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Library

RESEARCHES ON FUNGI

VOLUME VI

RESEARCHES Sf^'
ONFUNGI ^^

VOLUME VI

THE BIOLOGY AND TAXONOMY OF PILOBOLUS,
THE PRODUCTION AND LIBERATION OF SPORES
IN THE DISCOMYCETES, AND PSEUDORHIZAE
AND GEMMIFERS AS ORGANS OF CERTAIN

HYMENOMYCETES

BY
A. H. REGINALD BULLER, F.R.S.

B.Sc. (LoND.) ; D.Sc. (BtRM.) ; Ph.D. (Leip.) ; LL.D. (Manitoba)
LL.D. (Saskatchewan) ; D.Sc. (Pennsylvania) ; F.R.S.C.

MEMBRE ASSOCIE DE LA SOCIETE ROYALE DE BOTANIQUE DE BELGIQUE
PROFESSOR OF BOTANY AT THE UNTVERSITY OF MANITOBA

WITH TWO HUNDRED AND THIRTY-ONE FIGURES IN THE TEXT

B

HAFNER PUBLISHING CO.

NEW YORK
1958

Reprinted by arrangement

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. THE DISTINGUISHED DIRECTOR

OF THE IMPERIAL MYCOLOGICAL INSTITUTE

IN RECOGNITION OF HIS CONTRIBUTIONS

TO OUR KNOWLEDGE OF FUNGI

AND OF HIS HELPFULNESS

TO FELLOW" WORKERS

PREFACE

The object of this volume is to make contributions to our knowledge
of certain Phycomycetes, Ascomycetes, and Basidiomycetes.

Part I is devoted to a study of Pilobolus. The ocellus function
of the subsporangial swelling has been treated of in detail. A new
species of Pilobolus has been described, and a final Chapter on the
Systematics of the Pilobolidae has been contributed by my friend,
Mr. W. B. Grove.

Part II is concerned with the production and liberation of spores
in the Discomycetes. The phenomenon of puffing has been discussed ;
and attention has been called to the fact that the asci of many
Discomycetes are heliotropic, so that light is of great importance
in directing the ascus guns toward the mouths of cup-shaped
fruit-bodies and toward the openings of the hymenial depressions
in Morchellae. Finally, a simple method for making audible the
puffing of Discomycetes has been described.

The first two Chapters of Part III treat of the pseudorhizae of
Collybia radicata, C. fusipes, Coprinus macrorhizus , and other
Hymenomycetes, while the final Chapter treats of Omphalia flavida
as a luminous and gemmiferous Coffee leaf-spot fungus. The
gemmae of this fungus are unique, for they appear to have been
derived from pilei which have become sterile and detachable. With
a view to enabling the reader to compare the gemmifers of 0. flavida
with those of Sderotium coffeicola (another Coffee leaf-spot fungus),
a brief account of S. coffeicola based in the main on Stahel's
investigations has been appended.

This volume contains two hundred and thirty-one illustrations

vii

viii PREFACE

in the text, including one hundred and thirty-four drawings and
ninety-seven photographs. Forty of the drawings have been
borrowed from other authors. The other drawings were executed
by my own hand or in conjunction with Miss Ruth Macrae. Of the
ninety-seven photographs fifty-six were made under my direction,
ten have been borrowed from other authors, and the rest were
kindly contributed by friends and correspondents : one each by
S. F. Ashby. Jessie S. Bayliss Elliott, W. S. Odell, and H. H.
Thornbury, two by F. Dickson and W. R. Fisher, two by Somerville
Hastings, three each by B. 0. Dodge, G. L. Fawcett, and W. H.
Long, five by A. E. Peck, and nine by the Photographic Division
of the Geological Survey of Canada. The source of each borrowed
illustration is acknowledged in the text.

For the session 1933-1934 I was granted leave of absence from
the University of Manitoba, and this period has been spent at the
Herbarium of the Royal Botanic Gardens, Kew, in completing for
the press the MS. and illustrations of Volumes V and VI of these
Researches. For the facilities placed at my disposal for carrying out
this work I here desire to express to Sir Arthur Hill, Director of
Kew Gardens, and Mr. A. D. Cotton, Keeper of the Herbarium,
my hearty appreciation.

My best thanks are due once more to the Canadian National
Research Council for grants in aid of the work. These grants
have enabled me to employ in succession two research assistants,
Miss Ruth Macrae, M.Sc. (McGill), and Miss Eleanor S. Dowding,
Ph.D. (Manitoba). The investigations on the gemmifers of Omphalia
flavida and on the heliotropism of the asci of Ascobolus magnificus
were carried out in conjunction with Miss Macrae, and certain
investigations upon the life-history and structure of Pilobolus in
conjunction wdth Dr. Dowding. I here desire to express my
indebtedness to these two ladies for their valuable services. Once
again Mr. W. B. Grove, M.A., has been kind enough to give me the
benefit of his assistance in reading the proofs.

A. H. REGINALD BULLER.

Kew, August 19, 1934.

TABLE OF CONTENTS

TAtlE

Preface ............. vii

PART I

THE BIOLOGY AND TAXONOMY OF PILOBOLUS

CHAPTER I

INTRODUCTORY AND HISTORICAL

Pilobolus and its Subsporangial Swelling — The Discovery, Structure, Tax-
onomy, and Life-history of Pilobolus — Sex in the Pilobolidae — The
Cytology of Pilobolus — Crystalloids — The Orange-red Pigment-
Parasites of Pilobolus — The Excretion of Drops by the Sporangiophore and
its Cause — Premature Discharge of the Sporangia — Influence of External
Conditions on the Breadth of the Subsporangial Swelling — The Ballistics
of the Projectile — Pilobolus in its Relations with Light — The Effect of
Light on Fruit-body Development — The Heliotropic Response of the
Fruit- body to Light of Various Colours — Allen and Jolivette's Investiga-
tions— The Subsporangial Swelling as an Ocellus — The Solution of the
Problem of the Non-resultant Heliotropic Reaction of Pilobolus to Two
Beams of Light — The Discharge of the Sporangium ....

CHAPTER II

PILOBOLUS AND THE OCELLUS FUNCTION OF ITS SUBSPORANGIAL

SWELLING

Culture Methods — Germination of Spores, Growth of Mycelium, and Forma-
tion of Primordia of Fruit -bodies — A Colourless Sporangial Wall as an
Abnormality in Pilobolus longipes — Species observed — General Description
of the Pilobolus Gun and its Projectile — The Discharge of the Projectile —
Development of the Pilobolus Gun and its Projectile — The Heliotro{)ism
of the Pilobolus Gun demonstrated by a Simple Experiment — The Range
of the Pilobolus Gun — The Structure of the Sporangiophore and Spoian-
gium illustrated by Pilobolus Kleinii and P. lo?igipes — The Two Functions
of the Subsporangial Swelling — The Heliotropism of the Sporangiophore
with Special Reference to the Ocellus Function of the Subsporangial

ix

TABLE OF CONTENTS

PAGE

Swelling — The Mechanism of Heliotropic Response in Pilobolus and in
the Leaves of Certain Flowering Plants — The Ocellus of Pilobolus and the
Eye-spots of Volvox — The Ocellus of Pilobolus and the Human Eye — A
Heliotropic Experiment made on Pilobolus longipes — A Solution of the
Problem of the Reaction of the Sporangiophore of Pilobolus to Two
Equal Beams of White Light— A Model for illustrating the Pilobolus
Fruit-body in its Relations with Light — The Periodicity in the Develop-
ment of Pilobolus Fruit-bodies — The Subsporangial Swelling and the Dis-
charge of the Pilobolus Gun— The Osmotic Pressure of the Cell-sap of
Pilobolus— Factors in the Efficient Working of the Pilobolus Gun— An
Analysis of the Cell-sap of Pilobolus longipes— The Landing of the Pilobolus
Projectile and the Attachment of the Sporangium to Herbage — The
Relations of Pilobolus w ith Flowering Plants and with Herbivorous Animals 47

CHAPTER III

PILOBOLUS UMBONATUS, A NEW SPECIES, WITH REMARKS ON THE

PILOBOLIDAE

Introduction — General Description— Taxonomic Description and Latin

Diagnosis — Remarks on the Pilobolidae . . . . • .169

CHAPTER IV

A SYSTEMATIC ACCOUNT AND ARRANGEMENT OF THE PILOBOLIDAE

Contributed by W. B. Grove

Introductory Remarks— Historical Account — Systematic Arrangement-
Bibliography .......•••

PART II

THE PRODUCTION AND LIBERATION OF SPORES IN THE

DISCOMYCETES

CHAPTER I

THE PHENOMENON OF PUFFING IN SARCOSCYPHA PROTRACTA AND

OTHER DISCOMYCETES

Introduction— Historical Remarks— Puffing illustrated by Photography—
The Significance of Puffing— The Genus ^a,Tcoscy^h?i—8arcoscyp}ui
protracta — The Perennial Pseudorhiza — The Direction of Puffing and the
Campanulat« Form of the Apothecium— The Ascus as an Explosive
Mechanism— Radial- longitudinal Sections and Surface Views of the

190

TABLE OF CONTENTS xi

PACE

Hymeniuin — Correlations and Fruit-body Efficiency— What Factor
determines the Oblique Position of the Opening of each Ascus ? — Experi-
mental Proof that a Fruit-body, when it puffs, produces a Blast of Air —
The Cause of the Blast of Air — The Blast of Air and the Dispersal of the
Spores — Concluding Remarks ........ 227

CHAPTER II

THE HELIOTROPISM OF THE ASCI AND THE DISCHARGE OF THE SPORES IN
ASCOBOLI, CILIARIA SCUTELLATA, ALEURIA VESICULOSA, THE MORCHEL-
LACEAE, AND OTHER DISCOMYCETES

Introduction — The Heliotropism of the Asci of Ascobolus magnificus—Ascobolus
stercorarius — Our Present Knowledge of Ciliaria scutdlata — The Helio-
tropism of the Asci of Ciliaria scutellata — The Heliotropism of the Asci
of Melastiza miniata and Cheilymenia vinacea — Aleuria vesiculosa and its
Identification — Results of a Previous Investigation on Aleuria vesiculosa
— The Heliotropism of the Asci and the Discharge of the Spores in Aleuria
vesiculosa — Puffing of Aleuria vesiculosa under Natural Conditions — The
Heliotropism of the Asci and the Discharge of the Spores in Galactinia
badia — Urnula Craterium — Otidea onotica and O. leporina — The Helio-
tropism of the Asci and the Discharge of the Spores in the Morchellaceae
— The Helvellaceae — Concluding Remarks ...... 264

CHAPTER III

THE SOUND MADE BY FUNGUS GUNS AND A SIMPLE METHOD FOR
RENDERING AUDIBLE THE PUFFING OF DISCOMYCETES

Fungus Projectiles— Type I : Sphaerobolus— Type II : Pilobolus— Type III :
Ascobolus— Type IV : Peziza— A Simple Method for Rendering Audible
the Puffing of Discomycetes — Tj-pe V : Empusa and Entomophthora,
Uredmeae and Hymenomycetes — Sounds Made by Fungus Guns are of
No Biological Significance .....•••• 325

PART III

PSEUDORHIZAE AND GEMMIFERS AS ORGANS OF CERTAIN

HYMENOMYCETES

CHAPTER I

THE PSEUDORHIZA

Introductory B.ema,rks—Collybia radicata—Mycena gakriculata—Coprtnus
ruacrorhizus .....••••••

347

xii TABLE OF CONTENTS

CHAPTER II

THE PERENNIAL PSEUDORHIZA OF COLLYBIA FUSIPES

PAGE

Introduction — Historical Remarks — Fruit-body Clusters and their Pseudo-
rhizae — The Supposed Sclerotium — Evidence that the Pseudorhiza
Persists — Mode of Development of a Compound Pseudorhiza — Lateral
Grafting — Healing of Pseudorhizal Wounds — The Mycelium and the
Problem of Parasitism — The Functions of the Pseudorhiza and the
Significance of its Persistency — Sarcoscypha protracta .... 374

CHAPTER III

OMPHALIA FLAVIDA, A GEMMIFEROUS AND LUMINOUS LEAF-SPOT

FUNGUS

Introduction — Omphalia flavida and the American Coffee-leaf Disease —
Stilbum flavidum as a Stage in the Life-history of OmpJmlia flavida — The
Structure of the so-called Stilbum-hody — The Omphalia flavida Sporophore
— The Origin of the Stilbum-hodies — The Stilbum-hody as a Gemmifer — The
Basal Curvature of the Pedicel and its Significance — The Sigmoid
Curvature of the Pedicel and the Abscission of the Gemma — The Detach-
ment of a Gemma from its Pedicel — The Attachment of a Gemma to a
Leaf — Mode of Germination of a Gemma — The Effect of Desiccation on
the Vitality of a Gemma — Inoculation Experiments with Living Leaves —
Omphalia flavida as a Non-specialised Parasite — Sterility of the Mycelium
Induced by Prolonged Cultivation on Artificial Media — The Effect of
Light on the Formation of Gemmifers — Luminescence of the Mycelium
and its ^'alue as a Diagnostic Character of the Coffee-leaf Disease — Tlie
Gemmifers of Sclerotiutn coffeicola ....... 397

GENERAL SUMMARY :

Part I ........... . 455

Part II . 462

Part III 408

GENERAL INDEX 473

PART I

THE BIOLOGY AND TAXONOMY OF PILOBOLUS

RESEARCHES ON EUNGI

CHAPTER I

INTRODUCTORY AND HISTORICAL

Pilobolus and its Subsporangial Swelling — The Discovery, Structure, Taxonomy,
and Life-history of Pilobolus — Sex in the Pilobolidae — The Cytology of Pilobolus
— Crystalloids — The Orange-red Pigment — Parasites of Pilobolus — The Excre-
tion of Drops by the Sporangiophore and its Cause — Premature Discharge of
the Sporangia — Influence of External Conditions on the Breadth of the Sub-
sporangial Swelling — The Ballistics of the Projectile — Pilobolus in its Relations
with Light — The Effect of Light on Fruit-body Development — The Holio-
tropic Response of the Fruit-body to Light of Various Colours — Allen and
Jolivette's Investigations — The Subsporangial Swelling as an Ocellus — The
Solution of the Problem of the Non-resultant Heliotropic Reaction of Pilobolus
to Two Beams of Light — The Discharge of the Sporangium.

Pilobolus and its Subsporangial Swelling. — The genus Pilobolus
belongs to the Phycomycetes, is a close relative of Mucor, and
includes about sixteen species. Most of these species come up along
with those of Mucor and other moulds upon the solid excrement of
herbivorous animals, such as the horse and the cow, while one
species occurs upon river mud. The general appearance of a
Pilobolus, when growing on horse dung, is shown in Figs. 1, 5
(pp. 2, 8), and 13 (p. 37).

Pilobolus differs from Mucor in that, as a prehminary to the
dissemination of the spores, the sporangium is shot away from the
sporangiophore, whereas in Mucor this does not take place. The
sporangiophore of Mucor is an organ which serves merely to raise
the sporangium above the substratum, and thus to put it in a
favourable position for the passive dispersion of the spores by
insects and other agencies. On the other hand, the sporangiophore

VOL. VI. B

RESEARCHES ON FUNGI

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of Pilobolus not only raises the sporangium above the substratum
but is also adapted for shooting the sporangium away to a consider-
able distance. With this difference of function is associated a very
marked difference in the structure of the two sporangiophores, that
of Pilobolus being morphologically much more highly speciahsed
than that of Mucor.

Pilobolus, owing to its very common occurrence, the beauty of
its form, its unique subsporangial swelling, its very pronounced

heliotropism, the
beads of water with
which its sporangio-
phore is usually orna-
mented, and the great
distance to which its
sporangium is dis-
charged, has attracted
the attention of my-
cologists for more
than two centuries,
and to-day it is de-
scribed in many text-
books of Botany. As
a contribution to our
knowledge of a fungus
which is of such per-
ennial interest, there
will be presented : in this Chapter a historical review of the
literature on Pilobolus ; in Chapter II an account of the author's
researches on Pilobolus, of which a brief report ^ was made in
1921 ; in Chapter III a description of a new species, Pilobolus
umbonatus ; and in Chapter IV a taxonoraic description of all
the known species of Pilobolus, drawn up by Mr. W. B. Grove.
In Chapter II, from the point of view of the organism as a
whole, it will be shown : (1) that the subsporangial swelling, in
addition to acting as part of a squirting apparatus, has the function

1 A. H. R. Buller, " Upon the Ocellus Function of the Subsporangial Swelling of
Pilobolus," Trans. Brit. Myc. Soc, Vol. VII, 1921, pp. 61-64.

Fig. 1 . — Pilobolus longipes. A group of sporangiophores
which came up spontaneously on horse dung in the
laboratory at Winnipeg. They were all directed
toward the source of brightest daylight. Natural
size.

HISTORY OF PILOBOLUS 3

of an optical sense-organ or simple eye (ocellus) ; (2) that this
simple eye, owing to the manner in which it responds to heUo-
tropic stimuli, causes the Pilobolus gun to be so laid that the
sporangium with its load of spores is shot away as far as possible
into an open space ; (3) that this mode of discharge causes the
sporangium to lodge on herbage where it may be swallowed with
the herbage by some grazing herbivorous animal ; and (4) that the
sporangium fastens itself to a grass-stem or grass-leaf, etc., in such
a way that it cannot be washed away from its place of attachment
even during a heavy shower of rain.

The Discovery, Structure, Taxonomy, and Life-history of
Pilobolus. — The earliest record of Pilobolus appears to have been
made in 1688 by John Ray ^ in his Historia Plantarum from a
description sent to him from Virginia by John Banister. The
fungus was illustrated (Fig. 97, p. l^d'l) by Plukenet ^ in 1691, was
"observed on horse dung about London" by Petiver ^ in 1696,
and was observed again by Henry Baker * in 1 744 on mud brought
from the Thames.^

In 1778, and more fully in 1782, Otto F. Miiller,^ a Danish
zoologist who studied the lower animals, described a Pilobolus as
a new kind of zoophyte. He regarded the ghstening subsporangial
swelling as a crystalline body, and a little worm which, doubtless,
was crawling over its outside he thought was inside, swimming

1 John Ray, Historia Plantarum, Vol. II, 1688, p. 1928.

^ L. Plukenet, Alinagentum butanicum, London, 1696, p. 164 ; also Phytographia,
London, 1691, Plate CXVI, Fig. 7. There can be but little doubt that this Figure
is a reproduction of Banister's original drawing made in Virginia.

^ In John Ray's Synopsis methodiai stirpium hritannicarum, London, ed. II, 1696,
p. 322.

4 Henry Raker, Xatural History of the Polype Insect, 1744, Chap. XI, Plate XXII,
Figs. 9, 10.

^ Coemans, in liis Monograph ie du genre Pilobolus (p. 1), remarks that Baker's
description and illustrations leave no doubt that his Pilobolus was P. oedipus, this
conclusion being strengthened by the fact that the fungus was found on mud,
a substratum \ipon which P. oedipus has often been observed. Nising (Coemans'
Monographic, p. 6U) observed it on mud of the river Oder, and I have observed it on
mud obtained from the Rod River at Wimiipeg.

*• Otto F. Miiller, " Von dor Entdeckung eines neuen Geschlechts von Thier-
pflanze," Berlinische Sanniihaigen zur Beforderung der Arzneiu'issenscluift, Stiiek I,
1778, pp. 41-52 ; also " Von einem Kristallschwammchen," Kleine Schriflen a.d,
Naturhistorie, herausg. v. J. A. E. Goeze, Bd. I, 1782, pp. 122-132.

RESEARCHES ON FUNGI

about in any direction it pleased '' as if in a tiny ocean " (c/. Fig. 2).

Hence Miiller described his Pilo-
bolus as a plant which enclosed
a living worm in a crystalhne body
and he, therefore, regarded the
fungus as a marvellous organism
combining characteristics of all the
three realms of nature — animal,
vegetable, and mineral. Midler's
conception of Pilobolus, which is
reminiscent of the fabulous mon-
sters of antiquity, received wide-
spread attention ; but it was
shown by later workers to have
been based on erroneous obser-
vation. Tode, Persoon, Currey,
and Coemans all found the worms
on the outside of the sporangio-
phore and never inside as Miiller
and his followers Durieu de
Maisonneuve and Leveille had
supposed. 1

Curiously enough, Miiller's
error about the position of the

Fig. 2. — Pilobolus Kleinii. A, a rudimen-
tary sporangiophore : a, the rnj-celium ;

b, tlie basal reservoir ; c, the stipe
elongating apically ; the whole filled
with dense orange-red protoplasm.
B, a mature sjiorangiophore : a, the
mycelium ; b, the basal reservoir ;

c, the stipe now fully elongated ; d, the
subsporangial swelling, erroneously
supposed to contain two worms swim-
ming in its vacuole ; e, the sporan-
gium about to be discharged. L)rawn
by ]5. Boudier ; photographically
copied from Plate 582 of his Icones
Mycologiaie ; letters added by the
autlior. Magnification, 25.

^ For the literature on this controversy vide Coemans, Monographie,
pp. 48^9.

HISTORY OF PILOBOLUS 5

worm has been repeated in recent years by Boudier ^ who, in one of
the Plates of his splendid Icones Mycologicae (1905-1910), illustrates
Pilobohis Kleinii in colours and shows us two worms in the middle
of a subsporangial swelling enlarged twenty-five times (Fig. 2).
The worms look as though they might have been on the exterior of
the under side of the swelling, but that Boudier intended us to
think that they were inside the great vacuole is shown by his
description of the drawing : " Autre adulte, on remarque dans la
vesicule superieure 2 anguillules qui s'y sont introduites." A priori
it seems most unhkely that two worms should succeed in penetrating
into a sporangiophore without injuring or killing it or leaving any
trace of their mode of entrance ; and, in view of the critical observa-
tions of Tode, Persoon, Currey, and Coemans, already cited, it must
be concluded that Boudier, like Miiller one hundred and thirty years
earlier, was the victim of an optical illusion.

When a fruit-body of a Pilobolus has been removed from its
substratum and has been placed horizontally on a glass slide, any
worm which may be in the film of moisture where the subsporangial
swelling is in contact with the slide is magnified by the swelling
which acts as a lens. It may well be that this optical effect originally
suggested the idea that a AVTiggling worm, which in reality is on the
exterior of the swelling, seems to be moving about inside.

Miiller's worm was probably a larval Roundworm (one of the
Nematoda) and, if it was, it may have belonged to a species of the
genus Strongylus. There are several species of Strongylus, e.g.
S. vulgaris, which are parasites of horses. They deposit their eggs
in great numbers in the caecum and colon of the alimentary canal of
the horses concerned, and the eggs pass to the exterior in the faeces.
After a mass of dung has been dropped upon the ground, the eggs
hatch within twenty-four hours and, after seven days, the larvae
(Fig. 3), which have fed on the faecal matter, begin to swarm on to
grass blades, etc., where they pass through a few moults and are in
a favourable position to be swallowed by grazing horses. Within
these animals they grow to a length of two inches or more and become
sexually mature. In unsterilised horse-dung cultures, such as are

1 E. Boudier, Icones Mycologicae on Icoiiographie dcs Cliampignons dc France
principedcmcnt Discomycetcs, Paris, 1905-191U, PI. 582, e.

6 RESEARCHES ON FUNGI

so often made in mycological laboratories, it is during the swarming
time that the larvae of Strongylus species find their way on to
Pilobolus fruit-bodies, up bits of straw, the tips of which they often
cover, and up the sides of the dish upon which, when very numerous,
they may arrange themselves so as to form a curious retiform
pattern (Fig. 4). Persoon, Tode, Grove, the writer, and many
others have seen one or more of the little worms wriggling about in
drops or films of moisture on the exterior of a subsporangial swelling ;

Fig. 3. — Strongylus larvae (Nematode worms) which swarmed up the side of a
glass culture-dish from horse dung, about seven days after the dung
(fresh) was placed in the dish (c/. Fig. 4). They were separated from one
another by immersing them in water on a slide, where they wriggled
violently. With the addition of iodine, they came to rest, straightened,
died, and took on a yellow colour, whereupon they were photographed.
Magnification, 51.

but, hitherto, mycologists may not have realised that the worms are
but larvae and that, when climbing on to a Pilobolus or up the side
of a dish, they are only following a swarming instinct which, when
it leads them under natural conditions to ascend grass-blades, gives
them a chance to be swallowed by a horse and thus to enter an
animal in which they may continue their development.^ When a
Pilobolus fruit-body explodes, any Strongylus larvae which may
be present on the sporangiophore must be thrown down violently on
to the surface of the dung, while, if a larva should happen to be on
the sporangium, it will be carried away with the projectile. 0. F.

^ For the facts concerning the life-history of the Roundworms of the horse, I am
indebted to Dr. G. Hadwen of the Ontario National Research Foundation.

HISTORY OF PILOBOLUS 7

Miiller, according to Coemans,i depicts along with a discharged
sporangium a worm. This may have been carried with the projectile
during its flight through the air.

To test the supposition that Nematode worms may travel
through the air upon a discharged sporangium, I placed a sheet of

Fig. 4. — Strongylus larvae (Nematode worms) swarming up the side of a
glass culture-dish from horse dung, seven days after the dung (fresh)
was placed in the dish. Fruit-bodies of Pilobolus longipcs appeared on
the dung a few days before and, to the left, some of their black dis-
charged sporangia can be faintly seen sticking to the surface of the
glass^ Some of the larvae swarmed up the sporangiophore.s, and tlio.se
which reached the sporangia may have been shot away with the sporangia
when these were discharged. At Winnipeg. Natural size.

clean dry glass in front of a large number of fruit-bodies of Pilobolus
longipes that had appeared on horse dung infected with Nematodes
which had begun to swarm. Soon fifty or more sporangia struck
and stuck to the glass plate. On examining the discharged sporangia
I found that worms were associated with two of them. Under the
free turned-out edge of one of these sporangia two worms were
partly hidden. The other sporangium was in contact with one end

1 E. Coemans, Monographie, p. 49.

8 RESEARCHES ON FUNGI

of a worm which was freely exposed in the liquid drop that had
accompanied the sporangium during its flight. Thus conclusive
evidence was obtained that Nematode larval worms may occasionally
be shot through the air along with a Pilobolus projectile.

In 1772 Scopoli ^ recognised the true affinities of Pilobolus, as
is indicated by the fact that he gave the name Mucor obliquus
to the species which he studied. The first good description

* • *^- ' ■

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.3 ,1

CT-. '4 - ^ ,^

• -

Fig. 5. — Pilobolus (Kleinii ?). A photomicrograph of a
group of fruit-bodies growing on dung in the
laboratory, showing black sporangia, subsporan-
gial swellings, stipes, and drops of mucilaginous
fluid excreted on the swellings and stipes. Photo-
graphed by B. O. Dodge. Magnification,about 3 • 5.

of the genus was given in 1784 by Tode,^ who named one of
its species Pilobolus crystallinus — a name which is still retained.
Among the later observers who contributed most to our know-
ledge of the species of Pilobolus are Persoon,^ Montagne,* Cohn,^

1 J. A. Scopoli, Flora CarnioHca, Vienna, ed. II, 1772, Vol. II, p. 494.

2 H. J. Tode, " Beschreibung des Hutwerfers (Pilobolus)," Schrift. der Naturf.
Berlin. GeselL, Bd. V, 1784, p. 46, Plate I.

^ C. H. Persoon, Synopsis method ica fungorum, 1801, Part I, pp. 117-118.

* J. F. C. Montagne, " Note sur le genre Pilobolus et description d'une espece
nouvelle," Mem. de la Soc. Linn, de Lyon, 1836, 7 pp., 1 Plate. The species described
was P. oedipus.

^ Ferdinand Cohn, " Die Entwicklungsgeschichte des Pilobolus crystallinus,"
Nova Ada Acad. Caes. Leop., Bd. XXIII, 1851, pp. 495-534, Taf. LI and LII.

HISTORY OF PILOBOLUS 9

Coemans,^ Klein,^ van Tieghem,^ Bainier,'* Grove,^ Palla,® and
Morini.'

In 1875 van Tieghem ^ founded the genus Pilaira on two mould-
species which have simple cylindrical non-exploding sporangiophores,
like those of Mucor, and dehiscent adhesive sporangia, like those
of Pilobolus. The genus Pilaira, as is evident, serves to connect
Pilobolus with Mucor .^

In 1884 appeared Grove's Monograph of the Pilobolidae,^^ which
contained a history of the family, a full discussion of the synonymy
involved, and a key to the ten species then known. The species
were arranged as follows :

Order, MUCORINI, de Bary.
Family, PILOBOLIDAE, van Tieghem.

Genus I — Pilobolus, Tode.

1. Pilobolus oedipus, Montague.

2. ,, exiguus, Bainier.

1 E. Coemans, " Monographic du genre Pilobolus Tode, specialement etudie au
point de vue anatomique et physiologique." Mem. cour. et des Sav. etrang. Acad,
roy. de Belgique, T. XXX, 1861, 68 pp., 3 tab.

