diversity as those of the galls of the dipterous insects. 

CECIDIAL TISSUE FORMS 

We are next concerned with a study of the different kinds of tissue 
forms in galls and in their consideration we will treat first the two most 
important, namely, the protective and nutritive tissues. 



398 GENERAL PLANT PATHOLOGY 

Protective Tissues. — The protective tissues of galls consist of the 
epidermal, or covering tissues, and the stone cells which form part of 
the mechanic tissue. The epidermal tissue will be considered as a pro- 
tective tissue irrespective of its origin whether from the epidermis of the 
host, or as a new formation. The outer epidermis of sac and walled 
galls consists of relatively large, ofteti flat cells which have a cuticle of 
moderate development. Occasionally this epidermis may consist of 
more than one layer. A gall found on a Calif ornian oak Quercus Wisli- 
zeni, has the outer walls of its epidermal cells and the upper part of the 
side walls thickened so that the cell cavity becomes conic in shape (Fig. 
162). Cork, as a covering for galls, is extremely rare. Wound-cork 
is found occasionally in these galls, while bark is even rarer in a few 
apterous galls. 

Hair structures, or trichomes, are not unusual in galls. The 
majority of prosoplasmatic galls are naked or only slightly pubescent 
and some galls are entirely without any covering tissue. 

Mechanic Tissue.- — These consist of stereids (sclerotic, or stone cells) 
or sclerenchyma fibers almost entirely and they surround the larval 
chambers so that their occupants are protected from outside pressure, 
or sudden blows. Lacaze-Duthiers called the stone cell tissues in galls 
"couche protectrice." The arrangement of the stone cells, their 
structure and their position in the gall tissues are of the greatest diver- 
sity. In the majority of cases, the stereids are round, in other galls 
they are angular, while in others, they are stretched like palisade cells 
and stand perpendicular to the upper surface of the gall body similar to 
those in many fruit and seed shells. Sometimes the sclereid cell is thick- 
ened only on one side, the delicately walled part being outside as in the 
galls of Andricus quadrilineatus and sometimes they are inside as in an 
elliptic gall of the oak, etc. The walls of the sclereids may be pitted, 
and, therefore, porous, while in other cases the pitting may be very 
scanty and other peculiarities have been described by pathologists 
who are intimately acquainted with the structure of galls. 

Nutritive Tissues.- — The tissues of galls which are eaten by the animal 
occupants of the different galls, or the contents of which are beneficial 
to the larvae have been termed by cecidologists nutritive tissues. The 
position of these nutritive tissues in the galls and their contents must 
be considered next. No gall is entirely without nutritive tissues and 
these not infrequently form the largest part of the gall and in those 



GALLS 



399 



formed by dipterous insects the nutritive layers are often sharply sepa- 
rated from the mechanical tissue adjoining. The epidermis of the gall 
may represent the nutritive tissue when it develops as an inner hairy 
lining to the larval chamber. Albuminous substances are found in such 
papilla, or hairs, as well as drops of fat and small grains of starch, so 
that the larvae are surrounded by abundant supplies of a rich pabulum. 
Nutritive parenchyma may be formed within the mechanic mantel and 
here it is available to the larval occupant of the cell (Fig. 162). In 




Fig. 162. — Cross-section of an un- 
known gall on Quercus Wlslizeni. Ep, 
pidermis; Mi, outer mechanic mantle; 
St, starch-filled outer nutritive layer; 
Ms, inner mechanic mantle. (After 
Kiister, p. 252.) 



Fig. 163. — Insect gall on scrub oak, 
Quercus nana, due to gall insect, Amphi- 
bolips ilici folia with interior of gall. 
Pine Barrens near Chatsworth, N. J., 
May 27, 1916. 



Other cases, the food materials are stored outside the mechanic mantel, 
and they become available only by the larvae breaking through the 
stereid layer. The cells of the nutritive parenchyma are usually iso- 
diametric, elongated and sac-like forms, or as delicate cell threads. In 
the highly organized galls of the Cynipidae, the cells of the innermost 
layers on which the larvae feed contain a cloudy dense cytoplasm in 
which small fat globules are seen and this layer may be termed appro- 
priately the protein layer. A starch layer lies outside of the protein 
layer. Here the cells contain starch. Besides the nutritive bodies 



400 GENERAL PLANT PATHOLOGY 

just mentioned occur tannic substances and lignin bodies. The latter 
are produced at corners where several cells come together as local 
thickenings of the walls. It is improbable that this lignin is nutritive 
in function. 

Tissues of Assimilation.- — Almost all galls are characterized by the 
almost entire absence of chlorophyll. In a few galls, if present, the 
chloroplasts are small, twisted and feebly colored besides being extremely 
scanty. 

Vascular Tissues. — The tissue of galls is intimately associated with 
the vascular bundles of the host plants on which the galls occur and 
some are actually formed from the tissue of the vascular bundles. In- 
side the galls the vascular strands are usually delicate cords both in 
cataplasms and prosoplasms. Where they occur inside galls, we find 
that their individual elements resemble those of the normal bundles. 
In a few exceptional cases, as in the galls of Andricus albopundatus, 
these are concentric bundles. The arrangement of the gall bundles 
varies greatly for we find them in a circle, or they pass through the bark 
of the gall as a delicate network. 

Tissues of Aeration. — The structure of many galls is an open porous 
one (Fig. 163). The gall parenchyma cells in some cases are star- 
shaped, fitting together by their projections, so that large intercellular 
spaces are formed. Stomata and lenticels constituting pneumathodes 
are found in galls. The stomata, however, have lost their ability to 
close and remain, therefore, permanently open. Lenticels are present 
in some cases. The stomata and parts of the epidermis disintegrate and 
large roundish lenticels develop beneath them. Perhaps this aerating 
tissue enables the larva to get sufficient oxygen for its metabolism. 
Anthocyanin is present in the cells of many galls, as their red cheeks 
abundantly testify. 

Secretions and Secretory Reservoirs. — -The elements concerned with 
secretion in the normal epidermis are present in galls in unchanged form, 
or they are increased, richly furnishing the secretions which are asso- 
ciated with gall formations. Less frequently new forms of secreting 
cells and tissues are found in galls. Crystals of calcium oxalate are not 
found usually in galls, but yet their entire absence is a rare feature. 
In some cases, the crystals when present are associated with the stereids. 

The presence of tannic bodies has been noted previously, and it 
seems that the tannin is found in the cells of certain gall tissues. The 



GALLS 401 

outer cell layers in some of the galls produced by Cynipid.e is rich in 
tannin, so that these galls have been used from time immemorial in 
the tanning of leather and in the production of ink. Tannin balls occur 
in the nutritive parenchyma of many galls and are devoured by the 
larvie of the same. 

BIBLIOGRAPHY OF GALLS 

Adler, Hermann, Transl. b}- Straton, Charlks R.: Alternating Generations. 

A Biological Study of Oak Galls and Gall Flies. Oxford, at the Clarendon 

Press, 1894, pages 198. 
AsHMEAD, W. H.: Galls of Florida. Proc. Ent. Spc. Am., new ser., 1881: ix-xx, 

xxiv-xxviii, 1885 and x-xix. Trans. Am. Ent. Soc, xiv: 125—128. 
BEUTENMtJLLER, WiLLiAM: Catalogue of Gall-producing Insects Found Within 

Fifty Miles of New York City, with Descriptions of Their Galls, and of Some 

New Specjes. Bull. American Museum Natural History, iv: 245-278, with 

8 plates. 
Beutenmuller, William: The Insect Galls of the Vicinity of New York City, 

Guide Leaflet No. 16, American Museum of Natural History. Reprinted from 

American Museum Journal, iv. No. 4. 
CoNNOLD, Edward T.: British Vegetable Galls: an Introduction to Their Study, 

1902, pages 312, with 130 plates. 
Cook, Mel T.: Some Problems in Cecidology. Botanical Gazette, 52: 386-390, 

November, 191 1; A Common Error concerning Cecidia. Science, new ser., 34: 

683-684, Nov. 17, 19 II. 
CosENS, A.: A Contribution to the Morphology and Biology of Insect Galls. Trans. 

Canadian Institute, ix: 297-387, 1912, with 13 plates. 
Darboux, G. and Hovard, C: Hilfsbuch fii.r das Sammeln der Zoocecidien, mit 

Beriicksichtigung der Nahrpflanzen Europas und des Mittelmeergebietes. 
Felt, Efhraim Porter: A Study of Gall Midges II. 29th Report of the New 

York State Entomologist, 1913: 79-213, with 16 plates, Albany, 1915. 
Howard, C: Les Zoocecidies des Plantes d' Europe etdu Bassin dela Mediterranee. 

Description des Galles. Illustration. Bibliographic detaillee. Repartition 

geographique. Index bibliographique, 2 tomes, Paris, 1908. 
Kerner, Anton: Natural History of Plants, transl. by F. W'. Olh-er, ii: 518-554, 

1895. 
KtJSTER, Dr. Ernst: Die Gallen der Pfianzen. cin Lehrbuch fiir Botaniker und 

Entomologen, mit 158 Abbildungen. 
KtJSTER, E.: Pathologische Pflanzenanatomie, Gustav Fischer in Jena, 1903; Zweite 

Auflage, 1916. 
KtJSTER, E.: Pathological Plant Anatomy, authorized translation by Fr.xnces 

Dorrance, 19 13-19 1 5. 
L.\caze-Dltthiers, H.: Recherches pour servir a I'historie des Galles. Ann. Sc. 

Nat. Eot., xii: 353, 1849; xiv: 17, 1850; xLx: 273, 332, 1853. 
26 



402 GENERAL PLANT PATHOLOGY 

Magnus, Prof. Dr. Werner: Die Entstehung der Pflanzengallen verursacht durch 

Hymenopteren, Jena, 1914. 
Mayr, Dr. GustavL.: Die Mittel-Europaischen Eichen Gallen in Wort und Bild, 

Berlin, 1907. 
Osten-Sacken, C. R. von: On the Cynipidae of the United States and Their Galls. 

Proc. Ent. Soc. Phil., I: 47, 62 (1861); IV: 380 (1865). 
Ross, Dr. H.: Die Pflanzengallen (Cecidien) Mittel-und Nordeuropas ihre Erreger 

und Biologie und Bestimmungs tabellen, 191 1. 
RtJBSAAMEN, Ew. H.: Die Zoocecidien durch Tiere erzengte Pflanzengallen Deutsch- 

lands und ihre Bewohner, Leipzig, 191 1. 
Thompson, Millett Taylor: An Illustrated Catalogue of American Insect Galls, 

published and distributed by Rhode Island Hospital Trust Co., executor in 

accordance wdth the provisions of the will of S. Millett Thompson, edited by 

E. Felt, 1915, pages 66, with 21 plates. 



CHAPTER XXXII 
MECHANIC DEVELOPMENT OF PATHOLOGIC TISSUES 

Our study of plant pathology would not be complete without a brief 
reference to the reactions which influence the genesis of the abnormal 
tissues of diseased plants. The investigation of these questions is a 
matter of recent development ever since prominence has been given to 
the experimental methods of studying plant diseases and abnormalities. 
Kiister gives considerable prominence to these problems in the second 
edition of his " Pathologische Pflanzenanatomie" (pages 328-398), 
where we have the last and most authoritative treatment of the subject. 
As an important factor he mentions the reaction ability of the living 
cells, both in normal cell division and with inequalities in cell division, for 
it is recognized that unequal division of the dividing cells plays an im- 
portant part in pathologic plant anatomy. The polarity of cells is 
another important element to be considered by the pathologic anatomist, 
for if by unequal division, there is produced a change in the polarity of 
the cells concerned in such division, the tissues which arise from such 
cells will show a different kind of differentiation. 

Miehe has demonstrated the physiologic polarity of cells by plas- 
molyzing the cells of a marine species of Cladophora. He found, after 
the destruction of the continuity of the protoplasm from cell to cell by 
plasmolysis, and the transference of the plant into a solution of deter- 
mined concentration, that elongated filaments developed, and that 
rhizoids developed from the basal pole of each of the cells. The epi- 
dermal cells of the leaves of linden, Tilia platyphylla, when attacked by 
Eriophyes tilicB develop long cylindric trichomes from the same pole 
of each cell. 

The reaction capabilities of the cells of different tissues are both 
quantitative and qualitative. The cells of the epidermis, parenchyma, 
sap bundles react differently and this is expressed in the formation of 
intumescences, callus wound-cork and wound-wood out of them. 
The change in the reaction of cells is also a noteworthy feature in the 
study of abnormal plant structure. There is a difference between young 

403 



404 GENERAL PLANT PATHOLOGY 

organs, tissues and cells, as expressed in the growth, plasticity and 
processes of differentiation under the influence of the exciting cause, as 
is evidenced in the formation and nutrition of galls comprehended 
under the general head of cecidogenesis. 

The recent study of the developmental mechanics of pathologic 
tissues calls for an investigation of stimuli, and the reaction to stimuli 
where every reaction presupposes a capacity for reaction and where the 
cells of different tissues vary in this respect and no cell remains always 
the same, but changes without any influence of the external world with 
the age of the cell, as well as the fact that every reaction presupposes 
previous conditions which permit the reaction to take place. Such 
considerations as these introduce the student to the investigation and 
terminology of Roux, as set forth in his " Terminologie der Entwick- 
lungs Mechanik der Tiere und Pfianzen," 191 2, and to the work of 
Vochting, Kiister, Klebs, Haberlandt, N^mec and others along experi- 
mental lines. Correlation, Neoevolution, Neoepigenesis are terms with 
which the pathologic student must become acquainted. He learns that 
Osmomorphosis comprehends all osmotic and turgor influences which 
determine the form and differentiation of cells and tissues; that mechano- 
morphosis is where plant cells and tissues have been modified in develop- 
ment by mechanic pressure and pull; that chemomorphosis is where 
chemic influences are the determining factors in molding the form and 
controlhng the differentiation process; that trophomorphosis is where 
abnormal nutrition is influential locally in the transformation of plants. 

The consideration of chemomorphosis shows us that we may deal 
with known chemic bodies the action of which can be studied experimen- 
tally, or we may be concerned with unknown chemic substances, as the 
poisons injected into the tissues of a plant by the gall forms which pro- 
foundly influence the formation of the gall tissues. 

Trophic correlation, or trophomorphosis, exists between the parts of 
a cell, as well as between the organs of a plant, or the tissues of the 
organs. The action within the cell may be between the nucleus and the 
cytoplasm, and its importance in pathologic plant anatomy has been 
experimentally studied by Gerassimoff and N^mec. Gerassimoff's 
research dealt with the influence of the size of the nucleus on the cyto- 
plasm, while N^mec discovered that in chloralized roots of Viciafaba the 
cells with normal diploid chromosome content had didiploid and tetra- 
diploid chromosome-rich nuclei, and that the greater the content of the 



MECHANIC DEVELOPMENT OF PATHOLOGIC TISSUES 405 

cell in nuclear material the greater becomes its volume. Equally re- 
markable discoveries were made in an investigation of the action of tis- 
sues and organs upon one another. Vochting has produced a bending 
growth in the root of the kohlrabi by removal of the leaves of one 
side of the plant, so that the development of the normal side was 
markedly greater than that of the other. The same effect was secured 
in the petiole of a compound leaf of Pklea mollis by removal of a lateral 
leaflet and the result of this experiment is displayed in the accompany- 
ing figure. Narcotics and the vitiation of the atmosphere by poisonous 
gases inhibit growth in length. Mathuse figures the effect of removal 
of the growing point of a plant in the promotion of superficial leaf 
growth and other anatomic changes in the leaves of Achyranthes 
VerschafeUii. Other experiments of a somewhat similar nature are 
equally illustrative. Hardly a more important and inviting field of 
research has been opened than that which has been revealed by the 
investigation of the experimental plant morphologists, or the experi- 
mental pathologic plant anatomists. 

BIBLIOGRAPHY OF DEVELOPMENTAL MECHANICS 
OF PATHOLOGIC TISSUES 

BoRDNEE, J. S.: The Influence of Traction on the Formation of Mechanical Tissue 
in Stems. Botanical Gazette, 48: 251, 1909. 

BucHER, H.: Anatomische Veranderungen bei gewaltsamer Kriimmung und geo- 
tropischer Induktion. Jahrbucher ftir wissenschaftliche Eotanik, 43: 271, 1906. 

CowLES, H. C: A Text-book of Botany for Colleges and Universities, vol. ii, Ecol- 
ogy, 1911. 

Daniel, W.: Zur Kenntnis der Riesen- und Zwergblatter, Dissertation, Gottingen, 

1913- 
EwART, A. J. and Mason- Jones, A. J.: The Formation of Red Wood in Conifers. 

Annals of Botany, 20: 201, 1906. 
GoEBEL, K.: Organography of Plants (English edition), i: 206, 1900. 
H.^BERLANDT, G.: Verglcichende Anatomic des assimiherenden Gewebesystems der 

Pflanzen. Jahrbucher fiir wissenschaftliche Botanik, 13: 74, 1882. 
Haberlandt, G.: Zur Physiologic der Zellteilung. Sitzungsber. Akad. Wiss., Ber- 
lin, 1913, Nr. xvi. 
Haberlandt, G. transl. by Drummond, Montagu: Physiological Plant Anatomy, 

Macmillan and Co., London, 1914. 
Hoffmann, R.: Untersuchungen iiber die Wirkung mechanischen Krafte auf die 

Teilung, Anordnung und Ausbildung der Zellen beim Aufbau des Stammes der 

Laub und Nadelholer. Dissertation, Berlin, 1885. 
Hartig, R.: Das Rotholz der Fichte. Forstl. naturwiss. Zeitschr., 5: 96, 1896. 



4o6 GENERAL PLANT PATHOLOGY 

HiBBARD, R. P.: The Influence of Tension on the Formation of Mechanical Tissue 

in Plants. Botanical Gazette, 43: 361, 1907. 
Keller, H.: Ueber den Einfluss von Belastung und Lagelauf die Ausbildung der 

Gewebe in Fruchtstielen. Dissertation, Kiel, 1904. 
Kny, L.: Ueber den Einfluss von Zug und Druck auf die Richtung der Scheidewande 

in sich teilenden Pflanzenzellen. Jahrbiicher fiir wissenschaftliche Botanik, 

37: 55, 94, 1901- 
KiJSTER, Ernst: Histologische und experimentelle Untersuchungen liber Intumes- 

zenzen. Flora, 96: 527, 534, 1906. 
KtJSTER, Ernst-. Aufgaben und Ergebnisse der entwickelungsmechanischen Pflan- 

zenanatomie Progressus Rei Botanicae, 2: 455, 1908. 
KiJsTER, Ernst: Gallen der Pflanzen, Leipzig, 191 1. 
MiEHE, H.: Wachstum, Regeneration und Polaritat isoliertcr Zellen. Berichte der 

Deutschen botanische Gesellschaft, 23: 257, 1905. 
N£mec, B.: Studien iiber die Regeneration, 1905. 
Newcombe, F. C.: The Regulatory Formation of Mechanical Tissue. Botanical 

Gazette, 20: 441, 1895. 
Nordhausen, Max: Ueber Richtung und Wachstum des Seitenwurzeln unter dem 

Einfluss ausserer und innerer Faktoren. Jahrbiicher fiir wissenschaftliche 

Botanik, 44: 557, 1907. 
Pieters, A. J.: The Influence of Fruit-bearing on the Development of Mechanical 

Tissue in Some Fruit Trees. Annals of Botany, 10: 511, 1896. 
Prein, R.: Ueber den Einfluss mechanischer Hemmung auf die histologische Ent- 

wicklung der Wurzeln. Dissertation, Bonn, 1908. 
Roux, Wilhelm: Der Kampf der Telle im Organisms, Leipzig, 1881. 
Roux, Wilhelm; Terminologie des Entwicklungs mechanik der Tiere und Pflanzen 

Leipzig, 19 1 2. 
Schulte, W.: Ueber die Wirkung der Ringelung auf Blattem. Dissertation, 

Gottingen, 191 2. 
Simon, S.: Experimentelle Untersuchungen iiber die Entstebung von Gefassver- 

bindungen. Berichte der Deutschen botanische Gesellschaft, 26: 364, 393, 

1908. 
Smith, L. M.: Beobachtungen iiber Regeneration und Wachstum aus isolierten 

TeLlen von Pflanzen embryonen. Dissertation, Hallea S., 1907. 
Snow, L. M.: The Development of Root Hairs. Botanical Gazette, 40: 12, 1905. 
Strasburger, E.: Ueber die Wirkungssphare der Kerne und die Zellgrosse Histo- 
logische Beitr age, 1893: 5. 
Strasburger, E.: Die Ontogenie des Zelle seit 1875. Progressus Rei Botanicae, 

i: I, 90, 1907. 
Vochting, Hermann: Ueber die Bildung der Knollen. Bibliotheca Botanica, 4: 11, 

1887. 
Vochting, Hermann: Untersuchungen zur experimentellen Anatomie und Patholo- 
gic des Pflanzenkorpers, Tubingen, 1908. 
voN Schrenk, H.: Intumescences Formed as a Result of Chemical Stimulation. 

Report Mo. Bot. Gard., 1905: 125. 
WoRGiTzKY, G.: Vergleichende Anatomie der Ranken, Flora, 70: 2-25 etseq., 1887. 



MECHANIC DEVELOPMENT OF PATHOLOGIC TISSUES 407 

WoRTMANN, J.: Zur Kenntnis der Reizbewegungen, Botanische Zeitung, 45: 819, 
1887. 

Suggestions to Teachers and Students 

The investigation of plant diseases in general is most important and 
it should be approached from a number of standpoints.^ The teacher is 
interested in it, because he desires to arrange the subject matter, so that 
it may be presented in the laboratory and lecture course. The experi- 
ence of the writer along these lines may be of service to other teachers, 
and it is given, therefore, with some detail. Living plants should be 
kept for experimentation along pathologic lines. The best plants for 
this purpose will be determined by the locality, by their availability, by 
the ease of their cultivation and by their successful growth in the green- 
house during the short days of winter. The experiments outlined in the 
lessons of part IV can be tried upon these plants, such as the influence 
of chemicals upon growth, the action of illuminating gas on the health of 
the plant, and the extremely minute, or excessive action of amounts of 
chemic reagents, for some experiments conducted by Free at Johns Hop- 
kins University indicate that various plants react in a specific way to 
extreme dilution of poisonous substances. ^ 

The plants can be wounded in various ways and on different organs. 
The repair tissue can be studied by sectioning the healed part and stain- 
ing with appropriate stains. Various infection experiments can be tried 
with fungi and the lesions produced can be fixed and imbedded in paraf- 
fin for sectioning, mounting, and for study later under the microscope. 
The stock of such material for study can be increased materially by 
collecting galls, insect depredations on plants, examples of callus for- 
mation from street trees, which have been injured by horses biting off 
the bark, or by abrasion with wagon wheels. This material, collected 
from the streets and highways, from the woods and fields, should be 
fixed and hardened and finally embedded in paraffin for sectioning and 
microscopic study. These sections should be furnished along with 
alcoholic, or dried material of the abnormal plant, so that the student 

^ Cf. Shear, C. L.: Mycology in Relation to Phytopathology. Science, new, 
ser., xli: 479-484, April 2, 1915. 

Smith, E. F.: Plant Pathology. Retrospect and Prospect. Science, new ser. 
xv: 601-612, April 18, 1902. 

^Free, E. E.: Symptoms of Poisoning by Certain Elements, in Pelargonium 
and other Plants. Contributions to Plant Physiology, The Johns Hopkins Uni- 
versity, March 191 7; 195-198. 



4o8 GENERAL PLANT PATHOLOGY 

becomes familiar with the gross anatomy, as well as the microscopic. 
Photomicrographs can be made readily by the use of the Edinger appara- 
tus which has been used successfully at the University of Pennsylvania 
in class work. It adds materially to the interest of the work to take 
photographs of the sections studied and make permanent prints of the 
diseased structures. After a few years, the alcoholic stock material 
will have increased to such an extent that all phases of pathologic 
plant anatomy can be demonstrated, not only by actual specimens, 
but also by sections. The sections, if made directly by the sliding 
microtome, can be kept in large numbers in small bottles in 50 per 
cent, alcohol, where they are available for class use at any time. The 
paraffin mounts can be kept in block form ready for use when required 
by the sequence of laboratory exercises and lectures. If alcohol is not 
available on account of its high price, other materials may be used in its 
place. 

The sections and alcoholic material having been prepared for use 
can be studied for hypertrophy, for metaplasia, hypoplasia and other 
pathologic conditions. Such an investigation presupposes a thorough 
grounding in the technique of plant anatomy and histology, so that no 
time may be wasted in unnecessary explanations. From the stand- 
point of curriculum, such a course in mycology and pathologic plant 
anatomy should be given in the junior, or senior years, or deferred until 
the post-graduate years because of the special nature of the work. 

Written reports should be required of all students based upon the 
experiments with the inoculation and infection of various cultivated 
plants and their reaction to various fungi. Similarly, where pathologic 
anatomy and histology of plant organs and tissues are concerned photo- 
graphic prints may take the place of microscopic drawings. Each 
topic considered in the lecture course should receive attention in the 
laboratory and in the field and indoor experiments, because this work 
is designed to prepare future plant doctors, teachers and investigators, 
who are interested in the science of phytopathology and who are 
anxious to be proficient in the study of plant diseases. 

Stock material should be kept of all the more common insect and 
fungous diseases of cultivated and wild plants not only for such patho- 
logic study, but also for a systematic and morphologic work with insect 
and fungous parasites. The mycologic student should be able to 
identify not only the more common insects and fungi after such a 



MECHANIC DEVELOPMENT OF PATHOLOGIC TISSUES 409 

course, but should be able also to diagnose the more common diseases 
and suggest remedies in the form of insecticides, or fungicides, or other 
remedial measures from a knowledge of the physiology of pathologic 
plants. A change in the soil, or a change in the temperature and 
exposure may be all that is needed to keep a plant in a perfect state 
of health. 

The problems which may be assigned to the post-graduate student 
for experimental investigation are unlimited in America, where the 
nation is confronted by serious pests introduced from various lands. 
The anatomic and histologic characters and the development of cecidia 
have been the subject of extensive studies in Europe, but American 
botanists have done very little in the study of American galls along these 
lines of investigation. The character of the poisons which cause 
the stimulation of the plant to produce the galls is a matter well worth 
the attention of botanists experimentally inclined. The equipment of 
the laboratory and the facilities for experimentation should be con- 
sidered before the problem is assigned to the post-graduate student. 
The previous training and bias of the individual should be weighed 
carefully for the research work may be of a cytologic nature. It may be 
a histologic study pure and simple with pathologic tissues, or the prob- 
lem may deal with prophylaxis, or preventive measures. It may be 
that the student is better prepared to investigate the etiology of disease, 
or the composition of sprays and their effects on the plant tissues. 
Some advanced students would find keener zest in the systematic or 
biologic study of some fungus, or group of fungi, or the bias may be 
toward detailed experimentation with insects, or other forms of animal 
life. The teacher should weigh carefully all of these details and act 
accordingly. Problems with an economic bearing would be more suit- 
able for the students of agricultural colleges and experiment stations, 
while matters of pure science might be properly relegated to the 
endowed colleges and universities, where investigation with a practical 
trend would not be absolutely essential. The laboratory work should 
be combined with field work in the study of inorganic and organic dis- 
eases. The character of the field work will be determined by the 
nature of the investigation and by the season and by the climatic con- 
ditions. The work in the field at first would consist in the observation 
of diseases, the taking of notes from the living trees and the collection of 
material for more detailed study. The extent of the injury should be 



4IO GENERAL PLANT PATHOLOGY 

determined. Extension and the work of prevention can be carried on. 
Cooperative work with the progressive farmers and horticulturists can 
be inaugurated with profit to the farmer and the investigator. The 
etiology of diseases can be investigated by properly directed field experi- 
ments. Inoculations can be made on plants growing in the field, or in 
the laboratory or greenhouse.^ Such original investigation presup- 
poses the accumulation of apparatus and a suitable working library. 
With the limited appropriation available for the purchase of apparatus 
and books, such an equipment seems beyond the ordinary school and 
college, but it will be surprising to those who have not tried the plan how 
many books, diagrams, etc., can be accumulated, and how much 
apparatus can be secured by spreading the purchase of such needful 
things over a series of years. If the books and apparatus are cared for, 
little deterioration need be suffered and at the end of twenty or twenty- 
five years, a respectable stock of these desiderata will be on hand for use 
in the class room, laboratory, research rooms and greenhouses. 

The growth of the study of plant pathology as a distinct branch 
of science has been by leaps and bounds. It is now on a more satisfac- 
tory basis than ever before, and a larger number of men and women are 
directing their attention to phytopathology as a life work. The men 
who enter this field from now on must have a better and an all-sided 
training. This presupposes an acquaintance with the literature of the 
subject in his own and several foreign languages. There should also be a 
training in chemistry and physics. He should know something about 
zoology and should be conversant with the physiology and histology of 
plants and other phases of botanic inquiry. To meet this demand our 
American colleges and universities have introduced subjects which will 
be of direct benefit to the future plant pathologist. The curricula^ 
have been arranged to introduce the study, hot only of plant pathology, 
but also cognate subjects some of which may not have a direct bearing, 
but which make the man a well-trained and a competent "plant 
doctor." 

iC/. Heald, F. D.: Field Work in Plant Pathology. The Plant World, lo: 
104-109, May, 1907. 

2 Fink, Bruce: A College Course in Plant Pathology. Phytopathology, II: 
150-152, August, 1912. Consult Stevens, F. L.: Problems of Plant Pathology, 
The Botanical Gazette, Ixiii: 297-306, Apr., 191 7; also Harshberger, John 
W. : The Need of Competent Plant Doctors, Education, 1895, 140-144. 



PART III 
SPECIAL PLANT PATHOLOGY 

CHAPTER XXXIII 
LIST OF SPECIFIC DISEASES OF PLANTS 

The remarkable growth of the work of the United States Depart- 
ment of Agriculture, and that of the agricultural experiment stations of 
the different states, has been along the most diverse lines. Mycology 
has been given prominence and the number of trained workers in this 
field has increased to such an extent, that a separate organization, 
known as the American Phytopathological Society, has been found 
necessary. The meetings of this society have been largely attended 
and the papers read have been of the greatest value and interest. The 
organ of the society, "Phytopathology," has published already a con- 
siderable number of important papers, and it has set a high standard for 
the future work along mycologic and pathologic lines. One of the 
specific problems, which it has attempted to do through special com- 
mittes appointed for the purposes, has been to suggest the use of com- 
mon names of fungous diseases based on recognized rules of procedure 
and to prepare a list of the common and important diseases of economic 
plants in the United States and Canada. The preliminary report of 
the committee on common names has been made, but considerable 
time must elapse before the list of common and important diseases is 
completed. 

As this book will be printed and issued before the preliminary list of 
the American Phytopathological Society of fungous diseases appears, 
it has been deemed advisable to compile a list from various sources of 
information for the common host plants in the United States and 
Canada, using the "Literature of Plant Diseases" given by W. C. 
Sturgis in the Report of the Connecticut Agricultural Experiment 
Station for the year ending Oct. 31, 1900, part III, pages 255-293, as 
the basis of such a list. 

411 



412 SPECIAL PLANT PATHOLOGY 

That the list might be made as complete as possible and repre- 
sentative of the plant diseases of the United States and the tropic 
countries to the southward, the following publications have been 
used in its compilation. 

Atkinson, Geo. F.: Studies of Some Shade Tree and Timber-destroying Fungi. 

Cornell Univ. Agric. Exper. Sta., Bull. 193, June, iqoi. 
CoiT, J. E.: Citrus Fruits, 1915: 364-402, The Macmillan Co. 
Cook, Melville T.: The Diseases of Tropical Plants, 1913, The Macmillan Co. 
DuGGAR, Benj. M.: Fungous Diseases of Plants, 1909, Ginn and Co. 
Freeman, E. M.: Minnesota Plant Diseases, 1905. 
Graves, Arthur H.: Notes on Diseases of Trees in the Southern Appalachians. 

Phytopathology, III (1913) and IV (1914). 
Heald, Fredk. D. and Wolf, Fredk. A.: A Plant-disease Survey in the Vicinity 

of San Antonio, Texas. U. S. Bureau of Plant Industry, Bull. 226, 191 2. 
Hesler, Lex R. and Whetzel, Herbert H.: Manual of First Diseases, xx + 

146 pages, 126 figs., 191 7, The Macmillan Co. 
HuME,H. Harold: Citrus Fruits and Their Culture, 191 1: 466-492, Orange Judd Co. 
Jackson, H. S.: Some Important Plant Diseases of Oregon in Biennial Crop Pest 

and Horticultural Report, 1911-1912, Oregon Agric. E.xper. Sta., 177-308. 
Longyear, B. O.: Fungous Diseases of Fruits in Michigan. Michigan State Agric. 

Coll. Exper. Sta., Special Bull. No. 25, March, 1904. 
Meinecke, E. p.: Forest Tree Diseases Common in California and Nevada. U. S. 

Forest Service, A Manual for Field Use, 1914. 
Reed, Howard S. and Cooley, J. S.: Plant Diseases in Virginia in the Years 1909 

and 1910. 
RoBBiNS, W. W. and Reinking, Otto A.: Fungous Diseases of Colorado Crop 

Plants. Agric. Exper. Sta. Colo. Agric. Coll., Bull. 212, October, 191 5. 
Selby, a. D.: a Brief Handbook of the Diseases of Cultivated Plants in Ohio, 

Bull. 214, Ohio Agric. Exper. Sta., 1910. 
Shear, C. L. and Wood, Anna K.: Studies of Fungous Parasites Belonging to the 

Genus Glomerella. U. S. Bureau of Plant Industry, Bull. 252, 1913. 
Smith, Ralph E. and Smith, Elizabeth H.: California Plant Diseases. Coll. of 

Agric, Agric. Exper. Sta., Bull. 218, June, 1911. 
Stevens, F. L. and Hall, J. G.: Diseases of Economic Plants, 1910, The Mac- 
millan Co. 
von Schrenk, Hermann: Some Diseases of New England Conifers. U. S. Div. Veg. 

Physiol, and Pathol., BuU. 25. 
von Schrenk, Hermann: Sap-rot and Other Diseases of the Red Gum. U. S. 

Bureau of Plant Industry, Bull. 114, 1907. 
von Schrenk, Hermann and Spaulding, Perley: Diseases of Deciduous Forest 

Trees. U. S. Department of Plant Industry, Bull. 149, 1909. 
Whetzel, H. H. and Rosenbaum, J.: The Diseases of Ginseng and Their Control. 

U. S. Bureau of Plant Industry, Bull. 250, 191 2. 

This list will serve as an index of the diseases which will be described 



LIST OF SPECIFIC DISEASES OF PLANTS 413 

in full in the remainder of part III. As it will be impossible to describe 
in detail all of the diseases of the list, a selected number will be chosen, 
which will illustrate the subject and which, if mastered by the student, 
will lay the foundation for a more thorough acquaintance with the 
diseases, which are prevalent in the United States, and which the 
student, the teacher, the horticulturist, the forester, the agriculturist, 
and the practical mycologist are likely to meet in their plant-growing 
experience. It is recommended that for each of the diseases described 
in the following pages the outline for the use of students given in 
Lesson 29 be used to facilitate an investigation of the disease in the 
laboratory, greenhouse, or in the open field. This is a method of 
study approved by the best teachers of the United States. ^ The author 
wishes to state emphatically that he has designedly kept down the 
number of diseases described in the following pages because the 
thorough mastery of a limited number is better than a superficial study 
of a larger list. 

The general list precedes the descriptive pages of part III dealing 
with a series of specific plant diseases, especially chosen because of the 
author's familiarity with them, or because, they stand out prominently 
as some of the more important diseases, which concern the American 
plant-grower. 

These specific diseases are divided into two groups. One group 
includes the parasitic diseases due to fungi as the causal organisms. The 
other group includes the non-parasitic, or so-called physiologic diseases 
of plants. These have been treated in general in part II of this book, 
but certain of the non-parasitic diseases have become of such general 
interest that they merit a more detailed treatment. The literature of 
these diseases is very much scattered, the only general account being 
one published by Sorauer, Lindau and Reh in their "Handbuch der 
Pfianzenkrankheiten" (3d Edition of Sorauer), 1908. This work is be- 
ing translated by Frances Dorrance. Four parts of Vol. I have been 
printed and the other parts will appear as fast as translated and printed. 
The English edition beginning 1914 is entitled "Manual of Plant Dis- 
eases." To this work the student of plant pathology is referred for 
many details. 

1 Whetzel, H. H. and Collaborators: Laboratory Exercises in Plant 
Pathology, Ithaca, N. Y., 1916. 



414 SPECIAL PLANT PATHOLOGY 

Parasitic Diseases of Plants 

A LIST OF THE COMMON AND IMPORTANT DISEASES OF ECONOMIC 
PLANTS IN THE UNITED STATES AND CANADA 

Alfalfa 

{Medicago saliva, L.) 

Anthracnose {CoUetotrichum trifolii, Bain). 

Journ. MycoL, Vol. XII, p. 192 (1906). 
Bacterial Blight {Psendomonas mcdicaginis Sacket). 

Bull. 212, Colo. Agr. Exp. Sta. (October, 1915). 
Downy Mildew (Peronospora trifoliorum, de By.). 

N. Y. Agr. E.xp. Sta., Bull. 305, p. 394 (1908). 
Leaf -blotch {Pyrenopeziza medicaglnis, Fckl.). 

Phytopathology 6, Abstracts of Columbus Meeting. 
Leaf -spot {Pseudopesiza medicaginis (Lib.), Sacc). 

Ibid., p. 384. 
Root-gall {Urophlyciis alfalfa; (v. Lagerh.), Magn.). 

Duggar, Fungous Diseases of Plants, p. 140 (1909). 
Texas Root-rot {Ozonium omnivorum, Shear.) 

Tex. Agr. Exp. Sta., Bull. 22 (1892). 
Rust {Uromyces slriatus Schrot). 

Bull. 218, Calif. Exp. Sta. (June, 191 1). 

Iowa Bull. 131, p. 209 (April, 1912). 
Violet Root-rot {Rhizodonia crocorum (Pers.) DC.).- 

Phytopathology i, p. 103 (1911). 
Winter Injury. 

N. Y. (Cornell) Agr. Exp. Sta., Bull. 221, p. 6 (1904). 

Almond 
{Prunus amygdalus, Baill.) 

Armillaria Root- Rot {Annillaria mellea, Vahl.). 

Cal. Agr. Exp. Sta., Bull. 218, p. 1084 (191 1). 
Crown-gall {P seudomonas tiimefaciens, E. F. Sm. & Towns). 

Ariz. Agr. Exp. Sta., Bull. t,t, (1900). 
Die-back [N on- par.). 

Cal. Agr. E.xp. Sta., Bull. 218, p. 1086 (1911). 
Rust {Puccinia pruni-spinosm Pers.). 

Duggar, Fungous Diseases of Plants, p. 417 (1909). 
Shot-hole (Cercospora circumcissa, Sacc). 

Journ. MycoL, Vol. VII, p. 66 (1892). 

Ampelopsis 

Leaf-spot {Phyllosticla ampelopsidls, Ell. & Mart, Laestadia BidweUii (Ell.) V. & R. 
and SphcEropsis hedericola (Speg.). 



LIST OF SPECIFIC DISEASES OF PLANTS 415 



N. J. Exp. Sta., Rep. (1914). 
Die-back {Cladosporium sp.). 

N. J. Exp. Sta. Rep. (1914). 

Apple 

{Pirus mains, L.) 

Anthracnose {Gleosporium malicorticis, Cordley; Ascigerous stage said to be Neofab. 
rcea malicorticis (Cordley) Jackson, see Phytopathology 2: 94, 1912). 

Oregon Sta., Biennial Rep., pp. 178-197 (1911-12). 
Arsenical Poisoning. 

Cal. Agr. Exp. Sta., Bull. 131 (1908). 
Bark-canker (Myxosporium corticolum, Edg.). 

Ann Myc, Vol. VI, p. 48 (1908). 
Bitter-rot (Glomerella riifomaculans (Berk.) Spauld. & v. Schr.).' 

Bitter-rot canker, U. S. Dept. Agr. Bur. Plant Industry, Bull. 44 (1903). 
Black-rot {Sphceropsis malornm, Berk.). 

Black-rot Canker. 

N. Y. State Agr. Exp. Sta., Bull. 163 (1899). 

Black-rot Leaf-spot. 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 121, p. 47 (1908). 
Blight (Bacillus amylovorus (Burr.), Trev.). 

Blight-canker, N. Y. (Cornell) Agr. Exp. Sta., Bull. 236 (1906). 

Blossom- blight. Phytopathology, Vol. IV, p. 27 (1914). 

Collar-blight, Penn. Agr. Exp. Sta., Bull. 136, p. 7 (1915). 

Fruit-blight, Ibid., p. 20. 

Twig-blight, N. Y. (Cornell) Agr. Exp. Sta., Bull. 329, p. 322 (1913). 
Blister-canker {Nummularia discreta (Schw.) Tul.). 

111. Agr. Exp. Sta., Bull. 70 (1902). 
Blotch {Phylloslicta solitaria, Ell. & Ev.). 

Blotch canker, U. S. Dept. Agr. Bur. Plant Industry, Bull. 144, p. 10 (1909). 

Blotch leaf-spot. Ibid., p. 11. 

Fruit-blotch, Ibid., p. 9. 
Blossom End Rot (Alternaria sp.). 

N. J. Exp. Sta. Rep., p. 471 (1914). 
Blue Mold Rot (Penicillium spp.). 

Stevens Diseases of Economic Plants, p. 94 (1913). 
Brown-rot^ {Sclerotinia frucligena (Pers.) Schrot.). 
Stevens and Hall; Diseases of Economic Plants, p. 92 (1913). 
Canker (Pacific Coast) {Macrophoma curvispora, Pk.). 

Stevens & Hall, Diseases of Economic Plants, p. 83 (1913). 
Common Rust {Gymnosporangium juniperi-virginlance, Schw.). 

U. S. Dept. Agr., Rep., 1888, p. 376 (1889). 
1 Consult Shear, C. L. and Wood, Anna K: Studies of Fungous Parasites Belong- 
ing to the Genus Glomerella. U. S. Bureau of Plant Industry, Bull. 252, 1913. 

^For apple rots consult Phytopathology 4, p. 403, December, 1914, and Manual 
of Fruit Diseases by Hesler and Whetzel. 



41 6 SPECIAL PLANT PATHOLOGY 

Crown-gall (Pscitdomonas tumefaciens, E. F. Sm. & Towns). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. i86, p. 13 (1910). 

Hairy-root, Ibid., p. 14. 
Fly-speck {Leptothyrium pomi (Mont. & Fr.), Sacc). 

Ohio x\gr. Exp. Sta., Bull. 79, p. 133 (1897). 
Frost-blister (N on- par.). 

N. Y. Agr. Exp. Sta., Bull. 220 (1902). 
Frog-eye Spot {PhyUosticta pirina Sacc.) 

Va. Rep., pp. 95-115, figs. 16 (1911-12). 
Fruit-pit {Non-par.). 

Bull., Torr. Bot. Club, Vol. XXXV, p. 430 (1908). 
i Phyllachora pomigena (Sch-w.), SsLCC. 
Fruit-spot {Phonia pomi, Pass. (Phytopath., Vol. II, pp. 63-72). 
[Sphceropsis malorum, Pk. 

Bull. 121, U. S. Bureau PI. Indst. 
Leaf -spot (Frog-eye) {PhyUosticta pirina, Sacc). 

R. I. Agr. Exp. Sta., Rep. 7, pp. 188-192 (1895). 
Pink-rot {Cephalothecium roseum, Cda.). 

N. Y. Agr. E.xp. Sta., Bull. 227 (1902). 
Powdery Mildew {Podosphcera leucotricha (Ell. & Ev.) Salm. and P. oxyacantlicp {DC.) 
deBy.). 

U. S. Dept. Agr., Bull. 120 (1914). 
Ripe-rot {Glcosporium fructigenum, Berk). 

Journ. Mycol., Vol. VI, pp. 164, 172 (1891). 
Root-rot {Armillaria mcllea Vahl). 

Oregon State Biennial Report, pp. 226-233 (1911-12). 
Scab {Venturia inaequalis (Cke.), Wint.). 

N. Y. (CorneU) Agr. Exp. Sta., Bull. 335 (1913). 

Mont. Bull. 96, pp. 65-102, pi. I, figs. 3 (February, 1914). 
Scab {Fusicladimn dendriticiim (Wallr.) Fckl.) 

Wash. Bull. 64, pp. 24, pis. 2, figs. 5 (1904). 
Rusts {GymtiosporangimnJHniperi.virginiancB Schw. {Rmstelia pi rata (Schw.), Thaxt.); 

G. globosum, Farl. {Ra'stclia laccrata, y, z. Thaxt.). 
Scald {Non-par.). 

Vt. Agr. Exp. Sta., Rep. 10, p. 55 (1897). 
Scurf {PhyUosticta prunicola (Opiz), Sacc). 

Stevens & Hall, Disease of Economic Plants, p. 78 (191 1). 
Silver-leaf {Stercum purpureum, Pers.). 

Phytopathology i, p. 177 (1911). 
Sooty-blotch {Leptothyrium pomi (Mont. & Fr.), Sacc). 

Duggar, Fungous Diseases of Plants, p. 367 (1909). 
Spongy Dry-rot {VolutcUa friicti, Stev. & Hall). 

Duggar, Fungous Diseases of Plants, p. 316 (1909). 
Spray Injury {N on- par.). 

Bordeaux injury, N. Y. Agr. Exp. Sta., Bull, 287 (1907). 

Lime-sulphur injury, Ore. Agr. Exp. Sta., Research Bull. 2 (1913). 



LIST OF SPECIFIC DISEASES OF PLANTS 417 

Stem-blight {Pseiidomonas mcdicaginis, Sackett.) 

Col. Bull. 158, April, 1910, pp. 3-32; Bull. 159, pp. 3-15 (April, 1910). 
Stem-rot {Schizopkylliim commune Fr.) 

Bull. 218, Calif. Agr. Exp. Sta. (June, 191 1). 
Volutella Rot {Voluidla fritcti, Stev. & Hall). 

N. C. Agr. Exp. Sta., Bull. 196, pp. 41-48 (1907). 
Water-core (Non-par.). 

Phytopathology 3, p. 121 (1913). 
Winter Injury (Non-par.). 

Winter bark-splitting, Canada Exp. Farm. Rep., 1908, p. 112 (190S). 

Winter black heart. Ibid., p. 113. 

Winter bud-injury, Mont. Agr. Exp. Sta., Bull. 91 (191 2). 

Winter crotch-injury. Me. Agr. E.xp. Sta., Bull. 164, p. 17 (1909). 

Winter crown-rot, N. Y. Agr. Exp. Sta., Techn. Bull. 12, p. 370 (1909) 

Winter die-back, Canada Exp. Farms, Rep., 1904, p. 108; 1908, p. 113. 

Winter root-injurj^ Iowa Agr. Exp. Sta., Bull. 44, p. 180 (1899). 

Winter sunscald, Canada Exp. Farm Rep., p. 112 (1908). 

Apricot 
(Primus armeniaca, L.) 
Bacteriosis (Pseudomonas pritni, E. F. Sm.). 

N. Y. (Corn.) Agr. Exp. Sta., Mem. 8 (1915). 
Black-knot (Plowrightia morbosa (Schw.), Sacc). 

Bull. 212, Colo. Exp. Sta. (October, 1915). 
Blight (Bacillus amylovorus (Burr.), Trev.) 

Colo. Agr. Exp. Sta., Bull. 84 (1903). 
Blossom-rot (Scleroiinia lihcrliana, Fckl.). 

Cal. Agr. Exp. Sta., Bull. 218, p. 1097 (191 1). 
Brown-rot (Sckrotinia fructigena (Pers.), Schrt.). 

Ibid. 
California Blight (Coryneum Beijerinckit, Oud.). 

Cal. Agr. E.xp. Sta., Bull. 203, p. 33 (1909). 
Die-back (Valsa leucostoma (P.), Fr.) 

Heald & Wolf, Plant Disease Survey, San Antonio, Tex. (1912). 
Gummosis (Various causes). 

Amer. Card., Vol. XIX, p. 606 (1898). 
Shot-hole (Cylindrosporium padi, Karst). 

Heald and Wolf, Plant Disease Survey, San Antonio, Tex. (191 2). 

Arbor-vit.e 
(Thuja occidental is, L.) 
Die-back (Peslalozzia sp.) 

N. J. Agr. E.xp. Sta., Rep., p. 517 (1912). 
Root- rot (Polyporus Schiweinitzii, Fr.). 

U. S. Dept. Agr. Div. Veg., Phys. & Path., Bull. 25, p. 23 (1900). 
27 



41 8 SPECIAL PLANT PATHOLOGY 

Ash 

{Fraxinus sp.) 

Decay, or Brown-rot {Polyporus sulphureus (Bull.), Fr.). 
Heart-rot {Fomes fraxinophilus (Pk,), Sacc). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 32 (1903). 

von Schrenk, H., Diseases of Deciduous Forest Trees, U. S. Bur. of Plant 
Industry, Bull. 149 (1909). 
Leaf-spot {Cercospora fraxinites, Ell. & Ev.; Cylindrosporium viridis, Ell. & Ev., and 

Septoria submaculata, Wint.). 
Rust (yEcidium fraxini, Schw.). 

Rep., Conn. Exp. Sta., p. 304 (1903). 

Asparagus 
(Asparagus offi-cinalis, L.) 
Blight {Cercospora asparagi, Sacc). 

Heald & Wolf, Plant Diseases Survey in Texas (191 2). 
Rust {Puccinia asparagi, DC). 

N. J. Agr. E.xp. Sta., Bull. 129 (1898). 

Calif. Bull. 165, pp. 1-7, 18-9S, 98, 99, figs. 32 (Jan., 1905). 

Aster, China 
{Callistephus chinensis, Nees) 

Rust [Coleosporium solidaginis (Schw.), Thiim). 
Wilt {Fusarium sp.). 

Mass. (Hatch) Agr. Exp. Sta., Bull. 79, p. 5 (1902). 
Yellow (undetermined). 

Ibid., p. I r. 

Azalea 

Rust {Piicciniastrmn minimum (Schw.), Arth.). 
Conn. Exp. Sta., Rep., p. 854 (1907-1908). 

Bamboo 

{Phyllostachys henonis, Mitf. and P. quilioi, Riv.) 

Smut (Ustilago Shiraiana, Henn.). 

Patterson, Flora W. and Charles, Vera K., The Occurrence of Bamboo Smut 
in America. Phytopath. 6, pp. 351-356 (1916). 

Banana 

(Musa spp.) 

Trinidad Bud-rot {Bacillus miisce, Rorer.). 
Phytopath. i, pp. 43-49 (191 1). 



LIST OF SPECIFIC DISEASES OF PLANTS 419 

Ripe Fruit-rot {Gleosporium musorum, Cke. and Mass.). 
Root Disease {Marasmius semiustus, Bri. & Cav.). 

See Cook, Diseases of Tropical Plants, 1889, pp. 133-136 (1913). 

Barley 

{Hordeum sativum, Jess.) 

Anthracnose {CoUetotrkhum cereale, Manns) = graminicola (Ces.) Wilson Phyto- 
path, 4:110. 

Ohio Agr. E.xp. Sta., Bull. 203, pp. 187-212 (1909). 
Covered-smut {Ustilago hordei (Pers.), K. & S.). 

Kan. Agr. Exp. Sta., Rep. 2, p. 269 (1890). 

Nebr. Rep., pp. 45-53) figs- 4 (iQoT)- 
Ergot (Claviceps purpurea (Fr.), Tul.). 

So. Dak. Agr. Exp. Sta., Bull. 33, p. 38 (1893). 
Leaf-rust {Puccmia simplex (Korn), Erikss. & Henn.). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 216 (1911). 
Loose-smut {Ustilago nuda (Jens.), K. & S.). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 152, p. 7 (1909). 
Powdery Mildew {Erysiphe graminis, DC). 

Bull., Ill State Lab. Nat. Hist, Vol. II, pp. 387-432 (1887). 
Scab (Gibberella saubinetii (Mont.), Sacc). 

Ohio Agr. Exp. Sta., Bull. 203, pp. 212-232 (1909). 
Stem-rust {Puccinia graminis, Pers.). 

U. S. Dept. Agr. Bur. Plant Industry, Bull 216 (1911). 
Stripe Disease (Blade-blight) {H dminthos poritim gramineiim, Rabenh.). 

Iowa Agr. E.xp. Sta., Bull. 116, p. 179 (1910). 

Bull. 218, Calif. Agr. Exp. Sta. (June, 1911). 

Bean 

{Phaseolus vulgaris, L.) 

Anthracnose {Colletotrichum lindemuthianum (Sacc. & Magn.), Bri. & Cav.). 

N. Y. Agr. Exp. Sta., Bull. 48, p. 310 (1892). 

Cornell Bull. 255, pp. 431-447, figs. 6 (May, 1908). 

Mich. Spec. Bull. 68, pp. 12 (March, 19 14). 
Bacterial-blight {Bacterium phaseoli, E. F. Sm.). 

N. Y. Agr. Exp. Sta., Bull. 151, p. 11 (1901). 

La. Bull. 139, pp. 43, pis. 6 (January, 19 13). 
Leaf-spot {Cercospora canescens, Ell. & Mart.). 

Heald and Wolf, Plant Disease Survey in Texas. (1912.) 
Damping-off {Fungi spp.). 
Pod-blight {Phoma subcircinata, Ell. & Ev.). 

N, J. Exp. Sta., Rep., p. 472 (1914). 
Rhizoctoniose {Corticium vagum, Bri. & Cav. var. solani Burt). 



420 SPECIAL PLANT PATHOLOGY 

Rhizoctonia damping off, N. Y. (Cornell) Agr. Exp. Sta., Bull. 94, p. 266 (1895). 

Rhizoctonia pod-spot, Science, new ser., Vol. XIX, p. 268 (1904). 

Rhizoctonia stem rot. Science, new ser., Vol. XXXI, p. 796 (1910). 
Rust {Uromyces appendiculatus (Pers.), Lev.). 

N. Y. Agr. Exp. Sta., Bull. 48, p. 331 (1892). 
Southern Blight {Sderoiium Roljsii, Sacc). 

Fla. Agr. Exp. Sta., Bull. 21, p. 27 (1893). 

Bean (Lima) 
(Phaseohis liinalus, L.j 

Bacterial Blight {Pseudomonas phaseoU, E. F. Sm.). 

N. Y. Agr. Exp. Sta., Bull. 48, p. 331 (1892). 
Downy Mildew {Phylophthora phascoli, Thax.). 

Conn. Agr. Exp. Sta., Rep. 167 (1889). 

Beech 

(Fagiis gnindifolia, Ehrh.) 

Sap-rot {Polysticlus pergameniis, Fr.). 

von Schrenk, H., Disease of Desiduous Trees, U. S. Bureau of Plant Industry, 
Bull. 149 (1909). 
White Heart-rot (Pomes igniarlus (L.), Gill.). 

N. Y. (Cornell) Agr. Exp. Sta., Bull. 193, p. 214 (1901). 

Beet 

{Biia vulgaris, L.) ■ 

Bacterial Leaf-spot {Bacterium aptatum, Brown & Jamieson). 

Journ. Agr. Research i, p. 190 (19 13). 
Cercospora Leaf-spot {Cercospora belicola, Sacc). 

N. Y. (Cornell) Agr. Exp. Sta., Bull. 163, p. 352 (1899). 

Nebr. Bull. 73 (1902). 

Poole, V. W. and McKay, M. B., Relation of Stomatal Movement to Infection 
by Cercospora beticola, Journ. Agr. Research 5, pp. 1011-1038 (1916). 
Crown-gall (Pseudomonas tumefaciens, E. F. Sm. & Towns). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 213 (1911). 
Curly-top (undetermined). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 122 (igcS). 

Smith, Ralph E, and Boncquet, P, A.: Connection of a Bacterial Organism 
with Curly Leaf of the Sugar Beet Phytopath. 5 pp. 335-342 (1915). 
Damping-off (Fungi spp.). 
Downy Mildew (Peronospora Schachtii, Fckl.). 

Bull. 218, Calif. Agr. Exp. Sta. (June, 1911). 



LIST OF SPECIFIC DISEASES OF PLANTS 42 1 

Leaf-scorch (Non-par.). 

N. Y. Agr. Exp. Sta. Bull. 162, p. 167 (1899). 
Mosaic (undetermined). 

Science, new ser. Vol. XLII, p. 220 (1915). 
Phoma Crown-rot (Phoma beta: (Oud.) Fr.). 

Frank Die Krankheiten der Pflanzen Zweitl. Aufl. 2, p. 399 (1896). 

Journ. Agr. Research 4, pp. 135-168, pis. 11, pp. 169-177 (1915). 
Phoma Leaf-spot (Phoma beta; (Oud.), Fr.). 

Journ. Agr. Research 4, p. 169 (1915). 
Phoma Root-rot (Phoma beta; (Oud.), Fr.). 

Frank Die Krankheiten der Pflanzen Zweite. Aufl. 2, p. 399. 
Puccinia Rust (Puccinia siibnilens, Diet.). 

Phytopathology 4, p. 204 (1914). 
Rhizoctonia Root-rot (Cortkimn vagiim, Bri. & Cav. var. Solani Burt). 

N. Y. (Corn.) Agr. Exp. Sta., Bull. 163, p. 34 (1899). 
Rust (Uromyces beta;.). 

Bull. 218, Calif. Agr. Exp. Sta. (June, 1911). 
Scab (Actinomyces chromogenes). 

N. Dak. Agr. Exp. Sta., Bull. 4, p. 15 (1891). 
Soft-rot (Bac'erium leutlium, Mete). 

Nebr. Agr. Exp. Sta., Rep. 17, p. 69 (1904). 
Tuberculosis (Bacterium beticolmn, E. F. Sm.). 

Ct. Dept. Agr. Bur. Plant Industry, Bull. 213, p. 194 (1911). 
Uromyces Rust (Uromyces beta; (Pers.), Lev.). 

U. S. Dept Agr. Rep., 1887, p. 350 (1888). 



Bermuda Grass 

(Capriola daclylon (L.), Kuntze) 

Leaf-spot (Helminthos poriiim giganleum, Heald & Wolf). 
Heald and Wolf, Plant Disease Survey in Texas (191 2). 

Birch 

(Bclula spp.) 

Decay (Fomcs fomenlarius (L.), Fr.). 
Red Heart-rot (Fomes ftdvus, Fr.). 

von Schrenk, H., Diseases of Deciduous Forest Trees, U. S. Bureau Plant 
Industry, Bull. 149 (1909). 
Sapwood Decay (Polyporus bclulini(s (Bull.), Fr.). 

von Schrenk, H., p. 57. 
White Heart-rot (Fomes iguiariits (L.), Gill). 

N. Y. (Corn.) Agr. Exp. Sta., Bull. 193, p. 214 (1901). 



422 SPECIAL PLANT PATHOLOGY 

Blackberry 
{Riibus spp.) 

Anthracnose {Gleosporium venetum, Speg.)- 

U. S. Dept. Agr., Rep., 1887, p. 357 (1888). 

Wash. "Bull. 97, pp. 3-18 (1910). 
Cane-blight (Coniothyrium Fuckelii, Sacc). 
Crown-gall {Bacterium tumefaciens, E. F. Sm. & Towns). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 213 (1911). 
Double-blossom (Fiisarium ruhi, Wint.). 

Del. Agr. Exp. Sta., Bull. 93 (191 1). 
Gall {Pycnochytrium globosum, Schrot). 
Late-rust (Kuehneola albida (Kiihn), Magn.). 

Mass. (Hatch) Agr. Exp. Sta., Rep. 9, p. 74 (1897). 
Leaf-spot (Septoria ruhi, Westd.). 

Conn. Agr. Exp. Sta., Rep. 27, p. 309 (1904). 
Orange-rust {Gymnoconia Peckiana (Howe), Tranz). 

111. Agr. Exp. Sta., Bull. 29, pp. 273-300 (1893). 

Box Elder 

{Acer negiindo californicum (T. & G.), Sarg.). 

Leaf-spot {Glwosporlumncgundinis, Ell. & Ev.). 

Leaf-tip Blight {Septoria marginata, Heald & Wolf). 

Leaf-blight Buckeye {Aiscnlus octandra, Marsh). {Phylloslicla cesculi, Ell. & Mart.) 

Boxwood 

{Buxus sp.) 

Leaf-blight {Macrophoma Candollei (B. & Br.), Berl. and Vogl.). 
Leaf and Stem Disease {Volutella buxi (Cda.), Berk.). 

Buckwheat 

{Fagopyrum esculenlum, Moench) 

Leaf-blight {Ramularia rufomaculans, Pk.). 

Descr., Conn. Agr. Exp. Sta., Rep. 14, 1890, p. 98 (1891). 

Butternut 

{Juglans cinerea, L.) 

Leaf-spot {Gnomonia leptostyla (Fr.), Ces. & de Not.). 

Mass. (Hatch) Agr. Exp. Sta., Rep. 10, p. 69 (1898). 



LIST OF SPECIFIC DISEASES OF PLANTS 423 

BUTTONBUSH 

{Ccphalanthiis occidentaUs, L.) 

Leaf-blight {Cercospora perniciosa, Heald and Wolf). 
Leaf-spot {Ramularia cephalanthi (Ell. & Kell.), Heald). 

Cabbage 
{Brasska oleracca, L.) 

Bacterial Leaf-spot {Bacterium maculicoliim, McCul.). 

U. S. Dept. Agr. Bur. Plant Industry, Bull. 225 (191 1). 
Black-leg {Phoma lingam (Tode), Desm.). 

Phytopathology i, p. 28 (1911). 
Black-mold {Allcrnaria hrassicce (Berk.), Sacc). 

U. S. Dept. Agr., Farmers' Bull. 488, p. 31 (191 2). 

Black leaf-spot, Ibid. 

Black-mold storage-rot, Ibid. 
Black-rot {Pseudonionas campeslris (Pam.), E. F. Sm.). 

Wis. Agr. Exp. Sta., Bull. 65 (1898). 
Black-spot {Macros port urn brassiccB, Berk.). {Allcrnaria brassica, (B.), Sacc). 

Va. Agr. Exp. Sta., Rep. (1909-1910). 
Club-root {Plasmodio phora brassica, Wor.). 

Journ. Mycol., Vol. VII, p. 79 (1892). 

Va. Bull. 191, pp. 12, figs. 5 (Apr., 1911). 

Vt. Bull. 175, pp. 1-27, pis. 4, figs. 6 (Oct., 1913)- 
Damping-off {Fungi spp.). 

U. S. Dept. Agr., Farmer's Bull. 488, p. 31 (191 2). 
Downy Mildew {Peronos pora parasitica (Pers.), deBy.). 

Ibid., p. 29. 
Drop {Sclerotinia libertiana, Fckl.). 

Mo. Bot. Card. Rep. 16, p. 149 (1905). 
Leaf-spot {Cercospora Bloxami, B. & Br. (?)). 

Heald and Wolf, Plant Disease Survey in Texas (191 2). 
Root-rot {Corticium vagtini, Bri. & Cav., var. Sclani, Burt.). 
Soft-rot {Bacillus carotovoruss, Jone.) 

Journ. Science, new ser.. Vol. XVI, p. 314 (1902). 
Yellows {Fusarium conglutinans , Wollenw.). 

Ohio Agr. Exp. Sta., Bull. 228, p. 263 (191 1). 

Cacao 

{Theobroma cacao, L.) 

Bark Disease {Corticium javanicum, Ziram. = C. Zimmermanni, Sacc. & Syd.) 
Diseases of Tropical Plants, pp. 180-191 (1913). 



424 SPECIAL PLANT PATHOLOGY 

Black-rot {Phylophlhora Faheri, MaubL). 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Exovin-rot {Thyridaria tarda, HsLncxoit). 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Canker (Nectria theohromcB, Mass., and Caloneclrla jlavida, Massee) 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Pink Disease {Corticium lilacofiiscum, Berk, and Curt.). 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Root Disease {Macrophoma veslila, Prill & Del.). 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Scabby-pod {Lasidoplodia theohromce (Pat.) Griff. & Maubl). 

Diseases of Tropical Plants, pp. 180-191 (1913). 
Seedling Disease {Ramularia nccator, Mass.). 

Diseases of Tropical Plants, pp. 1 80-1 91 (1913). 
Thread-blight (Marasmius equicrinus, Mull.). 

Diseases of Tropical Plants, pp. 180-191 (1913). 

Calla 

{Richard la cthlopica, Spreng.) 

Soft-rot {Bacillus aroidecd, Towns.). 
Leaf-spot {Phyllosticta Richardia, Hals.). 
Black-edge {Cercospora RichardlcBcola, Atk.). 

Carnation 

{Dianthus caryophyllus, L.) 

Alternariose {Alternaria dianthi, Stev. & Hall). 
A.nihxdiCno?,e {Volulella dlanthi, Xikin'i), 

Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 385-386 (1894). 
Bud-rot {Sporotrichum anthrophilmn, Pk.). 

Nebr. Bull. 103, pp. 3-24 (Jan., 1908). 
Leaf-mold or Fairy-ring {Helerosporium cchinulatmn (Berk.), Cke.). 

Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 386 (1894). 
Die-back {Fusarium sp.). 

Descr. Illus., N. Y. Agr. Exp. Sta., Bull. 164, pp. 219-220 (1899). 
Leaf-spot {Septoria dianthi, Desm. and Heterosporlum cchinulatmn). 

Bull. 218, Calif. Agr. E.xp. Sta. (June, 1911). 

Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 384-385 (1894)- 
Rust {Uromyces caryophyllmus (Schrank), Wint.j. 

Descr. Illus., Gar. and For., Vol. V, pp. 18-19 (1892). 

Treat., N. Y. Agr. Exp. Sta., Bull. 100, pp. 50-68 (1896). 

Cf. N. Y. Agr. E.xp. Sta., Bull. 175 (1900). 
Wilt {Fusarium sp.?). 

Descr., Conn. Agr. Exp. Sta., Rep. 21, 1897, pp. 175-181 (1898). 



LIST OF SPECIFIC DISEASES OF PLANTS 425 

Carrot 

(Daucus carota, L.) 

Root-rot {Corlicium vagum, Bfi. & Cav., var. Solani, Burt.)- 
Rot {Phoma sanguinolenla, Grove). 
Soft-rot {Bacillus carotovoriis, Jones). 

Duggar, Fungous Diseases of Plants, p. 131 (1909). 

Catalpa 

{Catalpa hignonloides, Walt.) 

Leaf-blight {Macros porium catalpce, Ell. & Mart.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 364-365 (r888). 

Treat, (rec), U. S. Dep. Agr., Rep. for 1887, p. 366 (1888). 
Leaf-spot {Phyllosticta catalpce, Ell. & Mart.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 364-365 (1888). 

Treat, (rec), U. S. Dep. Agr., Rep. for 1887, p. 366 (1888). 
Soft Heart-rot {Polystictus versicolor (L.), Fr.). 

Stevens, Neil, Mycologia IV, p. 263 (September, 1912). 

Cedar 
{Libocedriis; Thuya; Juniperus) 

Leaf-pit {Keithia thujina, Durand). 

Phytopath 6, pp. 360-363, 1916, on T. plicata. 
Red-rot or "Pecky" Disease {Pomes carneus, Nees). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 21, pp. 16-20 (1900). 
{Gymnosporangium globosum, Farl). 
{Gymnos porangiimt junipcri-virginiance, Sch w. ) . 
Rust 1 Nebr. Rep. i, pp. 103-127, pis. 13, map i (1908). 

{Gymnos porangi urn sabinm, Plowr). 

Duggar, Fungous Diseases of Plants, pp. 425-426. 
White-rot {Polyporusjunipcrinus, v. Schr.). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 21, pp. 7-16 
(1900). 
\\'hitening {Cyanospora albiccdra:, Heald & Wolf). 

Celery 
{Apium graveolcns, L.) 

Bacteriosis {Bacterium apii, Brizi). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 12, 1891, pp. 257-258 (1892). 
Cf. U. S. Dep. Agr., E.xp. Sta. Rec, IX-9, p. 850 (1898). 



426 SPECIAL PLANT PATHOLOGY 

Late-blight (Septoria pdroselini, Desm, var. apii, Br. & Cav.). 

Oregon Sta. Biennial Rep., p. 273 (1911-12). 

Calif. Bull. 208, pp. 83-115, pi. I, figs. 18 (Jan., 1911). 
Leaf-blight {Cercospora apii, Fres.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1886, pp. 11 7-1 20 (1887). 

Treat, (pos.). Conn. Agr. Exp. Sta., Rep. 21, 1897, pp. 167-171 (1898). 
Leaf-spot {Phyllosticia apii, Hals.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 12, 1891, p. 253 (1892). 
Leaf-spot {Septoria petrosclini, Desm., var. apii, Bi. & Cav.). 

Descr. Illus., N. Y. Agr. Exp. Sta., Bull. 51, pp. 137-138 (1893). 

N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 132, pp. 206-215 (1897). 

Treat, (rec), N. Y. Agr. Exp. Sta., Bull. 51, pp. 139-141 (1893). 
Rust {Puccinia bullata (Pers.), Wint.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 12, 1891, p. 256 (1892). 

Century Plant 

{Agave amcricana, L.) 

Blight {Stagonospora gigantea, Heald & Wolf). 
Plant Disease Survey in Texas (1912). 

Cherry 

{Priinus cerasus, L.) 

Black-knot {Ploivrightia morbosa (Schw.), Sacc). 

Descr. Illus., Mass. Agr. Exp. Sta., Rep. 8, 1890, pp. 200-210 (1891). 
N. J. Agr. Exp. Sta.. Bui. 78. pp. 2-10 (1891). 
N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 81, pp. 638-646 (1894). 
Cf. N. Y. Agr. E.xp. Sta., Rep. 12, 1893, pp. 686-688 (1894). 
Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 81, pp. 646-653 (1894). 
Fruit-mold {Sclerotinia cinerea (Bon.), Schrot.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 349-352 (1889). 
Ky. Agr. Exp. Sta., Rep. 2, 1889, pp. 31-34 (1890). 
Mass. Agr. Exp. Sta., Rep. 8, 1890, p. 213 (1891). 
Treat (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 98, p. 409 (1895). 
Leaf-curl {Exoascus cerasi (Fckl.), Sadeb.). 

Descr., N. Y. Agr. Exp. Sta., Rep. 14, 1895, pp. 532-533 (1896). 
Leaf-spot {Cylindrosporium padi, Karst., = Septoria cerasina, Pk.). 
Descr. Illus., Scribner, Fung. Dis., p. 119 (1890). 

Iowa Agr. Exp. Sta., Bull. 13, pp. 61-65 (1891). 
Treat, (pos.), Iowa Agr. Exp. Sta., Bull. 30, pp. 291-294 (1895). 
Leaf-spot {Cercospora cerasella, (Aderh.); Sacc). 
Powdery Mildew {PodosphcEra oxycanth(B (DC), deBy.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 352-356 (1889). 
Treat, (pos.), Iowa Agr. Exp. Sta., BulL 17, pp. 421-433 (1892). 



Twig-blight 



LIST OF SPECIFIC DISEASES OF PLANTS 427 

Rust {Puccinia prtmi-spinoscB, Pers.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 353-354 (1888). 
Scab (Cladosporium carpophilntn, Thiim). 

{Sclerotinia fructigena (Pers.), Schrot.). 

(Sderotinia cinerea (Bon.), Schrot.). 

Chestnut 

{Castanea dentata (Marsh.), Borkh.). 

[ (Cylindrosporium castanicolum (Desm.), Berl.). 
Anthracnose \ {Cryptosporiiim epiphyllum, C. & E.). { = Marssonia ochrolenca 
[ (B. & C), Humph.). 

Treat, (pos.), Amer. Gardening, Vol. XX, p. 559 (1899). 
Blight {Endothia parasitica (Murrill), Anders. Hall). 

Diseases of Economic Plants, p. 436 (igio). 

Conn. Rep., pt. 5, pp. 359-453, pls- 8 (1912). 
Leaf-spot (Marssonia ochrolenca, (Bri. & Cav.), Humph.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 17, 1896, p. 412 (1897). 

Descr., Mass. Agr. Exp. Sta., Rep. 10, 1897, p. 69 (1898). 
Sap-rot {Polysticlus versicolor (L.) Fr.). 

Chrysanthemum 
{Chrysanthemum- sinense, Sabine & C. indicum, L.) 

Leaf-blight {Cylindrosporium chrysanthemi, Ell. & Dearn.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 365-368 (1895). 

Treat, (rec), N. J. Agr. Exp. Sta., Rep. 15, 1894, p. 369 (1895). 
Ray-blight {Ascochyta chrysanthemi, Stev.). 
Leaf-spot {Phylloslicta chrysanthemi, Ell. & Dearn.). 

Occ, N. J. Agr. Exp. Sta., Rep. 15, 1894, p. 368 (1895). 
Leaf-spot {Septoria chrysanthemi, Cav.). {=S. chrysanthemella (Cav.), Sacc.) 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 363-365 (1895). 

Treat, (pos.), N. Y. Agr. Exp. Sta., Rep. 11, 1892, pp. 557-560 (1893). 
Ray-blight {Ascochyta chrysanthemi, Stev.). 
Rust {Puccinia chrysanthemi, Roze). 

Occ, N. J. Agr. Exp. Sta., Circ, Nov. 15 (1899). 

Descr., Treat, (rec), Ind. Agr. Exp. Sta., Bull. 85 (1900). 
Cf. Gardening, Vol. VI, p. 277, '98. 

Chives 

{Allium schosnoprasum, L.) 

Rust {Puccinia porri (Sow.), Wint.). 

Conn. Exp. Sta., Rep., 1909-1910, p. 726. 



428 SPECIAL PLANT PATHOLOGY 

Clematis 

(Clematis spp.) 

Anthracnose (GlcBosponumdcmatldis, Sor.). 
Leaf-spot (Ascochyta clcmatidina, Thiim). 

Journ. Agr. Research 4, pp. 331-342 (igiS)- 
Root-rot (Phoma sp.) 

Descr., N. Y. Agr. Exp. Sta., Rep. 3, 1884, pp. 383-384 (1885). 

Clover 

{Trifolium spp.) 

Anthracnose (Collctolrichum Irifolii, Bain). 
Damping-off (Pythiiim de Baryanum, Hesse). 
Leaf-spot (Pscudopcziza IrifoHi (Pers.), Fckl.). 
Leaf-spot {Phyllachora trifoln (P.), Fckl.). 

Descr., N. J. Agr. Exp. Sta., Rep. 18, 1897, p. 319 (1898). 
Rust (UromycesTrifolii (Hedw. f.),Lev. and U. fallens (Desm.), Kern). 

Descr. lUus., N. Y. (Corn. Univ.) x\gr. Exp. Sta., Bull. 24 (1890). 
Iowa Agr. Exp. Sta., Bull. 13, pp. 51-55 (1891). 
Phytopath. i, pp. 3-6 (February, 191 1). 

Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 24, p. 139 (1890). 
Sooty spot {Polythrincium Irifolii, Kze.). 
Stem-rot {Sclerotinia trifoliorum, Eriks.). 