2 J. Klein, " Zur Kenntnis des Pilobolus," Pringsh. Jahrb.f. wiss. BoL, Bd. VIII,
1872, pp. 305-381, Taf. XXIII-XXX.

3 P. van Tieghem : (1) " Sur la structure et le mode de dehiscence du sporange
des Pilobolees et sur deux especes nouvelles de Pilobolus," Bull. Soc. Bot. France,
T. XXII, 1875, p. 274 ; (2) " Nouvelles recherches sur les Mucorinees," Ann. Sci.
Nat., 6 ser, T. I., 1875, pp. 41-61 ; (3) " Observations au sujet d'un nouveau travail
de M. Brefeld sur les Mucorinees et en particulier sur les Pilobolus," Bull. Soc. Bot.
France, T. XXIII, 1876, p. 35 ; (4) "Troisieme memoire sur les Mucorinees," Ann.
Sci. Nat., 6 ser., T. IV, 1876, pp. 335-349.

* G. Bainier, jStude sur les Mucorinees, Paris, 1882, 126 pp., 11 tab.

5 W. B. Grove, " Monograph of the Pilobolidae," The Midland Naturalist,
Birmingham, England, 1884. Reprint, pp. 1-39, PI. IV and VI.

« E. Palla, " Zur Kenntniss der Pilobolus-Arten," Oesterr. bot. Zeitschr., Bd. L,
1900, pp. 349-370, 397^01, tab. col. Under the title " Contribution a la connais-
sance des especes du genre Pilobolus " Palla's paper is reviewed and translated by
R. Ferry in Eev. Mycol., T. XXVI, 1904, pp. 19-33, tab.

' F. Morini, " Materiali per una monografia delle Pilobolee," Mem. delta R.
Accad. delle Sci. delVIstituto di Bologna, ser. VI, T. Ill, 1906 ; T. VI, 1909.

^ P. van Tieghem, loc. cit., pp. 51-61.

* The name Pilobolus is derived from Tciloq, a hat, and [iaXXco, I throw ; while
Pilaira is derived from ttTXoi;, and aipw, I raise.

^^ W. B. Grove, loc. cit. The arrangement of the species of Pilobolus in Saccardo
is based on Grove's Monograph.

10 RESEARCHES ON FUNGI

3. Pilobolus crystallinus, van Tieghem.

4. ,, Kleinii, van Tieghem.

5. ,, longipes, vari Tieghem.

6. ,, roridus, Persoon.

7. „ nanus, van Tieghem.

Genus II — Pilaira, van Tieghem.

1. Pilaira Cesatii, van Tieghem.^

2. ,, nigrescens, van Tieghem.

3. ,, dimidiata, Grove.

Cohn 2 (1851) traced the life-history of Pilobolus oedijms (his
P. crystallinus). He observed the germination of the spores, the
branched unicellular mycelium, the basal swelling cut off from the
rest of the mycelium by a wall, stages in the development of the
stipe, sporangium, and subsporangial swelling, the formation of
the columella, the ripening of the spores, and the discharge of the
sporangia. He estimated the number of spores in a sporangium
at 15,000-30 000.

Further observations on the life-history of Pilobolus oedipus and
P. crystallinus were made by Coemans ^ (1861). He observed that
some of the sporangia were shot to a height of 105 cm. ( = 3 feet
5-3 inches), 4 and he was the first to perceive that the violent dis-
charge of the sporangia and their adhesion to grass by means of
their gelatinous base provide for the swallowing of the spores by
herbivorous animals and lead to the germination of the spores in
dung-plats. He says : " But do not believe that the discharged
globule is left to chance, its fall is calculated and everything is
provided for : nature has endowed it with an adhesive wall which
permits of its attaching itself to anything on which it alights. As
Pilobolus in the open grows in meadows or in the midst of herbage
frequented by herbivora, its sporangia naturally attach themselves
to the surrounding grass ; if there comes along a cow or any other

1 According to the modern rules of nomenclature, this species is now known as
Pilaira anomala (Cesati) Schroter.

2 F. Cohn, loc. cit. ^ E. Coemans, loc. cit.
4 Ihid., p. 39.

HISTORY OF PILOBOLUS ii

herbivorous animal which eats the herbage and sporangia together,
the reproduction of the fungus is assured. The sporangia open in
the stomach, the spores are mixed with the food, the heat of the
animal favours their germination, and the spores, on passing out
with the residue of digestion, thus find themselves germinating in
a substratum indispensable for their development. Throughout
the summer of 1860, I thus saw two cows, which I had at my dis-
posal, quite unknown to themselves sow and propagate Pilobolus
crysiallinus and spread it in all the meadows into which I had them
driven ; it is beautiful to see here the two organic realms acting
together and assisting one another to assure the reproduction and
conservation of a delicate little fungus." ^

Both Cohn and Coemans, as indeed all later workers, were im-
pressed with the periodic development of Pilobolus, and with the
fact that each fruit-body grows to maturity and discharges its
sporangium within twenty-four hours. Grove (1884)2 remarks
with truth that " Pilobolus is the Ephemeron of plant life," and he
adds, a propos of the diurnal succession of crops of fruit-bodies :
" While contemplating the saucer in which I grew my specimens,
after Hstening to the mimic bombardment which raged so furiously
an hour before, standing as it were on the field of battle with nothing
but dead and dying soldiers stretched around me, I have felt as
Welhngton might have felt after Waterloo, but with a consolation
denied to that gallant hero. I knew that even then around my feet
another army was growing up among the mangled remains without
any help from me, and would be ready the next day wdth full
equipment to march with me to victory again."

Brefeld,^ in 1881, as a result of investigations made upon pure
cultures, described and illustrated the hfe-history of a Pilaira— then
known as Pilobolus anomalus Ces. but subsequently as Pilaira
Cesatii van T.— and of four species of Pilobolus. As Grove * has
pointed out, none of these four species was correctly named ;
Brefeld's P. crystallinus is P. Kleinii van T. ; his P. oedipus is

1 E. Coemans, loc. cit., p. 53. ^ w. B. Grove, he. cit., p. 18.

3 O. Brefeld, Untersuchnngen iiber Schimmelpilze, Heft IV, Leipzig, 1881,
pp. 60-80, Taf. Ill and IV.

* W. B. Grove, loc. cit., p. 30.

12

RESEARCHES ON FUNGI

P. Kleinii forma sphaerospora Grove ; his P. microsporus is P.
crystallinus Tode ; and his P. rorichis is P. longipes van T.

Sex in the Pilobolidae. — We still know comparatively little about
sex in the Pilobohdae. Van Tieghem ^ (1875) found the zygospores
of Pilaira anomala (Cesati) Schroter in two of his cell-cultures, in
one of which three spores had been sown and in the other five, while
Brefeld^ (1881) found about fifty zygospores of the same fungus on

Fig. 6. — Pilobolus crystallinus. Stages in tlie formation of a zygospore.
A, two aerial zygophores from two different hyphae have
approached one another and have come into contact. B, the
zygophores are increasing in size and have become progametes.
C, the progametes have each become divided by a septum into a
terminal gamete c and a proximal suspensor. D, the gametes have
fused and have become converted into a large, thick-walled, oil-
bearing zygospore to which the enlarged suspensors are still
attached. Drawn by W. Zopf. From his Die PtVze (1890, p. 84).
Magnification : A, B, and C, 160 ; D, 165.

horse dung. Zopf ^ (1888) observed the formation of the zygospores
of Pilobolus crystallinus (Fig. 6) and (1892) of P. Kleinii in cultures
in which the Piloboli were attacked by parasites * and suggested
that their formation was due to the action of the parasites ; but this

1 P. van Tieghem, " Nouvelles recherches sur las Mucorinees," Ann. Sci. Nat.,
6 ser., T. I, 1875, pp. 57-58.
- O. Brefeld, loc. cit., p. 65.

3 W. Zopf, " Zur Kennt. d. Infectionskrankh. nied. Thiere u. Pflanzen," Nova
Acta Acad. Leop., Bd. LIT, Nr. 7, 1888, pp. 352-358, Taf. VI, Figs. 8-17 ; Beitrdge z.
Morph. u. Physiol, niederer Organismen, Heft II, 1892, pp. 5-10, Taf. I, Figs. 4-7.

4 P. crystallinus and P. Kleinii were both attacked by Pkotrachelus fulgens, and
the former species also by an undetermined species of Syncephalis.

HISTORY OF PILOBOLUS 13

view, according to Blakeslee/ cannot be accepted, because Thaxter
subsequently found the zygospores of P. Kleinii on sheep dung but
without the parasites. Morini ^ (1906) observed zygospores in a
species which he has named P. Borzianus. He found them a httle
below the surface in cultures several months old. From Blakeslee's
discussion^ (1904) of the conditions under which zygospores have
been observed in Pilaira anornala, P. crystallinus, and P. Kleinii,
it is clear that at that time we did not know whether these species
are homothallic or heterothallic and that exact experiment alone
could throw light on this problem. The thick- walled tuberculate
"spores durables" which van Tieghem* described as developing
terminally on short curved stalks from the mycelium of Pilobolus
nanus (Fig. 106, G, p. 212), are regarded by Fischer ^ as azygospores.
Recently (1931), Krafczyk ^ has solved the problem of the condi-
tions required for the formation of zygospores in Pilobolus crystal-
linus. He isolated single sporangia from goat dung and made pure
cultures from each one on a decoction of hay and dung solidified
with agar.'^ Then he paired mycelia obtained from different sporangia,
two by two, and soon found a pair which yielded zygospores along
the line where they met. Then, using the ( + ) and ( — ) strains as
testers, he was able to determine the sexual nature of a large number of
other mycelia derived from sporangia collected in various localities.
Thus he has shown conclusively that P. crystallinus is heterothallic.^

1 A. F. Blakeslee, " Sexual Reproduction in the Mucorineae," Proc. Amer. Acad.
Arts and Sci., Vol. XL, 1904, p. 238.

2 F. Morini, " Materiali per una monografia delle Pilobolee," Memorie della R.
Accad. delle Sci. delVIst. di Bologna, Ser. VI, T. Ill, 1906, pp. 120-123.

3 A. F. Blakeslee, loc. cit., pp. 238-239.

* P. van Tieghem, " Troisieme memoire sur les Mucorinees," Ann. Sci. Nat.,
6 ser., T. IV, 1876, pp. 312-398, PI. X-XIII.

5 A. Fischer, in Rabenhorst's Kryptogamen Flora von Deutschland, Bd. I, Abt. IV,
p. 268.

^ H. Krafczyk, " Die Zygosporenbildung bei Pilobolus cristallinus," Ber. d. D.
hot. Gesell, Bd. XLIX, 1931, pp. 141-146, Figs. 1 and 2.

7 This medium was suggested by the work of E. Bersa (" Kultur und Ernah-
rungsphysiologie der Gattung Pilobolus," Sitzungsber. Akad. Wissensch. in Wien,
math.-nat. Kksse, Bd. CXXXIX, 1930, pp. 355-371) who cultivated Pilobolus
Kleinii and P. sphaerosporus on various media and found that they would grow very
easily on horse -dung agar.

8 Krafczyk holds that, judging by his illustrations, Zopf did not find zygospores
in Pilobolus crystallinus, but in P. Kleinii. Loc. cit., p. 141,

14 RESEARCHES ON FUNGI

The Cytology of Pilobolus. — Harper ^ in 1899, as the result of an
investigation made with modern technical methods, gave an account
of the cytological changes which take place during the formation
of the sporangiophore and sporangium of Pilobolus crystallinus,
P. oedipus, and P. microsporus. His observations were as follows.

In seven to eight days after the spores have been sown on steri-
Used horse dung, the sporangiophores begin to appear. The yellow
bulb-like swelUng of the mycehum, from which a sporangiophore
arises, appears in the afternoon and at that time the vegetative
nuclei within it divide rapidly. After these divisions have been
completed, the sporangiophore grows out from the swelHng and most
of the cytoplasm flows upwards into the sporangiophore carrying
nuclei with it. The end of the sporangiophore swells up to form
the sporangium, and cytoplasm and nuclei pass upwards into it
(Fig. 7, A-C). The protoplasm in the sporangium at first forms a
spongy framework in whose meshes is a considerable amount of
cell-sap ; but, later, it becomes truly vacuolated in that it comes to
contain rounded cavities whose outUnes are determined by surface
tension. A layer of larger flattened vacuoles comes to lie in the
curved surface which marks the outUne of the future columefla
(Fig. 7, D, v). Then protoplasmic cleavage starts from the edge
of the sporangiophore and pushes upwards (Fig. 7, D, c c) ; and
this cleavage, aided by the fusion of certain of the flattened vacuoles,
results in the formation of a dome-shaped furrow (Fig. 7, E, c)
which separates the sporangium from the sporangiophore. The
cell- wall is then deposited in the cleft between the two membranes.

A jelly-hke substance is excreted by the spore-plasma and is
deposited as a layer on the inside of the lower part of the wall of the
sporangium, and there is an extension of it up the wall of the
columella (Fig. 7, E, b, and H, a, and Fig. 8, D, d). The sub-
sporangial swelling begins to be formed beneath the sporangium late
in the afternoon. When full-grown its wall is Hned by a thin layer
of protoplasm containing many nuclei.

Cleavage of the spore-plasma begins shortly after the columella is
complete (Fig. 7, E). The protoplasm becomes somewhat vacuolar and
the nuclei are rather evenly distributed through its mass. Cleavage

1 R. A. Harper, "Cell-Division in Sporangia and Asci," Annals of Botany,
Vol. XIII, 1899, pp. 490-503, Plates XXIV-XXVI.

B

)-.;: :

e

H

Fig. 7. — Pilobolus crystallinus. Cytology of the sporangivim. A, median longi-
tudinal section of a sporangiophore bearing a yoiuig sporangium ; the cyto-
plasm is vacuolated and contains numerous nuclei, n, shown as dots. B, median
section of an older sporangimn showing the course of protoplasmic flow from
the mouth of the sporangiophore ; protoplasm highly vacuolated and containing
many nuclei, n. C, section of sporangial wall it' and spore-plasma p just before
cleavage begins ; n, the nuclei. D, median section of a sporangium at a stage
when the columella is forming, showing cleavage furrows c c at the base and
flattened vacuoles v above ; /(, the nuclei ; small rounded vacuoles throughout
the cytoplasm. E, section of spore-plasma e from base of sporangium during
cleavage, showing : a, the sporangial wall ; b, the gelatinous collar ; c, the
columella-cleft between thecoKnnella and the spore-plasma; d, tlie protoplasmic
lining of the columella ; c, the s[)ore-plasma undergoing cleavage to form pro-
tospores ; /, superficial cleavage furrows ; g, an angular vacuole of the spore-
plasma ; h, nuclei. F, section through upper part of a sporangium showing
sporangial wall w and irregular sausage-shapeil bodies *• formed by cleavage of
the spore-plasma, a little older than E. G, similar to F but older, showing
uninucleate protospores p formed by cleavage of the spore-plasma ; «', spo-
rangial wall. H, protospores p witli dividing nuclei, young daughter nuclei
connected by remains of spindle fibrils ; o, gelatinous collar ; b, protoplasm of
columella. Magnification : A, B, D, not stated ; C, S"J4 ; E-H, 500. Copied
by tlie author from R. Harper's CcU-Diri.sioii in Sporaiiijia and Asci {Annuls of
Botany, Vol. XIII, 1899, Plates XXIV and XXV).

i6

RESEARCHES ON FUNGI

Fig. 8. — Pilobolus crystallinus. Cytology of
the sporangium (continued) and of ger-
minating spores. A, a multinuclear
cell (embryonic cell) developed from a
protospore, about to undergo constric-
tion ; nuclei arranging themselves in
two groups and a central zone be-
coming hyaline. B, a similar cell,
slightly older. C, a still older cell
undergoing constriction into two
halves. D, outline drawing of part of a
median section through a sporangium
with binucleated spores (formed by
growth and constriction of proto-
spores) : a, wall of columella; 6, proto-
plasm of columella containing many
nuclei ; c, sporangial wall ; d, gela-
tinous collar with extension upwards
on the columella ; e, binucleated spor-
angiospores; and/, intersporal homo-
geneous slime. E, living spore about
to germinate in a nutrient medium.
F, spore swollen and germinating in
a nutrient medium. G, germinated
spore with its germ-tvibe, with
numerous nuclei. Magiiification :
A-C, E-G, 824; D, not stated. Copied
by the author from R. Harper's Cell-
Division in Sporangia and Asci
(Annals of Botany, Vol. XIII, 1899,
Plate XXV).

furrows then appear around
the base of the sporangium (/)
cutting the surface of the
protoplasm into irregular poly-
gonal areas. The rounded
vacuoles in the interior of the
protoplasm become angular (g),
and their edges cut through the
protoplasm to meet similar
cleavage furrows from adjacent
vacuoles. The surface furrows
grow deeper and meet and be-
come continuous with the edges
of the vacuoles. The spore-
plasma thus becomes roughly
marked into blocks of irregular
size containing a variable num-
ber of nuclei. Further furrowing
cuts these first-formed blocks
into oblong rounded sausage-
shaped masses generally con-
taining two to four nuclei in a row
(Fig. 7,F). These oblong bodies
are now divided transversely to
form rounded or spherical masses
each with one or a few nuclfei
(Fig. 7, G). The protospores so
formed now begin to grow,
and their nuclei divide rapidly
(Fig. 7, H) so that the masses
once more become multinucle-
ated (Fig. 8, A). Then each cell
divides by constriction, the nuclei
being separated into two groups
in the halves so formed (Fig. 8,
A-C). The nuclei may then
divide further, their division
being followed by further cell-

HISTORY OF PILOBOLUS

17

divisions but, finally, nuclear division ceases. Cell-division, however,
continues until the masses are cut up into regular oblong binucleate
cells (Fig. 8, D). The primary cleavage resulting in protospores is
complete about 4 a.m., and the period of embryonic growth and divi-
sion lasts until about 7 a.m. The binucleated spores (e), which at first are
naked masses of protoplasm, soon be-
come covered by a wall, and drops of
oil appear in their interior. The ripe
spores lie embedded in a shining mass
of intersporal substance (/) which can
be stained readily with gentian violet
and which appears to be nothing more
than an excretion of the protoplasm
made during the ripening of the spores.

The spores (Fig. 8, E), when sown,
swell tremendously (Fig. 8, F) before
pushing out a germ-tube, and the two
nuclei soon divide to form eight or more
which may be seen in the sporeling
when the germ- tube is still very short
(Fig. 8, G). The mycelium is unicellular
and multinucleate. When a sporangio-
phore is to be formed, the protoplasm
collects at a point in the mycelium and
there forms a barrel-shaped swelling.
This swollen portion is cut off from the
rest of the mycelium (in the species
studied) by both peripheral and proxi-
mal walls. The division of the protoplasm is accomplished by simple
constriction furrows ; and in the bulb so formed, as already
mentioned, a rapid multiplication of nuclei takes place.

Crystalloids.— In 1872, Klein ^ discovered crystalloids in the
sporangiophore of Pilobolus ; and, in 1875, van Tieghem 2 found
that these bodies are present not only in Piloboli (Fig. 9) but in
a large number of other Phycomycetes, e.g. Phycomycetes nitens,

1 J. Klein, he. cit., p. 337, Taf. XXIV, Fig. 23.

2 P. van Tieghem, " Nouvelles recherches sur les Mucorinees," Ann. Sci. Nat.,
6ser.,T. I, 1875, pp. 24-32.

VOL. VI. 0

Fig. 9. — Pilobolus roridus. Dia-
grammatic representation of
octohedral crystalloids in
the stipe of a fruit-body : a,
the cell -wall ; b, the parietal
protoplasm ; cc, the cell-sap
of the great vacuole ; d, a
crystalloid in the cytoplasm ;
e e, crystalloids in the cell-
sap ; /, a crystalloid which
is hollow in the centre. Some
of the crystalloids have con-
cave faces. Magnification not
stated. Copied by the author
from P. van Tieghem's
Nouvelles recherches sur les
Mucorinees {Ann. Sci. Nat.,
T. I, 1875, Plate I) and re-
produced on a larger scale.

i8

RESEARCHES ON FUNGT

Spinellus fusiger, Mucor plasmaticus, and Sporodinia grandis.
There is no evidence that van Tieghem used a camera lucida in
making his drawings and, doubtless, he represented the crystalloids
shown in his diagrammatic illustration reproduced in Fig. 9 as being
larger, relatively to the diameter of the stipe, than they are in nature.

The Orange-red Pig-ment. — In 1892 Zopf ^ investigated the
orange-red pigment which colours the protoplasm of Pilobolus and
found that it consists of carotin which is held within minute oil-
drops. Zopf expressed the opinion that the carotin is merely a
reserve food-substance ; but, as we shall see later, in the mature
sporangioj)hore carotin is especially concentrated in the mass of
protoplasm which forms a perforated septum at the base of the sub-
sporangial swelling and which is intensely illuminated when the
sporangiophore is in heliotropic equilibrium. It is therefore possible
that the carotin plays some part in the response of the sporangiophore
to heliotropic stimuli.

Parasites of Pilobolus. — The Piloboli, when growing wild on
horse dung, etc., are not infrequently attacked by parasitic fungi
which may attach themselves to or enter the young sporangiophores,
stop their growth, and entirely prevent the production of sporangia
and spores. Among these parasites, as shown in the accompanying
Table, are species of Pleotrachelus, Piptocephalis, Syncephalis,Mortie-
rella, and Dimargaris.

Parasites of Pilobolus

Group

Parasite

Host Pilobolus

Authority

Chytridiales .

Pleotrachelus fulgens .

P. Kleinii .

,

Zopf.

/

Piptocephalis microcephala .
Piptocephalis arrhiza .

•

Syncephalis reflexa

P. roridus
P. oedipus .
P. roridus
P. crystallinus

•

van Tieghem
van Tieghem

van Tieghem

Mucoraceae <

Syncephalis nodosa

P. roridus

van Tieghem

P. longipes
P. Kleinii .

Buller

Syncephalis sp. .
Mortierella polycephala

P. crystallinus

P. roridus

P. crystallinus

1

Zopf

van Tieghem

Dimargaris crystalligena

P. sp.

•

van Tieghem

1 W. Zopf, " Zur Kenntniss der Farbungsursachen niederer Organismen, No. III.
Phycomyceten-Farbungen," Beitrdge zur Physiologie und Morphologie niederer
Organismen, Leipzig, Heft II, 1892, pp. 3-12.

HISTORY OF PILOBOLUS

19

The mode of attack of
crystallinus (Fig. 10)
was described by
Zopf.i The same
author ^ discovered
Pleotrachelus fulgens,
a chytridiaceous spe-
cies, in P. Kleinii
and showed that, in
its turn, the Pleotra-
chelus is attacked by
a minute parasite
which he called Endo-
biella destruens.

The parasitism of
Piptocephalis micro-
cephala,^ P. arrhiza*
Syncephalis reflexa,^
S. nodosa,^ Mortie-
rella polycephala,'^ and
Dimargaris crystalli-
gena ^ on Pilobolus
species was observed
by van Tieghem in
the course of his re-
searches on the Mucor-
aceae. In treating of
the genus Mortierella,
he states that the
species grow very
vigorously as saprophytes

an unnamed Syncephalis on Pilobolus
A ^ B

Fig.

10. — Tlie sporangiophore of a fruit-body of
Pilobohis crystallinus parasitised by the mycelium
of a Syncephalis. A, the mycelium of the parasite
m has grown over the sporangiophore and has
produced club-shaped appressoria a a o at its
surface. Beneath each appressorium inside the
sporangiophore is a haustorial bladder b from
which haustorial hyphae have been produced. B,
a piece of a large sporangiophore : a, an appres-
sorium of the Syncephalis ; b, haustorial bladders ;
c, haustorial hyphae. Drawn by W. Zopf . From
his Die PiYse (1890, p. 15). Magnification: A,
250 ; B, 900.

on sterilised dung, but that when

^ W. Zopf, " Zur Kenntniss der Infectionskrankheiten niederer Thiere und
Pflanzen. No. IV. Einfluss von Parasitismus auf Zygosporenbildung bei Pilobolus
crystallinus,'' Nova Acta Acad. Caes. L.-C. Nat. Cur., Bd. LII, 1888, pp. 352-358.

^ W. Zopf, " Zur Kenntniss der Farbungsursachen niederer Organismen," 1892,
loc. cit., pp. 7-8.

3 P. van Tieghem, loc. cit., p. 148. ^ Ibid., p. 138. ^ Ihid., p. 136.

6 Ibid., p. 118. ' Ibid., p. 97. « Ihid., p. 157.

20 RESEARCHES ON FUNGI

they meet with a Pilobokis or a Mucor they at once parasitise it.
Thus the parasitism of Mortierella, so far as Pilobolus and Mucor
are concerned, is purely facultative.^ Syncephalis ^ is also a
facultative parasite, while the parasitism of Piptocephalis ^ and
Dimargaris * is obligatory.

At Winnipeg, cultures of Pilobolus longipes and P. Kleinii in
some years are much parasitised by Syncephalis nodosa. This
species, originally described by van Tieghem ^ in 1875 and recorded
by Seymour ^ as a parasite on undetermined Mucorineae in North
America, is characterised by having two or three nodular thickenings
on the mature and collapsed sporangiophore.

My own observations on Syncephalis nodosa as a parasite of
Pilobolus may be here briefly recorded. The spores of *S^. nodosa
germinate readily in hanging drops of dung-agar. The mycelium,
as found on young Pilobolus sporangiophores, consists of very fine
hyphae which by means of hyphal fusions form a reticulum with
enlargements where two or more hyphae are joined together (Fig.
11, C-E).' It creeps over the surface of a Pilobolus stipe and
there forms irregularly swollen appressoria {cf. Fig. 10, a). From
an appressorium one or sometimes two hyphae are sent into the
interior of the stipe. These hyphae, which may have haustorial
swelhngs just inside the wall of the stipe, form a mycelium which
grows within the interior of the stipe, soon invades the subsporangial
swelling if this has been formed and, finally, stops the growth of
the host-plant (Fig. 11, A and B). The interior mycehum at various
points then makes its way out of the stipe. On the surface of the
stipe, here and there, a hypha swells up, branches and rebranches,
and forms what we may call a mat of basal hyphae (D and E). From
these thickened hyphae cylindrical sporangiophores grow outwards
into the air. When the sporangiophores have attained a height of
about 0-2 mm., each of them becomes clavately swollen at its apex
and then sends out terminally three or four processes which become

1 P. van Tieghem, loc. cit., p. 97. ^ Ihid., p. 116.

3 Ibid., p. 138. " Ibid., p. 157. ^ Ibid., pp. 131-133.

^ A. B. Seymour, Host Index of the Fungi of North America, Cambridge, Mass.,
U.S.A., 1929, p. 5.

' Cotton-blue dissolved in lactic acid was used as a stain to show up the
Syncephalis mycelium against the stipe of the Pilobolus.

HISTORY OF PILOBOLUS

21

branched (E and F). Each final branch develops into a cylindrical
sporangium, and each sporangium forms within itself a chain of

Fig. 11. — Syncephalis nodosa as a parasite on Pilobolus Kleinii and P. longipes.

A, an immature fruit-body of P. Kleinii attacked by S. nodosa ; the subsporan-
gial swelling has ceased to develop, and the fruit-body is dying or already dead ;
the parasite has produced sporangiophores on the basal swelling and stipe.

B, another young fruit-body of which the subsporangial swelling ceased to de-
velop owing to the invasion of the fruit-body by S. nodosa; hyphae of the para-
site are growing upwards inside the stipe and subsporangial swelling. C,
mycelium of <S'. yiodosa, which was observed growing about a Pilobolus fruit-
body, showing characteristic swellings and hyphal anastomoses. D, a mat of
basal hyphae, which was observed on the surface of a Pilobolus stipe. E, part
of a stipe of P. longipes with jS. nodosa growing upon it ; a, ordinary hyphae of
S. nodosa ; b, a basal mat of S. nodosa hyphae from which have sprung three
sporangiophores ; c, a young sporangiophore with its swollen head ; d, a spo-
rangiophore bearing nine cylindrical sporangia ; e, an old sporangiophore,
from which the sporangia have fallen away, with a shaft showing three nodular
thickenings. F, a series of stages in the development of sporangia and spores of
iS'. nodosa. The end of the sporangiophore : is at first cylindrical, as at a ; then
becomes swollen, as at 6 ; and then sends out three or four processes, as at
c and d respectively. The processes soon branch, as at d. These branches
become cylindrical sporangia, as at e. Two or three spores develop in each
sporangium, as at /. Finally, the cylindrical sporangia break away from the
sporangiophore and break up into segments, so that each segment contains
one spore, as at g. Magnification : A, 8 ; B, 40 ; and C-F, 350.

two or three spores (F, /). At maturity the sporangia, of which
there are often nine on each sporangiophore, separate from the
sporangiophore and from one another, and then each sporangium

22 RESEARCHES ON FUNGI

breaks across transversely into two or three pieces. Each piece
encloses a single spore and appears as a short-cylindrical, wrinkled,
amber-coloured structure (F, g). As a sporangiophore collapses,
certain portions of it do not decrease appreciably in diameter
and these become the nodular thickenings so characteristic of the
species (E, e).

The Excretion of Drops by the Sporangiophore and its Cause. —
Everyone who has studied Pilobolus has had occasion to notice the
numerous drops of clear hquid which are excreted from the sporan-
giophore (Fig. 12).

Wilson,^ in 1881, working in Pfeffer's laboratory, observed :
(1) that, if sporangiophores of Pilobolus crystallinus are allowed to
stand for a short time in a dry atmosphere, the drops vanish and
in the place of each there can be seen a group of radiating crystals, ^
visible to the naked eye ; (2) that, if the same plants are then placed
in a moist atmosphere, many of the drops reappear and precisely
in those places where the crystals were ; (3) that, if the sporangio-
phores are very carefully washed with the most delicate brush and
distilled water and are then placed in moist air, the drops, as a rule,
do not quickly reapppear and often do not reappear at all ; and
(4) that, if the sporangiophore is washed and afterwards minute
particles of sugar are placed upon its wall, large drops of water
quickly form about the sugar particles. Wilson came to the con-
clusion that the formation of the drops is due, not to the internal
pressure of the cell-sap, but, as in nectaries, to the osmotic action
of substances which are present on the surface of the cell-wall.