Descr. lUus., Del. Agr. Exp. Sta., Rep. 3, 1890, pp. 84-88 (1891). 

N. J. Agr. Exp. Sta., Rep. 18, 1897, pp. 314-318 (189S). 

Treat, (rec), Del. Agr. Exp. Sta., Rep. 6, 1893, p. no (1894). 

COCKLEBUR 

{Xanthimn spp.) 



Rust {Piiccinia xantkii, Schw.). 



Coconut 
(Cocos niicifcra) 



Bud-rot {Bacillus coli, (Esch.) Mig.). 

Johnston, John R., The History and Cause of the Coconut Bud Rot, U. S. 
Bureau of Plant Industry, Bull. 228 (191 2). 
Godaveri Disease {Pylkiiim palmivorum, Butler). 

Cook, Diseases of Tropical Plants, pp. 197-206 (1913). 
Leaf Disease {Peslalozzia palmarum, Cooke.) 

Cook, Diseases of Tropical Plants, pp. 197-206 (1913). 
Stem-bleeding {Thiclaviopsis ethacelicus, Went.). 

Cook, Diseases of Tropical Plants, pp. 197-206 (1913). 



LIST OF SPECIFIC DISEASES OF PLANTS 429 

Coffee 
{Coffea arabica.) 

Foot Disease {EiiryachoraUberica, Oud.)- 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915). 
Leaf-rot {Pellicularia koleroga, Cke). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915)- 
Leaf -spot {Cercospora coffeicola, Bri. & Cav.). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915). 
Mancha de Hierro {Sphccroslilbc flavida, Massee). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915). 
Root Disease {Irpcx flaviis, Klotsch). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915). 
Rust {Hemileia vastatrix, Berk. & Broome). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. (Feb. 29, 1915). 
Stem Disease {Nccator dccretus, Mass.). 

Cook, Diseases of Tropical Plants, pp. 160-170 (1913). 

Porto Rico Bull. 17, pp. 29 (Feb., 1915). 

Corn 

{Zca mays, L.) 

Downy Mildew {Scleras pora macros pora, Sacc). 
Leaf-blight {Ilelminthosporiiim inconspicuum, C. & E.). 

Descr. lUus., N. Y. Agr. Exp. Sta., Rep. 15, 1896, p. 452 (1897). 
Dry-rot (Diplodia zece (Schvv.), Lev. = D. maydis (Berk. Sacc). 

Stevens & Hall, Diseases of Economic Plants, p. 335 (1910). 

111. Bull. 133, pp. 73-85, 92-100, pi. I, figs. 20 (Feb., 1909). 
Rust {Puccinia sorglii, Schw. = P. maydis Bereng.) 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, p. 390 (1888). 

Cf. U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 16, p. 65 (1899). 
Smut {Ustilago zecB (Beckm.), Unger) and (U. Reiliana, Kiihn). 

Descr. Illus., Kans. Agr. Exp. Sta., Bull. 62, pp. 179-189 & 198-201 (1896) 
Ind. Agr. Exp. Sta., Rep. 12, pp. 99-112 (1900). 

Treat, (rec), 111. Agr. Exp. Sta., Bull. 57, p. 335 (1900). 
Wilt (Pseudomonas Stewarti, E. F. Sm.). 

Descr. Illus., N. Y. Agr. Exp. Sta., Bull. 130, pp. 423-438 (1897). 

Treat, (rec), N. Y. Agr. Exp. Sta., Bull. 130, pp. 438-439 (1897) 



430 SPECIAL PLANT PATHOLOGY 

Cosmos 

(Cosmos hipinnahis, Cav.) 
Stem-spot {Phlydana sp.). 

Descr. lUus., N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 371-372 (1895). 

Cotton 

{Gossypium spp.) 

Angular Leaf- spot (Bacterium malvacearum, E. F. Sm.). 
Anthracnose (Colletotrichum gossypii, South worth); 

Descr. Illus., Ala. Agr. Exp. Sta., Bull. 41, pp. 40-49 (1892). 

U. S. Dep. Agr., Office Exp. Sta's, Bull. 33, pp. 293-299 (1896). 
Ala. Bull. 153, pp. 27-33 (Feb., 191 1). 
Boll-rot (Bacillus gossypina, Stedm.). 

Descr. Illus., Ala. Agr. Exp. Sta., Bull. 55 (1894). 

Treat, (rec), Ala. Agr. Exp. Sta., Bull. 107, p. 313 (1900). 
Damping-off (Corlicium vagum, B. & C, var. Solani, Burt.). 

Descr., Ala. Agr. Exp. Sta., Bull. 41, pp. 30-39 (1892). 

Cf. Ala. Agr. Exp. Sta., Bull. 107, pp. 295-296 (1900). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 355-356 (1888). 
Ala. Agr. E.\p. Sta., Bull. 41, pp. 58-61 (1892). 
Leaf-mold (Ramularia areola, Atk.). 

Descr. Illus., Ala. Agr. Exp. Sta., Bull. 41, pp. 55-58 (1892). 
Root-rot (Ozonium omnivormn, Shear). 

Descr. Illus., Tex. Agr. Exp. Sta., Rep. 2, 1889, pp. 67-76 (1890). 

U. S. Dep. Agr., Office Exp. Sta's, Bull. 2,3, P- 300 (1896). 

Treat, (rec), U. S. Dep. Agr., Office Exp. Sta's, Bull. 2,2,, p. 304 (1896). 
Rust (Uredo gossypii, Lagerh.) and (Mcidiiim gossypii. Ell. & Ev.). 

Descr., Journ. Mycol., Vol. VII, pp. 47-48 (1891). 
Texas Root-rot (Ozonium omnivorum, Shear). 
Smut (Doassansia gossypii, Lagerh.). 

Descr., Journ. Mycol., Vol. VII, pp. 48-49 (1891). 
Wilt (Neocosmospora vasinfecta (Atk.), Smith). 

Descr. Illus., Ala. Agr. E.xp. Sta., Bull. 41, pp. 19-29 (1892). 

U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 17 (1899). 

Cow Pea 
(Vigna catjang) 

Angular Leaf-spot (Cercospora cruenta, Sacc). 

Stevens and Hall, Diseases of Economic Plants, p. 395 (1910). 
Leaf-spot (Amerosporium cecotunnicum, Ell. & Tracy). 

Stevens & Hall, p. 394 (1910). 



LIST OF SPECIFIC DISEASES OF PLANTS 43 1 

Rust (Uromyces appendiculatus (P.), Lk.). 

Wilt (Neocosmospora vasinfecta (Atk.), E. F. Sm.)- 

Cranberry 
(Vaccinium oxycoccus, L.) 

Anthracnose {Glomerella rujomaculans (Berk.) Sp. & v. Schr. var. vaccinii, Shear). 
Gall [Synchytrium Vaccinii, Thomas). 

Descr. lUus., N. J. Agr. Exp. Sta., Bull. 64, pp. 4-9 (1889). 

Treat, (rec), N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 2,2>3 (1891). 
Hypertrophy (Exobasidium oxy cocci, Rost = Ex. vaccinii (Fckl.) Wor.). 
Rot (Acanlhorhynchus vaccinii. Shear). 

Shear, C. L., Bull. 10, U. S. Bur. Plant Industry. 
"Scald" {Guignardia vaccinii, Shear). 

Descr. lUus., N. J. Agr. Exp. Sta., Bull. 64, pp. 30-34 (1889). 

Treat, (rec), N. J. Agr. Exp. Sta., Bull. 64, pp. 39-40 (1889). 
Sclerotial Disease {Sclerotinia oxycocci, Wor.). 
Spot {Pestalozzia Guepini, Desm., var. vaccinii. Shear). 

Cucumber 

{Cucitmis sativus, L.) 

Anthracnose {Colletolrichum lagenarium (Pass.), Ell. & Hals.). 

Descr. lUus., Ohio Agr. Exp. Sta., BuU. 89, pp. 109-110 (1897). 

Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 17, 1896, pp. 340-343 (1897). 
W. Va. Bull. 94, pp. 127-138, pis. 5 (Dec. 2, 1904). 
Bacteriosis or Wilt {Bacillus tracheiphilns, E. F. Sm.). 
"Damping-off" or Seedling-Mildew {Pythium de Baryanum, Hesse). 

Descr. lUus., Mass. Agr. E.xp. Sta., Rep. 8, 1890, p. 220 (1891). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 8, 1890, p. 221 (1891). 
Downy Mildew {Plasmopara cubensis (Bri. & Cav.), Humphrey). 

Descr. lUus., N. Y. Agr. Exp. Sta., Bull. 119, pp. 158-165 (1897). 
Ohio Agr. Exp. Sta., Bull. 89, pp. 103-108 (1897). 

Cf. Ohio Agr. Exp. Sta., Bull. 105, pp. 219-220 (1899). 

Treat, (pos.), Ohio Agr. Exp. Sta., BuU. 105, pp. 223-229 (1899). 
Leaf-glaze {Acremonium sp.). 

Descr., Mass. Agr. Exp. Sta., Rep. 9, 1891, p. 227 (1892). 

Illus., Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 230 (1893). 
Leaf-spot {Phyllosticta cuciirbitacearum, Sacc). 

Occ, Ohio Agr. Exp. Sta., Bull. 105, p. 222 (1899). 
Powdery Mildew {Erysiphe polygoni, DC). 

Descr. Illus., Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 225 (1893). 

Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., BuU. 31, p. 138 (1891). 
Mass. Agr. Exp. Sta., Rep. 9, 1891, p. 225 (1892). 



432 SPECIAL PLANT PATHOLOGY 

Scab {Cladosporium cncunierinum, Ell. & Arth.). 

Descr. lUus., Ind. Agr. Exp. Sta., Bull. 19, pp. 8-10 (1889). 

Mass. Agr. Exp. Sta., Rep. 10, 1892, pp. 227-229 (1893). 
Stem-rot {Sclerolinia libertiana, Fckl.). 

Descr. lUus., Mass. Agr. Exp. Sta., Rep. 10, 1892, pp. 212-224 (1893). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 222 (1893). 

Currant 
{Rlbes, spp.) 

Anthracnose {Gloeosporium rihis (Lib.), Mont. & Desm.). 

Descr. lUus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 15, p. 196 (1889). 
Cane- wilt {Dothiorella). 

Descr., N. Y. Agr. Exp. Sta., Bull. 167, pp. 292-294 (1899). 
Cane-blight {Neclria cinnabarina (Tode), Fr.). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 125 (1897). 

Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 125, p. 38 (1897). 
Knot {Pleonectria beroUnensis, Sacc). 

Cornell Agr. Exp. Sta., Bull. 125 (February, 1897). 
Leaf-spot {Septoria rihis, Desm., and Cercospora angulata, Wint.). 

Descr. Illus., Iowa Agr. Exp. Sta., Bull. 13, pp. 68-69 (1891). 

Treat, (pos.), Iowa Agr. Exp. Sta., Bull. 30, pp. 289-291 (1895). 
Powdery Mildew {Sphcerotheca mors-itvce (Schw.), Bri. & Cav.). 
Rust {Puccinia Ribis, DC). 

See U. S. Dep. Agr., Exp. Sta. Rec, X-6, p. 559 (1899). 
Wilt {BotryosphcBria ribis, Gross. & Dug.). 

N. Y. Techn. Bull. 18, pp. 1 13-190, pis. 2, fig. i (July, 1911). 

{Cronartium ribicola, Diet.), representing the uredo- and teleuto-stages of the 
white pine blister rust, Peridermium slrobi, Kleb, a serious disease of 
white pines against which a strict quarantine is maintained. 
N. Y. State Techn. Bull. 2, pp. 61-74, pls. 3 (1906). 

Cyclamen 

Dark Leaf -spot (Phoma cydamena, Halst.). 

Watery Leaf-spot (Glomerclla rufomaculans (Berk.), Spauld. & v. Schr., var. 
cyclaminis, Patt. & Ch.). 

Cypress 
{Taxodium distichiim (L.), Rich.) 

Leaf -blight {Pestalozzia funerea, Desm.). 
"Pecky" Disease {Fungus indet.). 



LIST OF SPECIFIC DISEASES OF PLANTS 433 

Dandelion 

{Taraxacum officinale, Web.) 
Leaf-spot {Ramtilaria taraxaci Karst.)- 



Conn. Agr. Exp. Sta., Rep., p. 862 (1907-08). 



Egg-plant 

{Solanum meJongena, L.) 

Anthracnose {Ghvosporiitm melongcnce. Ell. & Hals.). 

Occ, N. J. Agr. E.xp. Sta., Rep. 12, 1891, p. 281 (1892). 

Cf. N. J. Agr. Exp. Sta., Rep. 13, pp. 330-333 (1892). 
Blight {Pseudomonas solanacearum, E. F. Sm.). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 12 (1896). 

Treat, (rec), U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 12, pp. 23-24 
(1896). 
"Damping-off," or "Seedling-mildew" {Pylhium de Baryannm, Hesse). 

Descr., N. J. Agr. Exp. Sta., Rep. 13, 1892, p. 286 (1893). 
Fruit-mold, Gray Mold {Botrylis fascicularis (Cord.), Sacc). 

Descr., N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 357 (1891). 
Leaf-spot Phomopsis vexans (Sacc. & Wint.), Hart. = Ascochyla hortorum (Speg.), 

C. O. Smith, a fruit rot). 

Journ. Agr. Research H, pp. 331-338, pis. 5 (1914). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 11, 189c, pp. 355-357 (1891). 

Del. Bull. 70, pp. 10-15, pi. I, figs. 2 (March, 1905). 

Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 17, 1896, pp. 337-340 (1897). 
Rot {Penicilliiim sp.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 362-366 (1894). 
Seedling-rot {Phomopsis vexans, Sacc. & Syd., Hart.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 12, 1891, pp. 277-279 (1892). 

Treat, (rec), N. J. Agr. Exp. Sta., Rep. 12, 1891, p. 279 (1892). 
Stem-rot {Neciria ipomcecE, Hals.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 12, 1891, pp. 281-283 (1892), 

Elder 
{SambucHS canadensis, L.) 
Rust {Aecidiiim samhiici, Sacc). 
Leaf- spot {Ccrcospora catenas pora, Atk.). 

Elm 

(Ulmus spp.) 

Black-spot {Dolhidella idmi (Duv.), Wint.) and {Gnomonia uhnea (Sacc), Thiim ) 
Blister-canker {Nmnmularia discreta, (Schw.) TuL). 
Duggar, p. 282 (1909). 
28 



434 ' SPECIAL PLANT PATHOLOGY 

Leaf-scab (Gnomonia nlmea (Sacc), Thiim.). 
White-rot {Polyporus squamosus (Huds.), Fr.)- 
Duggar, p. 453 (1909). 

English Ivy 
{Hedera helix, L.) 

Anthracnose {CoUetolrichum glceosporioides, Penz, var. hedera, Pass. 
Leaf-blight {Phyllosticla concentrica, Sacc). 
Leaf-spot {Ramidaria hedericola, Heald & Wolf). 



Evening Primrose 
{Oenothera biennis, L.). 

Gall, or Chytridiose {Synchytriiim fulgens, Schrot.). 
Duggar, p. 139 (1909). 

. Fig 
{Ficiis carica, L.) 

Anthracnose {Glomerella riifomaculans (Berk.) Spauld & von Schr. = G. Jrucligena 

(Clint.), Sacc.) 
Canker {Tubercularia fici, Edgerton). 

Cook, Diseases of Tropical Plants, p. 139 (19 13). 

Phytopath. i, pp. 12-17 (February, 191 1). 
Die-back {Diplodia sycina, Mont., var. syconophila, Sacc). 
Fruit-rot {Glomerella riifomaculans (Berk. Spauld. & von Schr.). 
Leaf-blight {Cercospora Bolleana (Thiim.), Sacc). 

Occ, U. S. Dep. Agr., Div. Pomol., Bull. 5, pp. 27-28 (1897) 
Leaf-spot {Cercospora fici, H. & W.). 
Limb-blight {Corticium latum, Karst.). 
Rust {Uredofici, Cast. = Physopella fici (Cast.), Arth.). 

Occ, N. C. Agr. Exp. Sta., Bull. 92, p. 117 (1893). 
Scab {Fusarium roseum, Lk.) . 

Occ, N. C. Agr. Exp. Sta., Bull. 92, p. 117 (1893). 
Soft-rot {Rhizopus nigricans Ehrenb.). 

La. Agr. Exp. Sta., Bull. 126 (March, 1911). 



Filbert 

{Corylus avellana, L. and C amerlcana, Walt.) 

Black-knot {Cryptosporella anomala (Pk.), Sacc). 

Descr., N. J. Agr.Exp. Sta., Rep. 13, 1892, pp. 287-289 (1893). 



LIST OF SPECIFIC DISEASES OF PLANTS 435 

Fir 

{Abies balsamea (L.), Miller) 



Dry-rot {Trametes pini (Brot.), Fr.) 
Root-rot {Polyporus Schweinitzii, Fr.) 
Wet-rot {Polyporus subacidus, Pk.?) 
Rust {Aecidium elatinum, Alb. & Schw.) 



Descr. Illus., U. S. Dept. Agr., Div. Veg. 
Phys. & Path., Bull. 25 (1900). 



Flax 

{Liniim spp.) 

Rust {Melampsora lini (DC), Tul.). 

Occ, Journ. Mycol., Vol. V, p. 215 (1889). 
Wilt {Fusariiim lini, BoUey). 

Stevens & Hall, Diseases of Economic Plants, p. 406 (1910). 

N. Dak. Bull. 50, December, 1901, pp. 27-60, figs. 18. 

Geranium 

{Pelargonium spp.) 
Leaf-spot {Bacteria'^). 

Descr., Mass. Agr. Exp. Sta., Rep. le, 1899, p. 57 (1900). 
Kot {Bacillus i^.). 

Descr. Illus., Journ. Mycol., Vol. VI, pp. 114-115 (1891). 

Ginseng 

{Panax quinquefolium, L.).^ 

Anthracnose {Vermicular ia dematium (Pers.), Fr.). 
Blight {Alternaria panax, Whetz). 
Leaf Anthracnose {Pestolozzia funerea, Desm.). 

Wilt {Neocosmopara lasinfectum (Atk.) E. F. Sm. var nivea (Atk.) E. F. Sm.). 
Mo. Bull. 69 (October, 1905). 

Gladiolus 

Hard-rot {Septoria gladioli, Passer). 

Phytopathology 6 (Columbus Meeting Abstracts). 

GOLDENROD 

{Solidago spp.) 

Red-rust {Coleosporium solidaginis (Schw.), Thum). 
Rust Uromyces solidaginis (Somm.), Niessl. 

1 See Whetzel, H. H.: The Diseases of Ginseng and Their Control, U. S. Bur. 
of Plant Industry, Bull. 250 (191 2). 



436 SPECIAL PLANT PATHOLOGY 

Gooseberry 

{Ribes grossularia, L.) 

Leaf-spot {Septoria ribis, Desm., and Cercospora angulata, Wint.)- 
Leaf-spot {Sphmrella grossularia (Fr.), Awd.?). 

Occ. Illus., Iowa x\gr. Exp. Sta., Bull. 13, p. 70 (1891). 
Powdery Mildew {Spkarotheca mors-uvcR (Schw.), Bri. & Cav.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 373-378 (1888). 
Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 240 (1893). 

Treat, (pos.), N. Y. Agr. Exp. Sta., Bull. 161 (1899). 
Root-rot {Dcmatophora sp.?). 

Descr., N. Y. Agr. Exp. Sta., Bull. 167, pp. 295-296 (1899). 
Rust {Aecidium grossularicB, Schum.). 

Descr., Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 241 (1893). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 241 (1893). 

Grape 

{Vilis spp.) 

Anthracnose {S phaceloma ampdinitm, deBy. = GJocosporium ampdophagmn (Pass.) 
Sacc). 
Descr. Illus., Tenn. Agr. Exp. Sta., Bull. IV-4, pp. 111-112 (1891). 
Descr., U. S. Dep. Agr., Div. Veg. Path., Bull. 2, pp. 170-172 (1892). 
Shear, C. L. Grape Anthracnose in America. Rep. Int. Congr. Viticulture, 

San Francisco, July 11-13, 191 5: 111-117. 
Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 76, p. 443 (1894). 
Hawkins, LonA. Circ. 105, Bureau PI. Industry, 1913. 
Bacteriosis {Bacillus sp.). 

See U. S. Dep. Agr., Exp. Sta. Rec, VI-3, pp. 231-232. 
Bitter-rot {Melanconium fuligincmn (Scrib. & Viala.), Cav.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 324-325 (1888). 

Scribner, Fung. Dis., pp. 37-40 (1890). 
Cf. N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 61, pp. 302-305. 
Black-rot {Guignardia {Lacsiadia) BidweUii (Ell.), Viola. & Rav. and G. ba'cca (Cav.), 
Jacq.). 
Descr. Illus., U. S. Dep. Agr., Rep. for 1886, pp. 109-111 (1887). 
Del. Agr. Exp. Sta., Bull. 6, pp. 18-27 (1889). 
Tenn. Agr. Exp. Sta., Bull. IV-4, pp. 97-102 (1891). 
Tex. Agr. Exp. Sta., Bull. 23, pp. 219-228 (1892). 
Penna. Bull. 66, pp. 1-16, pis. 2, map. i (Jan., 1904). 
N. Y. Cornell Bull. 293, pp. 289-364, pis. 5 (March, 191 1). 
Treat, (pos.), Conn. Agr. Exp. Sta., Rep. 14, 1890, pp. loo-ioi (1891). 
U. S. Dep. Agr., Farm. Bull. 4, pp. 8-9 (1891). 
Tex. Agr. Exp. Sta., Bull. 23, pp. 228-231 (1892). 



LIST OF SPECIFIC DISEASES OF PLANTS 437 

Chytridiose {Cladochylrium vilicolum, Prunet.). 

See U. S. Dep. Agr., Exp. Sta. Rec, VI-7, pp. 642-644 (1895). 
Dead-arm {Cryplosporella viticola, Shear.). 
Circ. 55, N. J. Agr. Exp. Sta. 
N. Y. State Bull. 389, pp. 463-490 (Julj', 1914). 
Phytopath. i, pp. 116-119 (1911). 
Uowny Mildew (Plasmopara viticola (B. & C), Berl. & De Ton.). 
Descr. IIlus., U. S. Dep. Agr., Rep. for 1886, pp. 96-99 (1887). 
Tenn. Agr. E.\p. Sta., Bull. IV-4, p. 108 (1891). 
Mich. Agr. E.xp. Sta., Bull 83, pp. 9-12 (1892). 
Phytopath. 2, pp. 235-249 (1912). 
Treat, (pos.), U. S. Dep. Agr., Farm. Bull. 4, p. 8 (1891). 
Fruit- mold (Bolrytis sp.). 
Leaf-blight Isariopsis claviipora (B. & C.) Socc. 

Descr. Illus., Scribner, Fung. Dis., pp. 60-62 (1890). 

N. Y. Agr. Exp. Sta., Rep. 9, 1890, p. 324 (1891). 
Cornell Bull. 76, November, 1894. 
Treat, (rec), N. C. Agr. Exp. Sta., Bull. 92, p. 122 (1893). 
Leaf-mold {Leptosporium hderosporum, Ell. & Gall.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 381-383 (1889). 
Leaf-spot {Isariopsis davispora, Sacc). 

N. J. Exp. Sta., Rep., p. 474 (1914). 
Powdery Mildew {Uncimda necator (Schw.), Burr.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1886, pp. 105-108 (1887). 

N. Y. Agr. Exp. Sta., Rep. 9, 1890, pp. 322-323 (1891). 
U. S. Dep. Agr., Div. Veg. Path., Bull. 2, pp. 166-170 (1892). 
Treat, (pos.), U. S. Dep. Agr., Farm. BulL 4, p. 8 (1891). 

N. C. Agr. E.xp. Sta., Bull. 92, pp. 120-121 (1893). 
Ripe- rot or Anthracnose {Glceosporium fructigemim, Berk.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1890. p. 408 (1891). 
Journ. Mycol., Vol. VI, pp. 164-171 (1891). 
Root- rot {Demalophora necatrix, Hartig). 

Descr. Illus., Scribner, Fung. Dis., pp. 64-69 (1890). 

U. S. Dep. Agr., Div. Veg. Path., Bull. 2, pp. 153-159 (1892), 
Treat. N. C. Agr. Exp. Sta., Bull. 92, p. 122 (1893). 
Root-rot {Annillaria mcllca, Vahl.). 

Stevens & Hall, Diseases of Economic Plants, p. 173 (1910). 
Scab (Cladosporium vilicolum, Ces. = Cercospora viticola (Ces.) Sacc.) 

Descr., U. S. Dep. Agr., Div. Veg. Path., Bull. 2, pp. 173-174 (1892). 
Scald {Aureobasidium litis, Viala & Boyer). 

See U. S. Dep. Agr., E.xp. Sta. Rec, VI-3, pp. 230-231 (1894). 
Twig-blight {Bolrytis cinerea, Pers.). 

White-rot {Charrinia diphdiella, Viala & Rav.; Syn. Coniolhyriiim diplodidla 
(Speg.) Sacc). 
Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 325-326 (1888). 

Scribner, Fung. Dis., pp. 41-44 (1890). 
Treat, (pos.), U. S. Dep. Agr., Sec. Veg. Path., Bull. 11, p. 69 (1890). 



438 SPECIAL PLANT PATHOLOGY 

GUAVA 

{Psidium guajava, L.) 

Ripe-rot {Glonierclla psidii (G. Del.) Sheldon). 

Stevens & Hall, Diseases of Economic Plants, p. 191 (1910). 
W. Va. Bull. 104, pp. 299-315 (April, 1906). 

Hackberry 

{Cellis spp.) 

Leaf-spot {Cylindros poriuni defoliaium, Heald and Wolf and {Ramularia ccUidis, 

EU. & Kell.). 
Powdery Mildew {Uncinula polychccta, Bri. and Cav.). 

Hazel 

{Corylus spp.) 

Black-knot {Cryplosporella anomala (Pk.), Sacc). 

Descr. lUus., Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 242 (1893). 
Treat, (rec), Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 243 (1893). 

Hemlock 
{Tsuga canadensis (L.), Carr.) 

Dry-rot {Trametcs pini (Brot.), Fr.). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25 (1900). 
Heart-rot {Polyporus borealis (Wahl.), Fr.). 

Bull. 193 Corn. Univ. Agr. Exp. Sta. (June, 1901). 
Timber Rot {Fames pinicola, Fr.) . 

Graves, A. H., Phytopath. 4, p. 69 (April, 1914). 
Wet-rot {Polyporus siihacidus, Pk. ?) . 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25 (1900). 
Rust {Peridermium Peckii, Thiim.) . 

Phytopath. i, pp. 94-96 (191 1). 

Hemp 

{Cannabis saliva, L.) 

Leaf- wilt {Bolryosphceria Marconii (Cav.), Charles & Jenkins). 
Journ. of Agr. Research 3, pp. 81-84 (Oct. 15, 1914). 

Hickory 

{Carya spp.) 
Leaf-spot {Marsonia juglandis (Lib.), Sacc). 



LIST OF SPECIFIC DISEASES OF PLANTS 439 

Hollyhock 
{AlthcEa rosea, Cav.) 

Anthracnose {Colletolrichum malvarum (Braun. & Casp.), Southworth). 

Descr. Illus., Journ. Mycol., Vol. VI, pp. 46-48 (1890). 

Treat, (pos.), Journ. Mycol., Vol. VI, p. 50 (1890). 

N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 362 (1891). 
Leaf-blight [Cercospora althaina, Sacc). 

Descr., N. j. Agr. Exp. Sta., Rep. 11, 1890, p. 361 (1891). 

Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 361 (1891). 
Leaf-Spot {Phyllosticta althmina, Sacc.).^ 

Descr., N. J. Agr. Exp. Sta., Rep. 12, 1891, p. 297 (1892). 
Rust {Puccinia malvacearum, Mont.). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 25, p. 154 (1890). 
Phytopath. i, pp. 53-62 (191 1). 

Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 25, p. 155 (1890). 
Rust {Puccinia helerogenea, Lagerh.) 

Descr. Illus., Journ. Mycol., Vol. VII, pp. 44-47 (1891). 

Hop 

{Humuliis japonicus, Sieb & Zucc.) 

Powdery Mildew {Spharotheca hiimtdi (DC), Burr.). 

N. Y. Corn. Bull. 328, pp. 281-310, figs. 19 (March, 1913). 

N. Y. State Bull. 395, pp. 29-80, pis. 2, figs. 2 (February, 1915). 

Horse-chestnut 

{jEschIus hippocastaniim, L.) 

Leaf-blotch {Gitignardia csscidi (Pk.) Stewart). Phytopath. 6, 5-19, 1916. 
Leaf-spot {Phyllosticta pavice, Desm.). 

Descr., N. Y. Agr. Exp. Sta., Rep. 15, 1896, p. 456 (1897). 
Tr. (pos.), Journ. Mycol. Vol. VII, p. 353; Phytopathology 4, 399 (December, 
1914) 

Horseradish 

{Cochlearia armoracia, L.) 

Leaf-blight {Ramularia armoracia, Fckl.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 360 (1891). 
Leaf- mold {M acres porium herculeum. Ell. & Mart.). 

Occ, N. Y. Agr. Exp. Sta., Rep. 15, 1896, p. 452 (1897). 
' The dififerent species of Phyllosticta will be found described in The North Ameri- 
can Phyllostictas with Descriptions of the Species, published up to August, 1900 by 
J. B. Ellis and B. M. Everhart, Vineland, N. J., December, 1900. 



440 SPECIAL PLANT PATHOLOGY 

Leaf-spot {Scploria armoracice, Sacc.)- 

Descr., N. J. Agr. Exp. Sta., Rep. ii, 1890, p. 360 (1891). 

Huckleberry 
(Gaylussacia sp.) 
Gall {Exohasidiitm vaccinii (Fckl.) Wor.j. 

Hyacinth 
{Hyacintlius oricnlalis, L.) 
Yellow Disease {Pscudomonas hyacinihi (Wakk.) E. F. Sm.). 

Hydrangea 

{Hydrangea horlensia, Siebold) 

Leaf-spot {Pliyllostkta hydrangea, Ell. & Ev.). 

Occ, N. J. Agr. Exp. Sta., Rep. 12, 1891, p. 298 (1892). 
Rust {Melampsora Hydrangea = Thecopsora hydrangea B. & C.) Magn. 

Incense Cedar 
{Libocedrus decurrens, Torr.) 

Dry-rot {Poly poms amarus, Hedgcock). 

Rust {Gymnosporanglum Blasdaleanum (Diet. & Holw.) Kern). 

Meinecke, E. A., Forest Tree Diseases Common in California and Nevada, 1914. 

Iris 

{Iris spp.) 

Bulb-spot {Mystrosporium adustum, Mass.). 
Leaf-blight {Botrytis galanthina, (B. & Br.) Sacc). 

Johnson Grass 
{Andropogon halepensis (L.), Brot.). 

Leaf-blight {Helminthosporiuni turcicum Pass, and Septoria pcrlitsa Heald & Wolf). 
Leaf-spot {Cercospora sorghi (Ell. & Ev.) and Colletolrichiim lineola Cda var. hale- 

pense, Heald & Wolf). 
Rust {Puccinia purpurea, Cke.). 

Kaffir Corn 

{Sorghum vulgare, Pers.) 

Grain Smut {Sphacetolheca sorghi Lk.) Clint. 
Clint Conn., Exp. Sta. Rep., p. 351 (1912). 



LIST OF SPECIFIC DISEASES OF PLANTS 441 

Larch 

(Larix lan'cina (DR.) Koch) 

Canker (Dasyscypha Willkommii, Hartig). 
Dry-rot (Tramdes pint (Brot.) Fr.). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25, pp. 31-40 
(1900). 

Laurel 

{Kalmla laiijolia, L.) 

Leaf-spot {Seploria kalniicola (Schw.) Bri. & Cav.). 

Lemon 
{Citrus mcdica, L. var. Union, L.) 

Black pit {Bacillus citripuleale spp.) 

Coit, Citrus Fruits, p. 401, 1915; Phytopath. 3, pp. 277-281 (1913). 
Brown-rot {Pythiacystis dtrophthora, R. E. Smith). 

Calif. Bull. 190, pp. 1-72, pi. I, figs. 30 (July, 1907). 
Foot-rot {Fusisporium limonis, Bri.). 
Cotton-rot {Sclerotinia libertiana, Fuckl.j. Phytopath. 6, pp. 268-278 (1916). 

Fruit-spot {Trichoseploria alpci, Cav.). 
Leaf-spot {Ccrcospora aurantia.^ Heald & Wolf). 
Melanose {Fungus indel?). 

Canker {Pscudomonas citri, Hassej. Journ. Agr., Res. 4: 97-150 (1915). 
Scab {Cladosporium, sp.). 

Descr. Illus., U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 8, pp. 20-23 
(1896). 

Treat, (pos.), U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 8, pp. 23-24 
(1896). 
Sooty- mold {Mcliola Penzigi, Sacc. and M. Camdlice (Catt.), Sacc.j. 
Twig- blight {Diplodia aurantii, Catt and Sphceropsis maloruin, Berk.). 
White-rot {Sclerotinia libertiana Fckl.) Bull. 218, Calif. Agr. Exp. Sta. (June, 191 1). 
Wither-tip {Colletotrichum glceosporioidcs Penz. 

Plant Disease, Survey San Antonio Texas (191 2). 

Lettuce 
{Lactuca sativa, L.) 

Anthracnose {Marssonia perforans, Ell & Ev-.). 

Descr. Illus., Ohio Agr. Exp. Sta., Bull. 73, pp. 222-223 (1897). 
Treat, (rec), Ohio Agr. Exp. Sta., Bull. 73, pp. 225-226 (1897J. 



442 SPECIAL PLANT PATHOLOGY 

Downy Mildew (Breniia lacluca, Regel). 

Descr. Illus., N. Y. Agr. Exp. Sta., Rep. 4, 1885, p. 253 (1886). 

Treat, (pos.), Ohio Agr. Exp. Sta., Bull. 73, p. 226 (1897). 
Drop {Schrotinia libertiana, Fckl.). 

Descr. Illus., Mass. Agr. Exp. Sta., Bull. 69, pp. 12-15 (1900). 

N. C. Bull. 217, 1-21, figs. 8 (July, 1911). 

Treat, (pos.), Mass. Agr. Exp. Sta., Bull. 69, pp. 17-35 (19°°) 
Leaf-mold, Gray Mold or Rot {Botrytis cinerea, Pers.;. 

Descr. Illus., Mass. Agr. Exp. Sta., Bull. 69, pp. 7-12 (1900). 
Leaf-rot {Rhizoclonia sp.). 

Descr. Illus., Mass. Agr. Exp. Sta., Bull. 69, pp. 16-17 (1900) 

Treat, (pos.j, Mass. Agr. Exp. Sta., Bull. 69, pp. 39-40 (1900). 
Leaf-spot {Septoria conslmilis, Ell. & Mart.). 

Descr. Illus., Ohio Agr. Exp. Sta., Bull. 44, pp. 145-146 (1892) 
Stem-rot (Bacterial). 

Descr., Vt. Agr. Exp. Sta., Rep. 6, 1892, p. 87 (1893). 

Treat, (rec.) Vt. Agr. Exp. Sta., Rep. 6, 1892, p. 88 (1893). 

Lilac 

{Syringa vulgaris, L.) 

Leaf-spot {Phyllosticta Halstedii, Ell. & Ev.). 
Powdery Mildew {Microsphcera aim (Wallr.) Wint.). 
Leaf-blight {Cercospora macromaculans. Heald & Wolf). 

Lily 
(Liliiim spp.) 
Bermuda Disease. 

See U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 14 (1897) 
Bulb-rot {Rhizopus necans, Massee). 
Mold or Ward's Disease {Sclerotinia Fuckcliana deBy.). 
Treat, (pos.). Gar. and For., IX-414, p. 44 (1896). 
See N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 392-394 (1894) 

Linden 
{Tilia spp.) 

Leaf-blight {Cercospora microsora, Sacc). 

Occ, N. Y. Agr. Exp. Sta., Rep. 15, 1896, p. 454 (1897). 
Stem-rot {Botrytis cinerea, Pers.). 

Locust 
{Rohinia pseiidacacia, L.) 

Leaf-spot {Cylindrosporium solitarinm, Heald & Wolf). 
Heart-rot {Trametes robiniophila, Murr. and Fames rimosus Berk.) . 
Diseases of Deciduous Trees (1909). 



LIST OF SPECIFIC DISEASES OF PLANTS 44^3, 

LOQUAT 

(Eriobotrya japonica, Lindl.) 
Scab {Fitsicladium dendrUicum (Wallr.), Fckl. var. EriobolrycB, Scalia. 

Lupine 
{Lupinus, spp.) 
Blight (Fcstalozzia litpini, Sor.). 

Magnolia 
{Magnolia grandijlora, L.) 
Leaf-spot {PhyUoslicla magnolia Sacc. Duggar, p. 347 (1909). 

Mango 

(Mangifcra indica, L.) 

Anthracnose (Collelelolrichnm glceosponoides, Penz.). 
McMurran Bull. U. S. Dept. Agr. No. 52 (1914). 

Maple 
(Acer spp.) 

Anthracnose {Glaosporium apocrypium, Ell. & Ev.). 

Descr., N. Y. Agr. .Exp. Sta., Rep. 14, 1895, pp. 531-532. (1896). 

Treat, (rec), N. Y. Agr. Exp. Sta., Rep. 14, 1895, p. 532 (1896) 
Decay, Fomes fomentarins (L.) Fr. Duggar, p. 467. 
Gall, Pycnochylrium globosum, Schrot; Duggar, p. 139. 
Heart-rot, Fomes igniarius (L.) Gill.; Duggar, p. 465. 
Leaf-blotch, Rhytisma acerinum (Pers.) Fr. 
Leaf-spot {Phyllosticta acericola, Cke. & Ell.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 383-386 (1889). 

Treat, (rec), U. S. Dep. Agr., Rep. for 1888, p. 386 (1889). 
Powdery Mildew, Uncintila aceris (DC.) Wint. 
White-rot, Polyporus squamosus (Huds.) Fr.; Duggar, p. 453. 

Melon 

(Cucumis melo, L.) 

Anthracnose (Collclotrichnm lagenarium (Pass.) Ell. & Hals.). 
Descr., U. S. Dep. Agr., Bot. Div., Bull, 8, p. 64 (1889). 
Descr. Illus., Okla. Agr. Exp. Sta., Bull. 15, pp. 30-31 (1895). 
Treat, (pos.), Md- Agr. Exp. Sta., Rep. 4, 1891, p. 387 (1892). 



444 SPECIAL PLANT PATHOLOGY 

Anthracnosc {Collclolrichum oligochcetum, Cav.). 
Bacteriosis or Wilt {Bacillus tracheiphilus, E. F. Sm.). 
Downy Mildew {Plasmopara cubenis (B. & C.) Humph.). 

Occ. Descr., Conn. Agr. Exp. Sta., Rep. 23, 1899, pp. 277-278 (1900). 
Leaf-blight {Altcrnarla hrassica, Sacc, var. nigrescens, Regel.). 

Descr., Conn. Agr. Exp. Sta., Rep. 19, 1895, pp. 186-187 (1896). 
lUus., Ohio Agr. Exp. Sta., Bull. 73, pp. 235-236 (1897). 

Treat, (pos.), Conn. Agr. Exp. Sta., Rep. 22, '9Sj#%). 229-235 (1899)-. 

Cf. Conn. Agr. Exp. Sta., Rep. 23, 1899, pp. 270-573 (1900). 
Leaf-spot {Phyllosticta cuctirbitacearum, Sacc. ?) . 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 355 (1894). 
Scab {Scolecotrichutn melophlhorum, Pr. & Del.). 

Soft-rot (Bacillus melonis, Gidd.) Vt. Bull. 148, 363-416, pis. 8 (Jan. 1910). 
Southern Blight (Sclerotium Rolfsii, Sacc). 
Wilt (Neocosmospora vasinfccta (Atk.) E. F. Sm.). 

Cf. Conn. Agr. Exp. Sta., Rep. 22, 1898, pp. 227-228 (1899). 

Mesquite 

{Prosopis juliflora, DC.) 

Anthracnose {Glaosporium leguminum (Cke.), Sacc). 

Blight {Scleropycnium aureutn, Heald & Lewis). Trans. Amer. Micr. Soc, XXX F, 

5-9 (June, 19 1 2). 
Rust (Ravenelia arizonica, Ell. & Ev.). 

Mignonette 

{Reseda odorata, L.) 

Leaf-blight {Cercospora reseda;, Fckl.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1889, pp. 429-430 (1890). 
Treat, (pos.), U. S. Dep. Agr., Rep. for 1889, p. 431 (1890). 

Millet 

{Panicum miliaceum, L.) 

Purple-spot {Piricularia grisea (Cke.), Sacc). 
Smut {Uslilago Cramcri, Korn.). 

Mulberry 

{Morus spp.) 

Die-back {Myxos pari urn Dledickii, Syd.). 
Chytridiose {Cladochytrium mori, Prunet.). 

See U. S. Dept. Agr., Exp. Sta. Rec, VI-9, p. 830 (1895). 



LIST OF SPECIFIC DISEASES OF PLANTS 445 

Eye-spot {Ccrcospora moricola, Cke.). 

Leaf-spot {Ccrcospora missouriensis, Wint). 

Rooi-iot (Hclicobasidium mompa,Ta.naka..=Scptobasid!nm mompa (Tanaka), Rac.«). 



Mushroom 
(Agariciis campcslris, L.) 
Mold {Mycogone perniciosa, Magn.). 

Nasturtium 
{TropceoJtim majiis, L.) 

Wilt {Pscudomonas solanaccarum, E. F. Sm.). 

Journ. Agric. Research 4, pp. 451-457, pis. 64 (1915). 
Leaf-blight {Alternaria sp., and Pleospora tropceoli, Hals.). 

Descr., N. J. Agr. Exp. Sta. Rep. 13, 1892, p. 290-293 (1893). 

Oak 

(Quercus spp.)^ 

Anthracnose (Gnomonia veneta (Sacc. & Speg.), Kleb). 

Pocketed-rot {Poly poms pilotce, Schw.). 

Decay, or Brown-rot {Polyporus sulphureus (Bull.) Fr.). 

Atkinson, Bull. 193, Cornell Agr. Exp. Sta. (June, 1901). 
Heart- rot {Fames igniarius (L.) Gill.). 
Honeycomb Heart- rot {Stcreum subpileatiim, B. & C). 

Journ, of Agr. Research V; 421 (Dec. 6, 1915). 
Leaf-curl {Taphrina caerulescens, Desv. & Mont.), Tul. 
Leaf-spot {Marsonia quercus, Pk.}. 

f {Armillaria mellea, Vahl). Bull. U. S. Dep. Agr., No. 89 (1914). 
{Clitocyhe parasUica, Wilcox). 
{Polyporus dryadetis, Fr.). 
1^ {Rosellinia quercina, Hartig). 
Soft Rot {Polyporus obhisus, Berk). 
String and Ray-rot {Polyporus Berkeleyi, Fr.). 

Straw-colored Rot {Polyporus frondosus, Fr.), Journ. Agr. Research I, 109 (1913). 
Tar-spot {Rhyiisma erylhrosporum, Bri. & Cav.). 
White-rot {Polyporus squamosus (Huds.) Fr.). 



Root-rot 



1 Consult VON SCHRENK, HERMANN and Spaulding, Perley: Diseases of De- 
ciduous Forest Trees. Bull. 149, U. S. Bureau of Plant Industry, 1909. 



446 SPECIAL PLANT PATHOLOGY 

Oats 

(Aiena saliva, L.) 

Blight (Bacterial) Pseudomonas avence, Manns. 

Descr., Journ. Mycol., Vol. VI, p. 72; Ohio Bull. 210, Oct. 1909, pp. 91-167, 
pis. IS (1890). 
Leaf-spot {Phyllosticla sp.). 

Descr., N. J. Agr. Exp. Sta., Rep. 15, 1894, p. 319 (1895). 
Mildew {Helminthosporium inconspicuum, Cke. & Ell., var. hrillanicum Gr., and 
Cladosporiiim herbarum (Pers.), Lk.). 
Descr., Me. Agr. Exp. Sta., Rep. for 1894, pp. 95-96 (1895). 
Rust {Puccinia coronata, Cda., and P. graminis, Pers.). 
See Wheat (Rust). 

Cf. U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 16, pp. 45-52 & 60-65 
(1899). 
Smut (Uslilago avena (Pers.), Jens, and U. levis (Kell. & Sw.) Magn.). 

Descr. lUus., Kan. Agr. Exp. Sta., Rep. 2, 1889, pp. 215-238 & 259-260 (1890). 
Ohio Agr. Exp. Sta., Bull. 64, pp. 123-126 (1896). 
111. Agr. Exp. Sta., Bull. 57, pp. 297-298 (1900). 
Treat (pos.), U. S. Dep. Agr., Farm. Bull. 75, pp. 11-16 (1898). 
111. Agr. Exp. Sta., Bull. 57, pp. 309-316 (1900). 

Okra 

(Hibiscus esculentus, L.) 

Root- rot (Ozonium omnivorum, Shear). 

Wilt {Fusarium vasinfedum = Neocosmos pora vasinfcclum (Atk.), E. F. Sm.). 
See U. S. Dep. Agr., Div. Veg. Phys." & Path., Bull. 17, p. 31 (1899). 

Cf. N. Car. Rep. 191 1, pp. 70-73, figs. 4. 
{Verticillium albo-alrmn, Reinke & Berthold) Phytopathology IV, p. 393 (De- 
cember, 1914). 

Oleander 

{Neritim oleander, L.) 

Leaf-spot (Macrosporium nerii, Cke.). 

Bull. 218, CaHf. Agric. Exper. Sta. (June, 191 1). 

Olive 

(Oka europcea, L.) 

Anthracnose {Glosospormm olivarum, d'Almeida). 

Fruit-mold or Dry-rot (Alternaria sp. and Macrospoxium sp.). 

Descr. lUus. Cal. Agr. Exp. Sta., Rep. for '95-'97, pp. 235-236 (1898). 



LIST OF SPECIFIC DISEASES OF PLANTS 447 

Knot (Pseudomonas Savastonoi, E. F. Sm.). 

Cook Diseases of Tropical Plants, p. 144 (1913). 
Rot (Bacterial). 

Descr., Cal. Agr. Exp. Sta., Bull. 123, p. 19 (1899). 
Scab, Peacock Leaf-spot {Cycloconium oleaginum, Cast.). 

Descr., Cal. Agr. Exp. Sta., Rep. 1892-93, pp. 297-298 (1894). 

See U. S. Dep. Agr., Exp. Sta. Rec, XI-6, p. 554 (1900). 
Sooty- mold (Meliola sp., Syn. Capnodlunt cilri Berk. & Desm.). 
Tuberculosis {Bacillus clece (Arcang.) (Trev.). 

Descr. Illus., Cal. Agr. Exp. Sta., Bull. 120 (1898). 

Treat, (rec), Cal. Agr. Exp. Sta., Bull. 120, pp. lo-ii (1898). 

Cf. Cal. Agr. Exp. Sta., Rep. for '97-'98, p. 178 (1900). 

Onion 
{Allium cepa, L.) 

Anthracnose or Rot {Vermicular ia circinans, Berk). 

Descr. Illus., Conn. Agr. Exp. Sta., Rep. 13, 1889, p. 163 (1890). 

Treat, (rec), Conn. Agr. Exp. Sta., Rep. 13, 1889, pp. 164-165 (1890). 
Downy Mildew {Peronospora Schleideniana, deBy.). 

Descr. Illus., Wis. Agr. Exp. Sta., Rep. i, 1883, pp. 38-44 (1884). 

Descr., Conn. Agr. Exp. Sta., Rep. 13, 1889, pp. 155-156 (1890). 

N. Y. Cornell Bull. 218, pp. 137-161, figs. 17 (Apr., 1904). 

Treat, (rec), Vt. Agr. Exp. Sta., Rep. 10, 1896-97, pp. 61-62 (1897). 
Mold {Macrosporium sarcinula, B., var. parasiticum, Thiim., and M. Porri, Ell.). 

Descr. Illus., Conn. Agr. Exp. Sta., Rep. 13, 1889, pp. 158-162 (1890). 

Treat, (rec), Conn. Agr. Exp. Sta., Rep. 13, 1889, p. i6r (1890). 
Rot (Bacterial). 

Descr. Illus., N. Y. Agr. E.xp. Sta., Bull. 164, pp. 209-212 (1899). 
Smut {Urocyslis cepula, Frost). 

Descr. Illus., Conn. Agr. Exp. Sta., Rep. 13, 1889, pp. 129-146 (1890). 

Ohio Bull. 122, pp. 71-84, figs. 4 (Dec, 1900). 

Treat, (pos.), Conn. Agr. Exp. Sta., Rep. 13, 1889, pp. 147-153 (1890). 

(By transplanting), Conn. Agr. Exp. Sta., Rep. 19, 1895, pp. 176-182 

(1896). 
Cf. U. S. Dep. Agr., Farm. Bull. 39, pp. 16-20 (1896). 
N. Y. State Bull. 182, pp. 145-172, pi. i (Dec, 1900). 

Orange 

{Citrus aurantium; L.) 

Anthracnose {Collelotrichum gloeosporioides Penz.). 

Descr. Illus., Fla. Agr. Exp. Sta., Bull. 53, pp. 171-173 (1900). . 

Fla, Agr. E.xp. Sta., Bull. 108, pp. 25-47 (Nov., 191 1). 



448 SPECIAL PLANT PATHOLOGY 

Treat, (rec), Fla. Agr. Exp. Sta., Bull. 53, p. 173 (1900). 
Black-rot {AUcrnaria citri Ellis & Pierce). 

Colt, Citrus Fruits, p. 388 (1Q15). 
Cottony- mold and Twig-blight {Sdcrotinia libcrliana, Fkl.). 

Coit, Citrus Fruits, p. 382 (1Q15). 
Diplodia Rot {Diptodia natalensis Evans), Coit, p. 397 (1915). 
Flyspeck {Leptothyrium pomi (Mort & Fr.) Sacc.) Hume, Citrus Fruits and Their 

Culture, p. 481 (191 1 ). 
Foot-rot or Mal-di-gomma {Fusarium limonis, Bri.). 

Descr. Illus. Treat, (rec), U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 8, 
pp. 28-31 (1896J. 
Fla. Agr. Exp. Sta., Bull. 53, pp. 151-155 (1900). 
Fruit-rot {Penicilliiim digitatum. (Fr.), Sacc. & Penicillium Ualicum, Wehm.). 
Gum-disease {Bolrytis vulgaris, Fr.). 

Coit, Citrus Fruits, p. 366 (1915). 
Leaf-glaze {Strigula complanata, Fee). 

Occ, Journ. Mycol., Vol. VII, p. 36 (1891). 
Melanose {Phomopsis citri Fawcett). 

Descr. Illus. Treat, (pos.), U S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 8, 
PP- 33-38 (1896). 
Nail-head Rust {Cladosporium hcrharum (Pers.), Pk. var. citricolum Fawcett & 
Berger). 

Coit, Citrus Fruits, p. 395, 1915, Fla. Bull. 109, pp. 47-60 (May, 191 2). 
Scab {Cladosporium citri Mass.). 

Phytopath. 6, pp. 127-142 (1916). 

See Lemon (scab.). 
Sooty-mold {Meliola Penzigi, Sacc. and M. camellice (Catt.), Sacc. 

Descr. Illus. Treat, (pos.), U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 13 
(1897). 
Toadstool Root-rot (Armillaria mcllea Vahl.). 

Coit, Citrus Fruits, p. 373 (1915). 
Trunk-rot {Schizophyllum commune Fr.). 

Coit, Citrus Fruits, p. 399 (191 5). 
Wither-tip (Colletotrichum gloeosporioides, Penz.). 

Coit, Citrus Fruits; 380 (1915). 

Grossenbacher, J. G.; Some Bark Diseases of Citrus Trees in Florida, Phyto- 
path. 6, pp. 29-50 (1916). 



Orch.xrd Grass 

{Dactylis glomcrala, L.) 

Puccinia coronata, Cda.;Duggar, p. 420 (1909) 
Puccinia graminis, Pers.; Duggar, p. 408 (1909^ 
Scolecotrichose {ScoJetotrichum graminis Fuckl.). 



LIST OF SPECIFIC DISEASES OF PLANTS 449 

ORCHros 
(Orckidacca) 

Anthracnose {Glceosporium cincliim Bri. & Cav. Colletotrichum cinclum (Bri. & Cav.) 
Stonem.). 
Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 414-417 (1894). 
Anthracnose {Glceosporium macro pus, Sacc). 
Leaf-blight {Ccrcospora angrcci, Feuill & Roum.). 

Osage Orange 
(Toyxlon pomiferum, Raf.) 

Rust {Physopella ficl (Cast), \rt\\. = U redo fici Cast.) 
Blight {Sporodesmium maclurcr Thiim. 

Palm 

(Phoenix dactylifera, L.) 

Leaf-spot (Graphiola plicenicis (Moug.) Poit.). 
Bull. 218, Calf. Agr. E.xp. Sta. (June, 191 1). 

Pansy 

{Viola tricolor, L.) 

Leopard Petal-blight {Colletotrichum, viola-iricoloris), R. E. Smith. 

Smith, R. E., Bot. Gaz. 27, p. 203 (March, 1899). 
Dry-up {Fusarium djo/(5 Wolf.). 

Wolf, F. A.; Mycologia, 2, p. 19 (January, igio). 

Papaw 

{Carica papaya, L.) 
Leaf-spot {Pucciniopis caricce Earle). 

Parsnip 
{Paslinaca saliva, L.) 

Leaf-blight {Cercospora apU, Fres.j. 

Occ, N. J. Agr. E.Kp. Sta., Rep. 15, 1894, p. 351 (1895). 
Root-rot {Corticium vagum, Bri. & Cav., var. solani, Burt.). 

Heald & Wolf, Plant Disease Survey in Texas (191 2). 
29 



4SO SPECIAL PLANT PATHOLOGY 

Pea 

[Pisum salivuni, L.) 

Damping-off {Ascochyla pisi, Lib. and Pylhium sp.). 

Occ, Conn. Agr. Exp. Sta., Rep. 23, 1899, pp. 280-281 (1900). 

Ohio Bull. 173, pp. 231-246, figs. II (Apr., 1906). 
Pod-spot {Ascochyta pisi, Lib.). 

Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 358 (1894). 

Treat. (rec.J, Del. Agr. Exp. Sta., Bull. 41, pp. 9-1 1 (1898). 
Leaf-spot {Septoria pisi, West.). 

- Occ, N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 358 (1894). 
Mold {Pleospora pisi (Sow.), Fckl.). 

Occ, N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 358 (1894). 
Powdery Mildew {Erysiphe polygoni, DC). 

Descr., N. J. Agr. Exp. Sta., Rep. 14, 1893, p. 357 (1894). 

Peach 
{Primus persica, Benth. & Hook) 

Anthracnose {Glceosporium laeticolor. Berk.). 

Occ. Ohio Agr. Exp. Sta., Bull. 92, p. 225 (1898). 
Brown-rot {Sclerotinia cinerea (Bon.) Schrot.) Heald, F. W., Washington Agricul- 
turist, VIII, No. 9, June, 191 5. 
Crown-gall (Pseiidomonas tumejaciens, E. F. Sm. and Towns.). 
Die-back {Valsa leucostoma (Pers.) Fr.). 

Stevens & Hall, Diseases of Economic Plants, p. 129 (1910). 
California Peach Blight {Coryneum Beijerinckii Oud.). 

Oregon Stat. Biennial Report, p. 255 (1911-12). 
Cal. Bull. 191, pp. 73-98, figs. 17 (Sept., 1907). 
Frosty Mildew {Cercosporella persica, Sacc). 

Stevens & Hall, Diseases of Economic Plants, p. 133 (1910). 
Fruit-mold or Twig-blight {Sclerotinia friicligena (Pers.) Schrot.). 

Descr. Illus., Journ. Mycol., Vol. VII, pp. 36-38 (1891). 
Ga. Agr. Exp. Sta., Bull. 50 (1900). 

Treat, (pos.), Ga. Agr. Exp. Sta., Bull. 50, pp. 267-269 (1900). 
Cf. Conn. Agr. Exp. Sta., Rep. 24, 1900, pp. 252-254 (1901). 

Cf. Cherry (Fruit-mold and Twig-blight). 
Pustular-spot {Helminthosporitim carpophilum, Lev.). 

Occ, Mich. Agr. Exp. Sta., Bull. 103, p. 57 (1894). 

Treat, (pos.), Ohio Agr. Exp. Sta., Bull. 92, p. 225 (1898). 
Leaf-blight or Shot-hole {Cercosporella persica, Sacc). 

Occ, N. C. Agr. Exp. Sta., Bull. 92, p. 103 (1893). 

Treat, (rec), N. C. Agr. Exp. Sta., Bull. 92, p. 103 (1893). 
Leaf -blight or Frosty Mildew {Cercosporella persica, Sacc). 

Occ, Journ. Mycol., Vol. VII, p. 91 (1892). 



LIST OF SPECIFIC DISEASES OF PLANTS 451 

Leaf-curl {Exoascus deformans (Berk.), Fckl.). 

Descr. Illus., N. Y. (Corn, Univ.) Agr. Exp. Sta., Bull. 73, pp. 324-325 (1894)- 

U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 20 (1900). 
Treat, (pos.), N. Y. Cornell Bull. 276, p. 151-178, figs/s (Apr., 1910). 
U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 20 (1900). 
Powdery Mildew {Spharolhcca pannosa (Wallr.), Lev. ? and Podospkcsra oxyacantha 
(DC), de By.). 
Occ, Journ. Mycol., Vol. VII, p. 90 (1892). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 74, p. 381 (1894). 
Root-rot {Fungus indet.?). 

Occ, Journ. Mycol., Vol. VII, p. 377 (1894). 

Ohio Agr. Exp. Sta., Bull. 92, p. 23s (1898). 
Rust {Puccinia pruni-persicce Hori). 

Phytopath. 2, p. 143-145, also Tranzschelia punctata (Pers.) Arth. 
2d Biennial Crop Pest and Hort. Rep. Oregon (June, 1915). 
See Cherry (Rust). 
Scab {Cladosporium carpophilum, Thiim). 

Descr. Illus., Ind. Agr. Exp. Sta., Bull. 19, pp. 5-8 (1889). 

Del. Agr. Exp. Sta., Rep. 8, 1895-96, pp. 60-63 (1896). 
Ohio Agr. Exp. Sta., Bull. 92, pp. 220-222 (1898). 
Treat, (pos.), Del. Agr. Exp. Sta., Rep. 8, 1895-96, p. 63 (1896). 
Cf. N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 328-330. (On leaves). 
Conn. Agr. Exp. Sta., Rep. 20, 1896, pp. 269-271. (On twigs). 
Bull. 395, U. S. Dept. Agric, 1917. 
Shot-hole {Coryneum Beijcrinckii Oud.). 

Stevens & Hall, Disease of Economic Plants, p. 129 (1910). 
Stem-blight {Phoma persicce, Sacc). 

Descr. Illus., Ohio Agr. Exp. Sta., Bull. 92, pp, 233-234 (1898). 
Yellows. 

Stevens & Hall, Diseases of Economic Plants, p. 135 (1910). 



Peanut 
{Arachls hypogcea, L.) 

Bacterial Blight {Bacillus solanacearum, E. F. Sm.). 

Phytopathology IV; 397 (December, 19 14). 
Leaf-spot' {Cerccspora personata (Bri. & Cav.), Ell. & Ev.). 

Phytopathology IV; 397 (December, 19 14). 
Red-rot {Neocosmopora vasinfecta (Atk.) E. F. Sm.). 

Phytopathology IV; 397 (December, 1914). 
Sclerotial-rot {Sclerotium Rolfsii Sacc). 

Phytopathology IV; 397 (December, 19 14). 

' Consult also Wolf, Frederick A. : Further Studies on Peanut Leaf-spot. 
Journ. Agr. Res. 5, pp. 891-902, Feb., 1916. 



452 SPECIAL PLANT PATHOLOGY 



{Pirns conimunis, L.) 

Anthracnose {Collclotrichum sp.). 

Occ, N. J. Agr. Exp. Sta., Rep. 15, 1894, p. 331 (1895). 
Bitter- rot (Glomcrella rufomaculans (Berk.), Spauld. & v. Schr.). 
Stevens & Hall, Diseases of Economic Plants, p. 107 (1910) 
RIack-rot {Spharopsis malormn, Berk.). 
Brown-blotch (Macros porium Sydowianum, Farneti). 

Circ. 52, N. J. Agr. E.xp. Sta. 
Body-blight or Canker (Spkacropsis malar urn, Berk.). 

Occ, N. Y. Agr. E.xp. Sta., Bull. 163, p. 203 (1899). . 
Dry-rot {Thelephora pediceUata, Schw.). 

Descr., Journ. Mycol., Vol. VI, pp. 113-114 (1891). 
Treat, (pos.), Journ. Mycol., Vol. VI, p. 114 (1891). 
Fire-blight {Bacillus amylovorus (Burr.), Trev.). 

Descr. Illus., N. Y. Agr. Exp. Sta., Rep. 5, 1886, pp. 275-289 (1887). 
Descr., Conn. Agr. Exp. Sta., Rep. 18, 1894, pp. 113-116 (1895). 
U. S. Dept. Agr., Year-book for 1895, pp. 295-298 (1896). 
N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 145, pp. 622-625, 1898. 
Utah Bull. 85, Nov., 1903, pp. 45-52. 
Vt. Rep. 1902, pp. 231-239. 
Ark. Bull. 113, 1913, pp. 493-505. 
Treat, (pos.), Phytopath. 6, pp. 152-158, 288-292 (1916). 
Fly-speck {Leptothyriurn carpophilitm, Pass.). 

N. J. Agr. Exp. Sta., Rep. 18, 1897, pp. 378-383 (1898). 
Fruit Spot {Fabrcea maculatum, (Lev.), Atk.). 

Leaf-blight {FabrcRa maculaium (Lev.), Atk. and Cercospora minima, Tracy and 
Earle). 
Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 357-362 (1889). 
Del. Agr. Exp. Sta., Bull. 13, pp. 4-6 (1891). 
N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 145, p. 611 (1898). 
Heald and Wolf, Plant Disease Survey, San Antonio, Texas, 
(1912). 
Treat (pos.), R. L Agr. E.xp. Sta., Bull. 31, pp. 5-9 (1895). 
Cf. Quince (Leaf-spot). 
Leaf-spot {Septoria piricola, Desm.). 

Descr. Illus., Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 145, pp. 
597-611 (1898). 
Rust {Gymnos porangium globosum, Farl.). 

Occ, Conn. Agr. Exp. Sta., Rep. 14, 1890, p. 98 (1891). 
Scab {Fusicladinm pirinmn (Lib.), Fckl. = Ventnria pirina, Aderh.). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 145, pp. 616-620 (1898). 
Treat, (pos.), Vt. Agr. Exp. Sta., Bull. 44, pp. 85-90 (1895). 
Cf. Apple (Scab). 



LIST OF SPECIFIC DISEASES OF PLANTS 453 

Shot-hole {CyHndrosporium padi, Karst.). 

Bull. 212, Colo. E.xp. Sta. (October, 1915). 

Pecan 

(Iliioria pcain (Marsh.), Butt.)i 

Anthracnose (Glomerella cingulata (Stonem) S. & S.). 
Brown Leaf-spot {Ccrcospora fusca, Rand). 
Crown-gall (Pseudomonas tumefaciens, E. F. Sm. & Towns.). 
Kernel -spot (Coniothyrium caryogenum, Rand). 
Leaf-blight {Septoria carya, Ell. & Ev.). 

Heald & Wolf, Plant Disease Survey in Texas (191 2). 
Leaf -blotch (Mycosphcerella convcxula (Schw.), Rand). 

Phytopath. i, pp. 133-138 (iQ")- 
Mildew {Micros phccra alni (Wallr.), Wint. 
Nursery-blight {Phyllosticia caryce, Pk). 
Scab {Fiisidadium effiisiim, Wint.). 

Orton, W. A., Science, new ser. 21, p. 503 (March 31, 1905). 

Peony 

{Pceonia officinalis, L.) 

Mold {Botryiis pceonia, Oud.) 

Peppers 

{Capsicum anmmm, L.) 

Anthracnose {Colletolrichnm nigrum, Ell. & Hals, and Glmosporium piperalim, Eil. 
& Ev.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 11, 1890, pp. 358-359 (1891). 

Cf. N. J. Agr. Exp. Sta., Rep. 13, pp. ^^2-7,31 (1893)- 
Fruit-rot {Glceosporium piperatum, Ell. & Ev.). 
Mold {Macros porium sp.). 

Occ, N. J. Agr. E.xp. Sta., Rep. 15, 1894, p. 351 (1895). 
Leaf-spot {Ccrcospora capsici, Heald & Wolf). 

Persimmon 

{Diospyros spp.) 

Black Leaf-spot {Ccrcospora fuliginosa. Ell. & Kellem). 
Leaf-spot {Ccrcospora kaki, Ell. & Ev.). 
Fruit- rot {Phyllosticia biformis, Heald & Wolf). 

1 Rand, Frederick V. : Some Diseases of Pecans, Journal of Agricultural Re- 
search I, pp. 303-337, June ID, 1914. 



454 SPECIAL PLANT PATHOLOGY 

{Agaricus. 
Ccrcospora air a, EH. & Ev. 
Glososporium diospyri, EH. & Ev. 
See N. C. Agr. Exp. Sta., Bull. 92, p. 116 (1893). 

Phlox 
(Phlox spp.) 
Leaf-spot {Scptoria divaricala, Ell. & Ev.). 

Pine 

{Pinus spp.)i 

Blister-rust {Cronartium ribicola, Fisch. (= Peridermium slrobi (Kleb.), Spauld.). 
Bull. 206, Bureau of Plant Industry, 191 1; American Forestry (Feb., Dec, 
1916). 
Bluing (Ceraloslomdlapilif era (Fr.)Wmt.). 

von Schrenk, U. S. Bureau Plant Industry, Bull. 36 (1903). 
Chalky Quinine Fungus (Fames laricis (Jacq.), Murr.). 

Meinicke, 1914, p. 44. 
Dry-rot (Trametes Pini (Brot.) Fr., and T. radiciperda 'H.axiig =Fomes annosiis 
(Fr.), Cke.). 
Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25, pp. 31-40 
(1900). 
Gray Leaf- tip (Hypoderma Desmazicri, de By.). 

Stevens & Hall, Diseases of Economic Plants, p. 445 (1910). 
Leaf-blight (Lophodermium brachysporum, Rostr. = Hypoderma hrachysporum 
(Rostr.), Tubeuf.). 
Stevens & Hall, p. 445 (1910). 
Needle Disease (Hypoderma deformans, Weir on Finns ponderosa, Laws. Journ. Agric. 

Res. VI: 277-288, May 22, 1916). 
Pine Gall (Peridermium Harknessii Moore =P. cerebrum Pk.). 

Meinecke, E. P., Forest Tree Diseases Common in California and Nevada, 
U. S. Forest Service (1914). 
Punk-rot (Polyporus pinicola, Aik.^Fomes ungulalus (Schraeff) Sacc). 

Bull. 193, Corn. Univ. Agr. Exp. Sta. (June, 1901). 
Red-rot (Polyporus ponderosus, v. Schr.). 

U. S. Bureau of Plant Industry, Bull. 36 (1903). 
Root- rot (Polyporus Schweinitzii, Fr.). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25, pp. 18-24 (1900). 

* The twelve species of Peridermium found in American pines are described by 
Arthur and Kern in North American Species of Peridermium, Bull. Torr. Bot. 
Club 33, pp. 403-438, 1906. 



LIST OF SPECIFIC DISEASES OF PLANTS 455 

Rust {Coleosporium pini, GaX\=Gallowaya pinl (GalL), Arth. and Peridennium 
piriforme, Pk.). 
Descr., Journ. Mycol., Vol. VII, p. 44 (1891). 
Wet- rot (Polyporus subacidus, Pk. ?). 

Descr. Illus., U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 25, pp. 44-49. 
(1900). 

Pink (Sweet William) 

(Dianthus barbalus, L.) 

Mold (Heterosporium echinulalum (Berk.), Cke.). 
Rust {Puccinia arenarice (Schum.), Wint.). 

Descr. lUus., N. J. Agr. Exp. Sta., Rep. 13, 1892, pp. 278-280 (1893). 

Treat, (rec), N. J. Agr. Exp. Sta., Rep. 13, 1892, p. 280 (1893). 

Plum 

{Primus spp.) 

Bacterial Leaf-spot (P^ez^/owoHd^ />«<;»", E. F. Sm.). 

Heald & Wolf, Plant Disease Survey, San Antonio, Texas (191 2). 
Black-knot (Plourightla morbosa (Schw.), Sacc). 

Descr. Illus. Treat., Ky. Agr. Exp. Sta., Bull. 80, pp. 250-256 (1899). 

Cf. Cherry (Black Knot). 
Canker (Neclria ditissima, Tul.). 

Descr., See U. S. Dep. Agr., Exp. Sta. Rec, IX-8, pp. 761-762 (1898). 
Die-back {Valsa leticostoma (Pers.), Fr.). 

Heald & Wolf, Plant Disease Survey, San Antonio, Texas (191 2). 
Fire-blight (Bacterial). 

Occ, Conn. Agr. Exp. Sta., Rep. 18, 1894, pp. 117-118 (1895). 
Fruit-mold {Sclerotinia frnctigena, Kze. & Schm.). 

Descr. Illus., Oreg. Agr. Exp. Sta., Bull. 57, pp. 3-12 (1899). 

Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 86, pp. 71-72 (1895). 
Mo. Agr. Exp. Sta., Bull. 31, pp. 16-18 (1895). 

Valleau, W. D.: Varietal Resistance of Plums to Brown Rot, Journ. Agr. Re- 
search V, pp. 365-395 (1915)- 

Cf. Cherry (Fruit-mold). 
Leaf-curl {Exoascus mlrabllis, Atk.). 

Descr. Illus., Conn. Agr. Exp. Sta., Rep. 19, 1895, pp. 183-185 (1896). 

Treat, (pos.). Conn. Agr. Exp. Sta., Rep. 20, 1896, p. 281 (1897). 
Leaf-spot {Cylindrosporium padi, Karst. and Phyllostida congesta, Heald & Wolf). 

Descr. Illus., N. Y. Agr. Exp. Sta., Rep. 5, 1886, pp. 293-296 (1887). 
N. Y. Agr. Exp. Sta., Rep. 6, 1887, pp. 347-35© (1888). 

Treat, (pos.), U. S. Dep. Agr., Div. Veg. Path., Bull. 7, p. 30 (1894). 
N. Y. Agr. Exp. Sta., Rep. 15, '96, pp. 384-401 (1897). 

Cf. Cherry (Leaf -spot). 



456 SPECIAL PLANT PATHOLOGY 

Plum-pockets {Exoascus pruni, Fckl.). 

Descr. lUus., U. S. Dep. Agr., Rep. for 1888, pp. 366-369 (1889). 

N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 73, pp. 329-330 (1894), 

Treat, (rec), N. C. Agr. Exp. Sta., Bull. 92, p. iii (1893). 
Powdery Mildew {Podosphccra oxyacanthcB (DC), de By.). 

See Cherry (Powdery Mildew). 
Root-rot {Armillaria mellea, Vahl). 

Bull. 59, pp. 14 (1903). 
Rust {Puccinia pruni spinosa, Fers. = Tranzschelia punclala (Pers.), Arth.). 

Descr., Journ. Mycol., Vol. VII, pp. 354-356 (1894). 

Treat, (pos.), Journ. Mycol., Vol. VII, pp. 356-362 (1894). 

Cf. Cherry (Rust). 
Scab {Clados pori urn carpophilum, Thiim). 

Descr., Journ. Mycol., Vol. VII, pp. 99-100 (1892). 

Descr. Illus., Iowa Agr. Exp. Sta., Bull. 23, pp. 918-920 (1894). 

Cf. Cherry and Peach (Scab). 
Shot-hole (Cylindros porium padi, Karst). 

Pomegranate 
{Punka granatum, L.) 
Leaf-spot {Ccrcospora lylhraccarum, Heald & Wolf). 

Pomelo 

(Citrus decumana, Murr.) 

Anthracnose (CoUctotrichum glceosporioides, Penz.). 

Fla. Bull. 74, pp. 159-172, jdIs. 4 (August, 1904). 
Canker {Pscudomonas citri, Hasse). 

Journ. Agr. Research VI, pp. 69-99 (April, 1916). 

Poplar 
{Populus spp.) 

Anthracnose (Marssonia populi (Lib.), Sacc). 

Descr., N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 394-396 (1895). 
Leaf-spot (Septoria musiva, Pk.) and {Septoria populicola, Pk.). 
Rust (Melampsora populina (Jacq.), Lev.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 390-392 (1889). 

Treat, (pos.), Mass. Agr. Exp. Sta., Rep. 7, 1894, p. 20 (1895). 

Potato : 

{Solanum tuberosum, L.) 

Anthracnose {Vcrmicularia, sp.). 
Black-leg {Bacillus phylophlhorus, Appel). 

Orton, W. A., Potato Tuber Diseases, Farmers' Bull. 544 (1913). 



LIST OF SPECIFIC DISEASES OF PLANTS 457 

Blight (Bacillus solanaccamm, E. F. Sm.). 

Descr. Illus. Treat, (rec), U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 12 
(1896). 
Chytridiose or Black Scab (Synchytriutn cndohioikum (Schilb.) Vcxa\a.l = Chryso- 

phlyclis cndohioiica, Schilb.) 
Downy Mildew or Rot {Phytophthora infcslans, de By.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 337~33S (1889). 
N. H. Agr. Exp. Sta., Bull. 22, pp. 3-5 (1894). 
N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 113, pp. 249-254 (1896). 
Vt. Bull. 168, pp. 100, pis. 10, figs. 10 (August, 191 2). 
Conn. Rep., pt. 10, pp. 753-774 (1909)- 

Melhus, I. E., Hibernation in the Irish Potato, Journ. Agr. 
Research V, pp. 71-102 (1915). 
Treat, (pos.), U. S. Dep. Agr., Farm. Bull. 91 (1899). 
Dry-rot {Fusarium solani (Mart.) Sacc. and F. radicicola, WoUenw.). 

Occ, 111. Agr. Exp. Sta., Bull. 40, p. 139 (1895). 
Internal Browning (Bacterial ?). 

Descr., 111. Agr. Exp. Sta., Bull. 40, pp. 138-139 (1895). 
N. Y. Agr. Exp. Sta., Bull. loi, pp. 78-83 (1896). 
Leaf-blotch {Cercospora concors (Casp.) Sacc). 

Stevens & Hall, Diseases of Economic Plants, p. 278 (1910). 
Leaf-mold or Early-blight (AUernaria solani (Ell. & Mart.), Jones & Grout). 
Descr. Illus., Del. Agr. Exp. Sta., Rep. 4, 1891, pp. 58-59 (1892). 