In 1897 Pfeffer,^ in a discussion of the excretion of water from
uninjured plants, remarked: "Bearing in mind all these possi-
bilities it is impossible to say whether the drops which appear upon

^ W. P. Wilson, " The Cause of the Excretion of Water on the Surface of
Nectaries," Unters. a. d. hot. Inst, zu Tubingen, 1881, p. 15.

2 Each drop contains a colloidal gelatinous substance {vide infra, Figs. 42 and 43,
pp. 86 and 87) and, when the drop dries up, this substance contracts so as to form
a tiny, often angular, lump of solid matter. I have never seen the " radiating
crystals " of which Wilson speaks nor, apparently, did he realise that a drop contains
colloidal matter. It seems probable that he mistook angular lumps for groups of
crystals.

3 W. Pfeffer, Pflanzenphijsiolwfie, 1897, English edition, Oxford, Vol. I, 1900,
p. 275.

HISTORY OF PILOBOLUS 23

the sporangiophore of Pilobolus, when it is kept in a saturated
atmosphere, are formed by the active or the plasmolytic excretion
of water. As a matter of fact a drop of the fluid leaves a crystalline

Fig. 12. — Pilobolus Kleinii. Sporangiophores in various
stages of development represented semi-diagrammati-
cally in one drawing : h, the substratum of horse dung ;
in a the stipe is elongating ; in b the sporangium is de-
velopmg terminally; in c each sporangiophore has
developed a large subsporangial swelling beneath the
sporangium, and the sporangium is about to be dis-
charged : in d the sporangium has been discharged and
only the collapsed stipe and subsporangial swelling remain
behind. The sporangiophores are bedecked with numer-
ous watery drops which glisten in the light like dew-
drops. Drawn by E. Boudier ; photographically copied
from Plate 582 of his Icones Mycologicae ; letters added
by the author. Magnification, 16.

deposit when allowed to dry upon a cover-slip. It is therefore
possible that the excretion of water is plasmolytic in this case, for
any osmotic substance must tend to withdraw water from a fully
turgid cell with which it is in contact."

24 RESEARCHES ON FUNGI

Lepeschkin,! jjj endeavouring to elucidate the mechanism of
active water-excretion in plants, used Pilobolus as his chief material
for experimentation. Among his numerous observations on water
excretion by Pilobolus and the factors which influence it were the
following.

The young naked stipe, that grows, upwards from the basal
swelling, usually excretes at its apex a large transparent drop. If
this drop is removed with a capillary pipette, it is replaced by a new
drop in the next 30-50 minutes. With further growth of the stipe,
smaller drops appear at intervals down the whole length of the stipe.
After separation of the sporangium by a wall, excretion of water
from the sporangium proceeds very slowly or ceases. Three to
five hours before the sporangium is shot away, the excretion of
water from the sporangiophore diminishes gradually and then
ceases.2 {Cf. Fig. 42, C, p. 86.)

The excretion of water from the sporangiophore was studied
under the microscope. The fruit-bodies were enclosed in a damp-
chamber (with the coverglass smeared with glycerine). The drops
were measured with an ocular-micrometer and were drawn off with
a capillary pipette already introduced into the chamber. It was
found that water excretion always occurs at the same places on the
surface of the sporangiophore and quite regularly and continuously.
The drops became about 0-2 mm. in diameter and were drawn off
five to ten times in succession. The time taken for the renewal of
a drop at a particular place on the sporangiophore was very constant
and varied with the place from seven to twelve minutes. At
different places on the sporangiophore the amount of water excreted
is very unequal. The most energetic excretion of water takes place
directly under and above the orange-yellow zone which lies at the
top of the stipe and just beneath the subsporangial swelling.^

The chemical composition of the cell-sap in the great vacuole
of the sporangiophore of Pilobolus longipes and that of the excreted
drops were determined and compared. The turbid liquid expressed
from a number of sporangiophores was dried at 60° C. and the

^ W. W. Lepesclikin, " Zur Kenntnis des Mechanismus der aktiven Wasseraus-
scheidung der Pflanzen," Beihefte z. Bot. Centralb., Bd. XIX, 1906, pp. 409-452.
2 Ibid., pp. 412, 418-419. ^ /^y^^ pp 412-413.

HISTORY OF PILOBOLUS 25

deposit was treated with cold water. Only two-thirds of the deposit
was dissolved. The percentage composition of the soluble portion
of the deposit was found to be : 38-8 organic substances (no carbo-
hydrates) ; 20-5 K2O and 'Na.^fi (chiefly K2O) ; 19-3 AUOg and
FegOa: 1-5 SO3 ; 14-5 P2O5 ; 4-2 CI; 1-4 CO.^ and, finally,
traces of SiO^. Altogether, the sap contained 1-2 per cent, of
soluble and 2-9 per cent, of insoluble substances. It was found
that the excreted drops contain 0-5 per cent, of mineral salts of the
same nature as those contained in the cell-sap, but no organic sub-
stances. The drops have an alkaline reaction, as may be determined
with Utmus paper, and this reaction is due to KoCOa.^

Lepeschkin's statement that the excreted drops are completely
devoid of organic substances cannot be accepted ; for, as Knoll ^
subsequently discovered, the drops contain a colloid in consequence
of which, as they dry up, their surface assumes an uregularly
wrinkled appearance (Fig. 42, C, p. 86). However, it may well
be that this colloidal substance is not excreted along with mineral
salts from the vacuole of the sporangiophore but, as Knoll beheves,
is formed b}^ local mucilaginisation of the cell- wall. ^ {Cf. Fig. 43,
p. 87.)

If the sporangiophores are transferred to dry laboratory air,
even although the substratum contains plenty of water, they at
once begin to dry, soon become flaccid, and eventually bend and fall.
With the diminution of cell-turgor, the energy of excretion becomes
smaller and smaller and soon the excretion of drops ceases com-
pletely. To revive a flaccid sporangiophore, it is necessary to place
it in air which has at least 90 per cent, moisture in it.*

Tufts of Pilobolus {Pilzrasen) were set on salt solutions which
diminish the cell-turgor. In spite of very great air-moisture, a 1 per

^ W. W. Lepeschkin, " Zur Kenntnis des Mechanismus der aktiven Wasseraus-
scheidung der Pflanzen," Beihefte z. Bot. Centralb., Bd. XIX, 1906, p. 421.

2 F. Knoll, " Untersuchungen iiber den Bau und die Funktion der Cystiden und
verw-andter Organe," Jahrb.f. wiss. Bot., Bd. L, 1912, pp. 488-489.

^ Knoll {loc. cit., pp. 453-500) found that the cystidia of a number of Hymeno-
mycetes excrete potassium oxalate which crystallises out in the slime formed from
the cell-wall. Whether or not the drops excreted by Pilobolus contain traces of
organic substances other than colloidal slime, which Lepeschkin failed to detect,
remains to be determined by further analyses.

* W. W. Lepeschkin, loc. cit., p. 413.

26 RESEARCHES ON FUNGI

cent, solution of sodium chloride caused water excretion to cease,
and even a 0-5 per cent, solution brought about a very much
diminished excretion.^

The fruit-body primordia (the red bulbils, c/. Fig. 2, A, p. 4),
if cut away from the rest of the mycehum in the evening and supphed
with water, develop into normal fruit-bodies during the night, and
the next morning it is found that water excretion from the sporan-
giophores has taken place normally. This shows that water
absorption and water excretion take place in Pilobolus in one and
the same cell.^

The water-excretion energy (the volume of the fluid excreted
from ten sporangiophores during one hour in divisions of the col-
lecting pipette 3) increases almost proportionally to the temperature.
It was found to be : at 0° C, 0-0 ; at 3°-4°, 0-2 ; at 18°, 1-9 ;
at 25°, 2-8 ; at 30°, 3-6 ; and at 35°, 4-5. At 0° C. the stipes do
not swell at their apex and there is no excretion. At 35° C. the
excretion is so great that it is not covered by the absorption of
water by the basal swelhng. An exposure to 35° C. for a few hours
results in so great a loss of turgor that the sporangiophores bend
and fall.4

In the evening a tuft of Piloboh was set in a glass tube and the
air in the tube was replaced with pure nitrogen. The sporangio-
phores continued their development and next morning the excretion
of drops was found to have taken place quite normally. Oxygen
therefore appears to have httle or no effect on the development of
a fruit-body primordium into a mature fruit-body or on the energy
of water excretion.^

1 W. W. Lepeschkin, loc. cit., p. 413. ^ /j/^.^ p. 414.

3 The volume of each division of the graduated pipette was 0' 03 cubic mm.

* W. W. Lepeschkin, loc. cit., pp. 414-416.

^ Ibid., p. 416. Verification of Lepeschkin's statement that fruit-bodies of
Pilobolus can develop from primordia to maturity without any oxygen supply
seems desirable. There is the possibility that a very small amoxmt of oxygen diffused
out of the substratum on which the fruit-bodies grew after his experimental tube
was closed. One evening I covered some primordia of Pilobolus longipes fruit-bodies
and a small mass of horse dung on which they were growing with liquidum paraffinum
(depth upwards of one inch). Next morning I found that a number of the primordia
had developed during the night into normal mature fruit-bodies. The presence of
the liquidum paraffinum doubtless much reduced the access of oxygen to the fruit-
bodies, but whether or not it cut it off completely is uncertain.

HISTORY OF PILOBOLUS 27

When chloroform or ether vapour is introduced very slowly
into the air surrounding the sporangiophores and the first amounts
are small enough, water excretion ceases, but with larger doses
water excretion is increased. Sufficient vapour of alcohol, hydro-
chloric acid, ammonia, or sulphuretted hydrogen also increases the
energy of excretion. An increased excretion can be obtained if
one sets the fungus tuft on a solution of any of these substances or
caffeine. When some of the sporangiophores of Pilobolus longipes
were exposed to the vapour of alcohol for five minutes, the energy
of water excretion, which during the night had been 4 • 1 , was raised
to 250 ; and when a tuft of sporangiophores of P. Kleinii was set
on a 0-5 per cent, solution of caffeine for two minutes, the energy
of excretion, which during the night had been 2, was raised to 42.
The increase of water excretion caused by anaesthetics and other
poisonous substances is accompanied by a decrease in the cell-
turgor. The drops excreted under the action of alcohol vapour
contained 1 • 9 per cent, of dissolved substances instead of the usual
0-6 per cent.^

Diffused fight has no influence on the excretion of water, but
direct sunlight causes its cessation. ^

On the basis of his experimental results Lepeschkin discussed
various theories devised to explain how it is that a cell, such as the
sporangiophore of Pilobolus, is able to absorb water in one part and
excrete water in another part. Since the excretion of water in the
form of a drop at one spot in the sporangiophore is continuous and
steady, he rejected the hypothesis of Godlewski which postulates
alternating periods of greater and less osmotic pressure in the cell
and corresponding periods of non-excretion and excretion due to
the expansion and contraction of the protoplasm .^ Having observed
that a sporangiophore which has been washed by dipping in water
and has been again brought into moist air continues to excrete
water in the form of drops,* he also rejected the theory of Wilson

1 W. W. Lepeschkin, he. ciL, pp. 416-il8, 434.

2 Ibid., p. 418. 3 /ij^^ p_ 419,

* Wilson (loc. cit.) washed sporangiophores in water with a brush, then set them
in moist air, and thereafter observed that, often, the sporangiophores did not excrete
any more drops. Hence he concluded, according to Lepeschkin erroneously, that
washed sporangiophores do not excrete water. Lepeschkin states that washing

28 RESEARCHES ON FUNGI

that the formation of drops on the sporangiophore, hke the forma-
tion of drops on the epidermis of nectaries, is due to a substance
which issues from the cell-walls and by osmosis attracts water to
itself. 1 Having observed that there is a most plentiful discharge
of water from the sporangiophore and that the excretion of water
from the sporangium at the time of ripening of the spores is small
or has entirely ceased, Lepeschkin refused to accept the view of
Brefeld according to which the excretion of water is due to the
protoplasm becoming denser during the formation of the spores. ^
Of the two hypotheses of Pfeffer, (1) that the excretion of water in
a cell is due to the unequal distribution of osmotic substances in the
vacuole, water being absorbed where osmotic substances are in
greatest concentration and excreted where the osmotic substances
are in least concentration, and (2) that the excretion of water is due
to the unequal permeability of the protoplasmic membrane for
water and dissolved salts, water being absorbed where the membrane
is less permeable and best able to withstand osmotic pressure and
excreted where the membrane is more permeable and least able to
withstand osmotic pressure, Lepeschkin accepted the latter. ^ He
concluded that the facts elucidated by his investigations justify the
conclusion that water excretion in Pilobolus is due to the difference
in permeability of the plasma-membrane for dissolved substances
in its upper and lower parts, and that all the phenomena caused by
the action of anaesthetics, poisonous substances, temperature, and
strong light are due to the great changeableness of the plasma-
membrane in respect to permeability.*

That differential permeability may lead to excretion of drops
seems to be proved by some experiments of Weis ^ who lowered the
permeability of one part of a cell by means of alcohol. Weis sub-
jected one half of a long (30-50 mm.) intact internodal cell of
Nitella to alcohol vapour or bathed it in a 10 per cent, alcohol

with a brush removes a coat of fat from the exterior of the sporangiophore, that such
a washed sporangiophore excretes water, and that the excreted water instead of
forming drops runs at once over the surface of the cell-wall.

1 W. W. Lepeschkin, loc. cit., pp. 419-421. ^ /jj^/., p. 421.

3 Ibid., pp. 421^25. " Ibid., pp. 434^35.

^ A. Weis, " Zur Mechanik der Wasserausscheidung aus lebendcn Pflanzenzellon."
Planta, Bd. II, 1926, pp. 241-248.

HISTORY OF PILOBOLUS 29

solution. The treated haK of the cell was allowed to project into
the air while the untreated half was immersed in water. Under
these conditions the treated half excreted drops. These drops were
of so large a volume (62 per cent, of the cell volume when alcohol
vapour was employed) that it could be concluded with certainty
that, while the treated half of the cell had been excreting water, the
untreated half had been absorbing water. In this experiment,
however, while the absorbed water was doubtless pure, the excreted
water may well have been nothing more than escaped cell-sap
becoming more and more diluted.

The excretion of water from the sporangiophore of Pilobolus is,
as we have seen, not general over the whole surface but at certain
definite places on the wall. These places are very small in area and
may be over one hundred in number. They become covered by
as many drops, each of which seems to issue at a point. The drops
do not run down over the surface of the sporangiophore because the
wall is covered with a thin layer of fat.^ According to Lepeschkin's
theory of excretion : (1) the plasma-membrane just beneath each
point of the cell-wall where a drop exudes must be regarded as
exceptionally permeable for water and dissolved substances ; and
(2) the driving force causing exudation is the osmotic pressure of
the cell-sap.

As Lepeschkin's analyses indicate, the drops excreted by
Pilobolus are more watery than the cell-sap. In 1921, V. H.
Blackman 2 showed that " the claim of Lepeschkin that the osmotic
pressure of the stronger cell-contents is responsible for the exudation
from the cell of a weaker solution cannot be substantiated " and
pointed out that Pfeffer himself ^ in 1890 had withdrawn this
hypothesis as physically unsound. Blackman suggested other

1 No proof has been offered that the sporangiophore is covered with a layer of
fat or wax. There is the possibility that the drops do not run down the sporangio-
phore because the surface of the latter bears numerous fins crystals of calcium oxalate.

2 V. H. Blackman, " Osmotic Pressure, Root Pressure, and Exudation," The
New Phytologist, Vol. XX, 1921, .pp. 106-115, with three diagrams.

3 W. Pfeffer proposed this hypothesis (along with others) in 1877 in his Osmotische
Untersuchungen, Leipzig, pp. 224-225, and repudiated it first in 1890 in his " Zur
Kenntnis der Plasmahaut und Vacuolen," Abk. K. Ges. d. Wiss., Leipzig, p. 302,
and again, in 1897, in his Pflanzenphysiologie (English edition, Oxford, 1900,
pp. 271-272).

30 RESEARCHES ON FUNGI

mechanisms for excretion but felt that without more knowledge of
cell-dynamics it was impossible to treat the problem of exudation
satisfactorily.

Weis 1 set a Pilobolus fruit-body on a slide, placed a glass thread
and some vaseline across the sporangiophore just under the sub-
sporangial swelling, pressed the glass thread down with a cover-
glass, and thus compressed the sporangiophore into two parts.
This enabled him to apply plasmolytic solutions to the subsporangial
swelling by itself and to the stipe by itself. He found that, with
a 0-4-0-5 gram-molecule cane-sugar solution, plasmolysis took place
in the swelling slowly or not at all and in the stipe considerably
faster. From this he concluded that the osmotic value of the
cell-sap (or the resistance to filtration of the wall as a whole) must
be greater in the swelling than in the stipe, but added that his
conclusion still leaves us free to regard the tiny places in the wall
where drops are excreted as more permeable than the rest of
the wall. 2

Ursprung and Blum ^ submerged a Pilobolus fruit-body in
paraffin oil {liquidum paraffinum) and with a compression apparatus
applied pressure to the liquid. As the pressure was slowly increased,
drops came out of the wall of the subsporangial swelhng and the
adjacent part of the stipe at about the same time. If the screw of
the pressure apparatus was not further tightened, the sporangiophore
sucked in the drops again. With renewed increase of the pressure,
the drops appeared again, but none were observed on the basal
part of the stipe. From this experiment the authors concluded that,
if the turgor pressure is the same throughout the whole of the
sporangiophore, the suction pressure of the contents in the upper
part is smaller than in the lower part, and they add that this
difference may be due to differences in the osmotic values of the

1 A. Weis, "ZurMechanikderWasserausscheidung aus lebenden Pflanzenzellen,"
Planta, Bd. II, 1926, p. 247.

2 Weis, unfortunately, does not state whether or not the compression of the
sporangiophore into two parts injures the cell in any way nor whether or not his
sporangiophores had ceased to excrete water before they were used for his

experiment.

3 A. Ursprung and G. Blum, " Eine Methode zur Messung Polarer Saugkraft-
differenzen," Jahrb.f. wiss. BoL, Bd. XLV, 1925, p. 11.

HISTORY OF PILOBOLUS 31

contents in different parts of the cell or to the plasma-membrane
differing in permeability in different places.

In 1919, Stern ^ suggested that bleeding from wounds in flowering
plants is due to electro-osmosis ; and, in 1921, Blackman ^ discussed
electro-osmosis as a possible cause of the excretion of drops in
Pilobolus. Hitherto, however, the electrical phenomena which
accompany the excretion of drops in Pilobolus have not been
investigated.

From the review of the Hterature given in the foregoing pages
it appears that we are still far from understanding the mechanism
by means of which Pilobolus excretes its drops. It is possible that
further hght might be thrown on the problem : (1) by measuring,
with the help of Barger's or Ursprung and Blum's capillary-tube
method,^ the osmotic pressure of a series of drops exuded from one
and the same point on the sporangiophore ; (2) by comparing the
osmotic pressure of the drops and of the cell-sap ; (3) by obtaining
more accurate chemical analyses of the drops and cell-sap than
hitherto has been attempted ; and (4) by investigating the suction
force of the basal swelling and of the subsporangial swelling by the
method used by Ursprung and Blum * in their measurements of the
difference in the suction force exerted through opposite walls of
endodermis and other cells.

^ K. Stem, " Uber elektroosmotische Erscheinungen und ihre Bedeutung fiir
pflanzenphysiologische Fragen," Zeit. f. Botanik, Bd. XI, 1919, p. 600.

^ V. H. Blackman, loc. cit., p. 114. He cites the work of Bartell and Madison
who found that with various solutions the normal osmotic tendency of gold-beaters'
skin membranes might be increased, decreased, or reversed. " The results can be
explained by the electrical relations of the membrane ; a difference of potential
between the faces of the two membranes is developed if electrolytes are used and this
electro -endosmosis may aid or retard the normal process of osmosis ; we thus have
an additional force superimposed on the ordinary osmotic relations." Among the
most recent papers treating of electro -osmosis through organic membranes with
numerous citations of the relevant literature is that of L. Bruner, " Untersuchungen
iiber die Elektrolyt-Permeabilitat und Quellung einer leblosen natiirlichen Mem-
brane," Jahrb.f. wiss. Bot., Bd. LXXIII, 1930, pp. 513-632. His experiments were
made with the testa of the Horse Chestnut.

^ For Barger's method vide infra, pp. 141-142. For the method of Ursprung and
Blum, vide their " Zwei neue Saugkraft-Messmethoden," Jahrb. f. wiss. Bot., Bd.
LXXII, 1930, pp. 257-306.

* A. Ursprung and G. Blum, " Eine Methode zur Messung Polarer Saugkraft-
differenzen," loc. cit.

32 RESEARCHES ON FUNGI

Premature Discharge of the Sporangia.— In the evening
Lepeschkin i placed a tuft of fruit-body primordia on a 2 per cent,
solution of sodium chloride. Next morning it was found that some
of the fruit-bodies had not developed sporangia and that others
had developed to maturity in the usual way. Plasmolytic experi-
ments showed that, whereas in the previous evening plasmolysis
of the fruit-bodies began with a 1-4 per cent, sodium-chloride
solution, in the morning it began with a 3-5 per cent, solution.
Thus the osmotic pressure had increased two and one-half times
during the night. Lepeschkin, in the morning, removed the fruit-
bodies from contact with the 2 per cent, salt solution and set them
on water. Two phenomena were then noticed : (1) the imperfectly
developed fruit-bodies greatly increased their excretion of water ;
and (2) the perfectly developed fruit-bodies, which had ceased or
were ceasing to excrete water, did not increase their excretion of
water but, instead, within 1-5 minutes exploded and shot away
their sporangia with a bang.^ These phenomena were doubtless
due to the increase of the turgor pressure in the sporangiophore
brought about by the transference of the fruit-bodies from the
2 per cent, salt solution to water.

Lepeschkin also observed that, when mature fruit-bodies of
Pilobolus are subjected to chloroform or ether vapour by the
gradual method beginning with very small amounts, the discharge
of the sporangia is prematurely hastened. Thus by the gradual
method he subjected 70 fruit-bodies to chloroform or ether and
in other vessels kept 95 fruit-bodies in ordinary moist air. The
experiment began at 9 a.m. Of the 70 fruit-bodies treated with
narcotics, 20 had shot away their sporangia by 9.30 a.m., 65 by
10 A.M., and all by 11.30 A.M., whereas of the 95 untreated sporangia
not one had shot away its sporangium by 11.30 a.m. Lepeschkin
explained the earliness of discharge of the sporangia under the
influence of chloroform and ether by supposing that these narcotics
diminish the permeability of the plasma-membrane of the sporangio-
phore and so increase the turgor of the sporangiophore to the degree
required for the discharge of the sporangium before the usual time.
There are two forces to be taken into account in the discharge
1 W. W. Lepeschkin, loc. cit., p. 429. ^ Ibid., pp. 432-433.

HISTORY OF PILOBOLUS 33

of a sporangium of Pilobolus or of the eight spores from the ascus
of a Peziza : (1) the turgor pressure of the cell-sap, and (2) the
resistance of the wall to breakage. Both in Pilobolus and in an
ascus the wall is so constructed that it breaks along a particular
Une of ultimate weakness. It is possible that shortly before dis-
charge the wall, along its break-hne, is gradually weakened and
that the turgor pressure of the cell-sap is incapable of causing dis-
charge of the sporangium or spores until the weakening has pro-
ceeded far enough. Under natural conditions, as Lepeschkin ^
found, the concentration of the cell-sap of the sporangiophore of
Pilobolus steadily diminishes as development proceeds ; but whether
or not this concentration, and with it the turgor pressure, is markedly
increased just before the discharge of the sporangium remains to be
determined by experiment.

1 have observed that the application of poisonous substances,
such as iodine, mercuric chloride, silver nitrate, copper sulphate,
sulphuric acid, acetic acid, and alcohol, to the hymenium of Peziza
vesiculosa (my P. repanda) lying in water at once causes the asci to
explode and discharge their spores. ^ It seems unlikely that the
discharge of the asci, which takes place within a few seconds of the
application of the reagents, can be due to increase of cell-turgor.
It was found that asci which had contracted after treatment with
a neutral salt may be caused to explode when brought into contact
with iodine.^ It is possible that the early explosion of the sporangio-
phores of Pilobolus in Lepeschkin's experiments with chloroform
and ether was in part due to the action of the anaesthetics on the
protoplasm immediately beneath that part of the wall which
eventually ruptures. It may be that this protoplasm is stimulated by
anaesthetics to weaken the wall through enzyme action prematurely *

Influence of External Conditions on the Breadth of the Sub-
sporangial Swelling. — Lepeschkin ^ at 9 p.m. placed tufts of young
fruit-bodies on water and on 4 -5, 9, and 18 per cent, sugar solutions.

^ W. W. Lepeschkin, loc. 0(7., p. 422. Lepeschkin observed that a young spor-
angiophore (no sporangial swelling) and a ripe sporangiophore of Pilobolus Kleinii
plasmolyse with a 3 • 7 and a 2 • 3 per cent, solution of potassium nitrate respectively.

2 These Researches, Vol. I, 1909, p. 238.

3 Ibid., p. 239. " Cf. ibid., pp. 239-240.
^ W. W. Lepeschkin, loc. cit., p. 423.

VOL. VI. D

34

RESEARCHES ON FUNGI

These liquids were contained in vessels filled with glass beads.
Next morning it was found that the fruit-bodies had developed
normal sporangia and stipes of normal length and that the average
width of the subsporangial swelling in ocular-micrometer divisions
for the fruit-bodies grown on water and on the 4-5, 9, and 18 per
cent, sugar solutions was 49, 38, 29, and 14 respectively. It thus
appears that the width of the subsporangial swelhng is determined
in part by the osmotic value of the substances dissolved in the water
permeating the substratum.

Lepeschkin ^ washed off the " fat layer " from some young
fruit-bodies which had not yet developed subsporangial sweUings,
isolated the fruit-bodies from the mycelium, and then set half of
the fruit-bodies with only the basal swelling in water (normal apical
end in the air) and the other half of the fruit-bodies with only the
apical end in water (basal swelling in the air). Next day he found
that the fruit-bodies which had had the basal swelling in water had
subsporangial swellings of normal diameter (46 micrometer divisions),
whilst the fruit- bodies which had had their apical ends in water had
subsporangial swellings of much less than normal diameter (9-15
micrometer divisions).^ These results suggest that immersion in
water prevents the subsporangial swelling from developing to its
normal size.

The Ballistics of the Projectile.— Link, ^ in 1809, was the first
to attribute the projection of the sporangium to its true cause, the
tension in the swelling below the sporangium ; and this explanation
was endorsed by de Bary ^ in 1866. The osmotic pressure in the
cell-sap of the sporangiophore just before the discharge of the
sporangium is effected has been measured by the writer {vide infra)
and has been found equal to a pressure of several atmospheres.

AUen and Jolivette,* in the course of their studies of the helio-

1 W. W. Lepeschkin, loc. citt, p. 424.

2 H. F. Link, " Observationes in Ordines plantarum naturales," Magaz. d. Ges.
naturf. Freunde, Berlin, Bd. Ill, 1809, p. 32. He says : " Explosio fieri mihi
videtur, dum suprema pars stipitis buUata, sporangium inferne ambiens, contrahitur."

^ A. de Bary, Morphologic und Physiologic der Pilze, Flechten, und Myxomyceten,
Leipzig, 1866, p. 146.

* Ruth F. Allen and Hally D. M. Jolivette, " A Study of the Light Reactions of
Pilobolus," Trans. Wisconsin Acad., Vol. XVII, 1914, pp. 533-598.

HISTORY OF PILOBOLUS 35

tropic reaction of Pilobolus to white light and light of different
colours {vide infra), grew sporangiophores in the dark and observed
the accuracy with which the projectiles struck a small circular
window or two such windows. An account of their work was
published in 1914.

In 1921, I^ pointed out that, when discharge of the sporangium
takes place, the neck of the subsporangial swelhng just beneath the
sporangium is ruptured transversely, the wall of the swelling and
stipe contracts elastically, and the cell-sap is squirted out of the top
of the swelling, so that the sap carries the sporangium with it through
the air. I also stated that Pilobolus Kleinii and P. longipes can
both shoot their largest sporangia upwards to a maximum height just
exceeding six feet and to a maximum horizontal distance just
exceeding eight feet. The experimental evidence upon which this
statement rests will be given in the next chapter.

In 1927, Pringsheim and Czurda,^ in recording their investigations
on the ballistics of Pilobolus, again called attention to the fact that
a drop of sap expelled from the subsporangial SAvelling travels
with the sporangium on its journey through the air, but they
were unable to suggest the true form of the projectile during its
flight. A solution of this problem will be found in the next
chapter.