N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 140, p. 393 (1897). 
Vt. Agr. Exp. Sta., Bull. 72, pp. 16-25 (1899). 
Treat, (pos.), U. S. Dept. Agr., Farm. Bull. 91, pp. 5-7 (1899). 
Wise. Rep., pp. 343-354, figs. 7 (1907)- 
Leak (Pylhium de Baryaniim, Hesse.) 

Journ. Agr. Research VI, pp. 627-640, pi. i (1916). 
Powdery^ Scab {Spongospora siihkrranea). 

Orton, W. A., Potato Tuber Diseases, U. S. Farm. Bull. 544 (1913)- 
Bull., U. S. Dept. Agr., No. 82 (1914). 
Powdery Dry-rot {Fusarium Iriclwlhecoides Wollenw.). 
Orton, W. A., U. S. Farm. Bull. 544 (1913). 
Pratt, Journ. Agric. Res., VI: 817-831, Aug. 21, 1916. 
Root-rot {Entorrhiza solani, Fautr.). 

See U. S. Dept. Agr., Exp. Sta. Rec, VII-io, p. 873 (1896). 
Scab (Actinomyces chrcmogenes, Gasp.). 

Descr. Illus., Conn. Agr. Exp. Sta., Rep. 14, 1890, pp. 81-95 (1891). 
Descr. Illus., Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 153-160 (1892). 

1 Carpenter, C. W.: Some Potato Tuber-rots Caused by Species of Fusarium, 
Journal of Agricultural Research V, pp. 183-209 (Nov. i, 1915). 

^ Consult Melhus, I. E., Rosenbaum, J. and Schultz, E. S.: Studies of Spon- 
gospora subterranea and Phoma tuberosa of the Irish Potato, Journ. Agr. Research 
Vn, pp. 213-253, October, 1916, also IV, pp. 265-278. 



458 SPECIAL PLANT PATHOLOGY 

Cf. W. Va. Agr. Exp. Sta., Sp. Bull. 2, pp. 97-111 (iSqS). 

Treat, (pos.) Journ. Agr. Research IV, pp. 129-133 (1915). 
(Cor. Sub.) Mich. Agr. Exp. Sta., Bull. 108, pp. 38-45 (1894). 
Ind. Agr. Exp. Sta., Bull. 56, pp. 70-80 (1895). 
Conn. Agr. Exp. Sta., Rep. 19, 1895, pp. 166-176 (1896). 

(Formalin) U. S. Dep. Agr., Farm. Bull. 91, pp. 9-10 (1899). 
Scurf (Rliizoctonia solani, Kiihn = Coriicium vagum, B. & C, var. solani, Burt.). 
Silver-scurf (S pondylocladium alrovircns, Harz.). 

Orton, U. S. Farm. Bull. 544 (1913). 

Journ. Agr. Research VI, pp. 339-350 (June, 1916). 
Stem-blight (Fusarium acuminatum, Ell. & Ev. ?). 

Descr., N. Y. Agr. Exp. Sta., Bull. loi, p. 85 (1896). 

Cf. N. Y. Agr. Exp. Sta., Bull. 138, pp. 632-634 (1897). 
Stem-rot {Coriicium vagum, Bri. & Cav., var. solani, Burt.). 

Cal. Bull. 70, pp. 1-20, pis. 12 (March, 1902). 
Tuber-rot {Fusarium oxysporum, Schlecht). 

Orton, U. S. Farmer's Bull. 544 (1913). 

Bull., U. S. Dep. Agr., No. 64 (1914). 
Wart {Synchytritim endohioticiim (Schilb.), Percival). 

Orton, W. A., Potato Tuber Diseases, U. S. Farmer's Bull. 544 {igi^,). 
Wet-rot {Bacterial). 

Descr., Del. Agr. Exp. Sta., Rep. 4, 1891, pp. 54-57 (1892). 
Wilt {Bacillus solanacearum, E. F. Sm.). 
Yellow-blight {Sclerotinia liberliana, Fckl.; Syn. Peziza postuma, Berk. & WUs. ?). 

Primrose 
{Primula, spp.) 
C Phyllosticta primulicola, Desm. 



Miscellaneous Fungous Diseases. 



Ramularia primulce, Thm. 
CoUetolrichum primulce, Hals. 
[ Ascochyta primula. Trail. 
See N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 377-380 (1895). 



Privet 

{Ligustrum vulgare, L.) 

Anthracnose {Glceosporium cingulatum, Atk.). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 49, PP- 306-314 (1892). 
Leaf-spot {Cercospora adusta, Heald & Wolf, C. Hgustri, Roum and Phyllosticta 
ovalifolia, Brun.) 

Quince 
{Pirus cydonia, L.) 

Black-rot {Sphosropsis malorum. Berk.). 

Descr. Illus., N, J. Agr. Exp. Sta., Bull. 91, pp. 8-10 (1892). 
Treat, (rec), Conn. Agr. Exp. Sta., Bull. 115, pp. 6-7 (1893). 



LIST OF SPECIFIC DISEASES OF PLANTS 459 

Fire-blight {Bacillus amylovorus (Burr.), Trev.). 

See Apple and Pear (Fire-blight). 
Leaf-blight {Entomosporium maculatum, Lev=Fabraea maciihUum (Lev.) Atk. 

Descr. lUus., See Pear (Leaf-spot). 

Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 80, pp. 619-625 (1894). 
Mold {Sclerotinia cydonice, Schellenb.). 
Pale-rot (Phoma cydonia, Sacc. & Schulz.?). 

Descr. Illus., N. J. Agr. Exp. Sta., Bull. 91, pp. lo-ii (1892). 
Ripe-rot or Anthracnose {Glceosporiiim fructigenum, Berk.). 

See Apple and Grape (Ripe-rot). 
Rust {Gymnosporangimn clavipes, C. & P., Syn. Rcestelia aurantiaca, Pk.). 

Descr.^Illus., N. J. Agr. Exp. Sta., Bull. 91, pp. 2-5 (1892). 

N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 80, pp. 625-626 (1894). 
Mass. Hatch Rep., pp. 61-63 (1897). 

Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 80, p. 627 (1894). 

Radish 
{Raphantis sativus, L.) 

Club-root {Plasmodiophora brassica;, Wor.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, pp. 348-349 (1891). 
Downy Mildew (Peronospora parasitica (Pers.) deBy.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 349 (1891). 
White-rust {Cyslopus candidus (Pers.), Lev.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 350 (1891). 

Treat, (rec), N. J. Agr. E.xp. Sta., Rep. 11, 1890, p. 350 (1891). 

Raspberry 
(Rubus spp.) 

Anthracnose {Glceosporiiim venclum, Speg. = Gl. necator, Ell. & Ev.). 

Descr. Illus., U. S. Dept. Agr., Rep. for 1887, pp. 357-360 (1888). 
Ohio Agr. Exp. Sta., Bull. IV-6, pp. 124-126 (1891). 
N. Y. Agr. Exp. Sta., Bull. 124, pp. 262-264 (1897). 

Treat, (pos.), Conn. Agr. Exp. Sta., Rep. 23, '99, pp. 274-276 (1900). 
Black-blight {Fnsarium, sp. ?). 
Blue-stem {Acrostolagmiis caulophagus, Lawrence.). 

Washington Bull. 108, pp. 30, figs. 28 (October, 191 2). 
Cane-blight {Coniothyrimn Fuckelii, Sacc). 

Stevens & Hall, Diseases of Economic Plants, p. 177 (1910). 

Descr. N. Y. Agr. Exp. Sta., Bull. 107, pp. 305-307 (1899). 
Crown-gall (Possibly identical with Crown-gall of Peach, q.v.). 

See Ohio Agr. Exp. Sta., Bull. 79, pp. 108-112 (1897). 
Fire-blight (Bacterial). 

Descr., Ohio Agr. Exp. Sta., Bull. IV-6, pp. 128-129 (1891). 



460 SPECIAL PLANT PATHOLOGY 

Leaf-spot {Scploria riihi, Westd). 

Mushroom Root- rot (Armillaria hirllca Vahl). 

Ore. Sta. Bien. Rep. (1911-12). 
Orange-rust {Gyntnoconia interstitial is). 

Bull. 212, Colo. Exp. Sta. (October, 1915). 
Rust {Gymnoconia intcrstltialis (Schl.) v. Lagerh.). 
Spur-blight {Spharclla rubina Pk.). 

Bull. 212, Colo. Exp. Sta. (October, 1915). 
Wilt {Leptosphccria coniothyriiini (Fckl.) Sacc). 

Red Gum 

{Liqiiidamhar styracljlua, L.)' 

Sap-rot {Polyslictus versicolor, (L.) Fr.). 

von Schrenk, Diseases of Deciduous Forest Trees, U. S. Bur. Plant Industry, 
Bull. 149 (1909). 

Red Top 

(Agrostis alba, L.) 

Sclerotial Disease {Sclerotium rhizodes, Auersw.). 
Conn. E.xp. Sta., Rep., p. 23 (1914). 

Rice 

{Oryza saliva, L.) 

Blast {Piricularia oryza, Cav.). 

Stevens & Hall, Diseases of Economic Plants, p. 352 (1910). 

Cook, Diseases of Tropical Plants, p. 99 (1913). 
Smut (Tilletia corona, Scrib.). 

Descr. Illus., S. Car. Agr. Exp. Sta., Bull. 41, pp. 7-1 1 (1899). 

Treat, (rec.;, S. Car. Agr. Exp. Sta., Bull. 41, pp. 15-29 (1899). 

Rose 
{Rosa spp.) 

Anthra'cnose {Glososporium rosce, Hals.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 401-405 (1894). 
Cane-blight {Coniothyrium Fuckelii Sacc). 
Downy Mildew {Peronospora sparsa, Berk.). 

Occ, N. J. Agr. Exp. Sta., Rep. 13, 1892, p. 282 (1893). 

'von Schrenk, Hermann: Sap-rot and other Diseases of the Red Gum, U. 
S. Bureau of Plant Industry, Bull. 114, 1907, where all the important diseases 
are considered. 



LIST OF SPECIFIC DISEASES OF PLANTS 46 1 

Leaf-blotch {Actinonema rosa (Lib.), Fr.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 366-368 (1888). 

Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 13, 1892, p. 281 (1893). 
Leaf-spot {Splitrrella rosigena, EIL). 

Occ. 
Mildew {Peronospora sparsa, Berk.). 
Powdery Mildew {Sphcerotheca pannosa (Wallr.), Lev.). 

Descr., N. J. Agr. E.xp. Sta., Rep. 13, 1892, p. 281 (1893). 

Treat, (pos.), N. J. Agr. E.xp. Sta., Rep. 13, 1892, pp. 281-282 (1893). 
Rust {Phragmidium subcortkium (Schrank) Wint. and P/k speclomm, Fr.). 

Descr. Illus., U. S. Dept. Agr., Rep. for 1887, pp. 369-372 (1888). 

Treat, (pos.), See U. S. Dept. Agr., Exp. Sta. Rec, X-7, p. 651 (1899). 
Twig-blight {Botrylis clnerea, Pers.). 

Rye 

{Secalc ccrcale, L.) 

Anthracnose (Collciotrichum gramincola (Ces.) Wilson). 
Ergot (Claviceps purpurea, (Fr.) TuL). 

Descr. Illus., S. Dak. Agr. Exp. Sta., Bull. 33, pp. 40-43 (1893). 

Treat, (rec), N. C. Agr. Exp. Sta., Bull. 76, p. 20 (1891). 
Rust (Black-stem, Puccinia graminis, Pers., and Orange-leaf, P. rubigO'vera (DC), 
Wint.). 

See U. S. Dep. Agr., Div. Veg. Phys. & Path., Bull. 16, pp. 42-45 & 60. 
Smut {Urocystis occulta (Wallr.), Rabh.). 

Occ. Illus., Mass. Agr. E.xp. Sta., Rep. 9, 1891, p. 247 (1892). 

Treat, (pos.), see Oats and Wheat (Smut). 
Stem-blight {Leptosphceria herpotrichoidcs, de Not). 

Salsify 

{Tragopogon porrifoliits, L.) 
Rot (Bacterial). 

Descr., N. J. Agr. E.xp. Sta., Rep. 11, 1S90, p. 351 (1891). 
White-rust {Cystopus iragopogonis, (Pers.), Schrot.). 

Occ, N. J. Agr. E.Kp. Sta., Rep. 15, 1894, p. 355 (1895). 
Rust {Puccinia tragopogoni (Pers.), Cda.). 

Scrub Pine 
{Pinus virigitiiana, Mill) 

Burl Disease {Cronarlium quercus (Brand.) Schrot). 

Graves, A. H., Phytopathology IV (February, 1914). 
Heart-rot {Trameles pint (Brot.) Fr.). 

Graves, A. H., Phytopathology IV (February, 1914). 



462 SPECIAL PLANT PATHOLOGY 

Leaf-cast {Galloivaya pini (Gall.), Arth.). 

Graves, A. H., Phytopathology IV (February, 1914). 
Rust (Coleosporium inconspicuum (Long), Hedg.). 

Graves, A. H., Phytopathology IV (February, 1914). 

Shaddock or GRAPE-FRtni 
{Citrus decumana, Murr.) 
See Lemon and Orange 

Snapdragon 
{Antirrhinum niajiis, L.) 
Anthracnose {Colletotrichum antirrhini, Stewart). 

Descr. Illus. Treat, (pos.), N. Y. Agr. Exp. Sta., Bull. 179 (1900). 
Root-rot {Thielavia basicola, Zopf.). 
Rust {Puccinia antirrhini, Diet. & Holway.). 
Stem-rot {Phoma sp.). 

Descr. Treat, (rec), N. Y. Agr. Exp. Sta., Bull. 179, pp. 109-110 (1900). 

Sorghum 
{Sorghum vulgare, Pers.) 

Blight {Bacillus sorghi, Burrill). 

Descr., Kan. Agr. Exp. Sta., Rep. i, 1888, pp. 281-301 (1889). 

Treat, (rec), Kan. Agr. Exp. Sta., Rep. i, 1888, pp. 301-302 (1889). 
Head-smut {Sorosporlum reilianum (Kiihn) McAlpine). 

Journ. of Agr. Research II, pp. 340-371 (Aug. 15, 1914). 

Descr. Illus., Kan. Agr. Exp. Sta., Bull. 23, pp. 95-96 (1891). 
111. Agr. Exp. Sta., Bull. 47, pp. 374-388 (1897). 
111. Agr. Exp. Sta., Bull. 57, pp. 335-347 (1900)- 

Treat, (pos.), 111. Agr. Exp. Sta., Bull. 57, pp. 345-346 (1900). 
Kernel-smut {S phacelotheca sorghi). 

BuU. 212, Colo. Agr. Exp. Sta. (October, 1915). 

Journ. Agr. Research II, pp. 339-371, pis. 7 (1914). 

Soy 
{Soja hispida, Moench.) 

Wilt-disease {Fusarium tracheiphilum, E. F. Sm.), Journ. Agric. Res. 8: 421-439, 
with I pi., Mch. 12, 191 7. 

Spinach 
{Spinacia oleracea, Mill.) 

Leaf-blight {Cercospora beticola, Sacc). 

Descr., N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 355 (1891). 
Cf. N. J. Agr. Exp. Sta., Rep. 18, 1897, p. 303 (1898). 



LIST OF SPECIFIC DISEASES OF PLANTS 463 



Miscellaneous 
Fungous Diseases. 



Anthracnose {CoUetotrichum spinacecs, Ell. & Hals.). 

Downy MUdew {Peronospora effiisa, (Grev.), Rabenh.). 

Leaf-spot {Phyllostida chenopodii, Sacc.)." 

Scab {Cladosporium inacrocarpum, Preuss). 
^ White Smut (Entyloma Ellisii, Hals.) . 
Descr. Illus., N. J. Agr.' Exp. Sta., Bull. 70 (1890). 
Treat, (rec), N. J. Agr. Exp. Sta., Bull. 70, pp. 13-14 (1890). 

Spruce 

{Picea spp.)i 

Blight of Seedlings (Ascochyta piniperda, Lindsin = Dlplodina parasitica (Hart, Prill), 
and Sderotinia Fuckeliana, deBy). 
Graves, A. H., Phytopathology IV (April, 1914). 
Brown-rot {Polyporus sulphureus (Bull.) Fr.). 
Dry-rot (Trametes pini (Brot.) Fr. and T. abietis 

Karst.). 
Heart- rot {Polyporus borealis (Wahl.) Fr.). 

Atkinson, BuU. 193 (Corn. Univ.) Agr. Exp. Sta. 
(June, 1901). 
Root-rot {Polyporus Schweinitzii, Fr.). 
Wet-rot {Polyporus suhacidus, Pk. ?). 



Descr. Illus., U. S. Dep. Agr. 
Div. Veg. Phys. & Path. 
Bull. 25 (1900). 



Squash 

{Cucurbit a spp.) 

Anthracnose {CoUetotrichum lagenarium (Pass.), Ell. & Hals.). 

Bacteriosis or Wilt {Bacillus tracheiphilus, E. F. Sm.). 

Downy Mildew {Plasmopara cubensis (Bri. & Cav.), Humph.). 

Fruit-mold {Macrosporium sp.). 

Powdery MUdew {Erysiphe cichoracearum, DC. and E. polygoni, DC). 

Descr. Illus., See Cucumber (Powdery Mildew). 

Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 35, p. 330 (1891). 
Leaf-spot {Cercospora cucurbitce, Ell. & Ev.). 

Strawberry 

{Fragaria spp.) 
Blight {Micrococcus sp. ?). 

Descr., Mass. Agr. Exp. Sta., Rep. 9, 1896, pp. 59-61 (1897). 
Leaf-blotch {Ascochyta fragaria, Sacc). 

Descr. Illus., N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 14, pp. 182-183 (1889). 
Treat, (rec), N. Y. (Corn. Univ.) Agr. Exp. Sta., BuU. 14, p. 183 (1889). 
^ For species of Peridermium on spruce consult Arthur & Kern, North American 
Species of Peridermium, Bull. Torr. Bot. Club 2>2„ PP- 403-438, 1906. 



464 SPECIAL PLANT PATHOLOGY 

Leaf-spot {Aposphceria sp.). 

Descr. Illus., N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 329-330 (1894). 

Treat, (rec.) N. J. Agr. Exp. Sta., Rep. 14, 1893, pp. 331-332 (1894)- 
Leaf-spot {Mycosphcerclla fragarice, (Tul.) Lindau). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1887, pp. 334-339 (1888). 

N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 14, pp. 171-181 (iJ 
Oregon State Biennial Rep. p. 268 (1911-12). 
Leaf-spot {Mycos phcerella fragarice (Tul.), Lindau). 

Treat, (pos.), U. S. Dep. Agr., Rep. for 1890, p. 397 (1890). 
Conn. Agr. Exp. Sta., Bull. 115, p. 14 (1893). 
Powdery Mildew (Sphcerotheca Castagnei, Lev.). 

Descr., N. Y. Agr. E.xp. Sta., Rep. 5, 1886, pp. 291-292 (1887). 

Descr. Illus., Mass. Agr. Exp. Sta., Rep. 10, 1892, p. 239 (1893). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 10, 1892, pp. 243-245 (1893). 
Rot (Sphceroncemella fragarice, Stev. & Pet.). 

Phytopath. VI, pp. 258-266 (1916). 

Sugar-C.4ne1 

{Saccliarum officinarum, L.) 

Bundle-blight {Pseudomonas vascularum (Cobb.) E. F. Sm,). 
Cacao Disease (Diplodia cacaoicola, Henn). 

Cook, Disease of Tropical Plants, p. 85 (1913). 
Iliau {Gnomonia iliau, Lyon). 

Cook, p. 85 (1913)- 

Phytopath. 3, pp. 93-98 (191 3). 
Leaf-spot {Ccrcospora longipes, Butler). 

Cook, p. 89 (1913). 

Macrosporium gramimim, Cke. 



Miscellaneous Diseases. 1 ,,. ^^.., .. ,„ .. ^ ,^7 1 1 o -ht ^ 

Uromyces Kuhnii (Krug.j, Wakk. & Went. 

Pineapple Disease {Thielaviopsis ethacelicus, Went). 

Red- rot {Collelotrichum falcatum, Went). 

Rind Disease {Trichosphceria sacchari, Mass.). 

See U! S. Dept. Agr., Exp. Sta. Rec, X, pp. 56-57, '98, and XI, p. 759 (1900). 
Ring-spot {Leptosphceria sacchari, de Haan) . 

Cook, p. 89 (1913). 
Smut {Ustilago sacchari, Rabenh.). 
Stool Disease (Marasmius sacchari, Wakker). 

Cook, p. 92 (1913). 

1 Cf. Edgerton, C. W.: Some Sugar-cane Diseases, Bull. 120, La. Agric. Exper. 
Sta., July, 1910; Cobb, N. A.: Fungous Maladies of the Sugar Cane, Bull. 6, Exper. 
Sta., Hawaiian Sugar Planters Assoc, 1906. 



LIST OF SPECIFIC DISEASES OF PLANTS 465 

Sunflower 
(Helianthtis anntius, L.) 

Black-rot {SphcBronema fimbriatum (Ell. & Hals.) Sacc). 

Duggar, p. 348 (1909). 
Dry-rot (Phoma batata, Ell. & Hals.). 

Duggar, p. 344 (1909). 
Root-rot {Cortkium vagum, B. & C. var. solani, Burt.). 

Duggar, p. 444 (1909). 
Rust (Puccinia lielianiki, Schw.). 

Sweet Pea 
{Lathyrus odoratus, 'L.y 

Anthracnose {Glomcrella rufomacidans (Berk.), Spauld. & v. Schr.). 

Powdery Mildew (Erysiphe polygoni DC). 

Root-rot (Thielavia basicola, Zopf.; Rhizoctonia {Corticium vagum, Bri. & Cav. 

var. solani Burt); ChcBlomiiim spirochete, Pall.; Fusarium lathyri, Taub. 

& Manns). 
Stem or Collar-rot {Sclerotinia libertiana, Fckl.). 
Streak {Bacillus lathyrii, Manns & Taub.). 

Sweet Potato 
{Ipomceo batatas, Lam.) 

Black-rot (Sphoeronema (Ceratocystis) fimbriata (Ell. & Hals.), Sacc). 
Descr. Illus., N. Y. Agr. Exp. Sta., Bull. 76, pp. 7-13 (1890). 

Journ. Mycol., Vol. VII, pp. 1-9 (1891). 
Treat, (pos.), Md. Bull. 60, pp. 147-168, figs. 17 (March, 1899). 
(rec), U. S. Dept. Agr., Farm. Bull. 26, p. 21 (1895). 
Charcoal-rot {Sclcrollum bataticola, Taub.). 

Phytopathology 3, p. 161 (1913). 
Foot- rot (Plenodomus destruens. Hart.). 

Phytopathology. 3, pp. 242-245 (1913). 

Taubenhaus & Manns, Bull. 109, Del. Agr. Exp. Sta., May, 1915. 
Journ. Agr. Research I, p. 251 
Java- rot {Las iodiplodia tuber icola, Ell. & Ev.). 
Soil-rot {Acrocystis batatae, Ell. & Hals.). 

Descr. Illus., N. J. Agr. Exp. Sta., Bull. 76, pp. 14-18 (1890). 
Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 20, 1899, pp. 345-354. 

N. J. Spec. Bull. 5, February, 1900, pp. 22-31, pis. 3 (1900). 

1 Consult Taxjbenhaus, J. J.: The Diseases of the Sweet Pea, Bull. 106, Del. 
Agric. Exper. Sta., November, 1914. 
30 



466 SPECIAL PLANT PATHOLOGY 

Stem-wt {Fusanum hyperoxysporum Wollenw.). 
U. S. Farmers' Bull. 714, March 11, 1916. 
Phytopath. 4, pp. 277-303 (1914). 

Dry-rot {Phoma batatce, Ell. & Hals, conidial stage of Diaporlhe 

batatatis (Ell. & Hals.), Hart & Field). 
Leaf-spot {Phyllosticla bataticola, Ell. & Mart.) . 

U. S. Farmers' Bull. 711. 
Scurf {Monilochates infuscans (Ell. & Hals.) Hart). 
Miscellaneous N. J. Bull. 76, pp. 25-27 (Nov., 1890). 

Diseases. | Soft-rot {Rhizopus nigricans, Ehrb.). 
Phytopath. 4, pp. 305-320. 
Trichoderma Rot (Trickoderma Koningi, Oud.). 

Taubenhaus & Manns, Bull. 109, Del. Agr. Exp. Sta., May, 
1915- 
White-rot {Penicillium sp.). 

White-rust {Cystopus ipomaos-pandurance (Schw.), Farl.). 
Descr. Illus., N. J. Agr. Exp. Sta., Bull. 76 (1890). 
Md. Agr. Exp. Sta., Bull. 60 (1899). 
Treat, (rec), U. S. Dept. Agr., Farm. Bull. 26 (1895). 
Vine- wilt {Fusarium batatatis, Wollenw.). 

Taubenhaus and Manns, Bull. 109, Del. Agr. Exp. Sta., May, 1915. 
Wollenweber, H. W., Journ. Agr. Research 2, pp. 251-283 (191 1). 

Sycamore 

(Platanus occidentalis, L.) 

Anthracnose {Glceosporinm nervisequum (Fckl.), Sacc, stage of Gnomonia veneta 

(Sacc. & Speg.) Kleb.). 
Blight {Gnomonia veneta (Sacc. & Speg.), Kleb.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 387-389 (1889), 
Treat, (rec), U. S. Dep. Agr., Rep. for 1888, p. 389 (1889). 
Cf. Journ. Mycol., Vol. V, pp. 51-52. 
Gar. and For., X-488, pp. 257-258. 

Tea 

{Thea chinensisY 

Bark Disease (Corticium javanicum, Zimm. = C Zimmermani, Sacc. & Syd,). 

Blister- blight {Exobasidium vexans, Massee.). 

Copper-blight {Loestadia tliece, Show). 

Grey- blight (Pestalozzia guepini, Desm.). 

Horsehair-blight (Marasmius sarmentosus. Berk.). 

Internal Stem Disease {Massaria theicola, Petch.). 

Red-rust {Cephaleus mycoidea, Karst.). 

1 For all consult Cook, Diseases of Tropical Plants, pp. 170-180 (1913). 



LIST OF SPECIFIC DISEASES OF PLANTS 467 

Root Fungus {Roscllinia radicipcrda, Massee.)- 
Soot- blight (Capnodium Footii Berk, and Desm.). 
Thread- blight (Stilbum nanum, Massee.). 

Teosinte 
{Euchlcena mexicana, Schrod.) 
Smut {Ustilago zeoe (Beckm.), Ung.). 

Timber 

Decay (Stereum fmstulosum (Pers.), Fr.). 

von Schrenk, Diseases of Deciduous Forest Trees, U. S. Bureau of Plant Industry, 
Bull. 149 (1909). 
Sap-rot {Dadalea quercina (L.), Pers.)- 

Mainly on oak timber, von Schrenk (1909). 

Timothy 
{Phleum pratense, L.) 

Ergot {Claviceps purpurea (Fr.), Tul.). 

Phytopath. 4, pp. 20-22 (1914). 
Rust {Puccinia phlei-pratensis, Eriks & Henn.) 

Phytopath. 4, pp. 20-22 (1914). 
Smut {Ustilago stricef omits (West.), Niessl.). 

Tobacco 
{Nicoliana labacum, L.) 

Black- rot {Sterigmatocystis nigra v. Tieg.) . 

Wise. Res. Bull. 32, pp. 63-83, figs. 7 (June, 1914). 
Blue Mold {Fungus indet.). . 
Brown-spot {Macros poritim longipes, Ell. & Ev.) 

Descr., Journ. Mycol., Vol. VII, p. 134 (1892). 

Cf. U. S. Dept. Agr., Exp. Sta. Rec, XII-4, p. 359 (1900). 
"Damping-o2" {Altertiaria tenuis, Nees). 

Downy Mildew | J^f'^^f f '^ hyoscyami, deBy.). 

1^ {Phytophthora nicottanoe, de Haan). 
Leaf-blight {Cercospora nicotianoe, Ell. & Ev.). 

Descr. Illus., Conn. Agr. E.xp. Sta., Rep. 20, 1896, pp. 273-277 (1897). 

Treat, (rec), Conn. Agr. Exp. Sta., Rep. 20, 1896, pp. 277-278 (1897). 

Mosaic, Bull. U. S. Dept. Agr., p. 40 (1914). 



468 SPECIAL PLANT PATHOLOGY 

Pole-burn (Fungi and Bacteria). 

Descr., Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 168-173 (1892). 

Descr., Conn. Agr. Exp. Sta., Rep. 17, 1893, pp. 84-85 (1894). 

Treat, (rec), Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 180-184 (1892). 
Powdery Mildew {Erysiphe cichoracearum, DC, Syn. E. lamprocarpa (Wallr.), Lev.). 
Root-rot {Thielavia basicola, Zopf.). 

Gilbert, W. W., Bull. 158, U. S. Bur. of Plant Industry (1909). 
Conn. Rep., pt. 5, p. 342 (1906.) 

Phytopath. 6, pp. 167-181 (,1916). 
Stem-rot (Botrylis longihradiiata, Oud.) . 

Cook, Diseases of Tropical Plants, p. 149 (191 3). 

Descr., Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 184-185 (1892). 

Treat, (rec). Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 185-186 (1892). 
White-speck {Macros porium tabacinum, Ell. & Ev.). 

Descr., Journ. Mycol., Vol. VII, p. 134 (1892). 

Cf. Conn. Agr. Exp. Sta., Rep. 20, 1896, p. 276 (1897). 

Tomato 
{Lycopersicum esculentum, Mill.) 

Anthracnose {Collctotrichum phomoides (Sacc), Chester). 

Descr. Illus., Del. Agr. Exp. Sta., Rep. 4, 1891, pp. 60-62 (1892). 

Cf. Del. Agr. Exp. Sta., Rep. 6, 1893, pp. 111-115 (1894). 

Nebr. Rep., 1907, pp. 1-33, figs. S3- 

Treat, (rec), Me. Agr. Exp. Sta., Rep. for 1893, p. 155 (1894). 
Blight {Pscudomonas solanacearum, E. F. Sm.). 

Descr. Illus., See Egg-plant (Blight). 

La. BuU. 142, pp. 1-23, figs. 3 (October, 1913). 

Treat, (pos.), Md. Agr. Exp. Sta., Bull. 54, pp. 123-125 (1898). 
Fla. Agr. Exp. Sta., Bull. 47, pp. 133-136 (1898). 
Blight {Sclerotium sp.). 

Descr., Fla. Agr. Exp. Sta., Bull. 21, pp. 25-27 (1893). 
Ala. Agr. Exp. Sta., Bull. 108, pp. 28-29 (iQoo)- 

Treat, (pos.), Fla. Agr. Exp. Sta., Bull. 21, pp. 32-36 (1893). 
Downy Mildew {Pliyloptliora infestans (Mont.), deBy.). 

Fruit-rot {Macrosporium solani, E. «fe M. and Phoma dcstructiva, (Plowr.), 
Jamies.) 

Descr., Ala. Agr. Exp. Sta., Bull. 108, pp. 19-25 (1900). 

Cf. N. Y. Agr. Exp. Sta., Rep. 3, 1884, pp. 379-380. 1885. 

Cf. N. Y. Agr. Exp. Sta., Bull. 125, pp. 305-306. 1897. 

Journ. Agr. Research 4, p. i (April 15, 1915)- 
Leaf-blight {Cylindros porium sp.) . 

Descr., N. Y. Agr. Exp. Sta., Rep. 14, 1895, p. 529 (1896). 

Treat, (rec), N. Y. Agr. E.xp. Sta., Rep. 14, 1895, pp. 530-531 (1896). 
Leaf-mold {AUernaria solani (Ell. & Mart.), Jones & Grout). , 



LIST OF SPECIFIC DISEASES OF PLANTS 469 

Descr., Fla. Agr. Exp. Sta., Bull. 47, pp. 124-125 (1898). 
Treat, (pos.-), Fla. Agr. E.xp. Sta., Bull. 47, pp. 125-127 (1898). 
Leaf-spot {Septoria lycopersici, Speg.). 

Descr. Illus., Del. Agr. Exp. Sta., Rep. 7, 1894-95, p. 123 (1895). 

Ohio Agr. Exp. Sta., Bull. 73, p. 241 (1897). 
Treat, (pos.), Va. Bull. 192, pp. 16, figs. 9 (April, 191 1). 

Ala. Agr. Exp. Sta., Bull. 108, pp. 32-33 (1900). 
Rust (Macrosporium solani, Ell. & Mart.). 

Stevens & Hall, Diseases of Economic Plants, p. 312 (1910). 
Scab (Cladosporium fulvum, Cke.). 

Descr. Illus., U. S. Dep. Agr., Rep. for 1888, pp. 347-348 (1889). 
Treat, (pos.), U. S. Dep. Agr., Sec. Veg. Path., Bull. 11, p. 47 (1890). 
Ala. Agr. Exp. Sta., Bull. 108, p. ^^ (1900). 
Wilt {Fusarium lycopersici, Sacc). 

Trumpet Creeper 
(Tecoma radicans (L.) Jass.) 

Leaf-blight (Cercospora sordida, Sacc.) . ' . 

Duggar, p. 315 (1909). 
Leaf-spot {Septoria lecomce, Ell. & Ev.). 

Tulip Tree 
{Liriodendron tulipifcra, L.) 

Leaf -blight {Glceosporium liriodendri, Ell. & Ev.). 
Sap-rot {Pclyst ictus versicolor (L.), Fr.). 

von Schrenk, H., Diseases of Deciduous Forest Trees, U. S. Bur. of Plant In- 
dustry, Bull. 149 (1909). 

Turnip 

{Brassica campcstris, L. and B. rapa, Linn.) 

Brown-rot (Fseudomonas campestris (Pam.), E. F. Sm.). 

Descr. Illus., Iowa Agr. Exp. Sta., Bull. 27, pp. 130-134 (1895). 
Club-root (Plasmodiophora brassicce, Wor.). 

Descr. Illus.,- See Cabbage (Club-root). 

Treat, (pos.), N. J. Agr. Exp. Sta., Rep. 20, '99, pp. 354-367 (1900). 
Downy MUdew {Peronospora parasitica (Pers.) deBy.). 

Occ, Mass. Agr. Exp. Sta., Rep. 8, 1890, p. 222 (1891). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 8, 1890, p. 223 (1891). 
Dry-rot (Plioma brassicce, Thiim ?). 

See U. S. Dept. Agr., E.xp. Sta. Rec, XII-3, p. 256 (1900). 

Conn. Exp. Sta., Rep., p. 355 (191 2). 



470 SPECIAL PLANT PATHOLOGY 

Leaf- mold {Macros porium herculeum, E. & M.). 

Descr. Illus., N. Y. Agr. Exp. Sta., Rep. 15, '96, pp. 451-452 (1897). 
Powdery Mildew (Erysiphe polygoni, DC). 

Occ, N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 61, pp. 305-306 (1893). 
White-rust (Cystopus candidns, (Pers.) Lev.). 

Occ, Mass. Agr. Exp. Sta., Rep. 8, i8go, p. 222 (1891). 

Treat, (rec), Mass. Agr. Exp. Sta., Rep. 8, 1890, p. 223 (1891). 

Tree of Heaven 
{Ailanthus glandulosa, Desf.) 
Shot- hole (Ccrcospora glandiilosa, Ell. & Kell.). 

Verbena 

{Verbena sp.) 

Powdery Mildew {Erysiphe cichoraccarum, DC). 

Occ, N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 37, p. 405 (1891). 

Treat, (pos.), N. Y. (Corn. Univ.) Agr. Exp. Sta., Bull. 37, p. 405 (1891). 

Vetch 
( Vicia spp.) 

Powdery Mildew {Erysiphe polygoni, DC). 

Duggar, p. 227 (1909). 
Rust {Uromyces pisi (Pers.) de By). 

Duggar, p. 398 (1909). 

Violet . 

{Viola odorata, L. and V. tricolor, L.) 

Anthracnose {Glceosporinm violce, B. & Br.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 362 (1891). 
Anthracnose {Colletotrichum violce-iricoloris, Smith). 

Descr., Mass. Agr. Exp. Sta., Rep. 11, '98, pp. 152-153 (1899). 

Treat, (pos.), Mass. Agr. Exp. Sta., Rep. 11, '98, p. 153 (1899). 
Gall or Chytridiose {Cladochylrium violce, Berl.). 

See U. S. Dep. Agr., Exp. Sta. Rec, XI-3, p. 261 (1899). 
Downy Mildew {Peronospora violas, de By.) . 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 362 (1891). 
Dry-rot {Merulius lacrymans (Jacq.) Fr.) . 

See U. S. Dep. Agr., Exp. Sta. Rec, XI-io, p. 947 (1900). 
Leaf-bhght {Cercospora violce, Sacc). 

Occ Illus., N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 3S4-386 (1895). 

Treat, (rec) N. J. Agr. Exp. Sta., Rep. 15, 1894, pp. 386-389 (1895). 



LIST OF SPECIFIC DISEASES OF PLANTS 47 1 

Leaf-mold or Spot Disease {AUernaria violcc, GaH. & Dors.). 

Descr. Illus. Treat., U. S. Dep. Agr., Div. Veg. Phys. & Path., BulL 23 (1900). 
Leaf-spot {Phylloslida viola;, Desm. and AUernaria viola;, GaU. & Dors.). 

Descr., Mass. Agr. Exp. Sta., Rep. 10, 1892, pp. 231-232 (1893). 

Treat, (rec.) Mass. Agr. Exp. Sta., Rep. 10, 1892, pp. 232-235 (1893). 
N. J. Agr. Exp. Sta. Rep. 15, 1894, pp. 286-389 (1895). 
Root-rot (Tkielavia basicola, Zopf). 

Descr. Conn. Agr. Exp. Sta., Rep. 15, 1891, pp. 166-167 (1892). 
White Mold (Zygodcsmus albidiis, Ell. & Hals.). 

Occ, N. J. Agr. Exp. Sta., Rep. 11, 1890, p. 362 (1891). 

Virginia Creeper 

(Ampelopsis quinquefolia, Michx.) 

Leaf-spot {Phylloslida ampdopsidis, E. & M.) =Laestadia Bidwellii (Ell.). V. & R. 

Walnut 

(Juglans regia, L.) 

Bacteriosis {Pseudomonas jnglandis, Pierce). 
Ore. Sta. Rep., p. 260 (1911-12). 

See U. S. Dep. Agr., Exp. Sta. Rec, Vol. XI, p. 261 (1899). 
Cal. Bull. 231, pp. 320-383, figs. 19 (August, 191 2). 
Leaf-blight {Marsonia juglandis (Lib.) Sacc. oi Gnomonia leptosiyla (Fr.) Ces. & deN. 
Leaf-spot {Ascochyta juglandis, Boltsh. and Phleospora muUimaculans, Heald & 

Wolf.). 
Leaf Disease (Cylindrosporium juglandis, Wolf.) 
Mycologisches Centralblatt 4, p. 65 (1914). 

Watermelon ; . 

(Cilrullus vulgaris, Schrad.) 

Anthracnose (Colletotrichum lagenarimn (Pass.), Ell. & Hals.). 

Occ, N. J. Agr. Exp. Sta., Rep. 13, 1892, p. 326 (1893). 

Treat, (neg.), Del. Agr. Exp. Sta., Rep. 5, 1892, p. 79 (1893). 

Cf. N. J. Agr. Exp. Sta., Rep. 13, pp. 326-330 (1892). 
Del. Agr. Exp. Sta., Rep. 5, pp. 75-79 (1892). 
Downy MUdew (Plasmopara cubensis (Bri. & Cav.), Humph.). 

See Cucumber (Downy Mildew). 
Leaf-blight (Cercospora citrullina, Cke.). 

Occ, Ohio Agr. Exp. Sta., Bull. 105, p. 232 (1899). 
Leaf-mold (AUernaria brassica, Sacc, var. nigrescens, Regel.). 

See Melon (Leaf-mold). 
Leaf-spot {Phyllosticta sp. and (?) Spharella sp.). 

Descr. Ulus., DeL Agr. Exp. Sta., Rep. 5, 1892, pp. 75-78 (1893). 



472 SPECIAL PLANT PATHOLOGY 

Wheat 

{Trilicum viilgare, L.) 

Blight (Mysirosporium abrodens, Neum.). 
Chytridiose {Pyroctontim spharicum, Prunet). 

See U. S. Dept. Agr., Exp. Sta. Rec, VI-3, pp. 226-227 (1894). 
Ergot (Claviceps purpurea, (Ft.) Tul.). 

See Rye (Ergot). 
Foot-rot [Ophlobolus & Leptospharia). 

See U. S. Dept Agr., Exp. Sta. Rec, IX-ii, p. 1057 (1898). 
U. S. Dept. Agr., Exp. Sta. Rec, X-7, p. 650 (1899). 
Leaf-spot {LeptosphcBria eustoma (Fr.), Sacc, var. tritici, Garov.). 
Leaf-spot (Seploria graminum, Desm.). 

See U. S. Dept. Agr., Exp. Sta. Rec, X-s, p. 452 (1899). 
Mildew {Erysiphe graminis, DC). 

Iowa Bull. 104, pp. 245-248 (July, 1909). 
Mold (Cladosporiutn hcrbarum (Pers.), Lk.). 

Rust (Black-stem, Puccinia graminis, Pers. and Orange-leaf, P. rubigo-vcra (DC.), 
Wint., also P. glumarum (Schum.), Eriks. & Henn.). 
Descr. lUus., Ind. Agr. Exp. Sta., Bull. 26 (1889). 

Kan. Agr. Exp. Sta., Bull. 38, pp. 1-3 (1893). 
Treat, (rec), Idaho Agr. Exp. Sta., Bull. 11, pp. 33-34 (1898). 
Cf. U. S. Dept. Agr., Div. Veg. Phys. & Path., Bull. 16 (1899). 
Scab {Cladosporium herbarum (Pers.), Lk.). 

Scab (Fusarium culniorum (E. F. Sm.), Sacc.=i^. rubiginosuni, Appel & Wollenw.). 
Descr. Illus., Del. Agr. Exp. Sta., Rep. 3, 1890, pp. 89-90 (1891). 
Ohio Agr. Exp. Sta., Bull. 44, pp. 147-148 (1892). 
Scab {Gibberella Saubenetii (Mont.), Sacc, Stage oi Fusarium roseum, Lk.). 

Descr. Illus., Ohio Agr. Exp. Sta., Bull. 97, pp. 40-42 (1898). 
Stinking-smut {Tilletia fcetens (Bri. & Cav.), Schrt, T. tritici (Bjerk.), Wint.). 

Phytopath. 6, pp. 21-28 (1916). 
Loose-smut (Uslilago tritici (Pers.), Jens.). 

Descr. Illus., Kan. Agr. Exp. Sta., Rep. 2, 1889, pp. 261-267 (1890). 
N. Dak. Agr. E.xp. Sta., Bull. 1, pp. 9-20 (1891). 
U. S. Dept. Agr., Farm. Bull. 75, pp. 6-8 (1898). 
Treat, (pos.), Ohio Agr. Exp. Sta., Bull. 97, pp. 60-61 (1898). 

U. S. D^pt. Agr., Farm. Bull. 75, pp. 11-14 (1898). 

Willow 
(Salix spp.) 

Black-spot {Rhytisma salicinum (Pers.), Fr.). 

Duggar, p. 209 (1909). 
Crown-gall {Pseiidomonas tumefaciens, E. F. Sm. & Towns.). 

Duggar, p. 114 (1909). 



LIST OF SPECIFIC DISEASES OF PLANTS 473 

Decay, or Brown-rot (Poly poms stdphHreus (Bull.), Fr.). 

Duggar, p. 457 (1909)- 
Powdery Mildew {Undnula salicis (DC), Wint.). 

Duggar, p. 230 (1909). 
White-rot (Polyporus sqnamosus (Huds.), Fr.)- 

Duggar, p. 453 (1909). 
Rust {Mdampsora salickaprce (Pers.), Wint.) =M. Jariiiosa (Pers.), Schrot. 

Zinnia 

{Crassina ckgam (Jacq.) Kze.) 

Leaf-spot {Ccrcospora atrkincta, Heald & Wolf). 

Heald & Wolf, Plant Disease Survey in Texas (191 2). 

BIBLIOGRAPHY OF SPECIFIC PLANT DISEASES 

That the foregoing list may be made as useful to American students as possible, 
a partial bibliography of some of the publications dealing with specific diseases of 
our economic plants is herewith given. 

Arthur, Joseph C. and Kern, F. D.: North American Species of Peridermium on 

Pine. Mycologia, vi: 109-138, May, 1914. 
Clinton, G. P.: The Smuts of Illinois Agricultural Plants. Univ. 111. Agric. Exper. 

Sta., Bull. 57, March, 1900. 
Cook, Mel T.: Potato Diseases in New Jersey, N. J. Agric. Exper. Sta., Circular 33. 
Cook, Mel T.: Common Diseases of the Peach, Plum and Cherry. N. J. Agric. 

Exper. Sta., Circular 45. 
Cook, Mel T.: Common Diseases of Apples, Pears and Quinces. N. J. Agric. 

Exper. Sta., Circular 44. 
Duggar, B.' M.: Some Important Pear Diseases. Cornell Univ. Agric. Exper. 

Sta., Bull. 145, February, 1898. 
Duggar, B. M.: Three Important Fungous Diseases of the Sugar Beet. Cornell 

Univ. Agric. Exper. Sta., Bull. 163, February, 1899. 
Edgerton, C. W.: Some Sugar Cane Diseases. La. Agric. Exper. Sta., Bull. 

120, 1910. 
Eugerton, C. W.: Disease of the Fig Tree and Fruit. La. Agric. Exper. Sta., 

Bull. 126, March, 1911. 
Freeman, E. M., and Johnson, E. C: The Loose Smuts of Barley and Wheat. 

U. S. Bureau of Plant Industry, Bull. 152, 1909. 
Freeman, E. M., and Johnson, E. C: The Rusts of Grain in the United States, 

. U. S. Bureau of Plant Industry, Bull. 216, 1916. 
Freeman, E. M. and Stakman, E. C: The Smuts of Grain Crops. Minn. Agric. 

Exper. Sta., Bull. 122, February, 1911. 
Harter, L. L.: Sweet Potato Diseases. U. S. Farmers' Bull. 714, March 11, 1916. 
Hesler, Lex R., and Whetzl, Herbert H.: Manual of Fruit Diseases, 191 7. 

The MacMillan Co. 



474 SPECIAL PLANT PATHOLOGY 

Johnson, E. C: Timothy Rust in the United States. U. S. Bureau of Plant In- 
dustry, Bull. 224, 191 1. 

Orton, W. a.: Some Diseases of the Cowpea. U. S. Bureau of Plant Industry, 
Bull. 17, 1902. 

Orton, W. A.: Tomato Diseases, from Tomato Culture by Will W. Tracy, 
1907, Orange Judd Co. 

Orton, W. A.: Potato Tuber Diseases. U. S. Farmers' Bull. 544, 1913. 

Pool, Venus W.: Some Tomato Fruit Rots during 1907, 1908. 

Reed, Howard S. and Crabill, C. H.: Notes on Plant Diseases in Virginia ob- 
served in 1913 and 1914. Va. Agric. Exper. Sta., Tech. Bull. 2, April, 1915. 

Selby, a. D.: Some Diseases of Orchard and Garden Fruits. Ohio Agric. Exper. 
Sta., Bull. 79, 1897. 

Selby, A. D.: Prevalent Diseases of Cucumbers, Melons and Tomatoes. Ohio 
Agric. Exper. Sta., Bull. 89, December, 1897. 

Shear, C. L. : Cranberry Diseases. U. S. Bureau of Plant Industry, Bull. 1 10, 1907. 

Stevens, F. L.: Fungous Diseases of Apple and Pear. N. C. Agric. Exper. Sta., 
Bull. 206, March, 1910. 

Stone, Geo. E.: Tomato Disease. Mass. Agric. Exper. Sta., Bull. 38, June, 191 1. 

Taubenhaus, J. J.: Diseases of the Sweet Pea. Del. Agric. Exper. Sta., Bull. 
106, November, 19 14. 

VON Schrenk, Hermann: Two Diseases of Red Cedar caused by Poly poms 
jtmiperinus and P. carneus. U. S. Div. Veg. Physiol. & Pathol., Bull. 21, 1900. 

VON Schrenk, Hermann: The Decay of Timber and Methods of Preventing It. 
U. S. Bureau of Plant Industry, Bull. 14, 1902. 

VON Schrenk, Hermann, and Spaulding, Perley: The Bitter Rot of Apples. 
U. S. Bureau of Plant Industry, Bull. 44, 1903. 

Wilcox, E. Mead: Diseases of Sweet Potatoes in Alabama. Agric. Exper. Sta. 
of the Ala. Polytechnic Institute, Bull. 35, June, 1906. 



CHAPTER XXXIV 
DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 

This section of the book will be devoted to a consideration of the 
specific diseases of plants, and the treatment of the subject has been 
made possible by a selection of nearly loo parasitic and non-parasitic 
diseases. In this selection, several things have been kept in view, viz., 
the importance of the disease over wide geographic areas, the system- 
atic relationship of the fungus in order to connect up the practical and 
the systematic parts of the book, because our knowledge of the disease 
warrants its inclusion in the descriptive part which follows. As a con- 
sideration of the remedial measures used to combat the disease was 
omitted largely in the description of plant diseases in general, it is intro- 
duced incidentally with the study of specific plant diseases. The chief 
reference to such remedial substances and their use will be found in one 
of the appendices in the back of the book, where the manufacture of 
sprays and washes and their recommended use may best be made with 
the consideration of a spray calendar. A regular spraying program 
is now considered a necessity by every successful plant-grower, the 
expense of which, treated as insurance, can no more be escaped than the 
outlay for cultivation, manures, or pruning. In the control of plant 
enemies, including both insect pests and fungous parasites, there are 
essential points in practice which may not be evaded or neglected, 
namely: To spray at the correct time (hence the need of a calendar) to 
use the proper form and strength of spray (hence the need of formulae) 
and to make a thorough covering of the parts sprayed. Hence that 
important branch of phytopathology known as therapeutics will be 
mentioned incidentally in part III and treated in detail in the latter part 
of part IV. 

The description of each disease will be given in condensed form pur- 
posely, so that the student of plant pathology who wants to know more 
about the specific diseases of some particular crop in which his interest 
has been aroused will be compelled to study the literature and thus gain 

475 



476 SPECIAL PLANT PATHOLOGY 

access to the most important work which has been done. In this inves- 
tigation, the student should write descriptions of the diseased host 
plants and parasitic organisms concerned, according to the method out- 
lined in part IV, pages 639 to 642, and together with this detailed de- 
scription he should compile a bibliography. 

Pedagogically it is a mistake to give too full details in a text-book, 
because the student learns to depend on the statements in the book 
rather than on original observations of his own. The compilation of a 
bibliography becomes an important adjunct to all successful phyto- 
pathologic work. "Study things, not books" is a truism in this depart- 
ment of scientific knowledge, as in other departments of natural science. 
The teacher should so guide and stimulate the class of students that each 
member of the class will be led to independent study and investigation, 
so that they may be able to apply individually the modicum of knowledge 
which the strictures of the time allotted to the subject in the college has 
permitted them to obtain. Unless this independence of thought and 
action is secured, the results of the teaching have not been satisfactory. 
It is, therefore, hoped by the writer of this text-book that what has been 
included in its pages will be directive and helpful to teacher and student 
rather than a work of encyclopedic value. The subject of phytopa- 
thology is such a vast one, that it would be impossible without the coop- 
eration of a large number of specialists to make a work which would be 
of encyclopedic value. The design of this text-book has been to give an 
outline of the subject, so that the attention of the student may be direc- 
ted to the important phases of the subject of phytopathology. 

Alfalfa {Mcdicago sativa L.) 

Leaf-spot {Pseudopeziza medicaginis (Lib.), Sacc). — The fungus 
which causes this widely prevalent disease, where alfalfa is grown, 
belongs to a genus in which the apothecium is formed beneath the epi- 
dermis and as it grows it breaks through the epidermal covering and 
emerges as a shallow, relatively simple structure with asci that contain 
eight one-celled spores. It is related to a similar fungus Ps. trifolii, 
which attacks the leaves of clovers. It forms small brown, or black, 
spots on the upper leaf surface usually. These spots, which are about 
2 mm. in diameter, represent the sessile apothecia, which are sprinkled 
pretty copiously over the leaf surface in the latter part of summer. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 477 

The unicellular spores measure 10 to 14/i in length. No practical 
method has been devised for controlling the alfalfa leaf-spot disease. 

Rust {Uromyces striatus Schrot.). — The aecidiaof this rust are found 
on Euphorbia cyparissias in Europe and in Great Britain the uredinea 
and telia occur on a clover Trifolium minus. In California, it forms 
reddish-brown, dusty pustules on the surfaces of alfalfa leaves and 
in wet weather it may be destructive to the crop, but in dry weather 
it usually disappears. The spots are on close examination seen to be 
cinnamon-colored, due to the presence of globose to ellipsoid, faintly 
echinulate, yellowish-brown uredospores, which measure 15 to 22// 
with a spore wall i to 2^ thick, and with four to six germ pores each 
with a small cap. The telia are darker in color, and the teliospores are 
globose to ovate with a minute papilla striated from apex to base with 
lines of brown warts and measure 18 to 24 by 15 to 20/x with an epir 
spore 1 3^ to 2/i thick. The best way of combating this disease is to 
cut and burn badly affected crops. Frequent close mowing is useful 
in checking leaf-spot. 

Apple {Pyrus malus L.) 

Bitter-rot {Glomerella cingulata (Stonem.) S. & V. S.). — This 
fungus, which in some text-books is known as G. rufomaculans (Berk.) 
Spauld. & von Sch., causes one of the most serious losses in the apple- 
growing districts of the United States (Fig. 190). It is distributed 
widely, particularly eastward of the arid portions of the country and 
its effects are seen during July and August and later, especially during 
warm rainy weather, which produce sultry conditions of the atmos- 
phere, when the age of the fruits is such as to render them especially 
susceptible. Cold weather acts as a check to the spread of the dis- 
ease. The fruit is attacked chiefly, but the branches may also become 
diseased. 

The disease first appears as a small brown spot beneath the skin of 
the apple, which increases gradually in size, keeping nearly a circular 
outline with a well-defined margin. The central part of the spot soon 
becomes sunken and this is accompanied by the spread of the fungus 
throughout the fruit and the formation of pustules. Decay soon sets 
in and the products of the decay are invariably bitter. The fruits, if 
attacked on the tree, later fall off, but sometimes, they hang on and 
become mummified. Two stages in the life history of the fungus have 



478 SPECIAL PLANT PATHOLOGY 

been discovered. The gleosporial, or imperfect stage, usually develops 
on the fruit, while the ascigeral stage is occasionally produced on a 
fruit or twig, and in artificial cultures is readily obtained. Early in- 
fection of the fruit is probably due to the spores produced in pustules 
on the areas of stem, which have become cankered through the attack 
of the bitter-rot mycelium. Such cankers are sunken areas upon twigs 
or limbs, accompanied by a cracking and breaking of the bark over such 
regions. The pustules, which accompany the rot of the fruit, are formed 
beneath the apple skin as ccmdensed masses of the mycelium known 
as stroma and these emerge as a cone-shaped mass of erect hyphae, 
which are the conidiophores, which cut off conidiospores that emerge 
as a pink waxy strand, later becoming of a gray color. The ovate to 
oblong conidiospores, which measure in extreme cases 6 to 40 by 3.5 
to 7/1, more usually 12 to 16 by 4 to 6/i, are imbedded in a gelatinous 
matrix which dissolves in water setting the spores free. These spores 
germinate freely and become septate in doing so. Infection of apple 
fruits may be through the uninjured skin, but a slight abrasion facilitates 
the entrance of the germ tube of the spore. Berkeley, who first 
described this stage, named it Gleosporium Jructigenum and under this 
scientific name the disease is frequently quoted. 

Clinton discovered the perithecial stage in 1902, and as it is readily 
obtained in cultures on any of the ordinary nutrient media its character- 
istics are well-known. The perithecia which are developed contain 
oblong-clavate asci, 55 to 70 by g/x, which develop eight curved asco- 
spores, usually uniform in size, 12 to 22 by 3.5 to 5/1. The pomologist, 
who wishes to control the disease, should prune away all cankered limbs 
and keep the orchard free of diseased fruits. The spraying of the trees 
with Bordeaux or lime-sulphur (3-3-50) has been found efficacious, 
and the crop returns from sprayed trees, as contrasted with unsprayed 
trees, have abundantly repaid the trouble which the orchardist has 
taken in the application of Bordeaux mixture. The first application 
of the spray should be in the form of a mist about a month after the 
petals have fallen and subsequent applications should be made about 
two weeks apart until at least five sprayings have been made. 

Black-rot {Spharopsis malorum Berk.). — Although the apple is 
one of its host plants, the black rot fungus attacks other pomaceous 
trees, producing cankers so that the description of the disease and 
fungus, as applied to the apple, will serve with certain modifications for 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 479 

the other pomaceous trees as well, and this may be said of several of 
the other diseases treated of here that the description of a disease as 
specifically affecting a certain host, might equally apply to several 
other host plants. The black-rot fungus not only causes a fruit 
decay of apples, quinces and pears, but it causes the formation of 
canker on the limbs of these trees. The fruit rot is the generally 
recognized form of the disease. The disease begins as a small spot 
sometimes near the bud end of the fruit and it spreads until the whole 
fruit is involved. The apples do not shrink, as in the former disease. 
The canker form of the disease on the bark of the trees is accompanied 
by either a roughening of the bark in mild forms of the disease, or in 
more virulent forms by a destruction of the bark with the formation 
of depressed areas about which local swellings of the limbs occur. 

The sooty brown, or olivaceous, mycelium penetrates the bark 
of the tree, hardly extending into the wood. It soon forms pycnidia 
which are erumpent and surrounded by the remnants of the epidermis. 
The pycnospores are oblong-elliptic, 22 to 32 by 10 to 141JL, brown in 
color, and their size varies with the host plant on which the fungus lives. 
Artificial cultures of the fungus have successfully produced spores. 
Lime-sulphur solution has been found useful in combating the disease, 
but pruning and scraping the trees should not be neglected. 

Scab {Venturia inequalis (Cke.) Wint.). — The scab also appears on 
the pear, but mycologists now consider that the scab fungus of the 
apple is specifically distinct from that of the pear. Earlier mycologist^ 
were familiar with the conidial forms of the two fungi, and they 
were placed under the genus Fusicladium, as F. dendriticum and 
F. pyrimim, but since the perfect stages have been discovered the 
species have been put in the genus Venturia. The perithecial stage 
is saprophytic. Scab is found wherever the apple is grown from 
Maine to California. 

The fungus mainly attacks the fruit and leaves of the apple, but 
it has been found on the flowers, flower stalks and twigs. The leaf 
spots are more abundant on the lower surface, but sometimes also on 
the upper surface, as a velvety, olivaceous, superficial growth, occasion- 
ally accompanied by a curling of the leaf. The fruit spots are at first 
small and olivaceous, and as the mycelium spreads the epidermis is 
killed and the scabby areas arise (Figs. 164 and 165). Nearly all varie- 
tes of apple and pear are susceptible, but there is a varietal difference 
in this susceptibility. 



48o 



SPECIAL PLANT PATHOLOGY 



The hyphae grow beneath the epidermis and between the epidermis 
and cuticle spreading slowly. The erect conidiophores, which are 
produced, rupture the epidermis, giving the characteristic velvety, 




Fig. 164. — Two apples affected with scab {Venliiria inequalis), showing spots, 
deformation and reduction in size of the fruit. {After Heald, F. D., Bull. 35 {Sci. 
Ser. 14), Univ. of Tex., Nov. 15. 1909.) 




Fig. 165. — Two apples affected with scab {Vcnluria inequalis), showing spots, 
deformation and reduction in size of the fruit. {After Heald, F. D., Bull. 135 {Set. 
Ser. 14), Univ. of Tex., Nov. 15, 1909.) 



olivaceous character to the spotted surface, and as the scabby areas 
are formed, the epidermis disappears. Conidiospores arise at the tips 
of the conidiophores and in concatenation. These spores are ovate, 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 



truncate at the base and measure 28 to 30ju by 7 to 9/1. According to 
Clinton, they do not retain their vitality long. An investigation of 
perithecial formation indicates that perithecia begin to form in 
October, or even later, and reach maturity in the following April, 
when mature ascospores have been 
found especially on the under sur- 
faces of the leaves. They are im- 
bedded in the leaf tissues and are 
slightly pyriform in shape, includ- 
ing clavate slightly curved asci 
measuring 55 to 75// by 6 to 12^1. 
Each ascus contains eight two- 
celled ascospores, which are olive- 
brown in color with the following 
dimensions: 11 to 15/iby 5 to 7/x. 
They germinate readily in water. 
Spraying with lime-sulphur 
mixture 32° Beaume, 1-40, before 
the time of flowering has been rec- 
ommended for Scab, followed by 
a second, or even a third spraying 
after the petals fall, and at least 
two or three weeks after the 
second. 



Ash (Fraxinus americanus, L.) 

Heart-rot (Fomes fraxinophilus 
(Pk.) Sacc). — In the Mississippi 
Valley, white ash trees of all ages 
are attacked by this bracket 
fungus, which is a tree wound 
parasite, entering usually the stub 

of a branch, which has been broken off by the wind, or by snow. From the 
point of entrance, the mycelium grows into the heartwood of the trunk. 
The wood at first turns darker in color, later the disease is marked 
by a bleaching of the color in the spring wood of the annual rings, which 
turn to a straw color and then become blanched. The whole woody 
31 




Fig. 166. — An old sporophore of Fomes 
(Polyporus) fraxinophilus on white ash. 
(After Herynann von Schrenk, Bull. 32, 
U. S. Bureau of Plant Industry. 1903.) 



482 



SPECIAL PLANT PATHOLOGY 







Fig. 167. — Disease of ash caused by Fames (Polyporus) fraxinophilus. i, Cross- 
section of ash wood; 2, of medullary ray; 3, medullary ray, showing later stage of 
attack; 4, 5, of wood cells; 6, starch grains from medullary ray cell; 7 diseased 
wood; 8, transection from entirely rotted wood. (After von Schrenk, Hermann, 
Bull. 32, U. S. Bureau of Plant Industry, 1903) 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 483 

tissue becomes straw-colored and finally transformed into a loose 
spongy mass of fibers, which readily absorbs water (Fig. 167). 

The fruiting brackets, or sporophores, make their appearance from 
the mycelium at the base of the stubs, or from wounded surfaces, 
either alone, or a number together (Fig. 166). The mature sporophore, 
according to von Schrenk,^ is nearly triangular in cross-section with a 
broad rounded edge, which at first is white, turning gradually darker 
until it becomes straw-colored (Fig. 167). The older portions of the 
upper surface are dark brown, or black, and are very hard and woody, 
its upper surfaces obscurely zoned, pale brown and rust colored. Wound 
protection, as outlined in the section on prophylaxis, is an important 
method of preventing the white heart-rot from killing white ash trees. 

Asparagus (Asparagus officinalis, L.) 

Rust {Puccinia asparagi DC.) — The asparagus rust is well-known, 
having been investigated by a number of mycologists in this country, 
notably Halsted, Sirrine, Smith and Stone. ^ In Europe the disease is 
of little consequence, but in America it threatens the asparagus growing 
of our country, spreading rapidly, especially during times when dew is 
abundant, for Smith says: "The amount of rust varies directly and 
exactly with the amount of dew, and so long as there is little or no dew, 
there can be no rust." During dry summers rust is largely absent. 

All of the spore forms are found on the stems and twigs of the culti- 
vated asparagus and on several wild species of the genus. The uredi- 
nia and telia appear also on the leaf-like branches of the plant. The 
aecidia appear as long light-green cushion-like patches. They have a 
white peridium and are short cylindric, inclosing the orange-colored 
aeciospores, which are 15 to iS/z in diameter, and retain their power of 
germination for several weeks. Stomatal infection probably is the rule. 
Associated with these secia are spermagonia in small, yellow clusters. 
Early summer ushers in the red rust (uredo) stage of the disease with 
the deep brown sori more or less scattered at first, later becoming con- 
fluent. The urediniospores are yellowish-brown, thick-walled with 
four germ pores and measure 21 to 24^. The clothing of a person 

Won Schrenk, Hermann and Spaulding, Perley: Diseases of Deciduous 
Forest Trees. Bull. 149, U. S. Bureau of Plant Industry. 

''Smith, Ralph E.: Asparagus and Asparagus Rust in California. Calif. Agric. 
Exper. Sta., Bull. 165: 1-95, 1905. 



484 SPECIAL PLANT PATHOLOGY 

rubbing against the plant may be colored owing to the abundance pro- 
duced. Later in the season the black rust stage appears with the forma- 
tion of elliptic two-celled teliospores, 30 to dofx by 21 to 28/i, and with 
a thickened apex and long pedicels. Infection of asparagus plants in 
cultivated fields is, according to Duggar/ through the aeciospores pro- 
duced on wild or escaped plants and not directly from the germination 
of the teliospores, which remain in or about the soil. Bordeaux mix- 
ture, used as a spray alone, has not been very successful. A more 
successful treatment has been obtained by adding a resin mixture to 
the Bordeaux solution. Sirrine recommends the following: Bordeaux 
mixture, 5-5-40 formula, 40 gallons; resin mixture, 2 gallons, diluted 
10 gallons. The resin mixture consists of resin 5 pounds; potash lye i 
pound; fish oil i pint; and water 5 gallons. Under certain climatic con- 
ditions in California it has been found efficient to dust the young tops 
with dry powdered sulphur on a dewy morning at the rate of one 
and a half sacks of sulphur per acre, followed in a month by a 
second application, using two sacks of sulphur per acre. 

Banana {Musa sp.) 

Bud-rot {Bacillus musce, Rorer). — Bud rots of the banana have 
been reported from the greater Antilles (Cuba, Jamaica) from Central 
America and Trinidad. The disease in Trinidad has been investigated 
by a mycologist from the United States, J. B. Rorer, the mycologist 
of the island government, and he has proved that an organism which 
he has isolated and named Bacillus musce is the responsible parasite. 
However, the bud-rots of the banana are probably due to the same 
cause, but the matter has not been investigated satisfactorily outside 
of Trinidad. The disease usually appears on the young plants, attack- 
ing the young leaves and the core, which become brown. The tissues 
disorganize and a putrid rot sets in with the death of the parts 
attacked. 

March is the month in which the disease usually begins and in 
three or four months its destructive effects are seen. 

Beet (Beta vulgaris, L.) 

Leaf -spot (Cercospora beticola, Sacc). — This disease is distributed 
widely in America and Europe and the red garden beet is seldom free 
^ DuGGAR, B. M.: Fungous Diseases of Plants, 406. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 485 

from it. The leaf-spots are very small brown with reddish-purple 
borders, when they first appear, and later, when about 4 mm. in 
diameter, they become ashen gray at the center with the usual margin. 
They are scattered over the blade and eventually the leaves blacken 
and dry up, and as the lower leaves die, new ones are formed above 
until a characteristic elongated crown may be produced. The gray 
color of the spots is usually associated with the formation of conidio- 
sphores- and conidiospores. The conidiophores are clustered, arise 
from a few-celled stroma, and push through the leaf stomata. The 
conidiospores are elongated and needle-shaped, multicellular, 75 to 
200/1 by 3.5 to 4.SAi, and under moist conditions, the average length may 
be exceeded. They germinate readily in ordinary nutrient media 
and the submerged mycelium in agar grows as a dense colony oliva- 
ceous in color, while the aerial portion is grayish-green. The disease 
fortunately can be controlled by the use of Bordeaux mixture (4-4-50), 
and as the spores retain their vitality for some time, early spraying 
is important and frequent after sprayings. 

Rust {Uromyces betcB (Pers.), Tub). — The beet rust is known only 
from California. It is common in Australia and not unusual in 
Europe. Klihn thinks that the mycelium may be biennial in the host, 
forming aecia throughout the year. The spermogonia are found in 
small yellow groups associated with the Eecia, which are white and 
saucer-shaped with aecidiospores 17 to 36/i in diameter, filled with 
orange-colored contents. The uredinia and telia are irregularly scat- 
tered over the leaf surfaces. The urediniospores are obovate, 21 to 
24|U by 35M with echinulate walls, and two opposite germ pores. The 
short pedicellate obovate -teliospores are 18 to 24/i by 25 to 32/x, 
with an apical germ pore piercing a wall scarcely thicker at the apex. 

Cabbage (Brasska oleracea, L.) 

Black-rot (= Pseudomonas brassicce. (Pam.), Sm., Bacterium cam- 
pestris (Pam.), Sm.) — The cause of the black-rot of cabbage and other 
cruciferous plants is a yellow, uni-flagellate microorganism, which causes 
a yellowing of the cabbage leaves accompanied by a black stain in the 
vascular system, forming a conspicuous black network on a yellowish, 
or light-brown, background. The badly diseased leaves are shed, so 
that the stem may have a terminal tuft of badly distorted leaves. 



486 



SPECIAL PLANT PATHOLOGY 



A stem section shows a browning of the vascular ring and the vessels 
are found occupied by bacteria (Fig. i68). When the cabbage plant 
is attacked early in the season, it is killed outright, or else it fails 
to form the characteristic head. Infections may take place through 
injury of the surface, but the greater part of them are through the 
water pores, which exude drops of water, which collect during cool 




Fig. i68. — Brown-rot of turnip (Pseudomonas brassica). Cross-section from 
middle of turnip root showing small bundle fully occupied by the bacterial organism. 
{After Smith, E. F., Bull. 29, U. S. Bureau of Plant Industry, Jan. 17, 1903.) 



nights, and in natural infection slugs are responsible carriers of the 
organism. 

Russell has found that the cauliflower is the most susceptible plant, 
while turnips and rutabagas are not very susceptible. Edwards reports 
that the Houser cabbage is practically immune to black-rot under field 
conditions. The period of incubation is variable. In some cases with 
needle punctures, the first signs of the disease appear in seven to 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 487 

twenty-eight days on leaves and in from nine to thirty-one days on 
stems. E. F. Smith obtained with needle punctures first signs of 
disease in fourteen to twenty-one days. In a study of the morbid 
anatomy of the cabbage, it has been found that the parasite is 
confined for some time to the vascular system and even to particular 
leaf traces or bundles, especially to the spiral and reticulated vessels, 
which are very often filled with incalculable numbers of this organism. 
Later, as the walls of the vessels are destroyed, the organism finds its 
way into the surrounding parenchyma. Pseudomonas brassicoe is 
sometimes motile, especially when taken from the plant, and is 
examined in a hanging drop of water. Its measurements are 0.7 to 
3.0/i by 0.4 to 0.5^. It is often somewhat irregular in shape. The 
flagella is several times the length of the cell and arises at or near the 
end. The organism is wax-yellow, changing to a dirty yellow-brown 
in old cultures. 

The treatment of this disease falls principally under the head of 
restriction and prevention. Seasonal variations are found and the 
organism thrives well in cool, moist lands. Underdrainage of soils 
might prove advantageous in wet seasons. The diseased plants should 
not find their way into the manure heap, but all refuse should be de- 
stroyed. As E. F. Smith puts it, "Avoid infected seed, soil and manure; 
destroy insect carriers of infection, if the plants are attacked." Crop 
rotation is advantageous. Soaking the seed for fifteen minutes in a 
solution of mercuric chloride (one tablet to a pint of water) should be 
practiced. 

Club-root {Plasmodiophora brassiccB, Wor.) This disease, which 
has been known for a hundred years, has received a number of 
names, such as fingers and toes, Anbury, Hanbury (England), Kohl- 
hernie (Germany), maladie digitoire (France) Kapoustnaja Kila 
Russia). (The organism causes unsightly and destructive root dis- 
ease of cruciferous plants, such as cabbage, Brussels sprouts, turnips, 
rutabagas, radishes and certain mustards (Fig. 169). The parasite is 
a slime mould (Myxomycetes) named by Woronin {Plasmodiophora 
hrassicce). It lives in the parenchymatous cells, often in the vicinity 
of the cambium, and an abnormal development of phloem is notice- 
able. The infested cells are grouped together into packets and their 
contents are at first fluid, then turbid and granular, assuming the 
amoeboid form with distinct nuclei. The amoeba are increased by 



488 



SPECIAL PLANT PATHOLOGY 



division, and by a sort of gemmation. The myxamoeba are provided 
with several nuclei. The formation of spores soon begins by the suc- 
cessive simultaneous divisions of the myxamoebae, so that each nucleus 
and surrounding mass of cytoplasm is differentiated, as a spore by the 
formation of a spore wall about them. The diseased cells are crammed 

full of such spores, which escape 
only when the root disintegrates. 
The liberated spores will germi- 
nate in water in from four to 
twenty-four hours and later the 
parasite gains entrance to the 
roots of the cabbage plant. The 
•organism causes an excessive 
formation of new cells so that a 
gall, or canker results. 

In order to check the organ- 
isms, soils have been treated with 
lime, sulphur and other fungi- 
cides. Liming, using two tons of 
c|uicklime to the acre eighteen 
months before planting, has been 
found the most reliable with the 
destruction of the refuse of pre- 
vious crops by burning. 



Carnation (Diani/ms 
caryophyllus, L.) 




Alterniose {Alter naria 



Fig. 169. — Cabbage roots showing club- 
root caused by a parasitic slime mould, 
Plasmodiophora brassicce. {From Marshall, diantki, Stev. & Hall). — Through 
Microbiology. Second edition, p. 609, after ^ >• . t-> 1 •-!-.• 

Woronin.) y ^ ^ Connecticut, Pennsylvania, Dis- 

trict of Columbia and North 
Carolina this disease of the cultivated carnation has been recently quite 
troublesome. The leaves and stems, especially at the nodes, are dis- 
colored with spots of ashen whiteness with a central black fungous 
growth. The spot is dry, shrunken and thinner than the surrounding 
healthy parts of the leaf, and is either circular, or somewhat elongated 
in Hne with the long axis of the leaf. The nodal spots involve the leaf 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 489 

bases as well, and the mycelium finally grows into the stem killing its 
tissue which becomes soft and broken down (Fig. 170). The variety 
known as Mrs. Thomas W. Lawson is especially susceptible. 

Rust (Uromyces caryophyllinus (Schrank). Wint. — This disease 
was practically unknown in the United States prior to 1890, but now it 




Fig. 170. — Carnation alternariose {Allernaria dianlhi). i, Branched, septile my- 
celium; 2, hyphas below surface of stroma; 3, spore formation; 4, compound spores, 
5, young clustered hyphse; 6, older cluster. {After Stevens, F. L., and Hall, J. C; 
Bot. Gas., 47: 409-413, May, 1909.) 



is prevalent wherever the carnation is grown commercially. The dif- 
ferent varieties of cultivated carnations differ to a marked degree in 
susceptibility. Enchantress and Lawson have a high degree of resist- 
ance to rust, while Scott and Jubilee are very susceptible. 



490 SPECIAL PLANT PATHOLOGY 

The fungus is largely propagated by its urediniospores, which are 
ellipsoid to spheric in form and measure 24-35^1 by 21-26/i. The 
spore wall is thick and spinulose. The teliospores resemble in form 
the urediniospores and measure 20-35JU by 18-25/x. Their walls are 
chestnut-brown and uniformly thickened with terminal germ pores 
and are papillate. As the adult plants may be infected, the disease 
may spread rapidly during the growing season. 