The other results of Pringsheim and Czurda's ballistic investiga-
tions were summarised by those authors ^ as follows. The horizontal
range of Pilobolus is greatest when the sporangiophores are incUned
obliquely upwards, and the extreme range observed was about
2 metres. The accuracy of the shooting depends on the brightness
of the source of light and especially on the range : the greater the
distance of the target aimed at, the more pronounced the scattering.
With a not too distant disc of light the middle is hit more often than
the edge. The speed of the projectile just after discharge, on the
average, was found to be 14 metres per second. With the help of
a ballistic oscillating pendulum, on the basis of the amount of

1 A. H. R. Buller, " Upon the Ocellus Function of the Subsporangial Swelling of
Pilobolus," Trans. Brit. Myc. Soc, Vol. VII, 1921, p. 61.

^ E. G. Pringsheim and V. Czurda, " Phototropische und baUistische Problome
bei Pilobolus," Jahrh.f. wiss. Bot., Bd. LXVI, 1927, pp. 869-872.

3 Loc. ciL, p. 900.

36 RESEARCHES ON FUNGI

movement caused by the projectile, the mass of the projectile was
found to be 0-011 mg. By weighing, the dry weight of the pro-
jectile was found to be 0-0057 mg. The force of the discharge was
calculated to be 10-8 ergs or 26 x 10"^ calories.

Pilobolus in its Relations with Light. — The response of Pilo-
bolus to light has been studied by Sorokin (1873), Fischer von
Waldheim (1875), Brefeld (1881), Regel (1881), Allen and Jolivette
(1914), Parr (1918), BuUer (1921), Pringsheim and Czurda (1927),
and Van der Wey (1929).

The Effect of Light on Fruit-body Development. — Brefeld,^ for
Pilobolus crystallinus (his P. microsporus), found : (1) that, in the
absence of light, no sporangia are formed but the sporangiophores
continue to grow for 10-14 days until they become 8-10 inches long,
when they wither ; (2) that a two-hour exposure to light is sufficient
to cause a rudiment of a fruit-body to complete its development
in the dark ; and (3) that the fruit-bodies develop normally in blue
light but cannot develop their sporangia in red-yellow light. There
can be no doubt, therefore, that light stimulates P. crystallinus in
a formative or morphogenic manner.

The Heliotropic Response of the Fruit-body to Light of Various
Colours. — The sporangiophores of Pilobolus exhibit marked helio-
tropism {cf. Fig. 13). Sorokin ^ Fischer, ^ and Brefeld studied the
heliotropic effect of light passed through (1) a solution of potassium
bichromate and (2) an ammoniacal solution of copper oxide. The
results were divergent. Sorokin found that Pilobolus gives no
hehotropic reaction in blue light and is negatively heliotropic in
red-yellow light, while Fischer obtained a strong positive response
in blue light but no response in red-yellow light. Subsequent work
has shown that these conclusions were erroneous.

Brefeld ^ obtained a positive response in both blue and red-

1 O. Brefeld, Untersuchungen iiber Schimmelpilze, Leipzig, Heft IV, 1881,
pp. 76-78 ; Heft VIII, 1889, p. 276, Taf. XII, Figs. 1-6.

" N. Sorokin, " Ueber die Wirkung des Lichtes auf die Filze,'" Be ildge zu d. Proto-
collen der Sitz. d. Naturf.-Ges. an d. Univers. z. Kasan, 1875 (in Russian, cited from
Parr's paper).

^ A. Fischer von Waldheim, " Ueber den Heliotropismus niederer Pilze," Arh. d.
hot. Lab. d. k. Univ. Warschau, Warschau, 1875, Heft I {vide Just's Bot. Jahresbericht,
Vol. Ill, 1875).

* 0. Brefeld, loc. ciL, Heft IV, p. 77.

HISTORY OF PILOBOLUS

37

yellow light, with a better reaction in blue light. Grantz ^ re-
peated Brefeld's experiments and confirmed them. According
to Kegel, 2 Pilobolus is positively hehotropic in white, blue,
yellow, and red hght at all the intensities and temperatures
employed. The con-
clusions of Brefeld,
Grantz, and Regel, as
we shall see, have
been substantially con-
firmed by the more
recent work of Miss
Parr.

The first attempt
to express the photic
sensibility of plants in
quantitative terms was
made by Wiesner ^
(1879) in his classic
work on hehotropism.
The next considerable
advance in this direc-
tion was made by
Blaauw* (1909), who
for the first time em-
ployed modern physi-

FlG,

13. — Pilobolus (Kleinii ?). A photomicrograph of
a group of fruit-bodies growing on dung in the
laboratory showing long slender stipes bearing
drops of mucilaginous fluid, beautifully sym-
metrical pear-shaped subsporangial swellings,
and jet-black di^c-shaped sporangia. The
diameter of each subsporangial swelling consider-
ably exceeds that of the sporangium which crowns
it. Owing to the heliotropic curvature of the
stipes, the sporangia all faced the source of
strongest light. Photographed by B. O. Dodge.
, , , -1^, Magnification, about 3 -5.

cal methods. Blaauw

investigated the heliotropic response of Phycomyces nitens.

Miss RosaUe Parr ^ (1918), reahsing that the chief reason for the

1 F. Grantz, Ueber den Einfluss des Lichtes avf die Entwicklung einiger Pike,
Inaug. Diss., Leipzig, 1898 (cited from Allen and Jolivette).

2 K. Regel, " Ueber die Einwirkung des Lichtes auf Pilze," Sitzungsber. d. Bat.
Sect. d. St. Petersburger Naturf.-Oes., Jan., 1881 (in Russian) ; summary in Bot.
Zeit., 1882, p. 29 (cited froin Allen and Jolivette).

^ J. Wiesner, " Die heliotropischen Erscheinungen ini Pflanzenreiche," Denk-
schriften d. K.-k. Acad. Wien, Vol. XXXIX, 1879.

* A. H. Blaauw, " Die Perception des Lichtes," Rec. d. Trav. bot. neerl. Vol. V,
1909.

^ Rosalie Parr, " The Response of Pilobolus to Light," Annals of Botany,
Vol. XXXII, 1918, pp. 177-205.

38 RESEARCHES ON FUNGI

divergent results which had been obtained by others in their studies
of the heUotropic response in plants lay in the lack of accurate
measurements of the quantity and quahty of the light employed,
undertook the task of attempting to correlate all previous results

(1) by studying the heliotropic response of Pilobolus to carefully
caUbrated hght of different wave-lengths and intensities, and

(2) by a determination of the energy relation, if any, between this
Ught and hehotropic response.

In carrying out her work. Miss Parr made use of very dehcate
physical instruments which could be calibrated in standard units.
The hght sources were two, a Nernst lamp of single glower type and
a nitrogen-filled tungsten Mazda lamp. A beam of hght from one
of these lamps was broken up by means of a lens and prism. The
relative energy values of the hght in the different spectral regions
employed expressed in ergs per sec. per square cm. were determined
with the aid of a thermopile and galvanometer, the standard hght
energy used for comparison being a Hafner lamp kept at a distance
of 2 metres from the thermocouple (2-075 ergs). The spectral
regions used in the experiments were tested with a spectrometer
and the limits of the wave-lengths were thus obtained. Cultures
of Pilobolus, grown in coal-gas-free air under known conditions
of temperature, humichty, ventilation, etc., were kept in absolute
darkness for three hours preceding the formation of the sporangio-
phores. The sporangiophores, whilst still pointed and showing no
trace of the formation of sporangia at their ends, were then exposed
to measured spectral regions for a definite period of time which
varied from about 50 to 100 minutes (the presentation time). Each
culture, after exposure, was again placed in the dark and kept there
for an hour (the transmission time). Then with a reacUng glass
the number of curved sporangiophores was recorded. The presenta-
tion time which was required, before a transmission time of an
hour, to produce a curvature in approximately one-half of the
cultures was taken as the standard for the reaction of Pilobolus to
hght. To obtain this presentation time with a wave-length of any
one frequency it was necessary to make several experiments ; for,
with too short an exposure, none of the sporangiophores showed
any curvature while, with too long an exposure, all the sporangio-

HISTORY OF PILOBOLUS

39

phores showed curvatures. The mean wave-lengths to which the
cultures were exposed were as follows : 708 and 667 (red) ; 631 and

750

700

650

600

550

500

450

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rs

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Fig. 14. — Graph showing presentation times in relation to frequency
(not wave-length) of light waves in heliotropic experiments on
Pilobolus. The time required to cause one-half of the spor-
angiophores in a culture to bend toward the light is seen to decrease
as the light employed changes from red (long waves with Zow fre-
quency) through orange, yellow, green, blue, and indigo to violet
(short waves with high frequency). The graph also shows that
Pilobolus responds heliotropically to the light of all the regions
of the visible spectrum. Reproduced from Rosalie Parr's The
Response of Pilobolus to Light (Annals of Botany, Vol. XXXIT,
1918).

40 RESEARCHES ON FUNGI

612 (orange) ; 589 and 585 (yellow) ; 540 and 525 (green) ; 496 and
470 (blue) ; 465 and 438 (indigo) ; 414 and 398 (violet).

Miss Parr's investigation, carried out with so much care and
precision, yielded a series of important results (Fig. 14), some of
which may be summarised as follows. (1) Pilobolus responds
heUotropically to the hght of all the regions of the visible spectrum
from red to violet. (2) The presentation time required to produce
a heliotropic curvature decreases gradually from red to violet or,
conversely, the hehotropic response of the fungus increases gradually
from red to violet. The minimum response is in the red and the
maximum in the blue. There are no intermediate maxima or minima
such as others have supposed to exist. (3) The presentation time
does not vary in direct ratio with the measured value of the energy
of the Ught in the different regions of the spectrum. (4) The
presentation time varies in inverse ratio to the square roots of the
wave frequency. (5) While light energy is a factor in the relative
time required for hehotropic excitation, yet the quality of the hght,
i.e. the frequency of the waves, is of more importance. (6) The
divergent views held by previous investigators regarding the spectral
region of maximum response may be explained on the basis of the
energy value and frequency of the light employed.^

Allen and Jolivette's Investigations. — A series of interesting
experiments upon the reactions of Pilobolus to light were described
by Allen and Jolivette ^ in 1914. They studied the accuracy of
aim of the fungus when influenced by (1) a single source of white
light, (2) two sources of white light used simultaneously or suc-
cessively, and (3) two sources of hght differing in colour.

1 Miss Parr {loc. cit., p. 203) summarised her results in seven paragraphs, the first
four of which are substantially identical with (1) to (4) as given above. Her other
paragraphs were as follows. (5) The product of the square root of the frequency
times the presentation time decreases with the decrease in the energy value of the
spectral regions, and is an approximate constant for a given light source. (6) The
spectral energy in its relation to the presentation time may be expressed approxi-
mately in the Weber-Fechner formula, if the wave-frequencies be made a function
of the constant. (7) The relation of the spectral energy to the presentation time
may also be approximately expressed in the Trondle formula, the wave-frequencies
being a function of the constant.

2 Ruth F. Allen and Hally D. M. Jolivette, " A Study of the Light Reactions of
Pilobolus," Trans. Wis. Acad., Vol. XVII, 1914, pp. 533-598.

HISTORY OF PILOBOLUS 41

Allen and Jolivette remark : " Whatever the mechanism in
Pilobolus for the perception of hght may be. it is certainly efficient.
For example, in the white hght 95 per cent, of the sporangia struck
a four-centimeter (circular) opening (in the dark chamber) when the
culture was twenty centimeters distant from the light ; and, with
one or two exceptions, the remaining 5 per cent, struck within one
or two centimeters of the opening. It is plain that the aiming has
been done with remarkable precision."

Among the conclusions of AUen and Jolivette are the following.
(1) Pilobolus aims point blank at a hght and makes no allowance
for the distance through which the sporangia must travel. (2) Pilo-
bolus fires its sporangia very accurately toward white and blue
hght, much less accurately toward yellow hght, and very inaccurately
at red light.

Allen and Johvette also made the following interesting, un-
expected, and important discovery : when a culture is exposed to
two eqvAil beams of white light coming from two sufficiently different
directions (angle between the two beams greater than about 10°),
the sporangium of each Pilobolus fruit-body is aimed at one or the
other source of light and the aim is as accurate at the source of light
chosen as if the other source did not exist [cf. Fig. 15). The authors
were at a loss to explain their discovery and remark "apparently
there is nothing to prevent these simultaneous stimuh from acting
together to produce a resultant reaction. But this does not occur.
The visible reaction is to one and one only of the two possible sources
of illumination." That a Pilobolus fruit-body aims at one or the
other of two equal well-separated sources of light and not midway
between them is due, as we shall see shortly, to the pecuhar properties
of the subsporangial swelling.

The Subsporangial Swelling as an Ocellus. — In 1921, 1 ^ published
a short paper entitled " Upon the Ocellus Function of the Sub-
sporangial Swelhng of Pilobolus " in which it was pointed out that
the subsporangial swelling acts not only as part of a squirting
apparatus but as a lens and thereby plays an important part in
heliotropic response. A model of a Pilobolus fruit body, which can

1 A. H. R. Buller, " Upon the Ocellus Function of the Subsporangial Swelling
of Pilobolus," Trans. Brit. Myc. Soc, Vol. VII, 1921, pp. 61-64.

42 RESEARCHES ON FUNGI

be used for demonstrating the way in which light is refracted through
a subsporangial sweUing, was also described, and it was announced
that a fuller description of my observations, accompanied by illus-
trations, was in preparation for the press. The more elaborate

Fig. 15. — Pilobolus Kleinii. Result of a heliotropic experiment in which
the sporangiophores were illuminated with two equal beams of white light
which converged on each fruit-body at a relatively wide angle (about
25°). Natural-size reproduction of a photographic print made
directly from a sheet of glass which covered two openings in the
side of a dark chamber. The positions of the openings, each
1-0 X 0-5 cm., have been indicated by white lines. The discharged
sporangia, which adhered to the sheet of glass and were black, appear
as white dots. Direction of shooting was horizontal. Distance of the
vertically placed surface of the culture medium from the glass plate
was 12 cm. The distance between the two windows, measured from
centre to centre, was 5 • 5 cm. The sporangiophores were continuously
lighted during the whole course of their development. From the dis-
tribution of the discharged sporangia it is evident that the spor-
angiophores directed themselves toward one or other source of light
and not in the resultant direction midway between them. Photo-
graph bv Van der Wev (Proc. K. Akad. v. Wetensch. te Amsterdam,
Vol. XXXII, 1929, Plate I, Fig. 5).

treatment of the ocellus function of the subsporangial swelling
promised thirteen years ago was completed at that time ; but,
owing to my pre-occupation with other investigations, its pubUca-
tion has been delayed until now : it will be found in the next chapter
of this book.

The Solution of the Problem of the Non-resultant Heliotropic
Reaction of Pilobolus to Two Beams of Light.— In 1927, Pringsheim

HISTORY OF PILOBOLUS 43

and Czurda ^ repeated the experiments of Allen and Jolivette and
confirmed their statement that, when the fruit-bodies of Pilobolus
are exposed to two beams of light coming from sufficiently different
directions, the sporangia are shot to one or other of the two sources
of light and not in an intermediate direction. They also observed
that, before the development of the sporangium and the sub-
sporangial swelling, the young pointed stipe, when subjected to two
beams of light coming from different directions, is affected by both
beams and takes up a resultant phototropic position. In attempt-
ing to explain the non-resultant response of a mature fruit-body
to two beams of light, Pringsheim and Czurda made two assumptions :
(1) light here hinders growth, and (2) the refraction of the light
that enters the subsporangial swelling at a small angle on one side
is such that the waU on the same side at the base of the swelling is
brightly lighted. As Van der Wey has rightly pointed out, the
first of these assumptions is unjustifiable and the second is contrary
to facts.

Van der Wey,2 dissatisfied with the conclusions of Pringsheim
and Czurda, re-investigated the response of mature fruit-bodies of
Pilobolus Kleinii to two beams of light and, in 1929, in a paper
containing numerous statistical observations, graphs, reproductions
of photographs, and a construction diagram very similar to one of
my own {vide infra. Fig. 59, p. 124), gave an explanation of the
phenomenon which seems to be very satisfactory. He states that
we know : (1) that the orientation of the ripe sporangiophores does
not follow the resultant law (Fig. 15), and (2) that light falhng at an
acute angle on the subsporangial swelling has a greater heliotropic
influence the smaller the angle ; and he assumes that the pigment
zone at the base of the subsporangial swelling is the region of the
protoplasm where perception of the light takes place. He then
presents a picture of the course of the reaction of Pilobolus to two
beams of light as follows.

" Let us suppose that a sporangiophore during its first

1 E. G. Pringsheim and V. Czurda, " Phototropische und ballistische Probleme
bei Pilobolus," Jakrh. f. tviss. BoL, Bd. LXVI, 1927, pp. 863-901.

2 H. G. Van der Wey, " Ueber die phototropische Reaktion von Pilobolus,"
Proceedings, Koninklijke Akademie van Wetenschappen te Amsterdam, Vol. XXXII,
1929, pp. 1-13.

44

RESEARCHES ON FUNGI

development has grown in a resultant direction between two direc-
tions of light, A and B. What must happen in the second period of
reaction ? Let us assume that the subsporangial swelling has then
beome fully developed. So long as the sporangiophore stands in the
resultant direction, the distribution of light is quite symmetrical ;

the light cannot therefore cause a
reaction. The sporangiophore is in
a condition of equilibrium which,
however, is unstable. For, as soon
as it inclines towards A, it receives
the light of A at a smaller angle
and that of B at a greater angle,
in consequence of which the in-
fluence of A becomes greater and
that of B smaller. As a result of
this the sporangiophore will bend
toward A until finally a position
of stable equilibrium has been
attained. This final position is
expressed in illustrations of the
results of shooting-experiments
{Schuss-hilder) and in Figs. 8
and 9 (graphs) can be read for
every angle."

Van der Wey has also shown :
(1) that, when the angle between
the two beams of light is small
(about 7 °- 1 0 ° ) , the sporangiophores
take up a position which indicates that they are influenced strongly
by one beam of light and also to a shght degree by the other beam,
and (2) that, as the angle becomes very small (2°-4°), the effect of
the two beams becomes more and more nearly equalised. Evidence
of the almost equal effect of the two beams converging on the fruit-
bodies at an angle of about 4-5° is shown in the photograph
reproduced in Fig. 16.

Already, in 1920, I had solved the problem of the non-resultant
reaction of Pilobolus to two beams of white light in essentially the

Fig. 16. — Pilobolus Kleinii. Result of
another heliotrojiic experiment in
which tlie sporophores were illu-
minated with two equal beams of
white light, but here the beams
converged on each fruit-body at a
relatively narrow angle (about
4-5^). Conditions otherwise the
same as given in the description of
Fig. 15. The sporangia are most
densely disposed between the two
windows, from which it is evident
that the sporangia directed them-
selves not toward the one or the
other source of light but in
directions between the two sources of
light. Photograph by Van der Wey
(loc. cit.. Fig. 2).

HISTORY OF PILOBOLUS 45

same manner as Van der Wey has done in his recent paper, and my
solution was included in an address on the heliotropism of Pilobolus
which I gave in Canada ^ and in the United States ^ in 1920 and in
England^ in 1921. The address was accompanied by lantern slides,
among which were the construction diagrams shown in Figs. 46, 47,
and 59 (pp. 91, 92, and 124). In my paper ^ on Pilobolus published
in 1921 I treated of the heliotropic reaction of the sporangiophore
to one beam of light only and, in the expectation of publishing a
much fuller account of the fungus in the near future, did not even
mention my solution of the two-beam problem. Since 1921 until
now I have published nothing further on Pilobolus. Thus Van der
Wey, through the publication of his excellent paper in 1929, has
rightly obtained the credit for being the first to solve the two-beam
problem.

My own solution of the two-beam problem was written several
years before Van der Wey\s paper came into my hands, and I have
therefore included it without alteration in a section of the next
chapter.

The Discharge of the Sporangium.— In 1932, Ingold,^ in a brief
paper on the sporangiophore of Pilobolus Kleiiiii, described the mode
of discharge of the sporangium. He rightly affirmed that the
columella is shot away with the sporangium and that a drop of cell-
sap is attached to the gelatinous side of the sporangium as this
travels through the air. However, he failed to account correctly
for the fact that a sporangium becomes attached by its gelatinous side
to anij object that it strikes. He says : " The columella probably
begins to tear away at a point on the circumference of the line of
dehiscence, and the tear rapidly spreads. Through the aperture
thus produced water exudes, forming a drop which, as it grows,
increases the tear. This drop is moving with great velocity and

1 At Guelph, at the second annual meeting of the Canadian Branch of the
American Phytopathological Society, Dec. 10, 1920.

2 At Chicago, before the Physiological Section of the Botanical Society of
America, Dec. 28, 1920.

3 At London, before the Linnean Society of London, June 16, 1921 {vide Proceed-
ings of the Linn. Soc, 1921, p. 63).

* Loc. cit.

5 C. T. Ingold, " The Sporangiophore of Pilobolus," The Neio Phytologist,
Vol. XXXI, 1932, pp. 58-63.

46 RESEARCHES ON FUNGI

as it rounds off, in separating from the sporangiophore, tears away
the sporangium completely, so that in the projectile the sporangium
is at the bottom of the drop with the black cap undermost forming
an unwetted base to the drop." Thus Ingold holds that, from the
moment the sporangium is discharged, it trails behind the drop
which carries it forward. It seems most unlikely that the projectile
should rotate through 1 80° and no further. Rather we must suppose
that the sporangium and the drop begin to rotate at the moment
of discharge and continue to rotate as they progress through the air.
To become stuck to an obstacle by its gelatinous side it is not
necessary for the sporangium to strike the obstacle by that side.
As will be explained more fvilly in the next Chapter, the sporangium
is forced round into its final position — wettable gelatinous side
toward the obstacle and unwettable black convex side away from
the obstacle — by the drop at the moment the drop strikes the
obstacle and flattens out upon it.

Ingold says that " the stalk and upper bulb of the sporangio-
phore contain a clear liquid except where the stalk joins the bulb ;
here a conspicuous zone of oil is invariably found. This oil appears
to the naked eye as a minute orange spot at the base of the sub-
sporangial swelling." These statements give the impression that
the oil, hke the cell-sap, is contained within the vacuole. As a
matter of fact the oil is located in a biconcave mass of protoplasm
{vide infra. Fig. 28, g), and it consists not of one large drop but of
numerous very tiny drops embedded in the protoplasm.

Ingold also states that, when the sporangium is discharged, the
lower part of the sporangium- wall " partially breaks down." My
own observations do not support this view. Ingold failed to notice
that, when the sporangium dehisces, its wall spUts transversely
into two pieces : (1) a lower narrow band which remains attached
to the columella, and (2) a much larger convex cap {vide infra,
Figs. 29 and 30). He correctly illustrated the lower band of sporan-
gium-wall attached to a columella isolated from a discharged
sporangium, but failed to recognise it as such.

CHAPTER II

PILOBOLUS AND THE OCELLUS FUNCTION OF ITS
SUBSPORANGIAL SWELLING

Culture Methods — Germination of Spores, Growth of Mycelium, .and Formation of
Primordia of Fruit-bodies — A Colourless S^wrangial Wall as an Abnormality
in Pilobolus longipes — Species observed — General Description of the Pilobolus
Gun and its Projectile — The Discharge of the Projectile — ^Development of
the Pilobolus Gun and its Projectile — The Heliotropism of the Pilobolus Gun
demonstrated by a Simple Experiment — The Range of the Pilobolus Gun —
The Structure of the Sporangiophore and Sporangium illustrated by Pilobolus
Kleinii and P. longipes — The Two Functions of the Subsporangial Swelling —
The Heliotropism of the SporangiojAore with special reference to the Ocellus
Function of the Subsporangial Swelling — The Mechanism of Heliotropic
Response in Pilobolus and in the Leaves of certain Flowering Plants — The
Ocellus of Pilobolus and the Eye-spots of Volvox — The Ocellus of Pilobolus
and the Human Eye — ^A Heliotropic Experiment made on Pilobolus longipes^
A Solution of the Problem of the Reaction of the Sporangiophore of Pilobolus
to Two Equal Beams of White Light — A Model for illustrating the Pilobolus
Fruit-body in its Relations with Light — The Periodicity in the Development
of Pilobolus Fruit-bodies — The Subsporangial Swelling and the Discharge of
the Pilobolus Gun — The Osmotic Pressure of the Cell-sap of Pilobolus — Factors
in the Efficient Working of the Pilobolus Gun — An Analysis of the Cell-sap
of Pilobolus longipes — The Landing of the Pilobolus Projectile and the Attach-
ment of the Sporangium to Herbage — The Relations of Pilobolus with Flowering
Plants and with Herbivorous Animals.

Culture Methods. — At Winnipeg, during the winter months,
Pilobolus was usually obtained as follows. Horse-dung balls,
collected in the frozen condition from the streets or obtained fresh
from a stable, were placed unbroken in a compact layer on the floor
of a large culture chamber which was exposed to daylight on a table
in the laboratory. The chamber was 3 feet long, 1 • 5 feet wide, and
2 feet high, its four sides and its roof were made of glass, while its
floor was covered with a sheet of zinc having upturned edges. The
air of the chamber was kept moist by means of a standing beaker

47

48 RESEARCHES ON FUNGI

of water and also by occasionally spraying the dung-balls or pouring
water on the zinc floor.

After the dung had been in the chamber for a few days, usually
but not always Piloboli began to appear upon it ; and often many
hundreds or even thousands of fruiting structures came to maturity
each day for several days in succession. The sporangiophores
exhibited the usual positive heliotropism, in consequence of which

'. , .•■ .•♦,« •."• •••♦• . •.•*./.

• .-. /•.: • . •.. ... ..-...• ... •» • . • •.••.

.*. -^ • • . • *' .•••■ • . ^ \ . • •••••. "i

■ ' .♦ .• .• . •. ■• . • • • •;.».••••. '^^

... • • • .• . • • .. .• •

•••••■ • •* . • ;.-.». u'.' •• . ,, . .

* •, • . . • . • . • • • .•..•-••

I •••■•.. • . • .•

• • •

' • . . • • . '»•••; . • • . • . • . . V

i

• ' :• •.

• . •

• • • ■ ■

. • . •

,. • »

Fig. 17. — Sporangia of Pilobolus longipes which were shot on to a sheet of
white paper set against the best-ilkiminated side of a large glass chamber in
which numerous fruit-bodies had come up on dung introduced there a few
days before. The large drop of cell-sap which accompanied each spor-
angium was absorbed by the paper, so that the sporangia have not run
together in groups as they do on a glass surface but have remained where
they landed. Natural size.

they shot off their sporangia toward the side of the chamber through
which the strongest light entered. These projectiles adhered to
the glass where they struck, and thus a very large number of them
came to dot its surface (Fig. 17).

In other cultures horse-dung balls were spread over the floor of
an almost cubical glass chamber (base 20 X 21 inches, height 24
inches). Here, as in the other large glass chamber, there was a
considerable body of air above the culture medium, and thus
aeration of the dung was provided for. The cultures in this chamber
were very successful. As an example one may be described. On

THE PILOBOLUS GUN AND ITS PROJECTILE 49

February 13, 1929, fresh horse-dung balls taken from a stable were
spread over about three square feet of the chamber floor. Four
days later, upwards of twenty thousand fruit-bodies of Piloholus
longipes had appeared — every dung ball was covered with them.
At 2 P.M. I put my ear to the glass wall of the chamber nearest to
the source of daylight, and I could hear more than one hundred
sporangia strike the glass per minute. This miniature bombard-
ment had been in progress for some time and it persisted through
the mid-day hours until every Pilobolus gun had exploded.

Still other cultures were made by placing dung-balls in large
crystallising dishes (10 X 3 inches) each covered with a glass plate
(c/. Fig. 26, A, c, p. 64). A slight space was provided between
each dish and its plate, so as to permit deleterious gases emanat-
ing from the dung to escape from the chamber and fresh air to
enter.

It was observed that dung-balls which produced Mucors freely
usually produced but relatively few Piloboli, and vice versa, and also
that promising-looking crops of Piloboli were sometimes utterly
ruined by the attacks of parasitic moulds of which one sj^ecies proved
to be Syncephalis nodosa.^

The natural cultures of Pilobolus just described were so successful
that they were used to provide the supply of normal mature fruit-
bodies required for the study of (1) the structure, heliotropism, and
explosion of the Pilobolus gun and (2) the structure and character-
istics of the Pilobolus projectile.

A iew pure cultiu-es were also made. Sporangia of Pilobolus
longvpes were caught on sterilised slides or cover-glasses and then
sown on sterilised horse dung in a large crystallising dish covered
with a glass plate. The spores germinated, and, after a few days, a
crop of fruit-bodies began to appear. Similar results were obtained
when sporangia or isolated spores were sown on sterilised dung-
agar ^ in Petri dishes. The pure cultures on horse dung were
employed merely for the study of the production of abnormal
fruit-bodies {vide iyifra), while the dung-agar cultures were used
to permit of observations on the germination of the spores, the

1 Cf. p. 21.

2 For the technique of making dung-agar vide Vol. IV, 1931, pp. 195-197.

VOL. VI. E

50

RESEARCHES ON FUNGI

development of the mycelium, and the early stages in the forma-
tion and growth of the fruit-body.

Germination of Spores, Growth of Mycelium, and Formation of
Primordia of Fruit-bodies. — Sporangia of Pilobolus longipes {cf.

Fig. 18) were caught on a clean glass
plate and then crushed in warm water,
and some of the spores were then trans-
ferred with the help of a platinum loop
to a drop of dung-agar hanging in a van-
Tieghem cell. In other cultures the
powder from crushed sporangia was sown
and, in still other cultures, sporangia were
sown as wholes. In each culture, at room
temperatures, a small percentage of the
spores germinated.

On germinating, a spore swells up
considerably and then puts out one or
sometimes two germ-tubes (Figs. 19 and
20, A-G). The germ- tube then grows
rapidly in length and branches mono-
podially. A well-grown mycelium has
rather thick main hyphae from which
come off lateral hyphae which are much
thinner and which in their turn give
rise to still thinner branches (Fig. 20, G).
The main hyphae (Fig. 21, A) come to
contain numerous red particles, doubtless
oil-drops containing carotin, and it is these
branches alone which are destined to form
the primordia of fruit-bodies. Two days
after the spores have been sown, here and there in a well-grown my-
celium a thick main branch for some distance along its length begins
to swell laterally ; and, in the course of a few hours, the swelling
develops into a fruit-body primordium or tuber (Figs. 20, H, and 21,
B-D). As the primordium develops, protoplasm flows into it from
the apical and basal portions of the main hypha and from all the
adjacent smaller lateral hyphae. As a result of this flow, the tuber

Fig. 18. — Pilobolus longipes.
A group of fruit-bodies
in air, just before the
disi'liarge of tlie spor-
angia. In each fruit-
body are shown the
iqjper part of the
slender stipe, the large
.subsporaTigial swelling
fille(l with cell-sap, and
the terminal black
sporangium. The red
protoplasm at the
junction of the stipe
and su bspo rangial
swelling appears black
and may be readily ob-
served in the fruit-body
on the right. Magnifi-
cation, 20.

THEPILOBOLUS GUN AND ITS PROJECTILE 51

Fig. 19. — Pilobolus longipes. Photomicrograph of .spores
sown in dung-agar. Left, three spores which have not
germinated. Right, a spore which swelled up and
germinated. There are red particles in it and in the
mycelium. Magnification, about 400.

Fig. 20. — Pilobolus longipes. Germination of sj)ores in cleared dung-agar and the
production of mj'celia. A, spores, just placed in the culture medium ; they are
reddish-yellow, owing to the presence of carotin dissolved in oil-drops. B, one
of the spores which has been crushed, to .show the thick cell-wall. C, 14 hours
after sowing, two spores which have swollen. D, 24 hours after sowing, three
spores which have emitted germ-tubes. E, 25 hours after sowing, a young
mycelium produced from a single germ-tube. F, 25 hours after sowing, a young
mycelium produced from two germ-tubes. G, 26 hours after sowing, a more
advanced mycelium developed from a single germ-tube. H, 03 hours after
sowing the spores, part of a mycelium showing a thick main hypha and slender
secondary hyphae. The main hypha has swollen locally and has formed a
fruit-bodj' primordium (tuber or trophocyst) filled with dense red protoplasm.
Magnification : A-F, 293 ; G and H, 60.

52

RESEARCHES ON FUNGI

THE PILOBOLUS GUN AND ITS PROJECTILE 53

comes to contain a considerable mass of red protoplasm. This
protoplasm contains vacuoles, and a streaming movement can be
readily observed in it. As a tuber is forming, the main hypha
adjacent to the tuber may become somewhat moniliform in outline
(Fig. 21, C-G, m). On attaining maturity, each tuber becomes
separated from the rest of the main hypha on which it is situated by
two septa, one at each of its ends (Fig. 21, E-G). The lateral hyphae
attached to a tuber were produced by the mycelium before the tuber
came into existence and are therefore not comparable to rhizoids.
Each of them eventually becomes separated from the tuber by a
septum. As shown by Lepeschkin's experiments with isolated
tubers, a mature tuber contains all the materials, except sufficient
water, necessary for the formation of a fruit-body.^ On this account
Morini has called it a trophocyst.^

Soon after a tuber has been formed and cut off from the hypha
with which it is connected, it begins to germinate : at one end it
develops a coarse hypha which grows up into the air (Fig. 21, E-G)
and eventually becomes differentiated into the stipe, the sub-
sporangial swelling, and the sporangium. The tuber itself becomes

Fig. 21.- — Pilobolus longipes. Origin and early development of the fruit-body
primordium (tuber or trophocyst). Culture medium, cleared dung-agar. A,
part of a thick main hypha of a well-developed mycelium ; it is reddened with
carotin. B, another main hypha which is forming a fruit- body primordium
by swelling laterally for some distance along its length ; red protoplasm is
collecting in the swelling. C, a primordium, }3, which has attained full size,
it is filled with red protoplasm ; one of the main hyphae, in, which has passed
its contents into the primordium, has become moniliform. D, a primordium
which has developed to full size in the middle of a main hypha ; the inain hypha
has become moniliform at m ; the secondary branched hyphae have ceased to
grow in length. E, a primordium, cut off from the rest of a main hypha by
the cross-walls w w ; it has begun to form a fruit-body and is now differentiated
into a basal swelling b tuid a young stipe s. F, similar to E, but more advanced ;
at m the main hypha, which has now lost most of its contents, has become
moniliform. G, similar to E and F, but more advanced : w w, two cross-walls
which separated the fruit-body primordium from the rest of the main hypha ;
m, a part of the main hypha which has become moniliform ; b, the basal swelling
of the fruit-body ; s, the young stipe with red protoplasm densely aggregated
at its apex which is still imnaersed in the culture medium ; the basal swelling
and stipe contain a large central vacuole. The basal swelling of G is about
0-25 mm. long. Under natural conditions on horse dung, basal swellings often
attain a length of 1-2 mm. Magnification, 240.

^ Cf. supra, p. 26.

2 r. Morini, " Ricerche sopra una nuova Pilobolea," Mem. R. Accad. Sci. 1st.
Bologna, ser. 5, Vol. VIII, 1900, p. 86. Vide also his " Materiali per una monografia
delle Pilobolee," ibid., ser. 6, Vol. Ill, 1906, p. 118.

54 RESEARCHES ON FUNGI

the basal swelling or basal reservoir of the fruit-body and, owing to
its mode of origin, it is usually much elongated (under natural
conditions on horse dung 1-2 mm. long). It is on account of the
unusual length of the basal swelhng that P. longipes has received its
specific name. As the coarse hypha grows into the air, most of the
protoplasmic contents of the basal swelhng flow into it, and a thick
mass of red protoplasm always accumulates at the growing point
(Fig. 21, F, G). As soon as the hypha has attained a length of
several millimetres (under natural conditions on horse dung often
2-3 cm.), it ceases to grow in length and develops a sporangium at
its apex, and thereafter it develops a subsporangial swelling. Thus
the order of formation of the four parts of the fruit-body is as follows :
basal swelhng, stipe, sporangium, and subsporangial swelling.

A Colourless Sporangial Wall as an Abnormality in Pilobolus
longipes. — Some normal fruit-bodies of Pilobolus longipes, having
the usual long cylindrical foot, rounded spores, and black sporangial
wall, came up on horse dung spontaneously in the laboratory ; and
some of the sporangia, after they had landed on a sterilised glass
slide, were used to inoculate sterilised horse-dung balls contained in
a large crystallising dish. The dung consisted of fresh balls obtained
from a stable and it covered the base and filled up about half the
space in the dish. The dish, after the dung had been inoculated,
was closed by means of a well-fitting glass plate. About a week
after inoculation, fruit-bodies of P. longipes began to appear on the
dung. They had the characteristic cyhndrical foot and rounded
spores, but many of them, although by no means all, were otherwise
abnormal. The development of the abnormal fruit-bodies took place
so slowly that the sporangia were not ripe in the mornings and
many of them were not discharged. The subsporangial swelhngs
and sporangia were remarkably small — not much more and very
often less than one-half the usual size ; and many of the sporangia
never turned black and remained bright orange-yellow. The
persistent orange colour of the sporangia was due to the fact that the
sporangial wall had failed to develop any black pigment, so that it was
colourless, thus permitting the orange-yellow spores to show their
colour through it. Many of the orange-yellow sporangia were
discharged, so that they struck and stuck to the side of the dish

THE PILOBOLUS GUN AND ITS PROJECTILE 55

nearest to the light. Some of these discharged sporangia were
mounted in water on a sUde, and then the individual spores could be
seen through the colourless sporangial wall.

Suspecting that the abnormal development of the fruit-bodies
was due to the fumes emitted by the sterilised dung-balls, which
were unable to escape from the crystallising disb, I removed the
covering plate and set the dish under a large bell-jar. As a result of
the change in external conditions, the succeeding crops of fruit-
bodies became quite normal in time of development, in the size of
the subsporangial swellings and sporangia, and in the development
of the intensely black pigment in the sporangial wall. Thus the
supposition that the abnormal development of the fruit-bodies in
the pure culture of P. longipes was due to gaseous emanations from
the horse dung seems to have been well founded. As supporting
this view it may be mentioned that fruit-bodies of Coprinus curtus
became sterile when subjected to the fumes of fresh horse dung.^

In 1876, van Tieghem remarked that he had observed fruit-bodies
of Pilobolus oedipus in which the sporangium-wall had failed to
blacken, so that, just as in the abnormal P. longipes fruit-bodies
described above, the orange-yellow spores showed through the
uncoloured sporangium-wall and thus gave to the sporangium as a
whole an orange-yellow appearance. ^

Van Tieghem,^ also in 1876, gave the name Pilobolus nanus to
a minute species, not more than 1 mm. high, which he found on rat
dung (Fig. 106, p. 212). This species, according to van Tieghem,
differs from all other Piloboh in having a yelloiv (not black) sporan-
gium-wall when the sporangium is projected. P. nanus has not
been seen again since 1876. For the present, therefore, the possi-
bility is not excluded that the yellowness of the sporangium-wall in
this species may have been abnormal.

Species observed. — Among the species of Pilobolus which occur
at Winnipeg the following have been identified : P. longipes (Figs. 18
and 24), P. Kleinii (Fig. 27), and P. umhonatus nov. sp. (Fig. 105,

1 These Researches, Vol. IV, 1931, p. 9.

2 P. van Tieghem, " Troisieme Memoire sur les Mucorin^es," Ann. Sci. Nat.,
6 86r., T. IV, 1876, p. 342.

3 Ihid., pp. 340-342, PI. X, Figs. 16-22.

56 RESEARCHES ON FUNGI

p. 210), all of which came up in the horse-dung cultures just described,
and P. oedipus which fruited freely on a cake of drying mud brought
to the laboratory from the banks of the Red River. The species
chiefly used for observation were P. Kleinii and P. longipes. Pilo-
bolus umbonatus will be described in Chapter III. Pilobolus
crystallinus, so far as I know, has never come up in any of my
cultures.

General Description of the Pilobolus Gun and its Projectile. —
As is well known, the sporangiophore of Pilobolus shoots away its
sporangium to a distance of several feet and therefore acts as a gun.
The gun, as shown in Fig. 2 (p. 4), consists of three parts : (1) a
basal swelling which, with the aid of mycelial hyphae, serves to fix
the gun firmly to the substratum ; (2) a slender cylindrical stipe,
several millimetres long, which by means of a heliotropic response
serves to lay the gun in the direction in which it is to be discharged ;
and (3) a large oval subsporangial swelling which acts as part of a
squirting apparatus and also, as will be shown later, as an ocellus
which perceives the direction of the incident light and thereby
assists the stipe in its heliotropic movements. The projectile — the
sporangium — is seated on the free end of the subsporangial swelling,
is discoid, is covered with an intensely black membrane, and con-
tains many thousands of spores. Photographs of some Pilobolus
guns which are about to discharge their projectiles are shown in
Figs. 5, 13, and 18 (pp. 8, 37, and 50).

In every species of Pilobolus, the diameter of the subsporangial
swelling much exceeds that of the sporangium and still more that
of the stipe. This may be realised by reference to Fig. 22 which
shows a plan of cross-sections of these parts for typical large fruit-
bodies of Pilobolus longipes and P. Kleinii.

The Discharge of the Projectile. — Pilobolus Kleiriii and P.
longipes can both shoot their largest sporangia vertically upwards
to a maximum height just exceeding six feet and to a maximum
horizontal distance just exceeding eight feet. It is therefore evident
that the Pilobolus gun gives its projectile a high initial velocity.

When a Pilobolus gun is fully developed and ready to discharge
its projectile (Fig. 18, p. 50), the wall of the sporangiophore, i.e. of
the basal reservoir, stipe, and subsporangial swelling, is greatly

THE PILOBOLUS GUN AND ITS PROJECTILE 57

distended by the osmotic (turgor) pressure exerted by the cell-sap
in the large central vacuole. This pressure, as will be shown
subsequently, is equal to that of about 5-5 atmospheres. Since
the inward pressure of the cell-wall must be equal to the outward
pressure of the cell-sap, we must suppose that, when a Pilobolus
gun is about to be discharged, the distended cell-wall of the

OS

mml

Fig. 22. — To show the relative diameters of the black sporangium a, the subspor-
angial swelling 6, and the stipe c in two large wild fruit-bodies of two species
of Pilobolus. A, Pilobolus longipes (same fruit-body as that in Fig. 57). B,
P. Kleinii. In each drawing is represented an apical view of a fruit-body
facing the strongest rays of light and a cross-section of the stipe. In A the
radius of the sporangium is 56 per cent, of the radius of the subsporangial
swelling and in B 64 per cent. The light rays which strike the surface h are
refracted into the subsporangial swelling and form a spot of light which, when
the fruit-body is in heliotropic equilibrium, rests symmetrically upon the ring
of red protoplasm at the top of the stipe (c/. Fig. 50, D). As may be seen by
reference to the mm. scale, the diameters of the sporangium, subsporangial
swelling, and stipe in A are 0-58, 1-03, and 0-21 mm. respectively.

sporangiophore is compressing the cell-sap with a pressure equal
to that of about 5-5 atmospheres.

When discharge of a sporangium takes place, the neck of the
subsporangial swelling just beneath the sporangium is ruptured
transversely {vide the dotted line a in Fig. 28, p. 70), the wall of
the swelling and the stipe contracts elastically, and the cell-sap
is squirted out of the top of the swelling, with the result that a large
drop of sap carries the sporangium with it through the air. As
the projectile begins to describe its trajectory, the collapsing gun
(since action and reaction are equal and opposite) flies backwards
and immediately strikes the dung-ball to which it is attached.

58 RESEARCHES ON FUNGI

However rapidly the projectile may be travelling, on striking a
blade of grass or any other obstacle, it always sticks where it strikes.
Under natural conditions, Pilobolus guns are usually situated on
the dung of herbivorous animals in pastures, etc., in consequence
of which the projectiles usually land on, and adhere to, the
surrounding herbage.

Development of the Pilobolus Gun and its Projectile. — In a
good natural culture of Pilobolus a crop of Pilobolus guns and
projectiles is produced daily for several days in succession. Each
crop takes about 24 hours for its development which culminates in
the discharge of the sporangia between 9 a.m. and early afternoon.
In the late afternoon a new crop can be seen beginning to develop.

The successive development of the stipe, the sporangium, and
the subsporangial swelling of Pilobolus Kleinii is shown on a larger
scale in Fig. 23, while a series of successive stages in the develop-
ment of a diurnal crop of fruit-bodies of P. longipes, as affected by
external conditions, particularly light and darkness, is represented
diagrammatically on a smaller scale in Fig. 24.

The primordia of a new crop of Pilobolus guns and projectiles
consist of much swollen cells which are filled with dense orange-red
protoplasm and look like little tubers. These primordia, the
trophocysts of Morini,^ are formed in the mycelium at the surface
of the substratum by mid-day (Fig. 24, A). During the afternoon,
each primordium puts out a coarse cylindrical hypha which grows
away from the substratum into the air (Fig. 23, A). The red
protoplasm of the primordium flows up into the hypha which thereby
becomes reddened in its turn, particularly at its free end just below
the apical growing-point (Fig. 12, a, p. 23). The primordium
becomes the basal swelling of the new sporangiophore and the
coarse hypha the stipe. From the first the young sporangiophore
is positively heliotropic, and from early afternoon to dark, as it
grows in length, it keeps its long axis parallel to the strongest
incident rays of light (Fig. 24, B and C). If, as happens in the
depth of winter, darkness supervenes before the sporangium begins
to develop, the sporangiophore continues to grow in length
orthotropically (Fig. 24, C and D). Toward evening, the end of

^ Vide supra, p. 53.

THE PILOBOLUS GUN AND ITS PROJECTILE 59

the sporangiophore begins to develop into a sporangium (Figs. 12,

Fig. 23. — Pilobolus Kleinii, wild, on uii sterilised horse dung in
a culture chamber. Stages in the development of a fruit-
body and, in particular, of the subsporangial swelling : a,
basal swelling ; b, stipe ; c, sporangium ; d, subsporangial
swelling. A, in the afternoon : a tuber (trophocyst) has
begun to develop into a fruit-body : the tuber a is now to be
regarded as a basal swelling and its apical outgrowth 6 as a
stipe. B, at 6 p.m., a very short fruit-body : a sporangium
c has developed at the end of the stipe ; as yet there is no
trace of a subsporangial swelling. C and D at 12.20 a.m.
and E at 9 a.m., showing successive stages in the development
of the subsporangial swelling. Magnification, 27.

6, 23, B, and 24, D). The sporangium attains its full size before
midnight. At first, it is orange owing to its content of orange-

6o

RESEARCHES ON FUNGI

T^

^?\.

f^v.'' ■

j^

>t;

<

*j-tr.-.,-. ■ . \

la^^ '.;•-■■•-- A

K

S>vt

THE PILOBOLUS GUN AND ITS PROJECTILE 6i

coloured protoplasm ; but, subsequently, as its wall matures and
becomes pigmented, it turns black (Figs. 12, c, and 23, C-E). The
conical columella, which separates the sporangium from the stipe,
is developed early in the evening ; but the spores are not formed
until after midnight. Shortly after midnight, the top of the stipe
immediately under the sporangium begins to become transformed
into a subsporangial swelling. The development of the swelling
and the ripening of the spores take place simultaneously between
12 midnight and 6 a.m., i.e. while in winter it is still dark (Figs. 23,
C-E, and 24, D-F). In the morning, after daylight has appeared,
the top of the stipe just beneath the subsporangial swelling bends
heliotropically, so that the sporangium comes to face the strongest
incident rays of light with great precision (c/. Figs. 13, p. 37, and

Fig. 24. — Pilobolvs longipes. Rhythmic development and heUotropism of the fruit-
bodies, represented diagrammatically. In tlie right-top comer of a drawing,
arrows indicate daylight and the direction of the strongest incident rays, and
black triangles indicate night and the absence of effective heliotropic radiation.
A-H, successive stages in the development of three fruit-bodies of the first
diurnal generation ; I-K, successive stages in the early development of six
fruit-bodies of the second diurnal generation. The fruit-bodies are supposed
to be developing on a horse-dung ball in a field. The times given are those
which were observed in a laboratory culture (fresh unsterilised horse dung) late
in November. A, at 3 p.m. ; three red tubers (trophocysts) have appeared on
the surface of the dung-ball. B, at 4 p.m. ; each tuber, now to be regarded as
a basal swelling of a fruit-body, has given rise to a stipe which is elongating
apically and is positively heliotropic. C, at 6 p.m. ; darkness has set in ; the
stipes are still elongating ; in the absence of light they are growing straight
forward in the direction they took up in the afternoon. D, at 10 p.m. ; the
stipes temporarily have ceased to elongate ; each of them has given rise to a
terminal sporangium. E, at 12.30 a.m. (midnight) ; each fruit-body has now
developed a subsporangial swelling ; the stipes are about to resume their
growth in length. F, at 4 a.m. (still dark) ; the stipes have elongated con-
siderably. G, at 12 A.M. (noon) ; the direction of the strongest incident rays
of light, as indicated by the arrows, has changed since the previous afternoon ;
as daylight dawned, the fruit-bodies, with the help of their subsporangial
swellings, readjusted themselves heliotropically and so their stipes are now
curved. H, at 1 p.m. ; the climax of development has arrived ; two of the
fruit-bodies have discharged their sporangia in the directions indicated by the
long curved arrows ; the discharged sporangia have struck and stuck to near-by
grass ; the third fruit-body has just exploded ; the jet of sap squirted out from
the mouth of the subsporangial swelling has broken up into a series of drops of
which the largest is attached to the wettable gelatinous under side of the
sporangium ; the projectile (sporangium and sap-drop) may be rotating in its
flight ; the two sporangiophores which have discharged their projectiles are
lying on the dung-ball ; owing to action and reaction being equal and opposite,
they were of necessity forced backwards as the projectiles were forced forwards.
I, at 3 P.M. ; the three discharged fruit-bodies of the first diurnal generation
can be seen lying on the surface of the dung-ball where they are rapidly dis-
integrating ; six new tubers (trophocysts) of the second diurnal generation
have now appeared (c/. A). J, at 4 p.m., and K, at 6 p.m., show stages in the
development of the second diurnal generation of fruit-bodies resembling stages
B and C for the first diurnal generation. Magnification, 1 • 5.

62

RESEARCHES ON FUNGI

/

24, G). The Pilobolus gun continues to mature (Fig. 12, c), until
at last it explodes (Figs. 12, d, and 24, H). When this happens,
the gun dies instantly and is thrown backwards on to the sub-
stratum of dung, while the projectile, with its freight of living

spores, travels forward,
describes a parabolic
trajectory, and lands
safely on some object
which may be several
feet away from the
gun which has dis-
charged it (Fig. 24, H).
As soon as one crop of
fruit-bodies becomes
exhausted, another be-
gins its development
(Fig. 24, I-K).

The Heliotropism
of the Pilobolus Gun
demonstrated by a
Simple Experiment. —

;x

■ ■■■v-.'iH'-:--/- /

Fig. 25. — Result of a simple heliotropic experiment
with Pilobolus Kleinii. The fvmgus came up on
dung balls spread on the floor of a large dark
chamber which was illuminated with daylight
solely by a circular glass wall-window one inch in
diameter. The photograph here reproduced shows
the window and part of the surrounding interior
wall, after the end of the experiment. Most of
the projectiles hit the window as if it were a
target. The local aggregations of the sporangia
in the centre of the window were caused by
sporangia running together in the drops of cell-
sap which were shot on to the glass with the
sporangia. Natural size.

Some fresh dung baUs
were spread over the
surface of a large cubi-
cal culture chamber
which was illuminated
with daylight solely
by means of a circu-
lar glass wall-window
one inch in diameter.

After a few days, a number of fruit-bodies of Pilobolus Kleinii
appeared on the dung about a foot from the window. The spor-
angiophores bent heliotropicaUy toward the source of light and
discharged their sporangia at the window. The photograph repro-
duced in Fig. 25 shows the window and part of the surrounding
interior wall of the chamber at the end of the experiment, after
the chamber wall had been illuminated to enable the photograph

THE PILOBOLUS GUN AND ITS PROJECTILE 63

to be made. An inspection of the photograph shows that most of
the projectiles hit the window as if it had been a target. The local
aggregations of sporangia in the central part of the window were
caused by sporangia running together in the drops of cell-sap which
were shot on to the glass with the sporangia.

The Range of the Pilobolus Gun. — Experiments on the range
of the Pilobolus gun have been recorded by Coemans ^ in 1861,
by Grove 2 in 1884. by myself ^ in 1909, and by Pringsheim and
Czurda^ in 1927. Coemans observed a maximum vertical range for
P. oedipus of just over one metre (107 cm.) ; Grove observed a
maximum horizontal range for P. Kleinii of 4 feet 2 inches ;

1 observed a maximum horizontal range for P. longipes of 6 feet

2 inches, whilst Pringsheim and Czurda observed a maximum
horizontal range for P. sp. (? P. crystallinus) of 2 metres (6 feet,
7 inches). All these records have been broken in a series of experi-
ments which I have made since 1909 and which will now be described.

The vertical range of Pilobolus longipes and P. Kleinii was
determined with the help of the apparatus shown in Fig. 26. The
chamber A, made of beaver-board attached to a wooden frame and
painted black within, was so constructed that its upper part a,
which had a large round hole h in its roof, surrounded and enclosed
the upper half of the lower part b above which it could be raised
to various heights by inserting within it at its corners sticks of
various lengths such as those shown at I. To change a set of four
shorter sticks for four longer ones, the panel d was first removed,
the part a was then raised to the desired height, then the four
shorter sticks which had stood vertically between the corner frame-
posts of 6 and the roof of a were removed and the four longer sticks
were inserted in their place. To permit of a culture dish containing
dung balls bearing Piloboli (A, c) being put into or taken out of

^ E. Coemans, " Monographic du genre Pilobolus, specialement etudie au point
de vue anatomique et physiologique," Mem cour. et des Sav. etrang. Acad. Roy. de
Belgique, T. XXX, 1861, p. 39.

2 W. B. Grove, " Monograph of the Pilobolidae," The Midland Naturalist,
Birmingham, England, 1884, p. 16.

3 A. H. R. BuUer, these Researches, Vol. I, 1909, p. 259.

* E. C Pringsheim and V. Czurda, " Phototropische und ballistische Probleme
bei Pilobolus," Jahrb.f. wiss. Bot., Bd. LXVI, 1927, p. 873.

64

RESEARCHES ON FUNGI

Fig

26. — Experimental chamber used for finding the greatest height of projection
of the sporangia of Pilobolus longipes and of P. Kleinii. A, a case constructed
of beaver-board and wood, the upper part of which, a, can be moved up or
down about the lower part, b, which it partly encloses and conceals. B, a panel
which has been removed from the base of A, so as to show the culture-dish
containing horse-dung balls beset with Pilobolus fruit-bodies. C, three
Pilobolus loyigipes fruit-bodies which were looking upwards on the dung-balls
in the dish at the base of A : in one fruit-body the long basal swelling at the
base of the stipe can be seen. In the roof of the case A is a large circular
aperture, h. D, a circular sheet of glass which can be set over the top of A so
as to cover the aperture and catch any projectiles which may strike it from
below. E, a piece of beaver-board with a central rectangular aperture h over
which can be set a rectangular sheet of glass. E can be used instead of D to
cover the aperture in the roof of A and catch projectiles. When E has been
set on the top of A, light is reflected vertically downwards through its sheet of
glass by means of a mirror. The vertical section F shows in detail how the
light is reflected : a, a window facing a clear sky ; 6, black paper ; c, a block of
wood to which is fixed (by lateral attachment not here shown) the mirror d
which reflects light, as shown by the arrows e e, through the sheet of glass, i,
at the top of the case vertically downwards to the Pilobolus fruit-bodies on the
dung in the dish ; /, a cardboard box open above and below (shown separately

THE PILOBOLUS GUN AND ITS PROJECTILE 65

the chamber, the lower part of the chamber was provided with a
removable panel shown at B.

To catch any Pilobolus projectiles that might be shot vertically
upwards, the hole h in the top of the chamber was covered either
with a circular sheet of glass (like that shown at D) or with a sheet
of beaver-board (like that shown at E) having a slotted rectangular
aperture in its centre into which could be inserted a sheet of glass
of the same size as a photographic half-plate. In the critical
experiments the cover E was always used in preference to D.

To ensure that bright light rays should pass vertically down-
wards through the sheet of glass on the top of the chamber, a
four-sided box G without top or bottom was set over the sheet of
glass as shown at/ in F, and then light coming from the sky through
a window a was reflected by means of a mirror d vertically down-
wards through the sheet of glass as indicated by the arrow e.

About 10 A.M. on the day on which an experiment was to be
made, the air of the experimental chamber was first moistened by
spraying it with water and by enclosing in the chamber dishes of
water and wet sheets of blotting paper. As soon as the air of the
chamber had become sufficiently laden with water-vapour, the
panel B was removed, a culture dish (A, c) was set in the middle of
the floor of the chamber, and then the panel B was put back in its
place. The Pilobolus guns growing on the dung-balls in the culture
dish were then illuminated solely by rays of light coming vertically
downwards to them through the sheet of glass at the top of the
chamber. Under these conditions the guns adjusted themselves
heliotropically and soon came to look vertically upwards in the
manner shown at C. Later in the morning the guns discharged
their sporangia vertically upwards toward the glass window at the
top of the chamber. Since every sporangium sticks to glass where
it comes into contact with it, it was always possible to tell whether

Fig. 2() — cont.

at (ji) ; g, the top of the case A ; h, the beaver-board cover containing in its
slot a slieet of glass i. H, a cros.s-section of the lower part of the case A seen
from aVjove when the upper part a lias been removed : a, beaver-board ; b, wood ;
c, air. In A the roof of the upper part a rests on four sticks of equal length
(c/. a in 1) which in turn rest on the four wooden corners cf the lower part b
(cf. b in H). To enable one to change four sticks of the length a (in I) to
four of the length b, and so raise the height of the case, one takes away the
panel d in A.
VOL. VI. F

66 RESEARCHES ON FUNGI

or not any sporangia had been shot up as high as the sheet of
glass or the beaver-board sheet holding the glass by simply examining
the under surfaces of these structures and noting whether or not
any sporangia had become attached there. As a rule, not more
than one experiment was made on any one day.

In a series of experiments in which the top of the experimental
chamber was raised by successive increments (usually of 6 inches each)
from 3 feet to 6 feet 6 inches, it was found that the sporangia of Pilo-
bolus Kleinii and of P. longipes were shot from the top of the dung-
baUs vertically upwards : in considerable numbers to a height of 4 feet ;
in smaller numbers to a height of 5 feet ; and in still smaller numbers
to a maximum height of 6 feet 0 • 5 inch. We may conclude, therefore,
that both P. Kleinii and P. longipes can shoot up their sporangia
to a maximum height greater than the average height of a man.