The disease can be controlled undoubtedly by growing rust-resistant 
varieties of carnations. The leaves should be kept away from the 
moist soil by simple V-shaped wire mesh supports and lastly fungi- 
cides, such as a solution of copper sulphate (i pound copper sulphate 
to 20 gallons of water), might be used with success, Duggar also rec- 
ommends the use of potassium sulphide i ounce to a gallon of water. 
Sub-irrigation has been practised. 

Cacao (Theobroma cacao, L.) 

Brown-rot (Thyridaria tarda, Bancroft). — A number of different 
organisms have been thought at different times to cause the brown rot 
of the chocolate pods, but Bancroft in 191 1, an authority on the sub- 
ject, ascribed the disease to the above-named fungus. Circular brown 
patches appear on the chocolate fruits along the grooves that seam 
the surface. The disease spreads rapidly and the fruit falls in from six 
to ten days from the time that it is first infected. When the spots are 
2 cm. in diameter, their center becomes marked by wounds in which 
a brownish-gray mycelium appear. Wounded fruits are especially 
open to infection through the abraded surface and the seeds, or beans, 
are sometimes involved and are destroyed completely. The disease is 
widely spread in the eastern and western tropics (in Jamaica, Santo 
Domingo and the Philippines). It may be controlled to some extent 
by burning all diseased fruits, busks and prunings. 

Pink Disease {Corticium lilaco-fuscum, Berk & Curt.). — The genus 
Corticium belongs to the family of Thelephorace^, which includes 
the smothering fungi of the genus Thelephora. The leathery hymeno- 
phore of Corticium is membranous, fleshy, waxy with clavate basidia 
with four sterigmata. The basidiospores of our cacao fungus are 
sessile on the basidia. It attacks the younger branches of the chocolate 
tree covering them with a pinkish incrustation, which spreads over 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 49 1 

the bark and into the bark crevices, causing the bark to crack and 
peel. Later a new bark forms under the old. The new bark is not 
sufficiently resistant to the attacks of species of Diplodia and Neclria, 
so that these fungi may enter and complete the work of destruction. 
Corticium lilaco-fuscum grows more rapidly in damp, shady places, 
and it usually refuses to grow in sunny places, hence opening up the 
growth is beneficial. 

Cherry (Prunus spp.) 

Leaf-curl (Exoascus ccrasi (Fckl.), Sadeb.).^ — This fungus produces 
witches' brooms out of the twigs of the cherry, and when the leaves on 
affected twigs are parasitized, they become somewhat reddish and 
curled. The asci develop on the leaves and measure according to 
Sadebeck, 35 to 50)uby 7 to lo/x, or in specimens studied by Atkinson, 
25 to 2)2)1^ by 6 to 9/1. The asci are naked and arranged in rows over the 
leaf surface. Spraying, if done at all should be done when the buds 
begin to develop in the Spring, and again when the asci are mature 
and ready to discharge their spores. 

Powdery Mildew (Podosphcera oxyacanthcB (DC), deBy). — This 
disease, although found on a number of other rosaceous plants, 
such as plums and hawthorns and the like, is especially destructive to 
apples and cherries. The leaves become mildewed with large spots 
of white mycelium from which arise the perithecia, which are 65 to 90)u 
in diameter surrounded by the dichotomously branched hyphal append- 
ages four to thirty in number, which are usually five times as long as 
the diameter of the perithecium. A single ascus usually contains 8 
ascospores. It is recommended to spray with lime sulphur (1-40) 
or dust with powdered sulphur in combating this disease. 

Chestnut (Castanea dentata (Marsh.) Borkh.) 

Blight {Endothia parasitica (Murrill), Anderson).— When the chest- 
nut blight fungus was first described by Murrill he called it Diaporthe 
parasitica, but by the studies of Anderson and others it has been trans- 
ferred to the genus Endothia, where it seems rightly to belong,^ On 
account of its virulency and its rapid spread through the chestnut 

1 Shear, C. L., Stevens, Neil E., and Tiller, R. J.: Endothia parasitica 
and Related Species. Bull. 380, U. S. Dept. Agric. 



492 



SPECIAL PLANT PATHOLOGY 




Fig. 171. — Canker lesion that nearly surrounds the chestnut branch, sunken on 
one side and enlarged on the other. (,Photo by Wm. Ciirrie, Bull. 5, Penna. Chestnut 
Tree Blight Com., 1913.) 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 493 

forests of the eastern United States, it has been the subject of much 
legislation and also a copious bibliography has been formed by the 
appearance of papers on its parasitism, life history and the remedial 
measures to be taken to combat it. The chestnut blight fungus was 




Fig. 172. — Perithecial pustules of chestnut blight fungus (Endothia parasitica) 
in the crevices of bark of a fallen chestnut tree. (Photo by Wm, Currie, Bull. 5, 
Penna. Chestnut Tree Blight Com., 1913.) 



discovered by Merkel in 1904 on American Chestnut trees {Castanea 
dentata) in the New York Zoological Park. It was studied by Murrill 
during 1906 by pure culture and by inoculation on healthy chestnut 
trees, and an account was published of the fungus as a new species in 
Torreya (6 : 186-189) '^^ 1906. 



494 



SPECIAL PLANT PATHOLOGY 



The rapidity of spread has been phenomenal, and the completeness 
of destruction is without parallel in the annals of plant pathology. It 
is now found from New Hampshire to Albemarle County, Virginia, in 
the South. Summer is the best time to study the symptoms of the 
disease, which are manifested in the brown shriveled leaves, which 
may be seen at a distance. The dead leaves hang on the tree over 
winter, and if on the blighted branches, the girdling is completed while 
the burs are maturing. Burs smaller than usual, and unopened, re- 




FiG. 173. — Chestnut blight pustules producing gelatinous threads with summer 
spores. (After pictorial card issued by Penna. Chestnut Tree Blight Com., 1912.) 



main attached to the tree through the winter months and well into the 
next spring. If, however, the girdling takes place after the leaves and 
burs are shed and before the leaves open in the spring, the leaves do 
not attain their full size, but are pale and distorted and this is a com- 
mon symptom during May and June. Dead limbs without attached 
leaves, or burs, are often indications of the canker disease. Water 
sprouts, or suckers, may develop just below the cankered regions of 
the branches or stem and thick clumps of suckers on the trunk and 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 495 

branches, or at the base of the tree, are evidences that the trees are 
attacked by the chestnut blight fungus. 

The cankers on smooth bark are especially marked, and with a 
reddish-brown color in contrast with the healthy bark can be seen for a 
considerable distance (Fig. 171). As sunken, or swollen diseased areas 
of the bark, they occur on branches of all sizes and generally the cankers 
are ellipsoidal with the long axis up and down the stem (Fig. 171). 
The cankered areas of bark become covered with numerous small 
pimples (Fig. 172) from which emerge in wet weather long twisted 




Fig. 174. — Chestnut blight fungus, iiMffoi/u'o parasitica. A, Pustules on bark; 
B, escape of pycnospores as gelatinous cords; C, D, magnified views of the cord-like 
masses of pycnospores. {From Gager after Murrill.) 



yellow horns of a gelatinous nature (Figs. 173 and 174). As the 
canker ages the bark splits and cracks, and in a year or two it peels 
off from the tree leaving the wood exposed to the weather (Fig. 127). 
The mycelium forms thick, fan-Uke mats in the bark and cambium 
of the tree and it spreads both longitudinally and circumferentially 
(Fig. 175) until, having completed its growth around the stem, or 
branch, and killed the cambium and bark, the part of the tree above 
the girdled portion succumbs and the next year leafless branches 
show the irreparable damage done to the tree by the blight fungus 
(Fig. 127). 



496 SPECIAL PLANT PATHOLOGY 




Fig. 175. — Fan-shaped mycelium of chestnut blight fungus (Endothia parasitica) 
from rough bark of a chestnut tree. (Photo by E. T. Kirk, after Anderson, Bull. 5, 
Chestnut Tree Blight Com., IQIS-) 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 497 

Morphology. — On smooth bark, especially in summer, the outer cork 
layer is raised into numerous little blisters, with slender, yellow, waxy 
twisted horns emerging from a pore in their apices. A section across 
each blister reveals a somewhat globose pycnidium surrounded by a 
scanty loose mass of whitish, or yellowish hyphae, which merge with 
the tangled hyphae that make up the pycnidial wall. The conidio- 
phores arise inside the pycnidium, as a dense brush-like fungi and pro- 
ject into the fruit cavity (Figs. 174 and 176). They range in length 
from 20 to 40/1. From these conidiophores, spores (pycnospores) are 
abstricted, and as the cavity is filled with the hyphal stalks, the pyc- 
nospores are forced out at an opening in the top of the pycnidium in 
the form of a twisted slimy cord (Figs. 173 and 174). The smooth 
hyaline pycnospores are held together by a sticky material and they 
measure 1.28 by 3.56/i in size, and are oblong cylindric with rounded 
ends sometimes slightly curved. Heald and Gardner^ find that the 
pycnospores are to a considerable degree resistant to desiccation in 
soil in the field and that a large number may retain their viability 
during a period of 2 to 13 days of dry weather (Fig. 177). They 
found that with indoor desiccation a large number of spores survived 
two months and that in 5 out of 12 samples not all of the spores had 
succumbed after three months of drying. The longevity limit varies 
from 54 to 119 days, the average being 81 days. Studhalter and Rug- 
gles^ by experimental methods obtained some interesting results as to 
insects as carriers of the chestnut blight fungus. Tests were made 
with twenty-one ants in certain laboratory and insectary experiments 
in which they had been permitted to run over chestnut bark bearing 

1 Heald, F. D. and Gardner, M. W.: Longevity of Pycnospores of the Chestnut 
Blight Fungus in Soil. Journal Agricultural Research II: 67-75, April 15, 1914. 
Additional facts in the life history of the chestnut blight fungus are presented 
in the following: Heald, F. D., and Walton, R. C: The Expulsion of the 
Ascospores from the Perithecia of Endothia Parasitica (Murr.), Amer. Jour. 
Bot., 1:449-521, Dec, 1914; Heald, F. D., and Studhalter, R. A.: Seasonal 
Duration of Ascospore Expulsion of Endothia parasitica. Amer. Journ. Bot., 
2: 429-448, Nov., 1915; Ibid., The Effect of Continual Desiccation on the Expul- 
sion of Ascospores of Endothia Parasitica. Mycologia, 7: 126-130; Ibid., Lon- 
gevity of Pycnospores and Ascospores of Endothia Parasitica under Artificial 
Conditions. Phytopath, 5:35-44; Stevens, Neil E. : Some Factors Influencing 
the Prevalence of Endothiagyrosa. Bull. Ton. Bot. Club, 44: 127-144, Mch., 191 7. 

2 Studhalter, R. A. and Ruggles, A. G.: Penna. Dept. of Forestry. Bull. 12, 
April, 1915. 

32 



498 SPECIAL PLANT PATHOLOGY 

spore horns or active perithecial pustules of Endothia parasitica. They 
found that five of the twenty-one ants were carrying spores. Tests 
with other insects demonstrated that they were carrying spores. The 
number of viable spores carried varied from 74 to 336.960 per insect, 
and the last number was obtained on Leptostylus Macula, one of the 
beetles, which feeds on the pustules of the blight fungus. During 
these experiments, it was proved that the spores of Endothia parasitica 
were easily shaken from the body of the beetle during its own move- 
ments. Heald and Studhalter^ undertook to determine whether birds 
carried the spores. They found on birds shot on blighted chestnut 
trees after the bill, head, tail, feet and wings of each bird were scrubbed 
with a brush and poured plates were made from the wash water, which 
was retained and centrifuged for its sediment, that in the case of the 
36 birds tested, 19 were found to be carrying the spores of the chestnut- 
blight fungus. The viable spores carried by two downy woodpeckers 
numbered 757,074 and 642,341 respectively, while a brown creeper 
carried 254,019, and that the highest positive results were obtained 
from birds shot two to four days after a period of considerable rain- 
fall. Analyses of spore traps at West Chester and Martic Forge^ 
showed that viable pycnospores of the chestnut blight fungus were 
washed down the trees in enormous numbers during every winter 
rain. 

The mature stromata on older cankers have numerous projecting 
papillae on the surface. The black speck at the tip of each papilla is 
the opening of a perithecium, which is a bottle-shaped depression with 
a long neck-like, black canal opening at the surface. There are com- 
monly fifteen to thirty perithecia in a stroma. The mature perithecia 
(Fig. 176) measure about 350 to 400^1 in diameter, and are mostly 
spherical. The neck is usually four to six times the diameter of the 
perithecium and its black wall is composed of densely interwoven, 
septate, heavy-walled hyphae running parallel with the long axis of 
the neck. The asci are clavate, or oblong, and contain eight ascospores 
imbedded in an epiplasm. The ascospores are two celled and measure 

1 Heald, F. D. and Stud halter, R. A.: Birds as Carriers of the Chestnut Blight 
Fungus. Journal of Agricultural Research II: 405-422, Sept. 21, 1914. 

2 Heald, F. D. and Gardner, M. W.: The Relative Prevalence of Pycnospores 
and Ascospores of the Chestnut Blight Fungus during the Winter. Phytopathology 
3: 296-305, December, 1913. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 499 

4.5 to 8.6/i in size (Fig. 177). The walls are thicker than those of the 
pycnospores. Expulsion of the ascospores is dependent upon tempera- 




-^f 







■•^'^^:!d^>^ 



Fig. 176. — A, Vertical section of a pycnidial pustule. The filaments lining the 
cavity produce the spores that ooze out as "spore-horns;" B, vertical section of a 
perithecial pustule. ' Several of the perithecia are cut so as to show the fuUlengths 
of the necks in the chestnut blight fungus (Endoihia parasitica). (After Heald, 
F. D., Bull. 5, Chestnut Tree Blight Com., 1913.) 

ture, as well as moisture. There was no expulsion of ascospores under 
field conditions from late November until the rain of March 21, when 



500 



SPECIAL PLANT PATHOLOGY 



temperature conditions were favorable. Ascospores were not expelled 
during the warm winter rains, but during the summer rains ascospores 




Fig. 177. — Spore-sacs or asci with eight two-celled ascospores of chestnut blight 
fungus (Endoihia parasitica). Below diagram showing relative size of pycnospores 
(left) and ascospores (right). (After Heald, F. D., Bull. 5, Chestnut Tree Blight 
Cojn., 1913.) 



are forcibly expelled in large numbers from the perithecia during and 
after each warm rain in case the amount of rain is sufficient to soak up 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 501 




Fig. 178. — Photograph showing svtccessive stages in the germination of asco- 
spores and pycnospores of the chestnut blight fungus {Endolhia parasitica). Left, 
ascospore series from 8 to 22 hours at hourly intervals; right, pycnospore series from 
8 to 22 hours, taken every two hours. {After photo by Wm, Currie, Bull. 5, Penna. 
Chestnut Tree Blight Com., 1913.) 



502 SPECIAL PLANT PATHOLOGY 

the pustules.^ All of the experiments point to air and wind transport 
of the ascospores, as one of the very important methods of dissemina- 
tion. Infection is by means of wounds produced mechanically, as by 
insects and other animals (Fig. 178). It is still to be demonstrated that 
the parasite can enter without visible breaks in the bark.^ In the 
control of this disease inspection of nursery stock should be made 
and the use of gas tar following removal of diseased branches. 

Leaf Mildew {Phyllactinia corylea (Pers.), Korst). — The under leaf 
surfaces of the chestnut are marked frequently by irregular patches 
of mycelium, which constitute the mildew fungus (Fig. 53). Typical 
haustoria are absent, but there are special setalike branches which 
penetrate the leaf tissues. The subglobose perithecium is large and 
is garnished with rigid needle-like appendages with a swollen base 
(Fig. 53). There are many included asci usually containing two 
spores, occasionally three. It is a fungus of wide geographic distribu- 
tion throughout the temperate regions of the world. 

Clover (Tri folium spp.) 

Rust, Uromyces trifolii (Hedw.), Liv.- — The common clovers of our 
cultivated fields, such as the red clover, alsike clover, white clover, and 
crimson clover, are attacked by this rust, which causes serious disease 
conditions (Fig. 70, E and F). The prevalence of the disease varies 
greatly with the season. The clover rust fungus is autoecious, all of 
the stages being found on the same host plant. All of the stages 
occur on the white clover (T. repens). In general the spermagonia 
and aecia are not met with on the red clover, the host upon which the 
other stages are perhaps more frequent. The mycelium is local in its 
occurrence in the plant, from it secia and spermagonia arise in the early 
spring, or at almost any time during an open winter. They occur on 
the under leaf surfaces and on the leaf stalk. The aeciospores are 14 
to 23JU in diameter and germinate readily in water. 

Heald, F. D., Gardner, M. W. and Studthalter, R. A.: Air and Wind 
Dissemination of Ascospores of the Chestnut Blight Fungus. ■ Journal of Agricul- 
tural Research iii: 493-526, March 25, 1916. 

'^ For numerous other details consult Anderson, P. J. and Rankin, W. H.: 
Endothia Canker of Chestnut. Bull. 347, Cornell University Agricultural Experi- 
ment Station, June, 1914. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 503 

The urediniospores are about 22-26/x by 18-20/x, and repeated 
crops of these may be produced. The teliospores are formed in sori 
with the urediniospores, as the season advances. They are one- 
celled, thick walled and measure 20-35/x by 15-22^- The teliospores 
germinate in the ordinary way by the formation of a four-celled 
basidium each producing a basidiospore. No satisfactory method 
of controlling clover rust is known. 

Coffee (Cojfea arabica, L.) 

Leaf-spot {Cercospora caffeicola, B. & €.).■ — The leaves and fruits 
of coffee plants in the Dutch East Indies, Mexico, Cuba, Jamaica, 
Trinidad and Brazil are attacked by the leaf-spot fungus, which causes 
large blotches at first visible only on the upper leaf surface. The spots 
are dark brown at first, later becoming grayish above and clear below. 
The center of these blotches die and here the spores are borne. The 
disease causes the leaves to fall, thus reducing the vigor of the plant 
and preventing the proper maturing of the coffee berries. Infected 
berries fall before ripening. 

Rust {Hemileia vastatrix, Berkeley & Broome) .^ — The coffee rust is 
widely spread through the coffee-growing regions of the old world, 
and it has been reported from the American tropics, but there is some 
uncertainty about reports. It is the most destructive disease of the 
coffee plant and American coffee growers should be on the lookout 
for it. 

Orange-red spots appear on the leaves, which finally wither and drop, 
and frequently parts or whole plants die, especially during the rainy 
season, when the red spots increase in number. The spots appear as 
shghtly transparent discolorations, which are not easily observed until 
the leaf is held up to the Hght. An older spot is yellow in color and then 
a bright orange color. They vary in size, but are usually circular in 
outhne, and increase in number during June and July, when the disease 
reaches its culmination, if the weather conditions are favorable. The 
spores are produced in great abundance in the orange-red spots and on 
being set free are carried by the wind and insects to other coffee plants 
on the leaves of which they germinate sending a germ-tube into the 
leaf through the stomata. The urediniospores 35 to 40/x by 25 to 28ju 
are single, usually egg-shaped, provided with a papilla and without 



504 SPECIAL PLANT PATHOLOGY 

germ-pores. The teliospores are unicellular. As a remedial measure 
the use of tobacco water or Bordeaux mixture is recommended. 



Corn (Zea mays, L.) 

Dry-rot {Diplodia zees (Schw.), Lev.). — The dry rot fungus attacks 
the dry ears of corn soon after silking and does not usually manifest 
itself until husking time, when the kernels are found to be covered with 
a whitish mycelial growth, which dips down between the individual 
grains of corn. The grains so attacked become shrunken, loosely 
attached to the cob, lighter in weight, darker in color, and more brittle 
than the healthy grains. Pycnidia may be found imbedded in the 
mycelium, especially between the kernels. In the open field, these 
pycnidia may be formed in such numbers as to impart a black color 
to the grains of corn. Of course the feeding value of the corn is gone 
and some physicians even ascribe pellagra to the use of such moldy 
corn. When the fungus attacks the stalks, it forms small dark specks 
under the epidermis near the nodes and even on three-year-old stalks 
pycnidia have been found. Infection takes place through the roots 
and the fungus which enters in this way finally reaches the stem. Ear 
infection may also occur through the silk by wind-blown spores which 
come from old diseased stalks left in the field, so that by destroying 
the corn trash the disease can be controlled to some extent. Rotation 
of crops is probably more efficacious. 

Smut {Ustilago zem (Beckm.), linger). — The smut boils of Indian 
corn, or maize, are found not only on the ears as with most smuts, but 
also on the husks, on the tassels of male flowers, on the leaves, and even 
on the stem (Figs. 179 and 180). The attack first begins on any young 
and tender part of the plant. If the leaves are the part attacked, they 
assume a pale yellow hue and are puckered with smaller, or larger 
bladder-like swellings. The swellings are made up of masses of the 
hyphae of the smut fungus and their surface is covered with a smooth 
skin-like covering. Later the hyphae divide up into innumerable 
rounded cells, which develop into the smut spores, or chlamydospores. 
Finally, the silvery-white skin having been more and more stretched 
bursts, and the black chlamydospores are set free, as a powdery 
mass. The echinulate chlamydospores measures 8 to 12/i, and they 
readily germinate in manure-water giving rise to a four-celled basidium, 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 505 

each cell of which produces a basidiospore. Infection of the nascent 
tissue at any part of the growing corn plant is accomplished by the 




Fig. 179. — Smut boil of UsUlago zea on ear of corn, developed from one infected 
kernel. {After Jackson, F. S., Bull. 83, Del. Coll. Agric. Exper. Slat., December, 
1908.) 



basidiospores and not by the chlamydospores (Fig. 181). Wet weather 
is essentia] for the growth of the corn and the smut also. 



5o6 



SPECIAL PLANT PATHOLOGY 



The disease may be controlled by removing the smutted plants 
from the field and destroying them and also by a rotation of crops. 




Fig. i8o. — Corn smut on tassels of sweet corn. (After Jackson, F. S., Bull. 83, Del. 
Coll. Agric. Exper. Slat., December, 1908.) 



As the fungus may infect the adult plant, the treatment of the seed 
corn with fungicides has been unsuccessful. Rotation of crops also 
assists in keeping smut in check. 



DETAILED ACCOUNT OF SPJOCli'lC DISEASES OF PLANTS 507 

Wilt (Fseudomouas SkwaHl, Smith). — This is a specific communi- 
cable disease of sweet corn and other races of maize, caused by a yellow, 
polar-flagellate organism discovered in 1895 by F. C. Stewart. The 
disease has been found on Long Island, in New Jersey, Washington, 
D. C, Maryland, Michigan, Virginia and West Virginia. One of the 
first signs of the disease in well-grown plants is the whitening (drying 




Fig. 181. — Germination of the chlamydospores of corn smut (Ustilago zece); i. 
Various stages in germination from corn 3 days after being placed in water; 2, spores 
germinated in contact with air; 3, several days after spores were placed in 1/20 per 
cent, acetic acid, formation of infection threads, a. Spores; h, propiycelia; c, basidio- 
spores; d, infection threads; e, detached pieces of mycelia. {After Bull. 57, Univ. 
III. Agric. Exper. Stat., March, 1900.) 

out) of the male inflorescence. The leaves then dry out and the plant 
is dwarfed, later the stem dries. If the leaves or the stem be chosen and 
broken across, sHmy yellow contents ooze out. A cross-section of 
the stem shows that the organism fills the vessels of the host plant and 
the wilting is due to the stoppage of the water suppHes by the trachei'd 
plugging. 



508 SPECIAL PLANT PATHOLOGY 

The greatest pains should be taken to secure only sound seed corn, 
but in the present indififerent state of the seed-trade, even the best 
should be treated with mercuric chloride before planting. On fields 
subject to the disease, only resistant varieties should be planted. 
Manure containing corn stalks from diseased fields, or gathered from 
animals pastured in such fields, should never be used on land designed 
for corn.^ 

Cotton (Gossypium sp.) 

Boll Anthracnose (Glomerella gossypii (Southw.) Edg.) (= Colleto- 
trichum gossypii, Southw.),- — The same fungus causes an anthracnose 
of stem and boll of the cotton plant, especially in the Gulf states. The 
disease is more important when it attacks the boll, or the seedlings. 
The ^bolls lose their green color and become dull red, or bronzed. 
If the boll is nearly- mature when attacked, it may mature and 
open in the usual manner, but if attacked early, it may cause a prema- 
ture dying of the carpels and an unequal growth of the boll, which is 
liable to crack open and expose the immature lint to the action of the 
weather. The first evidence of the disease is a minute reddish spot, 
which later becomes black in the center and depressed with a reddish 
border, and these spots may run together. 

Two types of conidiophores break out from the stroma within the 
tissues. Some of the conidiophores are hyaline and abstrict conidio- 
spores that measure 4.5 to 7^1 by 15 to 20/x, while other conidiophores in 
the form of setae arise from the dark colored cells of the stroma. The 
setse are clustered and bear ovate, basally pointed spores. Spores and 
setae together form an acervulus. The spores germinate readily and 
produce a myceUum which grows vigorously in culture, is hyahne, 
flexuous and abundantly septate and it may give rise to appressoria. 

Proper remedial measures have not been discovered, and a field of 
experimentation is opened up along these lines. Use resistant 
varieties. 

Rust (Uredo gossypii, Lager.). — This is the uredo stage of Kuehneola 
gossypii (Lagerh.) Arth. which occurs on the cotton plant in Cuba, 
Puerto Rico, Florida and Guiana, ^cia are wanting in the life cycle, 

1 Smith, Erwin F. : Bacteria in Relation to Plant Diseases, Volume III: 89-150, 
1914,^ where full details of the experimental study of the disease and the causal 
organism will be found. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 509 

while the other spore forms are represented by urediniospores and 
teliospores. All parts of the green cotton plant may be rusted, 
spreading to the new leaves as they are formed. Small rounded, or 
angular, purplish-brown spots appear on the upper leaf surface and the 
urediniospores are borne in pustules just beneath the epidermis on the 
under leaf surface, which finally ruptures and sets them free. The 
varieties of cotton grown in the Southern United States are partially 
immune, while the tropic varieties are more susceptible. It is rec- 
ommended that the cotton grower destroys all rubbish in his fields 
and adopts a system of field culture in which only vigorous plants will 
be obtained. 

Cranberry {Vaccinium macrocarpon, Ait.) 

Gall (Synchytrium vaccina, Thomas) (Fig. 230). — The fungus which 
causes cranberry gall is a very much reduced phycomycetous one, which 
attacks the young stems and leaves, as well as flowers and fruit of the 
cranberry. It also lives on other ericaceous plants. The galls are 
small in size, reddish in color and are produced in great numbers on the 
parts affected. The fungous body is much reduced, consisting of a 
single cell which becomes a zoosporangium. The presence of this 
parasitic cell in the tissues of the host is to produce a small gall. Later 
the zoosporangium develops a mass of swarm spores, or zoospores, 
which escape into the water. Infection, therefore, probably takes 
place when water is abundant. 

Scald {Guignardia vaccinii Shear). ^ — The scald fungus (Figs. 182 
and 183) may attack the very young fruit and even the flowers of the 
cranberry and annually does considerable damage to the growing crop, 
as the annual loss has been estimated at $200,000. The pycnidia 
are usually found upon such parts. The berries are characterized by 
watery spots, which may remain small under certain conditions, while 
under others it spreads quickly, often concentrically until the whole 
berry becomes soft. The leaves are also spotted with irregular brown 
spots within which the pycnidia are found. 

The pycnidial stage is a characteristic Phoma, or Phyllosticta, 
measuring 100 to i20)u in diameter. These are scattered over the 
affected surface and abundant hyaline, obovoid pycnospores are formed, 

1 Shear, C. L.: Cranberry Diseases. U. S. Bureau of Plant Industry. Bull, 
no: 1-64, 1907. 



5IO 



SPECIAL PLANT PATHOLOGY 




Fig 182. — Cranberry scald {Guignardia vaccinii Shear). {After Shear; Bull, no, 
U. S. Bureau Plant Industry, pi. i, 1907.) 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 51I 




Fig. 183. — Details of cranberry scald fungus (Guignardia vaccinii). i, A cran- 
berry leaf, showing pycnidia of Guignardia vaccinii thickly scattered over the under 
surface; a, a cranberry blossom blasted by Guignardia vaccinii, showing pycnidia on 
calyx, corolla, and pedicel; b, a blasted fruit, showing pycnidia. 2, A vertical section 
of a single pycnidium of Guignardia vaccinii from a cranberry leaf, showing pycno- 
spores in various stages of development. 3. An immature pycnospore of the same 
fungus, showing the partially formed appendage; a, the same, showing a little later 
stage of development; h and c, fully developed pycnospores and appendages. 4, 5, 
6, 7, 8, and 9, Various stages in the germination and growth of pycnospores oiGuig- 
nardia vaccinii grown in weak sugar solution; 4, 5, 6, and 7, 72 hours after sowing; 
8 and 9, 86 hours after sowing. 10, A vertical section of a perithecium of Guignardia 
vaccinii, showing asci, from a cranberry leaf collected in New Jersey. 11, Three 
asci, with ascospores showing variations in length of the stipe and the arrangement 
of the spores; a and b, from perithecia on a leaf; c, from a pure culture. 12, A fresh, 



512 SPECIAL PLANT PATHOLOGY 

which measure 10.5 to 13. 5m by 5 to 6ju. The ascigeral stage is less com- 
mon. The perithecium has a rather dense wall inclosing a number of 
clavate asci, which are 60 to 80^1 long (Fig. 183). The ascospores are 
hyaline, elliptic to sub-rhomboidal in form with granular contents. 
The fungus has been grown successfully in artificial culture media, but 
after a few generations, it seems to lose in vitality. 

Preventative measures consist in an occasional renovation of the 
bag and in the proper regulation of the water supply. Spraying at 
least six times with Bordeaux mixture (5-5-50) is used with success; 
especially, if adhesive substances (4 pounds resin fish oil soap) are 
added to the mixture. 

Grape {Vitis spp.) 

Black-rot (Guignardia Bidwellii (Ell.) V. & R.). — Wherever the 
grape is grown this American fungus is a constant menace to the suc- 
cessful prosecution of the industry. It attacks not only the fruits, but 
also the leaves, fruit pedicels and stems. The disease, which is most 
important on the berries (.Fig. 184), begins as a small circular brown spot 
which enlarges until it is 5 to 10 mm. in diameter, when the center of the 
spot will be found to show a few black pimples which are the openings 
of the pycnidia, which have now appeared beneath the skin. The 
spots become darker in color and spread until more than one-half of 
the fruit surface is involved, when the fruit begins to lose its spheric 
contour and to shrivel, persistently hanging on the vine sometimes 
throughout the season. Nearly all of the dark colored grapes are 
susceptible, such as the universally grown Concord, while some light 
colored varieties are more resistant. The Scuppernong is apparently 
entirely resistant. 

As with many of the fungi which attack our cultivated plants, the 
different stages were known before the complete life cycles were de- 
termined and therefore, these stages received scientific names, which 
are relegated to synonymy, when the life history becomes known 

mature ascospore, showing the usual condition, in which the protoplasm is very 
coarsely granular. 13, An old ascospore from a dried specimen, having its contents 
homogeneous. 14, a, A portion of the coarse brown mycelium from the interior of 
a scalded berry, from which a culture was made December 23, producing pycnidia 
and ascogenous perithecia of Guignardia vaccinii; b, a portion of younger, lighter 
colored hyph^ from the same berry. (After Shear, C. L., Bull, no, U. S. Bureau of 
Plant Industry, 1907.) 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 513 



thoroughly. So it has been with tlie black-rot fungus. The pycnidial 
stage on the grape leaves (Fig. 185) was called PhyUosticla lahrusca, 
while on the fruit it was called Phoma uvicola. These have been 
determined to be merely stages of one and the same fungus, Guignardia 
Bidwellii. The mycelium of the black-rot fungus is never abundant in 
the outer portions of the berries where it is found. Here a stromatic 
mass of hyphse arises beneath the grape skin and develop the pycnidia, 
which are broadly elliptic, thick-walled and 
beakless depressions from the inner walls of 
which the pycnidiophores arise which abstrict 
off the ovate to elliptic pycnidiospores (pycno- 
spores) 8 to 1 0/1 by 7 to S^t. These are pushed 
out in twisted masses and can germinate im- 
mediately. 

Spermagonia-like pycnidia of smaller size 
are also found. These produce filiform con- 
idiophores, which cut off minute, slightly 
curved microconidia. The ascigeral' stage, 
discovered in 1880, may be had on fruit, 
which has been covered with grass and leaves 
in the dried up state. The perithecia are 
globose and bear broadly clavate asci con- 
taining eight unicellular ascospores, measur- 
ing 12 to i7Aiby 4.5 to 5M. 

The black-rot grape disease can be con- 
trolled by Bordeaux mixture (4-4-50). The 
first application should be made in the spring, 

just as the buds begin to swell, followed by Spring Harbor, L. I., July 

■' c ■> J 20, 1915. 

a second spraying, as the buds unfold. Sub- 
sequent sprayings, always before rain storms, to the number of five 
or six, should be made two weeks apart during the season. After 
July 20 use' 4-2-50 Bordeaux, or ammoniacal copper carbonate. 

Downy Mildew (Flasmopora viticola (B. & C.) Berl. & DeTon). — 
The consensus of opinion among mycologists is that the downy mildew 
fungus is of American origin, and it is now widely spread in Europe and 
eastern North America, where it probably did not originate. It has 
been noted on practically every variety of cultivated and wild grapes, 
and it attacks stems, leaves and berries. Usually it confines its attack 
3.5 




Fig. 184. — Black-rot 
fungus, Guignardia Bidwellii, 
attacking green grapes. Cold 



514 



SPECIAL PLANT PATHOLOCxY 



to the grape" leaves (Fig. i86), where it produces under ordinary 
conditions spots of mildew, especially on the lower leaf surface. In 
bad cases, the whole lower leaf surface may be covered with the downy, 
or cottony mass of hyphae which gives the fungus its common name. 
The parasitic hyphse live in the intercellular spaces of the host and 
send into the host cells small knob-like haustoria. The presence of 
the mycelium seriously interferes with the normal physiologic activity 
of the host. In light cases, the areas of upper leaf surface immediately 
overlying the hyphse turn brown in the form of angular spots. Through 




Fig. 185. — Black-rot fungus {Guignardia Bidwellii). a. Portion of an affected 
grape showing pustules; b, section of pustule (pycnium) showing pycnospores; c, 
ascus with ascospores; d, ascospores. {After Quaintance, A. L., and Shear, C. L., 
U. S. Farmers' Bull. 284, 1907-) 

the stomata emerge stifif projecting conidiophores which form short 
stub-Hke branches from which fall ellipsoidal conidiospores. These 
conidiospores are virtually zoosporangia for their protoplasmic con- 
tents divide into a number of biciliate zoospores which escape and 
swim about in the rain water which covers the leaf or stem, or are washed 
down, or splashed from plant to plant during a dashing rain storm. 
When the fungus appears on the fruit, it has been called gray rot, and 
occasionally, the berry may be completely covered with a downy mass 
of hyphae. 



DETAILED ACCOUNT OF SPECIFIC DISEASES OF PLANTS 515 

The oogonia and antheridia are not so common as the conidiospores. 
If the shriveled parts of the leaves are examined in September, the 




Fig. 186. — Grape leaf attacked by mildew, Plasnwpara vilicola, Cold Spring Harbor, 
L. I., Aug. 2, 1915. 

oogonia will be found as spheric organs attached to the intercellular 
hyphae by a short stalk. One or several filamentous curved antheridia 
are formed near the oogonia to the surface of which they become ap- 



5l6 SPECIAL PLANT PATHOLOGY 

plied. A germ tube is formed through which the antheridial con- 
tents pass over into the oogonium. A single large central egg-cell, or 
oosphere, becomes differentiated in the protoplasm of the oogonium; 
this contains a single nucleus in a central position, while the remaining 
nuclei pass into the peripheral layer of protoplasm (periplasm). A 
single male nucleus passes through the antheridial beak into the 
oosphere, which becomes surrounded by a cell wall. Nuclear fusion 
now takes place and the oosphere becomes an oospore with a single 
central nucleus. The oospores are about 30/x in diameter. 

Bordeaux mixture is the most important fungicide used in combating 
the downy mildew disease. It is applied as in black-rot. 



CHAPTER XXXV 

DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 
(CONTINUED) 

Hemlock (Tsiiga canadensis Carr) 

Heart-rot (Polyporus borealis (Wahl.), Fr.). — This bracket fungus is 
distributed widely in North Temperate regions. As a wound para- 
site, it occurs on hemlocks, pines and spruces, entering these trees 
through the stubs formed by the breaking ofif of branches. The 
mycelium gradually grows into the heart of the trees and from there 
downward into the roots and upward into the tops. It advances in 
definite directions through the wood in the form of cords, or strands, 
which run radially, or tangentially, in the channels dissolved by the 
action of the enzyme, which is formed by the living hyphae. The 
wood shrinks and the mycelial strands begin to dry up, and the wood 
is separated into cuboidal blocks marked off by the channels formed 
by enzyme action. If the mycelium attacks the cambium, the trees 
die. The bracket-like fruit bodies are soft and spongy and last only a 
season. They are, according to Atkinson, lo to 20 cm. (4 to 8 inches) 
by 6 to 15 cm. broad. Several of these sporophores may be joined 
together. The upper surface is rough, shaggy and has a sodden ap- 
pearance. The pores on the under side are quite regular with rounded 
openings in some specimens, or irregular, elongated and sinuous in other 
samples. 