In one experiment with P. Kleinii, the total number of sporangia
which were shot upwards from the top of the dung-balls to a height
of 5 feet 6-5 inches exceeded one hundred and twenty. Of these
sporangia fifteen had struck and stuck to the plate of glass (Fig. 26,
F, i) and over one hundred had struck and stuck to the sheet of
beaver-board {h) which held the glass and covered much of the hole
in the roof of the chamber.

The total number of P. Kleinii sporangia which were shot up
to a height of 6 feet 0 • 5 inch in the course of three successive daily
experiments was twenty. All of the twenty sporangia were found
to be of the largest size ^ and, from the unusually large diameters
of the haloes of precipitated matter by which they were surrounded,
it was evident that each one of them had been carried from its
sporangiophore to the roof of the experimental chamber by a very
large drop of expelled cell-sap. That the largest Pilobolus projectiles
should be shot to the greatest height was to be expected from
dynamical considerations ; for, the initial velocities being equal,
the larger the projectile, the greater is its momentum when shot
away and the higher will it be carried upwards through the air.

From the equation :

v^ = 2gs

where v = the initial velocity, g = the acceleration due to gravity,

1 One of them had a diameter of 0-54 mm.

THEPILOBOLUS GUN AND ITS PROJECTILE 67

and s = the vertical height to which a projectile is discharged when
shot vertically upwards, neglecting the resistance offered by the air
it can be calculated that a Pilobolus projectile, if shot vertically
upwards to a maximum height of 6 feet, has an initial velocity of
19-6 feet per second.

.When the resistance offered by the air to the flight of a Pilobolus
projectile is taken into account, it is clear that the projectiles of
P. Kleinii and of P. longipes which were shot up to a height of
6 feet 0-5 inch must have had an initial velocity which exceeded
20 feet per second.

Employing the equation :

s = Igt^
where s = the vertical distance of rise or fall, g = the acceleration
due to gravity, and t = the time of rise or fall in seconds, neglecting
the resistance offered by the air it can be calculated that, when a body
is shot up from rest to a height of 6 feet so that it falls back again
to where it started from, the total time of rise and fall = 2t = 2 x
0-61 =1-22 seconds. Because of the resistance of the air, the
projectiles of P. Kleinii and of P. longipes which rise to a height of
6 feet and then tall to earth must take upwards of 1-22 seconds to
complete their movement.

The horizontal range of the guns of P. Kleinii and of P. longipes
was investigated by putting the culture dish in a special experi-
mental chamber 12 feet long and 3 feet wide built of beaver-board
about a window in the laboratory. The culture dish was placed
on the floor under the window and tilted to an angle of 45°-50°
from the horizontal and light from an upper window-pane was re-
flected to it at an angle of about 40°-45° from the vertical by means
of a vertical mirror hanging four feet above the floor. The chamber
was painted black inside and its air was moistened by spraying it
with water. The floor of the chamber was covered with sheets of
white paper to receive any sporangia which might fall on it. The
sporangiophores, in consequence of their heliotropism, became
directed toward the light at an angle of 40°-45° with the horizontal
before they began to discharge their sporangia.

In a series of experiments made in the chamber just described,
the maximum horizontal distance to which any sporangium was

68 RESEARCHES ON FUNGI

discharged was observed to be : for P. Kleinii, 8 feet 0 • 5 inch ;
and for P. lo7igipes, 8 feet 7-5 inches.

Theoretically, if the resistance due to the air be neglected, a
gun can shoot a projectile twice as far horizontally as it can vertically.
If, therefore, a Pilobolus gun could shoot a projectile in a vacuum
to a height of 6 feet, it would be able to shoot it under the same
conditions to a maximum horizontal distance of 12 feet.^ In actu-
ality, however, the air offers a considerable resistance to the flight
of a projectile less than 1 mm. in diameter ; and it is on account
of air-resistance that P. Kleinii and P. longipes, which shoot their
sporangia to a maximum height of about 6 feet, shoot their sporangia
to a maximum horizontal distance of only about 8 feet instead of
12 feet.2

Since the calculations just recorded were made, Pringsheim
and Czurda,3 from measurements made with the help of a pair of
rotating slotted discs, have calculated that the velocity of the pro-
jectiles of the Pilobolus used in their experiments, just after discharge,
is approximately 46 feet per second (14 metres per second). Using
the equation given on page 66, it can be calculated that, if
the air offered no resistance, the height to which a projectile having
an initial velocity of 46 feet per second would rise, if shot verti-
cally upwards, is 33 feet. Since my own observations show that
the strongest Pilobolus guns shoot their projectiles vertically upwards
to a height of only 6 feet, it is obvious that, assuming the correctness
of Pringsheim and Czurda's observations and calculations, the air
must offer a very considerable resistance to the flight of the Pilobolus
projectile.

The Structure of the Sporangiophore and Sporangium illustrated
by Pilobolus Kleinii and P. longipes. — The sporangiophore of P.
Kleinii, like that of other Piloboli, consists of a basal swelling (which
differs from that of P. longipes in being bulbous instead of much

1 Cf. these Researches, Vol. V, 1933, Fig. 163, p. 328.

^ The smaller the projectile, the more nearly equal to the vertical range does
the horizontal range of the gun become. It is for this reason that the vertical
and horizontal ranges of a hymenomycetous basidium, which shoots away four
tiny basidiospores, are approximately equal. Cf. these Researches, Vol. I, 1909,
p. 186 and Fig. 65.

3 E. G. Pringsheim and V. Czurda, loc. cit., pp. 879-882.

THE PILOBOLUS GUN AND ITS PROJECTILE 69

elongated), a cylindrical stipe, a large
pear-shaped subsporangial swelling, and a
columella which is surrounded and hidden
from external view by the sporangium
(Fig. 27). The sporangium is a black
discoid body filled with thousands of
orange-yellow oval spores.

A fruit-body of Pilobolus Kleinii, which
was of typical form, full-grown, and just
about to shoot away its sporangium, was
placed on a slide in water under a raised
cover-glass, and its upper part was care-
fully drawn with the camera lucida. With
the help of this drawing, a median ver-
tical section of the upper part of a typical
fruit-body was constructed semi-diagram-
matically, and the drawing which resulted
is reproduced in Fig. 28.

As shown in Fig. 27, the basal swell-
ing, the stipe, the subsporangial swelling,

Fig. 27. — Pilobolus Kleinii. Diagram of an optical
longitudinal section of a living fruit-body, togetlier
with part of the mycelium to which the fruit-
body is attached in the substratum. The sub-
stratum (dung, dung-agar, etc.), s. The my-
celium : a-6, a main hypha from which the fruit-
body originated ; c c, thinner secondary hyphae,
branches of the main hypha ; d, an apophysis
(swelling on the main hyplia), separated from the
fruit-body by a septum. The fruit-body consists
of a unicellular sporangiophore e, f, g, h and of a
sporangium ni, )i, o. The sporangiophore : e, the
basal swelling ; /, the cylindrical stipe ; (j, the
pyriform subsporangial swelling ; h, the columella ;
i, the great vacuole of the sporangiophore filled
with clear cell-sap ; _/, drops of clear mucilaginous
licjuid excreted from the sporangiophore and spor-
angium ; k, a red, carotin-containing, biconcave,
perforate, protoplasmic septum at the top of the
stipe ; /, a shallow reddish ring of protoplasm
at the top of the subsporangial swelling. The
sporangium : 7U, the black sporangial wall ; )i,
colourless jelly situated in the lower part of
the sporangium between the spore-mass and
the wall of the sporangium and columella ; o,
numerous oval orange-yellow spores. Magnifica-
tion, about 23.

c

o

o

70

RESEARCHES ON FUNGI

and the columella are four parts of a single cell. Their wall is ex-
ceedingly thin, so thin indeed that, even in so large an illustration
as Fig. 28, it has to be represented by a single thin black line. The
wall is Uned by a layer of protoplasm which encloses a huge vacuole
filled with perfectly clear cell-sap.

The protoplasm of the basal swelHng, subsporangial swelhng,
and columella is in general colourless and disposed in a layer

which is no thicker than, or
scarcely thicker than, the cell-
wall against which it presses ;
but, around the top of the
subsporangial swelling (Fig.
28, /) and around the top of
the stipe where this passes into

Fig. 28. — Pilobolus Kleinii. A median-
longitudinal section through the
upper part of a fruit-body, just
before the discharge of the pro-
jectile : a, the stipe ; 6, the subspor-
angial swelling ; and c, the spor-
angium. The sporangium is filled
with spores and covered with an
intensely black wall d which has
split open circumscissilely, and has
thus allowed a thick gelatinous inner
ring e, present only arovind the base
of the sporangium, to bulge out-
wards. The subsporangial swell-
ing, which is pyriform, has a thin
elastic wall lined by a layer of proto-
plasm which is very thin except
at/ where it is slightly thickened and
at g where it bulges inwards so as to
form a large biconcave septum which
is perforated in the centre. The
protoplasm at /is reddish and at g,
as indicated by the shading, very
red, especially on its upper side. The
subsporangial swelling is continued
above into a conical columella and
below into the cylindrical stipe. The
protoplasm of the stipe, swelling,
and columella contains one large
continuous vacuole h filled with clear
cell-sap. The broken line i passes
through the plane of abscission and
indicateswhere the Pilobolus projec-
tile, consisting of the sporangium
and columella, separates from its
attachment when the Pilobolus gun
is discharged. Magnification, 69.

THE PILOBOLUS GUN AND ITS PROJECTILE 71

the subsporangial swelling (Fig. 28, g), it is coloured red and heaped
up. The redness of these thicker masses of protoplasm, as Zopf ^
has pointed out, is due to their containing carotin held within
minute oil-drops.

The upper heap of protoplasm (Fig. 28, /) is relatively shallow
and pale red in colour. It is so situated that, when the Pilobolus
gun faces the light, it receives the full force of the incident rays.
It is probably photosensitive, and it is possible that its photochemical
reactions may serve to bring about chemical changes which increase
the osmotic pressure of the cell-sap or weaken the wall of the sub-
sporangial swelhng at the place {Riss-slelle) where it is to be ruptured
transversely when the projectile is shot away. Since Coemans
published his Monographic in 1861, it has been known that, when
maturing Pilobolus fruit-bodies are placed in the dark, the discharge
of their sporangia is delayed for several hours. ^ There must be
some photochemical mechanism by which the light of the sun is
employed in preparing the Pilobolus gun for discharge, and it is
possible that in the working of this mechanism the upper heap of
protoplasm plays an important part.

The lower heap of protopjasm, shortly before the discharge of
the sporangium, usually has the form of a biconcave lens with a
rounded vacuolar passage-way in its centre, as shown at g in Fig. 28.
The passage-way varies in width but is never absent, so that the
protoplasTn at the top of the stipe never forms a complete septum
and the vacuole of the subsporangial swelling is always continuous
with that of the stipe.

The lower heap of protoplasm contains numerous oil-drops,
with carotin dissolved in them, which, as indicated by shading at
g in Fig. 28, are : (1) very densely packed in its upper surface layer
which, in consequence, is coloured bright orange-red ; (2) are sparsely
distributed in its lower surface layer which, in consequence, is
coloured very pale orange-red ; and (3) are practically absent from
its inner core which, in consequence, is colourless.

^ W. Zopf, " Zur Kenntniss der Farbungsursachen niederer Organismen,
No. Ill, Phycomyceten-Farbungen," Beitrdge zur Physiologic und Morphologie
niederer Organismen, Leipzig, Heft II, 1892, pp. 3-12.

2 E. Coemans, "Monographic du genre Pilobolus," 1861, loc. cit., pp. 45-46.

72

RESEARCHES ON FUNGI

The function of the lower heap of protoplasm will be discussed
in the Section which treats of the heliotropism of the sporangiophore.

A sporangium which is still young and intact (Fig. 27) is covered
externally on its upper and outer sides by a thin black convex cell-
wall which is continuous with the cell-wall of the top of the sub-
sporangial swelUng, while below it is separated from the columella
by the wall of the columella, which is a thin, almost colourless,
convex septum. The wall of the sporangium is remarkable for three
special quaUties : (1) its toughness and persistence as compared
with the sporangium- wall of Mucor, which is diffluent ; (2) its intense

Fig. 29. — Pilobolus Kleinii. Dehiscence of the sporangium. A, a ripe sporangium
shortly before dehiscence ; it crowns the top of a subsporangial sweUing s and is
covered by a black wall w. B, the sporangium just after dehiscence : a layer
of jelly a lining the interior of the lower part and sides of the sporangial wall
has swollen and thereby caused the sporangium -wall to break transversely into
two parts, an upper cap-like parti) and a basal band c ; d, spores which can be
seen through the protruding jelly. C, what is left of B after the sporangium
has been stroked away under water with a needle : s, the subsporangial swelling ;
e, the columella ; and c, the band of sporangium-wall encircling the base of the
columella. Magnification, 66.

blackness ; and (3) its complete resistance to being wetted by water.
As we shall see later, all these quaUties are biologically significant.

The contents of a sporangium which is still young and intact
are two : (1) a mass of several thousand orange-yellow oval spores
packed closely together and embedded in a matrix that swells up
somewhat when brought into contact with water ; and (2) a sohd
transparent mass of jelly which is disposed in the form of a ring
around the base of the columella between the sporangium-wall
and the spores (Figs. 27 and 30, A).

The spores are dichroic : when mounted in water under a cover-
glass and viewed with the low-power objective of a microscope,
they are orange-yellow in transmitted light and greenish in reflected
Ught.

THE PILOBOLUS GUN AND ITS PROJECTILE ^z

Shortly before the sporangium is to be discharged, the gelatinous
ring absorbs water, swells up considerably, presses strongly against
the sporangium-wall, and thus causes the wall to split transversely
into two very unequal parts : ( 1 ) a relatively small lower part in
the form of a narrow band which remains attached to the columella
and the subsporangial swelUng (Figs. 29, B, c, and 30, B) ; and (2) a
relatively large upper part in the form of a free convex cap. The
gelatinous ring pushes the sides of this cap outwards and somewhat

Fig. 30. — Pilobolus Kleinii. Dehiscence and discharge of a sporangium, illustrated
semi-diagrammatically with median vertical sections. A, before dehiscence :
a, the top of a subsporangial swelling and b, the columella, both lined with a
thin layer of protoplasm and having the great central vacuole filled with
cell-sap ; c, the black sporangial wall ; d, the spores ; and e, a layer of jelly
between the spores and the wall of the sporangium and columella, now swelling
and about to cause the dehiscence of the sporangium. B, after dehiscence :
the layer of jelly e has swollen to such an extent that it has caused the
sporangium -wall to break transversely into two parts, an upper cap-like part
and a basal band (c/. Fig. 29, B) ; the jelly now protrudes through the gap in
the wall ; the broken transverse line at the top of the subsporangial swellmg
indicates where abscission will take place when the sporangium is discharged.
C, the sporangium just after it has been shot into the air : e, the protruding
jelly which will serve to attach the sporangium to some substratum ; s, part of
a globule of cell-sap which has been shot out of the subsporangial swelling and
is attached to the gelatinous, wettable, under side of the sporangium.
Magnification, 66.

upwards and thus itself becomes exposed to view. After the
sporangium- wall has thus been pushed outwards and broken, the
sporangium has the appearance shown in Figs. 28, 29, B, and 30, B.
The breaking of the sporangium-wall into two parts a short
distance above its base and the exposure of the gelatinous ring has
been referred to by van Tieghem and other systematists as a process
of dehiscence. Usually, when a sporangium dehisces, e.g. in Mucor,
Saprolegnia, and Ascobolus, its spores are immediately Hberated,
but this is not so in Pilobolus ; for, when the sporangium- wall of
Pilobolus breaks, the spores are prevented from escaping from the
sporangium by the gelatinous ring which fills the gap between the

74 RESEARCHES ON FUNGI

edge of the wall and the columella (Fig. 30, B and C). The real
significance of dehiscence in Pilobolus Ues in this : that, whereas
it does not permit of the escape of the spores from the sporangium,
it leads to the exposure of the gelatinous ring which, as wie shall see
later, has the function of attaching the sporangium with its enclosed
spores to the herbage on which herbivorous animals feed. The
escape of the spores from a Pilobolus sporangium does not take place
when the sporangium dehisces but only when the sporangium,
having been eaten with grass by horses or cows, etc., is moistened
and compressed in an aUmentary canal. It is of interest to note
that the swelhng up and exposure of the gelatinous ring on the
outside of the sporangium is beautifully timed, for it takes place
only a few minutes before the sporangium is discharged and the
ring is to function in the service of spore-dispersion.

It was observed that, when a pane of glass is set just in front of
a large number of fruit-bodies of Pilobolus longipes, so that the
sporangia are shot against it, the force of the impact is so great that
sometimes a sporangium is sUghtly shattered to the extent that
(1) a few spores may be forced out of the sporangium owing to the
displacement of the gelatinous ring and (2) fragments of the peri-
pheral less darkly-coloured portion of the black sporangial wall may
be broken away from the main mass of the wall. The escaped
spores and the broken wall-fragments can then be seen lying in
the drop of cell-sap which forms a halo around the sporangium
(c/. Fig. 33). Under natural conditions in the open, the sporangia
are shot not against substances as hard and inelastic as glass but on
to herbage and, normally, after they have landed they contain their
full complement of spores. There is every reason to suppose that,
in pastures and woods, the partial rupture of a Pilobolus sporangium
due to impact on landing occurs either not at all or only as a rare

accident.

The number of spores contained in the sporangium of Pilobolus
oedipus (Cohn's P. crystallinus) was estimated by Cohn ^ to be
15,000-30,000, and Coemans ^ remarked that this estimate did not

1 Ferdinand Cohn, " Die Entwicklungsgeschichte des Pilobolus crystallinus,"
Nova Acta Acad. Caes. Leop., Bd. XXIII, 1851, p. 513.

2 E. Coemans, " Monographic du genre Pilobolus," 1861, loc. cit., p. 25.

THE PILOBOLUS GUN AND ITS PROJECTILE 75

appear to him to be too large. I have estimated the number of
spores in a very large sporangium of P. Kleinii, which was 0- 54 mm.
in diameter and had been shot up to a height of 6 feet 0* 5 inch, as
follows.

The sporangium was mounted in water and the cover-glass was
rubbed over it in such a way that the spores were arranged approxi-
mately in a layer two spores thick. Then the area occupied by this

Fig. 31. — Pilobolus longipes. Two fruit-bodies from which
the sporangium has been pulled off under water, so as
to expose the columella. The columella crowns thesub-
sporangial swelling and has a central peak. One of the
black sporangia is seen to the right below. Magnifi-
cation, 51.

spore-layer was measured and the upper spores occupying one-four-
hundredth of one square mm. were drawn and counted. With the
help of these data it was estimated that the sporangium had
contained approximately 90,000 spores. Smaller sporangia oi
P. Kleinii probably contain not more than half this number. In
P. Kleinii, therefore, the number of spores contained within the
sporangium varies with the size of the sporangium from about
30,000 to about 90,000.

A sporangium which has dehisced and has its gelatinous ring
protruding around its base can be stroked away from the sporangio-

76

RESEARCHES ON FUNGI

phore under water with the help of a needle without much difficulty.
After such an operation has been effected, the columella, while still
attached to the subsporangial swelling, becomes exposed to view as
shown in Figs. 29, C, and 31. The narrow band of sporangium-wall,
left attached to the columella and subsporangial swelhng and sur-
rounding the base of the columella when the sporangium dehisced,
can then be clearly seen (Fig. 29, C, c). It has a dark appearance
owing to its being covered externally with numerous minute

Fig. .32. — Pilobolus Kleinii. Level of abscission of the sporangium indicated by a
broken line. A, the top of a subsporangial swelling crowned by a ripe sporangium
which has dehisced ; the sporangium -wall has split transversely into a
convex upper portion b and a lower band c, and in the gap one can observe the
jelly a and the spores d. B, like A, but the sporangium has been stroked off
imder water, leaving behind the columella e and the basal band of the sporangium-
wall c ; s, the subsporangial swelling. C, like A, but with the sporangium shown
separate from the subsporangial swelling ; the separation has been effected at
the level of abscission ; the drawing serves to indicate that the basal band of
the sporangium -wall remains attached to the sporangium as a whole when this
is shot away. Magnification, 66.

particles which, as shown by microchemical reactions, are crystals
of calcium oxalate. The particles extend over the surface of the
subsporangial swelling below the band of the sporangium- wall, but
are less closely packed and less conspicuous there.

At the moment when a sporangium is discharged from the
sporangiophore, the wall of the subsporangial swelhng just under
the junction of the band of sporangium-wall and the columella
suddenly spHts transversely, so that the sporangium and the
columella are shot away together. The level of abscission of the
sporangium is indicated by a broken hne in Figs. 28 (p. 70), 30, B
(p. 73), and 32. A large drop of cell-sap remains attached to the
gelatinous ring and the columella as the projectile travels through

THE PILOBOLUS GUN AND ITS PROJECTILE j^

the air {vide infra), and the projectile, after landing, has the appear-
ance shown in Figs. 33-35,

An upper view of two projectiles which have settled on glass is

Fig. 33. — Pilobolus longipes. Pliotoinicrograph of the upper side of a discharged
sporangium and of the drop of cell-sap (now dried) which accompanied it. The
projectile struck and stuck to a sheet of glass. No. 1, the precipitate of the
cell-sap, in part crystalline ; No. 2, a broad ring-layer of jelly in contact with
the glass ; No. 3, the peripheral part of the sporangium-wall which is now
radially split and flattened out above the ring of jelly, isolated bits of it can be
seen at the periphery of the drop to the left ; No. 4, the convex, very black,
main portion of the sporangium-wall covering many thousands of spores ;
No. 5, two of four spores which were forced out of the sporangium as this struck
the glass. Magnification, 51.

shown in Figs. 33 and 34. Here one can distinguish : No. 1, a
precipitate of amorphous granules and small crystals produced by

78

RESEARCHES ON FUNGI

the drying of the cell-sap ; No. 2, the gelatinous ring which causes
the sporangium to adhere tightly to its substratum ; No. 3, the
paler peripheral part of the cap-like portion of the sporangium-wall,
now flattened, radially spUt, and in part fragmented ; No. 4, the
intensely black convex main part of the cap-like portion of the

Fig. 34. — Piloholus longipes. Photomicrograph of the upper side
of another discharged sporangium and of the drop of cell-sap
(now dried) which accompanied it. No. 1, the precipitate of
the cell-sap ; No. 2, a broad clear ring-layer of jelly in contact
with the glass ; No. 3, the peripheral part of the sporangium -
wall, now flattened and broken and overlying the jelly ; No. 4,
the convex, very black, main portion of the sporangium-wall
covering many thousands of spores ; No. 5, a few isolated spores
lying under the jelly ; they were forced out of the sporangium
when this struck the glass. Magnification, 51.

sporangium- wall, which covers and hides many thousands of spores ;
and No. 5, a few spores which, owing to the violence with which the
projectile impinged on a rigid piece of glass, were pressed out of the
sporangium between the wall and the gelatinous ring.

A lower view of a projectile obtained through a cover-glass to
which the projectile is attached is shown in Fig. 35. Here one can
distinguish : No. 1, a precipitate of amorphous granules and large
branched crystals produced by the drying-up of the cell-sap ; No. 2,
the gelatinous ring, the outer hmit of which is more easily seen here

THE PILOBOLUS GUN AND ITS PROJECTILE 79

than in Figs. 33 and 34 ; No. 3, the peripheral paler part of the cap-
like portion of the sporangium-wall, now flattened, more or less
radially spht and in part fragmented ; No. 4, the black tuck of the

Fig. 35. — Pilobolus longipes.. Photomicrograph ut Lh« under
side of a discharged sporangium and of the drop of cell-
sap (now dried) which accompanied it, taken through
a cover-glass to which the sporangium was attached.
No. 1, dried cell-sap containing long branched crystals ;
No. 2, a broad ring-layer of jelly attached to the glass
and covering a few isolated spores. No. 7, which were
forced out of the sporangium when this struck the glass ;
No. 3, the flattened peripheral part of the sporangivmi-
wall, seen through the jelly, a piece of which, No. 8, broke
away as the sporangium hit the glass ; No. 4, the black
flattened tuck of the sporangium-wall obscuring spores
from view (c/. Fig. 41, gr) ; No. 5, the main mass of the
spores, seen through the inner zone of the ring of jelly ;
No. 6, the columella flattened down on to the glass, its
peripheral band No. 9 (part of the sporangium-wall)
now forming a pentagon. Magnification, 51.

sporangium-wall (c/. Fig. 41, g, p. 85), seen through the inner zone
of the gelatinous ring ; No. 5, thousands of spores massed together ;
No. 6, the columella pressed down on to the glass, with its periphery
now pentagonal in form ; No. 7, a few spores which, owing to the
violence with which the projectile impinged on the cover-glass,
were pressed out of the sporangium so that they lie between the

8o RESEARCHES ON FUNGI

gelatinous ring and the surface of the cover-glass ; No. 8, a fragment
of the peripheral paler part of the cap-like portion of the sporangium-
wall (No. 3) ; and No. 9, a narrow band of sporangium-wall attached
to the rim of the columella.

The somewhat brittle, paler, radiately split, outer portion of the
sporangial wall of a discharged sporangium (No. 3 in Figs. 33, 34,
and 35) may be conveniently referred to as the fringe of the spor-
angium. It is to be noted in a dried-up discharged sporangium
that the pale fringe rests directly on the film of jelly and that the

Fig. 36. — Pilobolus longipes. Photomicrograph of a discharged spor-
angium which has been rubbed laterally in water under a cover-
glass : w, a mass of orange-red spores pressed out from under the
black sporangium-wall ; s, single spores ; in the centre the isolated
cap -shaped columella consisting of apeak a, a brim h, and a marginal
band (part of the sporangial wall) c. Magnification, 105.

covering of the spores and their protection from hght-rays, etc., is
restricted to that part of the sporangium-wall which is very tough
and intenselv black.

Cohn,^ in 1851, thought that, when a Pilobolus gun is discharged,
the wall of the columella does not travel with the sporangium but
remains behind upon the top of the subsporangial swelling ; but
this view was shown to be erroneous by Coemans ^ in 1861. That,
normally, the columella remains attached to the sporangium when
this is discharged can be readily proved by breaking up a dis-

1 Ferdinand Cohn, " Die Entwicklungsgescliichte des Pilobolus crj^stallinus,"
Nova Acta Cues. Leop., Bd. XXIII, 1851, pp. 516-517, Taf. LII, Figs. 12, 13.

2 E. Coemans, loc. cit., pp. 42-43, Plate II, Fig. 8.

THE PILOBOLUS GUN AND ITS PROJECTILE 8i

charged sporangium and examining the fragments under the
microscope. If one mounts a newly discharged moist sporangium
in water on a slide and then presses on the cover-glass so as to give
it a lateral movement, one can often separate the sporangium into
its component parts, namely : (1) the orange-yellow spores ; (2) the
intensely black, free, convex, cap-like portion of the sporangium-
wall ; (3) the annular mass of jelly ; and (4) the obtusely conical
wall of the columella, to the
rim of which is attached the
narrow band of sporangium-
wall (covered with fine par-
ticles) which separated from
the cap-like portion of the
sporangium-w^aU when the
wall, owing to pressure from
the annular mass of jelly,
was split transversely into
two parts. Photomicrographs
of columellae isolated in the
manner just described are
shown in Figs. 36 and 37.

An examination of isolated
columellae in side view, like
that shown in Fig. 36, revealed
the fact that each columella

Fig.

37. — Pilobolus longipes. Photomicro-
graph of a columella and some isolated
spores obtained bj' rubbing a discharged
sporangium laterally in water under a
cover-glass. The columella is cap-
shaped : a, its central peak, here
flattened irregularly ; b, its brim ; and
c, its marginal band (part of the spor-
angialwall). Isolated spores, d. Mag-
nification, 105.

is shaped like a cap and that,

whereas the wall of the brim (6) is relatively thin, the wall of the
peak (a) is thick and apparently gelatinously swollen. There can
be but little doubt that, as a discharged projectile dries up and
the columella comes to press against the substratum, the wall of
the columella assists the annular mass of jelly in causing the spor-
angium to become adherent to the substratum.

That the mass of jelly produced within a sporangium is truly in
the form of a hollow ring was established by dissection carried out
as follows. A ripe fruit-body of Pilobolus longipes was submerged in
a drop of water, and its sporangium was pulled away from the colu-
mella with the help of a needle. A cover-glass was then placed over

VOL. VI.

82

RESEARCHES ON FUNGI

the sporangium and moved laterally so as to disperse the spores in
the water. The cover-glass was now removed. Then pieces of the
sporangial wall were lifted from the jelly and the jelly was moved
about until it was free from spores. From three of the sporangia
treated in this way as many complete rings of jelly were obtained
(Fig. 38). It is clear that in a sporangium the jelly does not extend
over the top of the columella but is annular in form.

At the moment a sporangium with an attached drop lands upon

a grass-leaf or other object, its ring
of jelly is fully distended, the
cavity of the cone-shaped columella
is filled with cell-sap, and the con-
tents of the sporangium (spores
and substance lying between them)
are very watery. Immediately there-
after, the drop and the sporangium
begin to lose water by evaporation
and, in the course of a few minutes,
they become air-dried. From the
flattened drop there are deposited
on the substratum amorphous par-
ticles and branched crystals, which
form a halo around the sporangium
(Figs. 33-35, pp. 77-79). As the
sporangium dries, the gelatinous ring
contracts to a very thin hard flat film (Fig. 35, No. 2, and Fig. 41,6)
which sticks the sporangium tightly to the surface of the object on
which it lies. As the gelatinous ring dries and flattens, the pale
radiately-split fringe of the sporangial wall settles down on the top
of the jelly and thus comes to lie parallel to the surface of the sub-
stratum (Figs. 39 and 41). The cell-sap in the cavity of the colu-
mella is bounded by the conical wall of the columella and the surface
of the substratum, and it is free from air-bubbles As this ceU-sap
evaporates, the columella cavity (into which air cannot enter)
necessarily becomes more and more contracted, with the result that
the columella becomes compressed both laterally and from above
downwards. The lateral compression results in the free edge of the

Fig.

38. — Pilobolus longipes. A
gelatinous ring isolated from a
sporangium that had been
stroked away from the spor-
angiophore and columella under
water. Magnification, 75.

THE PILOBOLUS GUN AND ITS PROJECTILE 83

columella becoming more or less drawn together or becoming
polygonal (Fig. 35), while the compression from above downwards
causes the more or less swollen conical wall of the columella to
flatten and to come directly into contact with the surface of the
substratum. The columella-wall, when dry, adheres to the sub-
stratum (Fig. 41, c), and thus to some extent assists the gelatinous
ring in attaching the sporangium to a grass-leaf or other object.

Fig. 39. — Pilobolus Klein ii. Discharged sporangia, from a pure culture, attached
to a sheet of glass, photographed by reflected light. To show the characteristic
rounded depressions (dimples) which were developed in the sporangium -wall
as the sporangia dried up. Magnification, 60.

The sporangium as a whole, as it dries after discharge, contracts
considerably, perhaps to one-quarter of its original volume. This
contraction is due in part to the shrinkage and disappearance of the
large central columella cavity, as already described, and in part to
the loss of water from the spores and from the substance lying
between them. Loss of water from the interior of the sporangium
results in : (1) a flattening of a lower zone of the originally convex
part of the sporangium-wall, so that this zone becomes added to
the fringe {vide Figs. 33 and 34, between Nos. 3 and 4, and Fig. 41,

84

RESEARCHES ON FUNGI

between / and g) ; (2) the formation of a tuck in the wall beneath
the edge of the convex part of the sporangium ; (3) the formation of
depressions or dimples in the upper part of the sporangium-wall
(Figs. 39 and 40) ; and (4) the contraction of the spore-mass, the
adherence of the spores to one another, and a change of the shape of
each spore from rounded to polygonal (Fig. 41).

The existence of a tuck in the sporangium-wall of a dried
sporangium (Fig. 41, gr) has not been previously recorded by any
other observer, and it was discovered only as a result of a detailed

Fig. 40. — Pilobolus longipes. Discharged sporangia, from a pure culture, attached
to a sheet of glass, photographed by reflected light. To show the characteristic
wrinkles developed in the sporangium-wall as the sporangia dried up, Mag-
nification, 60.

investigation on dried and drying sporangia. If a sporangium which
has dried on a glass surface is pried loose from its substratum, the
fringe of the sporangial wall and the gelatinous ring are left behind
on the glass, but the wall- tuck remains attached to the under side
of the sporangium. The tuck extends centripetally to a distance of
about one-fifth to one-quarter the radius of the sporangium as a
whole. A sporangium was allowed to land on a cover-glass and dry
there, and then the cover-glass, with the sporangium beneath, was
set on a drop of sulphuric acid on a glass slide (c/. Fig. 35). With
the microscope the action of the sulphuric acid could be followed.
The acid dissolved away the sporangium- wall progressively from the
free edge inwards, until the whole wall disappeared leaving the mass
of spores behind. The fringe of the wall disappeared first, and soon.

THE PILOBOLUS GUN AND ITS PROJECTILE 85

as the acid made the re-
maining part of the wall
more and more translucent,
the tuck of the wall under
the edge of the convex
sporangium became clearly
revealed.

The depressions or dim-
ples formed in the upper
black portion of the sporan-
gial wall as the sporangium
dries up vary in number
with the size of the sporan-
gium and in pattern with
the species. As a rule, the
larger the sporangium, the
more numerous are the de-
pressions. The difference
between the pattern of the
depressions on the sporangia
of P. Kleinii and that on
the sporangia of P. longipes
can be readily reaUsed by
comparing Fig. 39 with
Fig. 40 : the depressions of
P. Kleinii are rounded,
those of P. longipes irregu-
lar and somewhat gyrose.

As a fruit-body from
which the sporangium has
been stroked off (Fig. 31,
p. 75) loses its turgidity, the
wall of the subsporangial
swelling just beneath the
columella contracts and
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RESEARCHES ON FUNGI

Fig. 42. — Pilobolus Kleinii. The excretion and drying of drops. A, the upper
part of a young fruit-body : a, tlie sporangium ; 6, the subsporangial swelling
beginning to expand. Numerous small drops have been excreted by the
sporangium, and two very large drops have appeared at the junction of the
sporangium and the subsporangial swelling. B, another young fruit-body,
similar to A, but seen from above. The drops attached at the junction of the
sporangium and the young subsjjorangial swelling are of the maximum size.
C, amaturefruit-bodyshortly before the discharge of the sporangium. The drops
on the sporangium a and the upper part of the subsporangial swelling b are drying
up and in doing so are becoming irregular in form, thus revealing the fact that they
contain a gelatinous substance. The excretion of drops has been especially active
in the lower part of the subsporangial swelling, but the largest drops are on the
stipe, c. Drawings made with the help of a camera lucida. Magnification, 90.

THE PILOBOLUS GUN AND ITS PROJECTILE 87

does not. This indicates that the upper part of the wall of the
subsporangial swelling, just under what is normally the line of
rupture when the sporangium is shot away, is highly elastic whereas
the wall of the columella is not. It may be added that with iodine
the thickened wall of the subsporangial swelling takes on a much
deeper red colour than the relatively thin wall of the columella.

The globular watery drops which are formed in large numbers
on the sporangium and sporangiophores are well shown in Boudier's
drawing reproduced in Fig. 12 (p. 23), and they are also shown
freshly excreted and uncontracted in the diagrammatic Fig. 27
(p. 69). These drops, as Knoll ^ discovered, resemble those on the
pileal hairs of Coprinus ephemerus and Psathyrella disseminata, etc.,
and on the gills of various Hymenomycetes, in that they contain a

Fig. 43. — Pilobolus longipes. From left to right, diagrammatic representa-
tion of two drop.s excreted from a sporangium, and of successive stages
in their d rying up. As the drops dry, they shrink in size, become irregular
in form (owing to their gelatinous contents), and finally become as black
as the sporangium-wall. Magnification, 100.

pellucid colloidal substance or slime — readily soluble in water but
insoluble in alcohol— which gives to the surface of the drops, as
these dry up, an irregularly wrinkled appearance. ^ With the help
of the microscope I myself have often observed the wrinkling of
the drops of Pilobolus as they lose water by evaporation (Figs. 42, C,
and 43).

The drops on the sporangium and upper part of the subsporangial
swelling usually dry up, leaving in their places tiny irregular gela-
tinous masses, before the sporangium is discharged (Fig. 42, C),
Doubtless, whilst they exist as large watery spheres, they interfere
to some extent with the course of the rays of light entering the
subsporangial swelling. Their early disappearance must therefore
be of advantage in that it enables the sporangiophore to direct the

^ F. Knoll, " Untersuchungen iiber den Bau und die Funktion der Cystiden
und verwandter Organe," Jahrb.f. wiss. Bot., Bd. L, 1912, pp. 453-501.

^ For drops. on the pileal hairs of Coprinus curtus and their mode of drying
vide these Researches, Vol. IV, 1931, Fig. 12, p. 18.

88

RESEARCHES ON FUNGI

, <^Va_tj^tjLi_t_L-LDjj_|Jl_Q_ij_l J > ■ fi ■ ■ .

4

sporangium with greater accuracy toward the source of brightest
light.

The drops excreted by the sporangium differ from those excreted
by the sporangiophore in that as they dry up they become brown
and ultimately as black as the subjacent sporangial wall (Fig. 43).

This fact, which does not seem to
have been previously recorded,
lends support to Knoll's view
that the mucilage in the drops
excreted by the pileal hairs and
cystidia of Hymenomycetes,
the fruit-bodies of Pilobolus, etc.,
is produced as a result of local
mucilaginisation of the cell-wall.
Knoll 1 supposed that the
drops are forced out of the
sporangiophore of Pilobolus
chiefly by turgor pressure, and
he suggested that their excretion
is a result of the operation of a
mechanism of the nature of a
valve which serves to prevent
the continual rise of the turgor
pressure and thereby to prevent
a premature discharge of the
sporangium. It may well be
that the excretion of drops is
concerned with the regulation of
the water and salt content and
the pressure equilibrium of the sporangiophore ; but that it is
specially concerned with preventing the premature discharge of the
sporangium seems very doubtful, for the drops begin to be excreted
on the naked stipe of the very young fruit-body long before the
sporangium or subsporangial swelling has been formed and some
twenty hours before the sporangium is to be discharged (Fig. 12, a
and b, p. 23). Moreover, similar drops are commonly excreted

1 F. Knoll, loc. cit., p. 489.

D

f ■ ■

• « •

• • • Q

Fig. 44. — Pilobolus longipes. Crystals
of calcium oxalate on : A, a piece
of the fringe of the wall of a dis-
charged sporangium, seen in face
view ; B, the black part of the spor-
angium-wall, seen in tangential
view ; C and D, the wall of the
subsporangial swelling and of the
stipe respectively, seen in face view.
Magnification, 1130.

THE PILOBOLUS GUN AND ITS PROJECTILE

89

from the sporangiophores of other Mucorineae which do not dis-
charge their sporangia, e.g. Mucor Mucedo ^ and Sporodinia grandis.
The wall of a Pilobolus fruit-body bears numerous very minute
crystals of calcium oxalate. In P. longipes these crystals are
arranged : most densely on the sporangium- wall, less densely on
the wall of the subsporangial swelling, and far less densely on the
wall of the stipe (Fig. 44, A, C, and D). They can be most readily
observed on the translucent
fringe (c/. Fig. 33, No. 3,
p. 77) of a discharged spor-
angium mounted in chloral
hydrate. On the wall of a
piece of fringe, in face view
(Fig. 44, A), the crystals can
be seen to be of two sizes :
(1) less numerous larger
crystals of various shapes,
and (2) far more numerous
smaller columnar crystals.
Some of these crystals are
shown in profile in Fig. 44,
B. The larger crystals are
2-3 [J, high and the smaller
ones about 1 y. high. Van
Tieghem, Brefeld, Zopf , and
others, in their somewhat
diagrammatic drawings of
Pilobolus sporangia (Figs. 100, 101, 106, 107, and 110, pp. 203-219),
have represented the crystals projecting from the sporangium-wall
as being much longer than they actually are. It may well be that
the unwettability of the sporangium- wall is due to the numerous,
closely-set crystals imprisoning air and thus preventing water
from coming into contact with the wall's surface (Fig. 45, A). It
is also probable that the drops excreted from the sporangium,

1 O. Brefeld, Untersuchungen uber Pike, Heft I, Leipzig, 1872, p. 12. Brefeld
remarks that the numerous drops excreted from the surface of the young sporangio-
phore of Mucor Mucedo have a weak acid reaction.

Fig. 45. — Pilobolus longipes. Water and the
cell-wall. A, diagram showing : a, the
black sporangial wall ; b, crystals of
calcium oxalate protruding from the wall ;
and c, water in which the sporangium has
been immersed. Owing to the presence of
the crystals and the surface tension of the
.water, it is supposed, as here represented,
that a layer of air is held between the water
and the cell -wall so that the latter cannot
readily be wetted. B, diagram .showing :
d, the wall of a subsporangial swelling ; e,
crystals protruding from the wall ; and
/, a drop of water, still very small, which
is being excreted. The drop has a very
small base and it is supposed that it touches
the crystals in the manner shown. Mag-
nification, about 2250.

go RESEARCHES ON FUNGI

subsporangial swelling, and stipe, as they grow larger, come to
touch the crystals in the manner shown in Fig. 45, B.

The Two Functions of the Subsporang-ial Swelling. — The sub-
sporangial swelling of the Pilobolus gun functions in two entirely
different ways : (!) as an ocellus which receives the heliotropic
stimulus which causes the stipe to direct the free end of the gun
toward the source of the brightest light ; and (2) as part of a squirting
apparatus which, by violently expelling cell-sap, shoots away the
sporangium from the sporangiophore.

The squirting function of the subsporangial swelling was recog-
nised by Link ^ as long ago as 1809, but the ocellus function
remained unknown until I ^ called attention to it in a brief paper
published in 1921. In what follows these functions will be treated
of in detail.

The Heliotropism of the Sporangiophore with Special Reference
to the Ocellus Function of the Subsporangial Swelling. — When a
Pilobolus fruit-body is exposed to unilateral light, the upper part
of its stipe just beneath the subsporangial swelling makes a positively
heliotropic curvature, with the result that, within about an hour,
the free end of the fruit-body, i.e. the subsporangial swelling and
sporangium, comes to point in the direction of the brightest incident
rays of light. The heliotropic reaction of the stipe, as we shall
see, is controlled by the subsporangial swelling which, in its mode
of refracting and collecting light, acts as a lens.

One morning in February, 1919, on looking at a large number of
fruit-bodies of Pilokolus longipes which were growing on horse dung
in a culture chamber, I observed that, although they all pointed
toward a distant window so that their free ends were parallel to the
incident rays of light (c/. Fig. 46), the top of each stipe glowed with
a reddish light. It at once became obvious in respect to each
fruit-body : (1) that, but for the existence of the subsporangial
swelling, the top of the stipe would be in the shadow of the black
sporangium directly in front of it ; and (2) that the glow must be

^ H. F. Link, " Observationes in Ordines plantarum naturales," Magaz. d. Ges.
naturf. Freunde, Berlin, Bd. Ill, 1809, p. 32.

2 A. H. R. BuUer, " Upon the Ocellus Function of the Subsporangial Swelling
of Pilobolus," Trans. Brit. Myc. Soc., Vol. VII, 1921, pp. 61-64, no illustrations.

THE PII.OBOLUS GUN AND ITS PROJECTILE 91

Fig. 46.- — A median longitudinal
section through the upper part
of a fruit-body of Pilobolus
Kleinii, just before the dis-
charge of the projectile. The
gun is shown directed toward
the source of the brightest
light, in which position it is,
heliotropically (or photo-
chemically), in a condition of
physiological equilibrium.

The sporangium is filled
with spores and covered with
an outer intensely black wall o
which is now broken below,
thus allowing a thick gelati-
nous inner ring, g, which is
only present around the base of
the sporangium, to bulge out-
wards. The subsporangial
swelling, which is pear-shaped,
has a thin elastic wall lined by
a layer of protoplasm which is
very thin everywhere except
at r, where it is slightly
thickened, and at p, where it
bulges inwards so as to form a
large biconcave septuni which
is perforated in the centre. The
protoplasm at r is reddish and
at p, as indicated by the
shading, very red, especially
on its upper side where it
receives the light rays. The
subsporangial swelling is con-
tinued above into a conical
columella c, and below into the
upper part of the cylindrical
stipe or shaft sh. The proto-
plasm of the stipe, swelling, and
columella contains one large
continuous vacuole filled with
clear cell-sap. The broken line
a passes through the plane of
abscission and indicates where
the Pilobolus projectile, con-
sisting of the sporangium and
the columella, separates from
its attachment when the Pilo-
bolus gun is discharged.

Twenty-one parallel rays
of light are shown diagram -

A.aR.B.

matically, by means of arrows, striking the fruit-body head-on in a direction
parallel to the longitudinal axis of the subsporangial swelling. Nine of these rays
strike the black cell-wall of the sporangium, which they cannot penetrate. The
other twelve rays strike the vipper surface of the subsporangial swelling and are
there refracted through the wall into the interior of the swelling and, as shown
by the arrows, converge upon the red perforated protoplasmic septum. The
septum, like the retina of an ocellus, comes to be lit up with a spot of light,
in consequence of which it gives out a red glow which in living fruit-bodies can
be seen with the naked eye. s, s, s are parts of the subsporangial swelling
which are not pierced by any direct rays of light and are therefore in the shade.
Some of the light of all of the rays Nos. 1-6 is reflected at the surface of the wall
of the subsporangial swelling ; and, in passing in succession from ray No. 1 to
No. 6, more and more light is reflected and less and less refracted. The size of
every part is shown by the scale. Magnification, (59.

92

RESEARCHES ON FUNGI

due to light refracted
through the subsporangial
swelling and focussed on
the mass of red proto-
plasm heaped up in the
stipe just where the stipe
joins the swelling (Fig.
46, p). The discovery
that the subsporangial
swelling acts as a lens and
that, when the fruit-body
is in heliotropic equili-
brium, it focusses its light
on the mass of red proto-
plasm at its base formed
the basis of all my
further studies on the
heliotropism of Pilobolus.
The lens action of the
subsporangial swelUng
was further investigated
by means of construction
diagrams which, as a
result of precise mathe-
matical calculations, show
how the swelHng refracts
light (1) when its axis is
parallel to the direction
of the incident rays of

Fig. 47. — A median longitudinal section through the upper part of a fruit-body of
Pilobolus Kleinii, just before the discharge of the projectile. The gun is shown
directed not toward the sourc§ of light but at an angle of 19° thereto, in which
position it is not, heliotropically (or photochemically), in a condition of
physiological equilibrium.

The section is exactly the same as that shown in Fig. 46 and there fully
described. Again we have : the sporangium filled with spores and covered
by an outer black cell-wall o, now broken and allowing an inner basally-situated
thick gelatinous ring i to bulge outwards ; the subsporangial swelling,
capped by the columella c and passing below into the stipe, its thin cell-wall
covered by a layer of protoplasm which is everywhere thin except at r where

THEPILOBOLUS GUN AND ITS PROJECTILE 93

light (Fig. 46) and (2) when its axis is inchned to the direction of the
incident rays at an angle of 19° (Fig. 47).

In constructing Figs. 46 and 47, an outline of a typical fruit-
body of Pilobolus Kleinii was first very carefully drawn with the
camera lucida. Then the parallel hues Nos. 1, 2, 3, 4, etc., were
added to represent the paths of a few rays of light directed toward
the fruit-body. Each ray was now treated separately : its angle
of incidence at the surface of the subsporangial swelling or stipe
was measured with instruments ; its angle of refraction into the
swelling or stipe was then calculated ; and, finally, the angle of
refraction being known, a line representing the path of the ray
through the interior of the subsporangial swelling or stipe was
drawn. In calculating the paths of the refracted rays of light, the
following refractive indices were used : air into cell-sap, ^ 1 • 34 ; air
into cell- wall and protoplasm taken together,^ 1 • 5 ; cell- wall and

Fig. 47 — cotit.

it is somewhat thickened and at p where it bulges inwards to form a large
biconcave perforate septum containing red particles massed especially near its
\]pper surface : the stipe ; the large clear vacuole enclosed by the protoplasm
of the stipe, subsporangial swelling, and columella ; and the abscission line a.

Twenty-three parallel rays of light are shown diagrammatically, by means of
arrows, all inclined at an angle of 19" to the axis of the subsporangial swelling.
Of these rays : eight strike the black cell-wall of the sporangium, which they
cannot penetrate ; eight strike the right-hand wall of the subsporangial
swelling and are there refracted through the wall into the interior of the swelling,
so that, as shown by the arrows, they converge to form a spot of light on the
left-hand wall at st ; and six strike the right-hand wall of the stipe and are there
refracted as shown by the arrows, s, s, s are areas in the subsporangial swelling
which are not pierced by any of the rays of light and which therefore are in
the shade. The concentration of the rays of light at the spot s< presumably
gives a photochemical stimulus to the protoplasm, which stimulus is conducted
down to m, the motor region of the stipe. The stipe grows faster on the side
TO than on the opposite side, with the result that the subsporangial swelling
and the sporangium are turned about the top of the stipe through an angle of
19-", i.e. until their axis becomes parallel to the direction of the incident rays
of light. As the subsporangial swelling and sporangium are turned, the spot
of light st descends to the base of the swelling until, finally, it comes to rest
symmetrically upon the red perforate protoplasmic septum, as shown in Fig. 46.
Heliotropically (or photochemically) the position of stable physiological equi-
librium has then been reached and no more turning takes place. The part of
the stipe below the motor region r«, at and below u, does not alter its position
whilst the motor region is making its curvature. The scale serves to indicate
the size of each part. Magnification, 69.

1 The cell-sap was regarded as pure water. The refractive index from air to
water is 1-34.

2 The refractive index 1 • 5 here used is the same as that found by Senn for the
refraction from air into the cell-wall of Vaucheria, etc. Vide G. Senn, Die Gestalts-
und Lageverdnderung der Pflanzen-Chromatophoren, Leipzig, 1908, pp. 363-366.

94 RESEARCHES ON FUNGI

protoplasm taken together into cell-sap/ 0-893. Where the proto--
plasm formed a thin even layer on the cell-wall, the cell-wall and
protoplasm were treated as forming a very thin negligible plate,
and the rays were regarded as being refracted directly from the air
into the cell-sap (refractive index 1-34). On the other hand, where
the protoplasm was heaped up around the top of the subsporangial
swelhng (rays 1,2, and 3 in Figs. 46 and 47), the path of each ray
was calculated first from the air into the cell-wall and protoplasm
taken together (refractive index 1 • 5) and then from the cell- wall
and protoplasm taken together into the cell-sap (refractive index
0-893).

An experiment which proves that the refractive index from air
into the cell- sap of Pilobolus is, as assumed above, approximately
equal to the refractive index from air into water, namely, 1 • 34, was
made by comparing the actual width with the calculated width of
the central illuminated part of a median cross-section of a sub-
sporangial swelhng when the swelling is placed with its axis hori-
zontal in air under the microscope, is illuminated from below with
a beam of parallel light rays, and is viewed from above. In Fig. 48,
the cross-section of the swelhng is represented by a circle, and the
observer is supposed to be looking downwards on it in the direction
shown by the arrow o and to be observing the width of its illuminated
central part. When an actual beam of parallel light rays was
reflected upwards from the mirror, the illuminated central part of
the median cross-section of the swelhng had a width of k-l and the
lateral dark parts widths of i-k and l-j. When a theoretical beam
of parallel Ught rays was represented as being refracted into the
interior of the swelling and when, in calculating the paths of the
rays through the cross-section, 1 • 34 was used as the refractive
index from the air into the cell-sap, the illuminated central part of

1 Knowing the refractive index from air into cell-wall and protoplasm and
from air into cell-sap, the refractive index from cell-wall and protoplasm into cell-
sap can be readily calculated from the equation :

a X fc X c = 1
where a ^ the refractive index from air into cell-wall and protoplasm (1-5),

b = the refractive index from cell-wall and protoplasm into cell-sap, and
C — the refractive index from cell-sap into air (1/1-34).

THE PILOBOLUS GUN AND ITS PROJECTILE

0

95

Fig. 48.- — Diagram showing how a beam of parallel light-rays is refracted within
the subsporangial swelling of Piloholus Kleinii. The disc represents a much
enlarged transverse section of a swelling which had its axis horizon-
tally directed. The rays of light 1-7 are passing upwards from the plane
mirror of a microscope. The rays on entering the swelling, assuming the
refractive index from the air to the cell-sap is 1 • 34, must be refracted as shown,
so that they all emerge between c and d, the parts of the swelling s and s receiving
no light whatever. An observer looking down the microscope in the direction
of the arrow o should, therefore, theoretically, perceive the upper wall of the
swelling brightly lighted between c and d and black between a and c and between
b and d. The lighted and unlighted portions of the wall are shown projected
above, the dark regions being represented by e-g and h-f and the illuminated
one by g-h. When actual observations were made with a beam of parallel
light rays, it was found that the dark regions of the wall were as projected at
i-k arid l-j and the illuminated one as projected at k-l. The theoretical results
showTi in the line e-J agree very well with the practical results shown in the
line i-j. This agreement justifies one of the assumptions underlying tlie
construction of Figs. 46, 47, and 59, namely, that the refractive index for light
in passing from air to cell-sap is approximately 1 • 34.

96 RESEARCHES ON FUNGI

the median cross-section had a width g-h (corresponding to o-d in
the constructional diagram below) and the lateral dark parts had
widths of e-g (corresponding to a-c) and h-f (corresponding to d-h).
It will be seen by inspection that the actual illuminated central part
of the cross-section, namely, k-l, is approximately equal to the
calculated, namely, g-h ; and this equaUty may be taken as justifying
the assumption that the refractive index from air into cell-sap is
approximately the same as that from air into water, namely, 1-34.

The subsporangial swelling has the optical properties of a bi-
convex lens. When sunlight strikes upon one side of it, the rays
are refracted through it and converge so as to form a spot of light
on the opposite side. The spot can be seen under the microscope
in living fruit-bodies which are unilaterally illuminated and its mode
of formation can readily be inferred from a study of the diagrams
reproduced in Figs. 46, 47, and 48.

When the incident rays of Ught strike the sporangium and sub-
sporangial swelling head on and are exactly parallel to the long axis
of the sweUing as shown in Fig. 46, the spot of Ught which is formed
by the rays entering that part of the swelling which bulges out
beyond and around the sporangium is symmetrically placed at the
base of the swelling. Under these conditions the sporangiophore
is in physiological equihbrium and no heliotropic reaction is possible.
When, however, the incident rays of light strike a sporangium and
subsporangial swelling obHquely, say at an angle of 19° as shown
in Fig. 47, the spot of Ught is formed on one side of the wall of the
swelling in a manner which is asymmetrical for the swelling as a
whole. Under these conditions the sporangiophore is in physiological
inequilibrium, in consequence of which it reacts heliotropically :
the top of the stipe bends toward the source of the hght and swings
the subsporangial sweUing and sporangium round until they face
the light head on.

The heliotropic reaction just described may be explained as
follows. The patch of protoplasm which is strongly illuminated
by the spot of light [st in Fig. 47) undergoes a photochemical change,
in consequence of which it sends out a stimulus which travels down
the protoplasm Uning the wall of the base of the subsporangial
swelhng to the protoplasm surrounding the top of the stipe. The

THE PILOBOLUS GUN AND ITS PROJECTILE 97

stimulus may be nothing more or less than a diffusible growth-
promoting substance ; but, whatever it is, in response to it the
top of the stipe (m in Fig. 47), which is the motor region of the
sporangiophore, reacts by growing in length and by growing in
length most rapidly on the side which is nearest to the spot of
hght, i.e. on the side which receives the strongest stimulus. As a
result of this differential growth-reaction of the stipe, the sub-
sporangial swelling is turned about its base through an angle, and
the spot of light gradually passes downwards on the wall of the
swelling until it comes to be symmetrically placed at the base of
the swelhng, as shown in Fig. 46. As soon as the spot of light
reaches this symmetrical position, a physiological state of equilibrium
becomes established in the sporangiophore and a further heliotropic
reaction of the stipe is impossible. At the end of the turning
movement the Pilobolus gun is directed toward the source of the
brightest light.

In support of the explanation of the heliotropic reaction of the
sporangiophore just given, which involves the passage of a stimulus
from the rigid subsporangial swelling to the plastic motor region
of the stipe, may be cited the fact (1) that, under conditions like
those represented in Fig. 47, the motor region of the stipe, m, when
the heliotropic reaction begins, is in a shadow, s, and receives no
direct rays of light whatever, and (2) that the most strongly
illuminated protoplasm is the patch shown at st which receives the
light concentrated upon it by the body of the subsporangial swelling
which acts as a lens.

We may noAv enquire to what degree, if any, the light falling on
the stipe acts as a stimulus which assists in bringing about the
heliotropic reaction of the stipe. It is true that in such a tilted
fruit-body as that shown in Fig. 47 the rays of light falling on the
stipe (rays 9-14) converge so as to form a bright band of light along
the middle of the back of the stipe ; but, as shown in Fig. 47, the
highest ray strikes the stipe at u some distance below the motor
region m ; and, as may be inferred by comparing Fig. 47 with Fig. 46,
as heliotropic bending takes place and becomes more and more
complete, the subsporangial swelling shades the upper part of the
stipe to a greater and greater degree from the direct rays of the sun,

VOL. VI. H

98 RESEARCHES ON FUNGI

so that during the last stages of the bending, in such a fruit-body as
that shown in Fig. 46, the upper part of the stipe for some distance
back from the motor region receives no direct rays of light what-
ever. It is further to be emphasised that, as the heliotropic re-
action of the sporangiophore becomes more and more complete,
whereas the spot of light in the subsporangial swelling approaches
nearer and nearer to the motor region of the stipe until finally it
comes to rest upon the annular heap of protoplasm just above it,
the band of light in the stipe recedes more and more from the motor
region.

The facts brought forward in the above discussion justify the
conclusion that the heliotropic reaction of the sporangiophore of
Pilobolus, at least in its final stages, is not due to the action of the
light which falls on the motor region or any other part of the stipe
but to the action of the light which falls on the subsporangial
swelling and, in particular, to the action of the light which forms an
asymmetrically situated light-spot on the protoplasm lining the
cell-wall of the swelling.