Hollyhock (AlihcBa rosea Cav.) (Fig. 187) 

Rust {Puccinia malvacearimi, Mont.).' — This fungus was introduced 
into France about 1868 from Chili, where it is native, and in the 
summer of 191 5, the writer found it very destructive to the hollyhocks 
in the gardens on the Island of Nantucket off the southern coast of New 
England. It spread rapidly over Europe and came to the United 
States in 1886 upon infected seed. The leaves are spotted with the 
yellowish-brown sori slightly raised above the leaf surface (Fig. 72), or 
they are found on the stem in the form of small wart-like elevations. 
The leaves dry up, as if blighted, and during August of 1915 on Nan- 

517 



5j8 



SPECIAL PLANT PATHOLOGY 




Fig. 187. — Hollyhock rust, Puccinia malvacearum. i, Typic mature telio- 
spore; 2-6, different stages in growth of promycelium (basidium); 7, forked promy- 
celium; 8, basidium dividing into 4 cells; 9, basidium resembling a germ tube; 10-12, 
cells breaking apart; 13-16, germination of promycelial cells; 17, empty cell; 18, 
mature basidiospores; 19, 20, same in germination; 25, 26, formation of chlamydo- 
spore-Hke bodies in old promycelia. {After Taubenhaus, J. J.: Phytopath. I, April, 
1911.) 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 519 

tucket only a few host leaves were left on a row of garden hollyhocks, 
all of the other leaves having fallen off. The sori consist of light- 
colored teliospores which are two-celled and measure 17 to 241J, by 35 to 
63M (Fig. 187). 

Bordeaux mixture (4-3-50) has been found efficient, as a spray, in 
controlling the hollyhock rust. Others recommend sponging the dis- 
eased parts with permanganate of potash, two tablespoonfuls of 
saturated solution diluted with one quart of water. 

Larch (Larix spp.) 

Canker {Dasyscypha Willkommii, Hartig). — The life history of this 
destructive fungus of larch trees has been studied by German plant 
pathologists, so that it is pretty well known. In the moist, marsh 
meadows in the mountains of Europe where the larch has been planted 
in pure forests, the fungus has been frequent in past years. The 
mycelium attacks the bast elements of the stem and its insidious char- 
acter is manifested in the death of the bark, which peels off. Pro- 
nounced cankers soon develop and the fungus lives perennially in the 
tree spreading rapidly when the larch tree is comparatively inactive, 
viz., autumn and winter. The diseased area, represented by wounded 
tissue, may heal over during the growing season, but when the fungus 
regains its activity the disease progresses until the branch is com- 
pletely girdled and its terminal part dies. 

Creamy white stromatic tufts appear, where the bark has been killed 
and on this superficial mycelium minute conidiophores arise, which 
bear simple hyaline conidiospores. As these probably do not germinate 
they have no influence in the spread of the canker. Short-stalked 
apothecia may appear on the canker areas later in the year. They 
are somewhat yellow on the outer surface and orange within. The 
cylindric asci (i20;u by gn) bear light ovoidal, unicellular ascospores. 
Filiform paraphyses are found between the asci. No efficient remedial 
measures are known. 

Dry-rot (Trametes pini (Brot Fr.). — This fungus is very common 
in the forests of New England, Canada and Newfoundland. It grows 
on nearly all coniferous trees; white pine, red spruce, white spruce, 
hemlock, balsam fir and larch attacking the living trees after they 
begin to form heartwood. In the tamarack, or larch, the decay goes 



520 SPECIAL PLANT PATHOLOGY 

much beyond that of the spruce and balsam fir. In the early stages, 
according to von Schrenk, small white spots appear, which occupy the 
entire width of an annual ring. Two or more of these spots soon join, 
at first in a longitudinal direction, then laterally also, so that one or 
more rings of woods are transformed to cellulose. The rings are thus 
separated from adjoining ones so that a series of easily separable 
tangential plates are formed. The line of separation between the 
rings is always at the point where the summer wood stops and the 
spring wood of the following year begins. 

The progress of decay is marked by the attack of more and more 
sound wood fibers which are reduced to loose fibers of cellulose until the 
wood has disappeared, when black lines appear, scattered irregularly. 
The tangential plates become ultimately extremely thin and they then 
consist of the resistant summer wood cells more or less infiltrated with 
resin. The whole of the former woody cylinder becomes a mass of 
separate fibers which can be pulled out individually. 

The fruiting organ is found commonly on all of the afi"ected trees. 
It is readily distinguished from allied forms by the light red-brown 
color of the hymenial surface, and the regular small round pores. The 
form of the pileus varies greatly. Sometimes the brackets are large 
on the larch, lo cm. (4 inches) in width laterally, 7 cm. (2.8 inches) from 
front to back, and 5 cm. (2 inches) in thickness, and are formed at the 
ends of old hard stubs and at scattered points on the bark. Some- 
times sessile sheets are formed inside of the brackets. The basidia, 
which form the hymenial surface that lines the pores, are smaller at 
the apex and form from slender, spore-bearing sterigmata. The 
basidiospores are brown at maturity. 

Lemon {Citrus limonum, Risso.) 

Brown-rot {Pylhiacystis citriophora, R. E. Smith). — The disease is 
characterized by a copious exudation of gum from the trunk just above 
the bud union. A certain area of the bark surrounding the part which 
shows gummosis dies, becomes hard and dry without any evidence of 
the fungous parasite. It appears especially destructive on the fruits 
after packing, and is recognized as a brownish, or purplish, discolora- 
tion of the rind, which is lighter green than on the ripe fruits. It 
spreads rapidly from fruit to fruit, and is also characterized by its 
peculiar odor and the presence of small flies attracted to it. The 



DETAILED ACCOUNT OP SPECIFIC PLANT DISEASES 521 

mycelium penetrates the lemon rind and consists of much-branched 
extensive hyphae of irregular diameter. Conidiospores which repre- 
sent zoosporangia appear under fayorable conditions. They measure 
20 to 60 by 40H to gofx and are lemon-shaped with a pronounced protu- 
berance at the apex. Upon opening a number of biciliate zoospores 
are liberated. 

Infection of the fruit usually takes place in the orchard and also 
during the operation of washing the lemons preparatory to packing 
them. The wash water, therefore, should be treated with copper 
sulphate, formalin, or potassium permanganate. In using formalin, 
il is made up in one part to ten thousand parts of water, or i pint to 
about 1200 gallons. Where the cheaper copper sulphate is more 
available, i pound should be dissolved in 250 gallons of water. 

Sooty Mold (Meliola Penzigi, Sacc, and M. camellice (Catt.) Sacc). — 
This fungus is widely distributed in those districts where citrus fruits 
are grown. It is most injurious to the orange, but occurs on the 
lemon as well, appearing on both leaves and fruits. The mycelium 
forms a sooty black covering on the leaves, twigs and fruits and is 
usually associated with various scale insects and aphids, which exude 
a honey dew upon which and the dead bodies of the scale "insects the 
fungus feeds as a saprophyte. The mycelium consists of large branched 
threads, which are closely septate, and the branches are cemented 
together to form a false stratum, which lives purely as a superficial 
saprophytic growth without penetrating into the tissues of the citrus 
plant on which it is found. Certain hyphal branches flatten out and 
probably serve as appressoria. The reproductive cells are of various 
kinds, such as stylospores in pustules, pycnidia with pycnidiospores 
(pycnospores) and perithecia. The stylospores arise from small 
conidiophores within peculiar, elongate, flask-shaped structures. The 
pycnidia are' small and scattered. The perithecia are spheric and in 
close asci with eight dark elliptic, three- to four-septate spores. 

The most effective substance for the treatment of sooty mold has 
been found by Webber to be the resin wash.^ The mixture consists of 

Resin 20 lb. 

Caustic soda (98 per cent.) 4 lb. 

Fish oil crude 3 lb. 

Water to make 15 gal. 

1 DuGGAR, B. M.: Fungous Diseases of Plants: 215. 



522 SPECIAL PLANT PATHOLOGY 

Webber prepares the mixture as follows: Place the resin, caustic 
soda and fish oil in a large kettle, pour over them 13 gallons of water, 
and boil until the resin is thoroughly dissolved, which requires from 
three to ten minutes after boiling has commenced. While hot, add 
enough water just to make 15 gallons. It is advised to make about 
two sprayings when the white fly (Aleyrodes) is in the larval stage. 
In Florida winter sprayings are important, but a spraying in May is 
also often desirable. In all cases dilute the stock solution with 9 
parts of water. 

Lettuce (Ladtica saliva, L.) 

Drop {Sclerotinia libertiana Fckl.). — This is one of the most disas- 
trous of the sclerotium-producing fungi to garden and greenhouse 
plants, being widely distributed and difficult to control. It attacks 
greenhouse lettuces, causing at first flagging, then indications of 
water-soaked areas over the stem and basal part of leaves, finally fol- 
lowed by the collapse of the whole plant into a formless mass. The 
mycelium may grow on the surface of the lettuce leaves and black 
sclerotia may be formed there commencing as white condensations 
which finally turn black. Conidiospore formation is not certainly 
known in the lettuce-drop fungus. Sclerotia, however, are commonly 
formed which measure 3 cm. in length and these are formed even on 
artificial culture media. The apothecia are wineglass-shaped with 
long black stalks. The asci formed on the upper depressed side of the 
apothecia are cylindric and measure 130 to 13 5^ by 8 to lo^u, while the 
ascospores are small, 9 to 13/i by 4 to 6.5/1. 

All dead and diseased lettuce plants should be destroyed by fire 
and the ground where they grew soaked with some suitable fungicide 
so as to confine, or practically exterminate the disease. The soil 
should be sterilized with steam before planting. 

Lilac {Syringa vulgaris, L.) 

Powdery Mildew {Microsphcsra alni (Wallr.) Wint.).— During the 
summer months and late in the autumn, the upper surface of the leaves 
of the lilac will be found covered with a whitish mildew which consists 
of interlacing hyphae, which form a cobwebby, superficial growth. 
Short haustoria are produced which grow into the epidermal cells. 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 523 

The mycelium develops upright vertical conidiophores which abstrict 
off conidiospores in chains. These conidiospores no doubt account 
for the rapid spread of the disease, which is never very serious to the 
Hlac shrubs, but no doubt to some extent interferes with the normal 
physiologic processes of the leaves. Subsequently perithecia are 
formed which are spheric in shape, almost jet black in color, and which 
are surrounded by a circlet of hyphae known as appendages, which are 
curved or dichotomously hooked at the extremities. Each perithecium 
produces 3 to 8 asci, and each ascus contains 4 to 8 relatively small 
ascospores, which measure 18 to 23/x by 10 to 12/x (Fig. 54). 

Maple (Acer spp.) 

Decay {Fomes fomentarius (L. Fr.) (Fig. 188). — The sporophores 
of this fungus are hoof-shaped and appear first as small rounded knobs 
on the surface of the trunk, or at branch stubs. The upper surface is 
smooth and more or less definitely marked by concentric ridges. The 
older fruit bodies owing to the action of the weather are uniformly 
gray and appear as if powdered. The lower surface is reddish-brown 
in color and shows numerous, small round pores. The margin of the 
new layer is grayish white and very soft and velvety. The sporo- 
phores are found usually singly, althoughby proximity of two, or several, 
they may appear grouped together. The decay produced in the wood 
of deciduous trees by Fomes fomentarius begins in the outer alburnum 
immediately beneath the barky layers, and extends inwardly, until 
it reaches the pith of the tree. The rotten wood is distinguished by 
a large number of irregular black fines outlining areas of sound wood. 
Wholly decayed wood is extremely soft and spongy, fight yellow and 
crumbles into numerous separate wood fibers when rubbed. The 
tinder fungus, Fomes fomentarius, is found in the deciduous forests of 
Michigan, Minnesota, New England, New York, Wisconsin and in 
other states. It grows rapidly in dead wood and the mycefium will 
form large masses if the infected timber is kept under moist conditions. 

Leaf-blotch (Rhytisma acerinum (Pers.), Fr.). — The tar spot of the 
maple is found about Philadelphia usually on the silver maple to which 
it does slight injury. The black irregular spots are, however, alwavs of 
interest to the laymen and questions are asked frequently about their 
cause. The spot begins, as a yellow thickened area, when the maple 



524 



SPECIAL PLANT PATHOLOGY 



leaves are expanded fully. The epidermis is pushed up by short conidio- 
phores which arise from a hyphal stroma beneath. These conidio- 
phores produce unicellular, curved conidiospores which serve to dis- 
tribute the fungus. Formerly this stage was called Melosmia. Later 



r-^ 




Fig. 1 88. — Cross-section of branch of dead beech rotted by Fomcs fomenlarius. 
(After von Schrenk, Hermann, Bull. 149, U. S. Bureau of Plant Industry, pi. viii, 
1909.) 



as the season advances, the hyphae become massed into a sclerotium- 
like area black without, but white within, and this persists after the fall 
of the leaf. Sometime the next spring, there arise from these sclerotia 
complex apothecia often 1.5 cm. broad, which break through at irregular 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 525 

fissures. The club-shaped asci bear eight acicular ascospores between 
which are found paraphyses with hooked tips. These ascospores 
measure 65 to 8o^t by 1.5 to 3/i and are ejected forcibly from the ascus. 
As the disease is not a serious one, usually no remedial measures are 
necessary. If the owner of maple shade trees wishes to keep it in 
check, he should burn the dry maple leaves which litter the ground 
about his place. 

Melons, Squashes, Watermelons {Cnciirbita spp.) 

Anthracnose (Colletotrichum lagenarhim (Pass.), Ell. & Hals. — As 
an illustration of a disease-producing fungus included among the Fungi 
Imperfecti, we may describe briefly the anthracnose of cucumbers, 
squashes, watermelons, Colletotrichum lagenarium, which attacks 
both leaves and fruits. The leaves are found with brown spots which 
cause their early maturity. If the fungus attacks the fruits, it produces 
sunken water-soaked spots in which the acervuH appear. The acervuH 
produce numerous conidiospores sticking together to form viscid 
masses of a pink color. During moist weather, the hyphae may grow 
out, superficially covering the fruit with a mold-Uke growth. The 
fungus eventually causes a complete decay of the fruit. The disease 
has been prevalent in Nebraska and New Jersey. If the disease 
appears in greenhouse culture, it is well to sulphur the greenhouses 
thoroughly when they are empty, and to clean and whitewash all the 
walls and woodwork to destroy any funguses present. Spraying with 
Bordeaux mixture (3-6-50) should begin when the vines begin to trail 
over the ground. Subsequent sprayings should be made every ten 
days, if the weather is dry. 

Wilt (Bacillus tracheiphilus, E. F. Sm.). — This serious disease of 
cucurbitaceous plants was first reported by Erwin Smith about 1893. 
It was first known in the northeastern states, but it is now common in 
the middle west and Rocky Mountain regions. Although pumpkins 
and squashes may be attacked by wilt, yet cucumbers and melons are 
most susceptible. This microorganism, which is a rod-shaped bacillus 
two or three times as long as broad, is actively motile by wavy cilia 
only when young. It measures 1.2 to2.5;u by 0.5 to 0.7/i. It causes a 
progressive wilting of the host which it attacks. Whether the whole 
plant dies depends upon the point of infection, which is usually ac- 



526 SPECIAL PLANT PATHOLOGY 

complished by^biting insects. If a leaf is attacked, it dies back to the 
stem. If the basal part of the stem is infected, the plant rapidly 
succumbs. This rapid wilting is due to the fact that the organism 
lives in masses in the vessels of the xylem by which the water taken 
up by the roots is distributed throughout the plant, hence any occlusion 
of these spiral and pitted vessels stops the water supply and the plant 
suffers. Advanced stages of the disease may be characterized by the 
disintegration of the vascular system and the formation of cavities in 
the adjacent parenchymatous tissue. Smith sums up the cultural 
characteristics of this organism, as follows: Stains readily; smooth; 
white; viscid; glistening; slow grower on media; surface colonies small, 
round, discrete; nogrowthat 37°C.orat 6°C. (i6days); aerobic; faculta- 
tive anaerobic (with grape-sugar, cane-sugar or fruit-sugar); usually 
it grays potato after a time; clouds peptone-bouillon and Dunham's 
solution thinly; growth retarded in acid juice of cucumber-fruits; 
also retarded or inhibited by juice of many vegetables, e.g. table-beet, 
sugar-beet, turnip, etc.; grows on many media at 25°C., carrot, coco- 
nut, etc.; thermal death point 43 °C.; optimum for growth 25° to 3o°C., 
maximum, 34° to 35°C.; easily killed by dry-air, sunlight, freezing; 
ammonia production moderate, in litmus milk persistent growth without 
reduction or distinct change in color of litmus; killed readily by acids. 
Group No. 222, 232, 2023. As the disease is distributed by insects, 
the grower of cucurbits should endeavor to reduce the number of 
these pests by the use of kerosene, or arsenate spray, and trap plants 
should be grown to attract the insects away from the more valuable 
plants. 

Oak {Quercus spp.) 

Decay {Polyporus sulphureus (Bull.) Fr. Figs. 189 and 190).- — The 
decay induced by Polyporus sulphureus is often called the red heart-rot. 
It attacks not only oaks, but also the chestnut, maples, black walnut, 
butternut, alder, locust, etc. It is widely distributed in North America 
and Europe. The sporophores of this fungus form a series of superim- 
posed, fleshy brackets of a sulphur-yellow color, weighing in the aggre- 
gate at times almost one hundred pounds (Fig. 189). The color some- 
times may vary to an orange-red. The under surface is usually a light 
yellow color and beset with numerous minute pores. At maturity, the 
fruit bodies lose their soft character and become harder and more brittle. 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 527 

and frequently, become the prey of maggots which riddle them with 
holes and burrows. It is also eagerly gathered by mycophagists who 
know it to be an excellent article of food. 

The mycelium of the fungus may live in the dead wood of a tree 
after it has been killed for a number of years, so that the same tree may 
produce successive crops of edible fruit bodies. The destruction, which 
the mycelium works, is characteristic. The heartwood is reduced to a 
crumbly brown mass which resembles charcoal in its fracture, but is 




Fig. 189. — Fruiting body of Polyporus siilphureus. {After von Schrenk, Hermann, 
Bull. 149, U. S. Bureau of Plant Industry, pi. iv, 1909.) 



red-brown in color. The decayed wood shows concentric and radial 
cracks extending irregularly through it (Fig. 190). As the wood is at- 
tacked and destroyed by the spreading mycelium, these cracks increase 
and in them are found leathery compact sheets of mycelium, which can 
be isolated by reducing the decayed wood to a fine powder by the blows 
of a hammer. The wood decays uniformly and is converted into a 
brittle brown substance, which can be rubbed to a fine powder between 
the fingers. Von Schrenk found that the youngest trees in which the 
red heart-rot occurred were about 50 years old. The removal of dis- 



528 



SPECIAL PLANT PATHOLOGY 



eased trees seems to be the only efficient method of checking the spread 
of Polyporus siilphiireus. 

Honeycomb Heart-rot (Stercum subpileatnm, W. H. Long). — The 
pocketed, or honeycomb, heart rot has been found on the following. 




Fig. 190. — Cross-section of a living post oak tree rotted by Polyporus sul- 
phureus. {After von Schrenk, Hermann, Bull. 149, U . S. Bureau of Plant Industry, 
pi. iv, 1909.) 



nine species of 02i\i's,:Querciis alba, Q. lyraia, Q. marilandica, Q. MichauxU, 
Q. minor, Q. palustris, Q. texana, Q. velutina and Q. virginiana} 

The first indication of this honeycomb heart-rot in white oak is a 
slight discoloration of the heartwood, which assumes a water-soaked 
appearance, which may extend from i to 6 feet beyond the actual decay. 

1 Long, W. H.: A Honeycomb Heart-rot of Oaks caused by Skrcuin subpileatnm, 
Journal of Agricultural Research V: 421-428, Dec. 6, 1915. 



DETAILED ACCOUNT OF SPFCIPIC PLANT DISEASES 529 

The water-soaked heartwoocl becomes tawny in color when dry. 
Light-colored, isolated areas now appear in the discolored wood and 
these areas originate the pockets. The rot spreads in all directions into 
the surrounding tissue, but more rapidly in the summer wood of the 
annual ring of the preceding year, so that the bulk of the pocket lies 
in the summer wood of one year and the spring wood of the succeeding 
year. Delignification now follows in which delignified wood fibers 
appear in patches in the light-colored areas, and this delignification 
spreads rapidly until white, oval to circular pockets are formed. 
These lens-shaped pockets are at first filled with white cellulose, which 
is later absorbed, leaving cavities. The diseased area increases in size 
until the pockets reach a large medullary ray, which seems to check the 
activity of the enzyme, so that the larger medullary rays become the 
radial walls of the pockets. All the cellulose finally disappears, leaving 
the pockets either (i) empty, (2) containing the shrunken white 
membranes of the included vessels, or (3) more or less filled with myce- 
lium. The last stage of the rot is characterized by the very light and 
honeycombed nature of the wood. The pockets are longer than 
they are broad, and all of the wood has disappeared, except the thin 
walls around the pockets, which remain distinct and usually involve the 
heartwood uniformly. The rotted wood is, therefore, in the shape of a 
cylinder and there is a brownish discoloration of the heartwood on the 
outer edges of the affected area. 

The growth of the mycelium seems to be preceded by the enzymes 
which cause the disintegration of the wood. A few of the larger vessels 
show hyphal threads and these become more 'numerous, as delignifi- 
cation advances, until they become stuffed with small, intricately 
branched, colorless hyphas. When the hyphae are exposed to the air, 
they become brown ia color. The sporophores are found on dead 
trees, or the dead areas of living trees. The sporophores are thin 
shelving bodies formed in. the cracks of the bark, sometimes assuming 
a conchate shape. They sometimes form in parallel lines, and range up 
to 5 cm. in width. These sporophores may be formed on the dead tree 
for a number of years. This fungus is widely distributed in the southern 
states and ranges as far north as Ohio. The only method of control 
is to prevent the infection of trees by eliminating forest fires, by pre- 
venting the formation of the sporophores, and the destruction of all 
diseased timber which has the rot. 



530 SPECIAL PLANT PATHOLOGY 

Root-rot (Armillaria mellea, Vahl).' — The "hallimasch" of the 
Germans, or the so-called honey mushroom, is a fungus of considerable 
interest to the forester (Fig. 15). The spores, ifblown to an exposed 
branch stub, may germinate and produce a mycelium which works up and 
down the tree. Infection may be also by the mycelium growing across 
from the roots of a diseased tree to a healthy one through the soil of 
the forest. In either case, the young mycelium grows into the cambial 
layer, attacks the living cells, and finally completely encircles the trunk 
of an infected tree. Later the hyphae are converted into strands, which 
show a characteristic apical growth, thus providing for the elongation 
of the strands through the host. The strands of hyphae turn a deep 
chocolate-brown color and are known as rhizomorphs (Fig. 15), which 
may anastomose under the bark of the tree. Ultimately, as the tree 
dies, the bark splits off and the rhizomorphs are found flattened against 
the woody cylinder of the tree. If such trees are used as mine props, 
the strands may keep on growing under the moist even temperature of 
the mine and there they may hang down in long streamers into the mine 
galleries, as specimens of such in the botanic museum of the Univer- 
sity of Pennsylvania indicate. The effect of the mycelium in the tree 
is to kill its top with the ultimate death of the entire tree. The 
rhizomorphs formerly known as Rhizomor pha subterranea grow out 
into the root system of the tree, which they kill, and here they may 
live for a number of years, endangering the nearby healthy trees, 
because they extend out into the soil toward other tree roots. It is 
this subterranean growth, which makes the honey mushroom an ex- 
tremely dangerous oife to the hardwood forests, where it is found. 
The fruiting bodies of this fungus usually occur grouped in considerable 
numbers about the base of the affected tree arising from the dark-brown 
rhizomorphs, which thus serve to connect together isolated groups of 
the sporophores. The sporophores produced most commonly from 
September to November are honey-colored, i.e., yellow to orange- 
brown, and their umbonate tops have a more or less viscid character 
with small black spicules scattered over the surface. The stipes are 
slightly swollen at the base and a short distance below the pileus is 
found the ring, or annulus. The lamellae are dirty-white and from 
each pyriform basidium four white basidiospores fall until surround- 

'LoNG, W. H.: The Death of Chestnuts and Oaks due to Armillaria mellea. 
Bull. U. S. Dept. Agric. No. 89, 1914. 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 53 1 

ing leaves and mosses may be coated with a mealy powder derived from 
the gills of several sporophores directly over them. 

Oat (A vena saliva, Linn.) 

Rust {Puccinia coronifera, Kleb) .■ — The oat rust, or crown rust, affects 
oats and also several other grasses. The summer stage appears on 
oats just prior to the period of ripening where it forms an elongated 
uredinium of an orange color on the leaves and sheaths. The globular 
spores germinate readily. The teliospores are formed later as black 
spots around the edge of the uredosori. As the teliospores bear at 
their apex a crown of blunt projections, or processes, the common name 
of "crown rust" has been applied. Such winter spores remain in a 
resting condition until the following spring, when they germinate in the 
usual way. The basidiospores, which are formed from the basid- 
ium, or promycelium, begin growth on the leaves of the buckthorn, 
Rhamnus cathartica, where within eight to ten days cluster cups 
(yEcidium catharticce) appear. The aeciospores germinate readily and 
are blown to the oat and other grasses, such as perennial rye grass, 
Yorkshire fog, so that at least eight forms of the species limited to 
certain hosts have been distinguished. The measurements of its spores 
are as follows: ^ciospores, orange, vermiculose, 16 to 25/x by 12 to 20^1; 
Uredospores globose to obovate, echinulate yellow, 18 to 2 7yuby 16 to 
24/i; teliospores brown, two-celled, crowned with rough projections; 
approximately 35 to 60^1 by 12 to 22)u. 

Smut (Ustilago avencB and U. levis). The a-ppearance of this dis- 
ease is illustrated in the figures (Fig. 191). 

Onion {Allium cepa, L.) 

Smut (UrocysHs ceptdcB, Frost). — This fungus, probably of Ameri- 
can origin, is found in the onion growing districts of the eastern United 
States where it has been known for about 50 years. The smut fre- 
quently appears soon after the first leaf appears, and is first in the form 
of dark spots at the base of the first leaf and on succeeding leaves, as 
they make their appearance. These spots are followed by longitudinal 
cracks, which show, a granular spore powder associated with threads 
of fibrous tissue. The spore powder under the microscope is found to 
consist of the spore balls, which number several compacted cells, the 



532 



SPECIAL PLANT PATHOLOGY 



central one of which contains cytoplasm, being surrounded by an 
envelope of sterile cells. Such spore balls are 17 to 25)11 in diameter 




Fig. 191. — Smut of oats. A, UsLilago avence; B, Usltlago levis {After Jackson, 
H. S., Bull. 83, Del. Coll. Agric. Exper. Slat., December, 1908.) 

and may retain their capacity for germination in the soil for a period of 
12 years. 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 533 

As the spores occur in the soil, it is useless to treat the onion seeds 
with chemic bodies. The most successful method of prevention is to 
transplant the seedlings into beds known to be free from smut. Some 
growers place sulphur (100 pounds to the acre) and air-slacked lime 
(50 pounds) in the drills as the seeds are planted. 

Orange (Citrus aurantium, L.) 

Black-rot {Alter naria citri). — Only navel oranges are subject to 
black rot which is recognized by the premature ripening, large size of 
the fruit and its deep red color. The fungus gains entrance through 
the navel end, because there imperfections of the skin occur. There 
soon arises a black area of decay under the peel which remains isolated 
for some time without spreading, therefore, the disease is not very 
virulent. In Alter naria, the conidiophores are in bundles, always 
unbranched and short. The conidiospores are club-shaped to flask- 
shaped, divided and united into chains by thinner cells. 

Fruit-rot {Penicillium italicum, Wehm.). — A large part of the decay 
of the orange and other fruits of the genus Citrus is due to blue and 
green molds. These molds usually cannot enter uninjured fruits, and 
so their attacks usually follow a bruise occasioned by careless handling, 
or when the fruit falls from the orange tree. Penicillium italicum seems 
to be more common than the other species, P. digitatum. Pure cultures 
of this fungus can always be secured from decaying oranges in the 
market, which have the blue-green areas of rot just beginning to appear 
upon them. These areas are usually blue-green in the center sur- 
rounded by white areas which are grouped usually into little white 
patches toward the vegetative margin and the whole superficial colony 
surrounded by an area of soft watery rot. Sometimes, as the colonies 
become older, P. digitatum mixes with P. italicum. 

The conidiophores are short (looju), or very long (6oo;u) and black 
in media containing sugar. They average about 250^ in length. The 
conidial fructifications are up to 300/1 or more in length, consisting usu- 
ally of a main branch and one lateral branch, each producing a whorl 
of branchlets bearing crowded verticils of conidiospores, 12 to 14^1 
by 3/i. The chains of conidiospores are cylindric to elliptic, slightly 
ovate, clear green by transmitted light and measure 2 to 3/x by 3 to 5)u. 
Decay of this sort can be prevented by careful handling of the fruit in 
field and packing house. 



534 SPECIAL PLANT PATHOLOGY 

Pea {Pisum sativum, L.) 

Pod-spot {Ascochyta pisi, 'Lih.). — The horticulturist, who attempts 
to grow the garden pea, will find that the leaves and pods become 
spotted with conspicuous, circular, sunken spots 3 to 6 mm. in diameter, 
which are dark bordered, pale in the centers and slightly pinkish when 
mature. Pycnidia are associated with these spots and out of their 
porous opening under favorable conditions the spore masses may be 
seen issuing. When the leaves are affected, it is usually the lower 
leaves which become diseased first, and such soon die. If the stems 
are attacked, the spots sometimes penetrate through the woody part. 
Different races of peas differ as to their susceptibility. The variety 
Alaska is slightly affected, while the varieties American Wonder, 
French June and Market Garden are frequently badly diseased. 
According to Stevens, the pycnidia consist of angular cells, 5 to 7/1 with 
a rounded ostiole and reddish-brown surface. The conidiospores are 
constricted slightly at the septum, are oblong and measure 12 to i6m by 
4 to 6ju. The mycelium perennates in affected seeds, reduces their 
power of germination and carries the fungus over to the next crop. 
Selby has indicated that healthy peas may be grown by spraying with 
Bordeaux mixture, and it has been suggested, that a two years' rotation 
of non-susceptible crops lessens the prevalence of the disease, if another 
pea crop is raised. 

Peach {Amygdalus persica, L.) 

Leaf Curl (Exoascus deformans (Berk.), Fckl.) (Fig. 192). — This 
disease is called by the French Cloque du pecker, by the Germans 
Krauselkrankheit and by Americans and English peach leaf curl. It 
is widely distributed through America, Europe, China and Japan and 
in Africa and Australia, so that it is practically cosmopolitan. 

The disease is most prevalent and most disastrous to the leaves and 
tender shoots of the peach, when the spring months are damp and cool, 
for records show that such conditions prevailed during April of the 
year 1893, 1897 and 1899, when peach leaf curl was especially abundant 
in Ohio and New York. Warm and relatively dry springs seem to be 
unfavorable to its occurrence. The susceptibility of the host plants 
differs to a marked extent, some being susceptible, others less so. 

The presence of the disease may be detected when the leaf buds 
unfold, for the coloring of the young leaves is heightened, and as they 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 



535 



open out, the curling and arching of the blades become manifest. 
The curling may be confined to a small portion of a leaf, or it may be 
general and all of the leaves of a tree may be affected, as well as the 
young stem on which \hey are found. The green, or reddish, color of 




Fig. 192. — Peach leaves deformed by leaf curl {Exoascus deformans). (After Heald, 
F. D., Bull. 135 (Set. Ser. 14), Univ. of Tex., Nov. 15, igoQ-) 

the leaves is lost as they mature, and they become pale, or slightly 
discolored. Diseased shoots may grow to twice their normal diameter 
and assume a characteristic paleness. The diseased leaves finally 
turn brown and drop off the tree, and if this defoliation is excessive 



536 SPECIAL PLANT PATHOLOGY 

the crop of peaches may be nil. The twig affection is sometimes 
associated with gummy exudations, particularly when the enlargement 
is terminal. It is doubtful whether the mycelium perennates in the 
twigs, as was supposed in former years. Infection must generally 
occur as the buds unfold. 

The mycehum of the fungus may be studied most advantageously 
in the leaf before the fungus has appeared on the surface. At that time, 
the hyphze show a greater protoplasmic content and sections reveal 
the fact that the intercellular inycelium is distributed through the 
mesophyll and cortex of the young stems. Pierce distinguishes vege- 
tative hyphae, distributive hyphae and fruiting hyphae. The latter 
push up between the epidermal cells and a series of short hyphal cells 
are formed, as ascogenous cells, which form an almost continuous layer 
beneath the cuticle. The ascogenous cells give rise to the asci, which 
push through the cuticle. An ascus is usually truncate at the exposed 
end and it gives rise to four to eight ascospores, which may bud within 
the ascus. 

Leaf curl may be controlled by the use of lime-sulphur solution 
(1-20), Bordeaux mixture (5^5-50) and copper sulphate in water 
(2-50), for the use of which the practical man is referred to the spray 
calendar given in the subsequent pages of this book. 

Pear (Pynis commurds L.) 

Fire-bhght (Bacillus amylovorus (Bun.), De Trev. Toni).^ — This 
bacterial disease is found on the apple, pear and quince, but more 
especially on the pear, so that it has been termed pear blight. It was 
first reported from the northeastern United States, but now it is dis- 
tributed throughout the country from the Atlantic to the Pacific 
oceans. The disease first makes its appearance in the early part of the 
season, when it appears in the form of a twig blight throughout the time 
of blossoming of apples and pears, when the blossoms and tips begin 
to wilt and show signs of blackening. This results in the complete 
blackening and death of all the short branches, or spurs, upon which 
flower clusters have been borne. The fire blight disease may continue 
to extend down the twig, or the branch, the branch being entirely 
killed, as it progresses. Under conditions more favorable to the host 

1 Orton, C. R. and Adams, T. F. : Collar-blight and Related Forms of Fire- 
blight. Bull. 136. Penna. Agricultural Experiment Station August, 1915. 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 537 

the blight may extend only a short distance, which results in tip prun- 
ing. The bark of the tree indicates the progress of the disease, for 
the soft bark assumes a water-soaked appearance followed by a blacken- 
ing and shriveling. When the organism ceases to spread rapidly in 
the tissues, there appears a sharp Hne of separation between the dead 
and the healthy tissues. The bark is broken and through the bark 
cracks appear gummy, or gelatinous, drops which vary in color from 
white to brown, or black. 

Bacilhis amylovorous was described first by Burrill in 1877, a dis- 
covery full of significance to plant pathology, because it established 
the first bona fide case of a plant disease due to bacteria. It has been 
established, that infection takes place through the visits of insects, 
especially bees, to the pear flowers. From the floral nectary, the 
bacillus spreads to the softer tissues of bark and cambium, where 
it is very largely confined, and where it winters over, spreading to 
other blossoms the next spring. Bacillus amylovorus is an oval 
microorganism 1.5^ to 2^1 long, growing singly, or several attached 
end to end, and is motile in fresh cultures. On agar, the cloudy 
and white surface colonies appear the second day, and attain a di- 
ameter of 2 to 3 mm. by the fourth or fifth day. Cloudiness appears in 
bouillon after twenty-four hours, and in milk, thickening of the medium 
begins at the third or fourth day, which increases until the fifth, or 
sixth day, when the product is finally partially gelatinous with a clear 
acid liquid above, changing to slightly alkaline. 

The work of Waite has shown that pear blight can be controlled 
by pruning out the blight during winter, so as to eliminate the source 
of infection during the next year, and if this pruning is done thoroughly, 
the disease can be kept in check. The stubs should be disinfected 
with corrosive sublimate (i-ioo). 

Pine (Pi litis spp.) 

Blister-rust (Cronartium ribicoliim, Fisch & Waldh. = Pcrl- 
dermium strobi, Klebahn).^ — This disease, as it appears on white pine, 

^ Spaulding, Perley: The White Pine Blister Rust Situation, American 
Forestry 22, pp. 137-138, March, 1916; The BHster Rust of White Pine, Bull. 206, 
U. S. Bureau Plant Industry, 191 1; also consult American Forestry. Feb., Mch., Dec, 
1916. In the December, 1916, number a map showing the distribution of the 
disease is given. A conference was held at Washington in January, 1917, to 
consider the establishment of stricter quarantine regulations of the methods of 
checking the spread into the western states. 



538 



SPECIAL PLANT PATHOLOGY 



has been considered to be of such great importance, that strict quaran- 
tine regulations were established in order to keep it out of the country, 
but the result of a thorough exploration of the New England States 
during the summer of 1916 has shown its general distribution through- 
out them and even as far west as Minnesota. It appears to have been 




Fig. 193. — White pine blister-rust, Cronarliutn ribicola. A, Diseased tree with 
aecial blisters broken open from which spores are blown to currant or gooseberry- 
leaves; B, D, teliosori on under leaf surface of currant, Ribes. {From Gager, after 
Perley Spaidding.) 

introduced into America on nursery stock from Holland, and all the 
trees in these advanced posts of infection have been destroyed. In 
igo6, there was an outbreak on currants at Geneva and measures were 
taken to destroy the fungus in that vicinity. The aicidial stage, known 
as Peridermium sirobi, appears on the pine tree and the uredinia and the 



DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 539 

telia on species of the genus. Ribes, viz., R. aureum, R. nigrum, R. 
rubrum with which intermediate hosts (it does little damage. The 
susceptibiHty of different currants varies considerably (Fig. 193). 

The attacked white pine trees are stunted, the tops show a bushy 
growth and the part of the tree where the mycelium occurs is swol