In Pilobolus Kleinii the protoplasm in the lower part of the
subsporangial sweUing and at the top of the stipe, as shown in Figs. 46
and 47 by shading, is strongly pigmented with carotin ; and, as
we have seen, at the top of the stipe just above the stipe's motor
region, the protoplasm is usually heaped up so as to form a strongly
biconcave, very red, centrally perforated septum. Direct observa-
tions with the microscope and a study of the course of the rays of
light represented in Fig. 46 make it clear that the protoplasmic
septum, owing to its peculiar shape and to its distance from the top
of the subsporangial swelling, is admirably adapted for receiving
the rays of light as they begin to diverge from one another after
coming to a focus in the cell-sap when the sporangiophore is in a
position of complete or almost complete physiological equilibrium.
From the point of view of general structure and function, the layer
of protoplasm lining the lower part of the subsporangial swelling
and forming the incomplete septum at the top of the stipe — in its
concave shape, its strong pigmentation, its position in respect to
the subsporangial lens, and its mode of functioning by sending a
stimulus to the motor region of the stipe — is comparable with the

THE PILOBOLUS GUN AND ITS PROJECTILE

99

retina, while the pear-shaped body of the subsporangial sweUing is
comparable with the lens, of the eye of certain Mollusca. In this
connexion one may compare Fig. 46 which shows a median vertical
section through a subsporangial swelling and stipe of Pilobolus
Kleinii with Fig. 49 which shows a median vertical section through
the ocellus of a Snail, Helix pomatia. Since the subsporangial
swelling is so like the ocellus of a Mollusc and
is used as an organ for detecting the direction
of the incident rays of light, there seems no
reason why we should not regard it as a very
simple eye which functions like an ocellus.

The fact that the photochemically sensi-
tive protoplasm in the basal part of the
subsporangial swelling and at the top of the
stipe is so rich in carotin and that this pig-
ment is so densely aggregated in the upper
surface layer of the perforate protoplasmic
septum (Fig. 46, p) suggests that the carotin
absorbs light and thereby plays an important
part in the heliotropic reaction of the spor-
angiophore. Zopf came to the conclusion
that the carotin of Pilobolus is simply a
reserve food material, but this explanation
does not account for the aggregation of the
carotin particles around the base of the sub-
sporangial swelling and at the top of the
stipe nor for the fact that the pigment

persists in this position until the Pilobolus gun is discharged.
When discharge of the gun takes place in water on a slide under
a cover-glass, the ring-like mass of orange-red protoplasm at
the top of the stipe is often shot out through the mouth of the
subsporangial swelling, and I have several times identified it as it
lay some distance from the mouth of the sporangiophore not merely
by its form but by its high content of carotin (Fig. 65, D-F, p. 137).

The diameters of the sporangium, the subsporangial swelling,
and the motor region of the stipe below the swelling in a typical
large fruit-body of Pilobolus Kleinii (the one shown in Fig. 46) were

Fig. 49.^The eye of a
snail, Helix pomatia,
retracted : ep, epider-
mis ; c, cornea ; I,
lens ; r, retina ; op.
n., optic nerve. For
comparison with the
subsporangial swell-
ing of Pilobolus. From
Vol. Ill of the Cam-
bridge Natural
History. By courtesy
of Macmillan and Co.

100 RESEARCHES ON FUNGI

observed to be 0-43 mm., 0-76 mm., and 0-16 mm. respectively.
A simple calculation based on these data shows that the sporangium,
when head on to a beam of parallel light rays, casts a shadow which
has an area 7* 2 times that of a cross-section of the stipe. If there
were no subsporangial swelling, the shadow of the sporangium
would cut off the light from the top of the stipe before the ortho-
heliotropic position had been completely attained. This would
prevent the gun from being accurately directed toward the source
of the strongest light. Evidently, the difficulty of supplying the
stipe with the delicate heliotropic stimulus which it requires has
been overcome in the course of evolution by the intercalation,
between the sporangium and the stipe, of the large light-collecting
subsporangial swelling. That part of the swelling which bulges
out laterally beyond the black sporangium receives the light and,
by refraction, concentrates it upon the base of the swelling. The
asymmetrical position of the spot of light so produced provides the
condition for the despatch of a stimulus from the swelling to the
motor region of the stipe, and to this stimulus the motor region of
the stipe can react with great precision, even when it lies in the
shadow of the sporangium and subsporangial swelling and is receiving,
as shown in Fig. 47, no direct rays of light whatever.

The spot of light which is formed within the subsporangial
swelling by sunlight and is of so much physiological importance for
the heliotropic reaction of the sporangiophore is not constant in
size, shape, and brightness, but varies in all these qualities with
the position in which it happens to be formed. A study of this
variability will now be attempted.

When the incident rays of light strike the subsporangial swelling
transversely, i.e. perpendicularly to its long axis, the spot of light
formed by the convergence of the rays on the back wall of the
swelling is oval in outline, of maximum size, and of minimum
brightness (Figs. 50, A, and 51, p. 105). Its oval shape is due to
the fact that the main mass of the swelling is oval like an egg, its
relatively large size to the fact that the swelling is not nearly so
wide as it is long, and its paleness to the fact that the rays of light
fall on the back wall of the swelling at a considerable distance in
front of their focal point. As may be seen by reference to Figs. 48

THE PILOBOLUS GUN AND ITS PROJECTILE loi

(p. 95) and 51 (p. 105), the width of the oval spot of light is about
equal to one- third of the width of the swelling.

When the incident rays of light strike the sporangium and the
subsporangial swelUng head on and are exactly parallel to the
long axis of the swelling as shown in Fig. 46
(p. 91), the spot of light rests symmetri-
cally on the perforate protoplasmic septum
at the top of the stipe, is round in outline,
relatively small, and of maximum bright-
ness (Fig. 50, C and D). Its roundness is
due to the fact that the top of the swelling
through which the rays are refracted is
round. Its relatively small size and its
brightness are due to the fact that the rays
of light reach their focal point and begin
to diverge just above the protoplasmic
septum on which the spot of light is formed.
A study of the course of the rays of light
represented in Fig. 46 shows that at the
level jp in the particular fruit-body drawn
no direct rays pass through the main central
portion of the perforation of the septum,
so that a spot of light formed on a trans-
verse surface placed at the level of p would
have a small dark centre. It is of interest
to note that the length of the subsporangial
swelling is equal to, or only just exceeds,
its focal length, with the result that the
rays of light diverge before they reach the
perforate protoplasmic septum and so strike the concave surface
of the septum almost perpendicularly, i.e. in the most effective
manner for acting on the protoplasm and causing it to undergo
a photochemical change. The fact that the subsporangial swelling
is shaped like a pear is, therefore, from an optical point of view,
highly significant.

For the further discussion of the nature of the spot of light
formed at the base of the subsporangial swelling of Pilobolus

Fig. 50. — Pilobolus Klcinii.
Variation in shape of a
spot of light produced
by a beam of parallel
liglit rays in a subspor-
angial swelling. Light
in A transverse to axis
(cf. Fig. 51), in B
oblique {cf. Fig. 47),
and in C and D vertical
(cf. Fig. 4G). D, whole
of underside of .swell-
ing, stipe represented
by dotted circle. Mag-
nification, 38.

102

RESEARCHES ON FUNGI

Kleinii. it is necessary to take into account the laws relating to the
reflection of light at the surface of a transparent medium. When
a ray of light strikes the surface of a transparent medium such as
water, glass, or the cell-wall bounding the subsporangial swelling
of Pilobolus, part of it is reflected from the medium and part of
it is refracted into the medium. The percentage of light reflected
varies with the refractive index from air into the medium and with
the angle of incidence. The higher the refractive index, the greater
the percentage of light reflected. Also the greater the angle of
incidence, the greater the percentage of light reflected. The
percentage of light reflected for various angles of incidence at the
surface of a transparent medium when the refractive index from
air into the medium is 1* 55 is given in Table I.^

Table I

Light reflected at the Surface of a Transparent Medium when the
Index of Refraction is 1 • 55

Angle of
Incidence

Percentage of
Light reflected

0°

4-65

5°

4-65

10°

4-66

15°

4-66

20°

4-68

25°

4-73

30°

4-82

35°

4-98

40°

5-26

45°

5-73

50°

6-50

55°

7-74

Angle of

Percentage of

InciJeiice

Light reflected

60°

9-73

65°

12-91

70°

18-00

75°

26-19

80°

39-54

82° 30'

49-22

85°

61-77

86°

67-82

87°

74-56

88°

82-10

89°

90-54

90°

100-00

1 F. E. Fowle, Smithsonian Physical Tables, Ed. 5, 1910, Washington, p. 191.
In tlie original Table the percentage of light reflected is set down as -^ (A + B).
According to Fresnel the amount of light reflected at the surface of a transparent

sin ^ {i — r) , tan ^ (i — r) '

medium = ^ (A + B)

sin

-U

{i + r) tan ^ {i + r) \

where A is the amount of

light polarised in the plane of incidence, B that polarised perpendicular to this,
i the angle of incidence, and r the angle of refraction.

THE PILOBOLUS GUN AND ITS PROJECTILE 103

Since the refractive index for light passing from air into the
cell- wall of Pilobolus, namely, 1-5, is approximately equal to the
refractive index from air into a transparent medium given in
Table I, namely, 1 • 55, we may apply the data embodied in Table I
in our study of Pilobolus.

The angle of incidence for each of the six rays, Nos. 1-6, repre-
sented as striking the subsporangial sweUing in Fig. 46 (p. 91)
was carefuUy measured, and then the percentage of light reflected
from each ray at the surface of the swelling was estimated approxi-
mately from the data given in Table I, with the result shown in
Table II.

Table II

Light reflected at the Surface of the Subsporangial Swelling of Pilobolus

Eay shown in

Angle of

rercentaRC of

Pig. 46

Incidence

Light reflected

No. 1

40° 30'

5-5

No. 2

46° 45'

6

No. 3

55° 45'

8

No. 4

67° 30'

15

No. 5

75° 30'

27

No. 6

90°

100

The greater the percentage of the light reflected, the feebler
will be any ray after refraction. From the data embodied in
Table II, therefore, we may draw the conclusion that the rays
refracted through the subsporangial swelling shown in Fig. 46
diminish in brightness in order from No. 1 to No. 6, the brightest
ray being No. 1, and the dullest ray being No. 6 (theoretically this
ray is not refracted at all since its angle of incidence is not less
than 90°). Since, as shown in Fig. 46, the refracted rays diverge
before impinging upon the basal protoplasm, it is evident that the
brightest part of the spot of light produced at the base of the sub-
sporangial swelhng is centrally situated and rests on the inner edge
of the protoplasmic septum ; and that the brightness of the spot
of light diminishes centrifugally. The protoplasmic septum pro-
trudes so far into the vacuole that it is just able to catch most, or

104 RESEARCHES ON FUNGI

possibly all, of the strongest rays of light which come to it through
the subsporangial swelling. Assuming that the pigmented proto-
plasm of which the septum is composed is photochemically sensitive,
this arrangement provides us with another beautiful example of
the way in which structure and function are correlated.

When bright sunlight strikes a Pilobolus fruit-body head on
and forms a concentrated spot of light at the base of the sub-
sporangial sweUing in the manner shown in Fig. 46, the protoplasmic
septum, owing to its high content of carotin particles, glows with
a rich orange-yellow light. The glow can be readily seen with the
naked eye when a fruit-body which faces the sun is viewed from

the side.

If, when a fruit-body is facing the sun as shown in Fig. 46, one
looks at the top of the fruit-body so as to see it almost in face view,
one observes that the fruit-body has the appearance of a lurid red
disc with a black spot in the centre. The black spot is formed by
the intensely black sporangium and the red zone which surrounds
it is formed by the subsporangial swelling at the surface of which
red light, emitted by the glowing carotin in the protoplasmic septum
and passing upwards through the swelHng's great vacuole, is refracted
to the eye. At first sight such an apical view of a Pilobolus fruit-
body as that just described reminds one of the pink eyes of certain
albino animals.

We have seen that, when the incident rays of light strike the
subsporangial swelling transversely, the spot of light is oval ; and
that, when they strike the sporangium and the subsporangial swelling
head on and are parallel to the long axis of the swelling, the spot of
light is round. It remains to add that, when the incident rays of
Hght strike the subsporangial swelling obliquely, say at an angle of
19° as shown in Fig. 47 (p. 92), the spot of light formed on the back
wall of the swelling is neither oval nor round but, owing to the shadow
cast by the black sporangium, convexo-concave or crescentic with
the two horns looking upwards toward the sporangium (Fig. 50,
B, p. 101). Such a convexo-concave spot of light can be perceived
when one looks down a microscope at a fruit-body which is directed
obliquely downwards in the air and is illuminated from below \vith
parallel rays coming from a plane mirror.

THE PILOBOLUS GUN AND ITS PROJECTILE 105

The subsporangial swelling is capable of producing not only a
spot of light but also a more or less well-defined image of the source
of light or of an illuminated object. Such images were observed
under conditions which will now be described.

A fruit-body of Pilobolus Kleinii was fixed in air over a shde
on the stage of a microscope, so that the long axis of the subspor-
angial swelling was horizontal and so that
the swelling was illuminated from below by
means of parallel rays reflected upwards from
a plane mirror. On looking down at the
swelhng, I observed on its upper wall an
oval spot of light like that already described.
When the microscope was placed at a distance
of fourteen feet from a window, the spot of
Ught was found to contain an image of the
window-bars ; and, when a hand was held
three feet in front of the microscope between
the mirror and the window, the spot of light
was found to contain a black image of the
hand.

Subsequently, images formed by the sub-
sporangial swelhng of Pilobolus longipes were
photographed, and two of the photographs
are reproduced in Figs. 51 and 52.

Fig. 51 shows a daylight shadow-photo-
graph of a hand. The microscope was pre-
pared by removing the condenser and turning
on the plane mirror. The fruit-body to be

used to form the image, together with a Uttle dung on which it was
growing, was taken from a culture dish and set in a closed com-
pressor cell (c/. Fig. 14, Vol. II, p. 45) so that its apical portion
projected freely in the air in a horizontal direction. The moist air
of the chamber prevented the fruit-body from drying up. The com-
pressor cell was placed on the stage of the microscope. Daylight
from a window was employed. Parallel rays were reflected upwards
from the flat mirror to the subsporangial swelling of the fruit-body
in the compressor cell. The hand was held one foot in front of the

Fig. 51.^ — Pilobolus longi-
pes. Photomicro-
graph of the image
of a hand. Fide text.
Magnification, 40.

io6

RESEARCHES ON FUNGI

mirror of the microscope and the image of its shadow as produced
on the wall of the upper side of the subsporangial swelling was then
focussed with the low power (ocular No. 10, objective No. 16 with
the end-lens removed, Bausch and Lomb system). The exposure
of the plate was for twenty seconds and the magnification of the
fruit-body on the plate was forty diameters. In the photomicro-
graph the oval spot of hght and the image of the shadow of four
fingers and part of the thumb of the hand, which could be seen

with the eye on the upper wall of the subspor-
angial swelhng, are clearly visible.

In Fig. 52 is shown a photograph of a white
card bearing a black printed letter A. The card
was 4-1 cm. long and 3-5 cm. wide, and the
letter A was 2-5 cm. long. The condenser and
the mirror were removed from the microscope
and the card was placed on the dark table within
the horse-shoe base of the microscope, so that it
was visible when the eye looked down the micro-
scope tube. The card was illuminated by direct
sunlight. The fruit-body, as before, was con-
tained in a compressor cell set on the stage of
the microscope. The exposure of the plate was
for a few seconds and the magnification of the
fruit-body on the plate was about thirty diameters
(ocular No. 5, objective No. 16 with the end-lens
removed, Bausch and Lomb system). In the photomicrograph the
image of the card with its letter A, which could be seen with the
eye on the upper wall of the subsporangial swelhng, is clearly
visible ; and, again, we have conclusive evidence that the sub-
sporangial swelling can act like a lens.

Although, hke other more or less globular lenses, the subspor-
angial swelhng of Pilobolus is able to form images of objects — albeit
rather imperfect ones — it must not be supposed that Pilobolus can
see hke an animal. The simple eye or ocellus of Pilobolus is specially
adapted not for the perception of images but for the mechanical
perception of the direction of the strongest incident rays of light
by means of photochemical reactions.

Fig. 52.^ — Pilobolus
longipes. Image
of letter A. Vide
text. Magnifi-
cation, about 30.

THE PILOBOLUS GUN AND ITS PROJECTILE 107

According to the modern conception of heliotropism, for which
Blaauw ^ is chiefly responsible, an organ, such as the sporangiophore
of Phy corny ces nitens or the coleoptile of Avena sativa, turns toward
or turns away from a source of Hght because its sides are at first un-
equally lighted and because, as a result of this unequal illumination,
one of the sides grows more rapidly than the other until the illumina-
tion of the two sides has become equalised. The turning of an organ
until it points toward a source of light is therefore in itself a secondary
phenomenon which results from unequal light-growth reactions.

The explanation of the heliotropism of Pilobolus which I have
already given is in reality but an extension of Blaauw's general
theory of hehotropism to the special case of a fungus provided with
an ocellus. In Phycomyces nitens, so thoroughly investigated by
Blaauw, the sporangiophore is a simple cylinder and therefore
relatively undifferentiated, and its upper part, when unequally
lighted, is the part which reacts by unequal growth. In Pilobolus,
on the other hand, the sporangiophore is differentiated into a sub-
sporangial swelhng and a stipe, and there is a division of labour
between these two structures of such a kind that, when the sporan-
giophore is bending hehotropically, the subsporangial swelhng
receives the rays of hght and becomes unequally illuminated but
does not alter in form, while the top of the stipe, which hes below
the swelhng and may or may not be illuminated, reacts to the
unequal lighting of the subsporangial swelhng by unequal growth.
In the sporangiophore of Phycomyces nitens one and the same part
both receives the light and responds to it, whereas in that of Pilobolus
one part receives the light but another part responds to it.

That the decisive condition for hehotropic response in Phycomyces
nitens is not the direction of the rays of light but unequal illumination
is shown by the results of a beautiful experiment made by Buder.^

1 A. H. Blaauw, " Licht und Wachstum," I and II in Zeitschrift fiir Botanik,
Jahrg. VI, 1914, and VII, 1915 ; III (" Die Erklarungdes Phototropismus") in part
XV of Mededeelingen van de Landbouwhoogeschool, Wageningen, 1918.

2 J. Buder, " Die Inversion des Phototropismus bei Phycomyces," Ber. d. D.
Bot. Gesellschaft, Bd. XXXVI, 1918, pp. 104-105. Some other ingenious experi-
ments made by Buder demonstrate that it is not the direction of the light but
imequal lighting that is responsible for the heliotropism of the coleoptile of Avena.
Ibid., Bd. XXXVIU, 1920, pp. 14-19.

io8

RESEARCHES ON FUNGI

Buder placed P. rtitens in two parallel-sided chambers with the
sporangiophores directed vertically upwards. In one chamber the
sporangiophores were, as usual, surrounded by air. The other chamber

Fig. 53. — Phycomyces iiitens. Diagrams to illustrate two com-
parative experiments on heliotropi.sm. The arrow
indicates the direction of the incident rays of light.
In A the sporangiophores developed in the air and have
turned toward the source of light. In B the spor-
angiophores developed in paraffimmi Uquidum (paraffin
oil) and have turned away from the source of light. After
J. Buder (Ber. d. D. Bot. Ge.sell., Bd. XXXVI, 1918,
p. 104). Re-drawn by the author.

was filled with paraffinum liquidum so that the sporangiophores
were immersed in it. Both chambers were then illuminated on
one side with equal intensity, with the result that the sporangio-
phores which were in the air turned toivard the light, while those
which were in the paraffin turned away from the light (Fig. 53).
The explanation of this difference in reaction is simple. In a

THE PILOBOLUS GUN AND ITS PROJECTILE 109

sporangiophore growing in air, since air is a less dense medium than
a sporangiophore and its contents, the rays of hght after refraction
converge and form a bright band of hght on the side turned away
from the hght. Hence the back of the growing zone of the sporan-
giophore is hghted more intensely than the front and consequently
grows faster, with the result that the end of the sporangiophore is
turned toward the light. In a sporangiophore growing in paraffinum
liquidum, since paraffin (refractive index 1-47) is a denser medium
than a sporangiophore and its contents, the rays of light after
refraction diverge from one another and, therefore, do not form a
bright band on the side turned away from the light. Hence the
front of the growing zone of the sporangiophore is lighted more
intensely than the back and consequently grows faster, with the
result that the end of the sporangiophore is turned away from the
light. In a letter ^ to the author, Buder states that he has experi-
mented with Pilobolus and has found that it reacts to unilateral
hght in air and in paraffin in exactly the same way as Phycomyces.
We thus have evidence which supports the view that the heho-
tropism of Pilobolus is due to light-growth reactions and not primarily
to the direction of the incident rays of light.

Assuming that a Pilobolus sporangiophore, when growing in
paraffin, turns away from the light, instead of toward the light as
it does when it is growing in air, the explanation of the phenomenon,
presumably, is as follows. The subsporangial swelhng, when
immersed in paraffin, owing to the divergence of the hght rays
after refraction, cannot form a spot of light on its wall away from
the source of light. Hence the side of the swelling toward the light
is more intensely illuminated than the side away from the light.
Hence the stimulus sent to the stipe from the front of the subspor-
angial swelhng is greater than that sent from the back. Hence,
therefore, the stipe grows faster in front than behind and so turns
the subsporangial swelling and the sporangium away from the
source of the light.

The Mechanism of Heliotropic Response in Pilobolus and in the
Leaves of Certain Flowering Plants. — The mechanism of hehotropic
response in Pilobolus is not necessarily unique in the plant world ;

1 Dated Sept. 12, 1921.

no RESEARCHES ON FUNGI

for, in general principle, it may be similar to that of the leaves of
many flowering plants.

As is well known, there are many shade-plants of which the
laminae are in a condition of heliotropic equiUbrium only when
they are placed at right angles to the direction of the most intense
diffuse illumination. These diaheliotropic leaves assume their
heliotropically fixed positions by means of appropriate curvatures
or torsions of the whole petiole or of a pulvinoid portion of the
petiole or of a typically developed pulvinus. It was suggested by
Dutrochet 1 in 1837 that the leaf -blade of the leaves in question
perceives the direction of the hght and exerts a directive influence
upon the petiole ; and Vochting,^ in 1888, by means of carefully
thought-out experiments, proved that this is so for Malva verticillata.
Haberlandt,3 in 1905, succeeded in demonstrating a similar directive
influence of the lamina in several other plants. Thus he found
that : in Begonia discolor the petiole, even when completely darkened
by a sheath of tin-foil, turns the lamina into its heliotropically
fixed position ; and that in Monstera deliciosa the upper region of
the petiole, which is developed as a pulvinus, even when completely
darkened by a sheath of tin-foil, executes the curvature or the
torsion necessary to restore the lamina to the position of heliotropic
equilibrium with the greatest possible precision.

To explain the diaheliotropism of the leaves of shade-plants,
etc., Haberlandt^ has put forward his ocellar theory, according to
which : (1) the power of perceiving photic stimuli is vested in the
upper epidermis ; (2) the epidermis sends a stimulus to the petiole ;
(3) the stimulus causes the petiole or its pulvinus to curve or tmst
until the lamina comes to be at right angles to the direction of the
strongest incident rays of light ; and (4) each cell of the epidermis
acts as a light-perceiving organ or ocellus and is only in a position

1 H. J. Dutrochet, Memoires pour servir a Vhistoire anatomique et physiologique
des Vegekmx et des Animaux, Paris, 1837, T. II, p. 107.

2 H. Vochting, " Ueber die Lichtstellung der Laubblatter," Botanische Zeitung,
Jahrg. XLVI, 1888, pp. 519-523. Vochting showed that the lamina, when obliquely
illuminated, forces the petiole to execute movements, when the petiole is kept in
the dark or, if it is lighted, in opposition to its own heliotropic tendencies.

3 G. Haberlandt, Die Lichtsinnesorgane der Laubblatter, Leipzig, 1905, pp. 17-19.
* G. Haberlandt, ibid., pp. 120-122 ; also Physiological Plant Anatomy, trans-
lated by M. Drummond, London, 1914, pp. 613-630.

THE PILOBOLUS GUN AND ITS PROJECTILE iii

of photic equilibrium when the protoplasm lining its inner wall,
which is sensitive to photic stimuli, is symmetrically illuminated
with the brightest light at its centre. Haberlandt showed that the
epidermal cells of the leaves of many plants have a more or less
rounded or convex external wall and act as lenses, so that the rays
of hght which enter them are refracted and condensed and form a
bright spot of light on their inner wall.

My own ocellar theory of the heliotropic mechanism of the
sporangiophore of Pilobolus is essentially similar to Haberlandt's
ocellar theory for the heliotropic mechanism of certain leaves. The
lens-like subsporangial swelling of Pilobolus corresponds in a leaf
to the thousands of lens-like epidermal cells ; and the stipe of
Pilobolus, which receives a stimulus from the photically sensitive
subsporangial swelling in consequence of which it bends the swelling
around until the spot of light within the swelling is symmetrically
situated at its base, corresponds in a leaf to the multicellular petiole,
which receives a collective stimulus from the thousands of photically
sensitive epidermal cells in consequence of which it bends or twists
until the thousands of spots of light in the epidermal cells, on the
average, have come to be symmetrically situated on their basal walls.

In the heliotropic reaction of Pilobolus, which is caused by the
asymmetrical position of a spot of light in the subsporangial swelling
with a consequent bending of the stipe, we have clear proof of
the theory, first suggested by Haberlandt, that heliotropic reactions
may take place in plants through ocellus action.

The sporangiophore of Pilobolus is the only ortho-heliotropic
plant organ known which takes up its positively heliotropic position
owing to the possession of a special light-perceiving cell structure.

Pilobolus may well be described as a fungus with an optical
sense organ or simple eye (ocellus) ; and, in using its eye for laying
its gun, it is unique in the plant world.

The Ocellus of Pilobolus and the Eye-spots of Volvox. — As is
well known, red eye-spots are present in many Protozoa, e.g. Euglena,
and in the Volvocaceae, e.g. Gonium, Pandorina, PJeodorina,
Eudorina, and Volvox ; and it is therefore not without interest to
enquire whether or not the ocellus of Pilobolus and the eye-spots
of these other organisms work on the same principle. According

112

RESEARCHES ON FUNGI

to Mast,^ the eye-spot in the zooid of a Gonium or a Volvox (Fig. 54)
consists of three parts : a pigment-cup, a lens which is situated at
the opening of the cup, and a photosensitive substance which is
located within the cup. Mast ^ regards these eye-spots as " primitive
eyes " and, in connexion with Volvox, explains their action as
follows. 3 Volvox swims in the direction of its axis with its anterior
end forwards.* Each of the zooids of which it is composed has an

Fig. 54. — Camera-lucida drawing of an optical section through the longitudinal axis
of a colony of Volvox : l-a, longitudinal axis ; G, gelatinous layer surrounding
the colony ; H, hyaline portion of cell ; Z, zooid ; n, nucleus ; /, flagella ;
c, chloroplast ; e, eye ; p, pignaent-cup ; /, lens ; mm, scale. Note that the eyes
on the two sides of the longitudinal axis face in opposite directions. Copied by
the author from Fig. 6 of Mast's Reactions to Light in Volvox ivith Special Reference
to the Process of Orientation. In the original Figure the chloroplasts are coloured
green, and the pigment-cups red. Reduced to three-quarters.

eye-spot and two cilia. The eye-spots are largest at the anterior
end of the colony (about 3 jj. in diameter) and decrease in size from
that end backwards so that, at the posterior end, they are so poorly
differentiated as to be scarcely visible. In the eye-spots at the
anterior end of the colony the lens is directed away from the axis
of the colony and slightly forwards (Fig. 54). The cilia of all the

1 S. 0. Mast, " Reactions to Light in Volvox with Special Reference to the
Process of Orientation," Zeitschrift fiir vergleichende Physiologie, Bd. IV, Heft V,
1926, pp. 648-649, 657.

2 Ibid., pp. 652, 657. ^ Ibid., pp. 643-657.

* This statement applies only to photopositive colonies. There are also photo-
negative colonies which swim away from the light.

THE PILOBOLUS GUN AND ITS PROJECTILE 113

zooids becat backwards obliquely, so that the colony progresses
forwards and, at the same time, rotates in a counter-clockwise
direction. When a colony which is swimming toward the light
with its anterior end facing the light is suddenly subjected to lateral
illumination only, in the zooids on the side of the colony facing the
light the hyaline portion of each eye is fully exposed to the light,
while in the zooids on the side of the colony facing away from the
light the hyaline portion of each eye is well-shaded by the pigment-
cup, with the result that the flagella of the zooids with shaded eyes
beat backwards more directly than before while the flagella of the
zooids with unshaded eyes beat backwards less directly than before
(Fig. 55). Owing to this change in the direction of the stroke of the
flagella on the two sides of the colony, the colony gradually turns
its axis until this again becomes parallel to the incident rays of
light and the anterior end of the colony faces the light directly
(Fig. 55). When the colony is in photic equilibrium, the incident
light falls on the eye-spots of any one lateral half of the colony in
the same way and with the same intensity as upon the eye-spots of
the corresponding other lateral half of the colony.

My own investigations on Pilobolus and those of Mast on Volvox
thus seem to show in both these plants — the one a lowly and seden-
tary fungus and the other a highly organised motile alga — that
photic orientation is accomplished by means of optical sense organs,
and that re-orientation is due in Pilobolus to the asymmetrical
illumination of a single eye and in Volvox to the combined effect
of the asymmetrical illumination of many eyes.^

There is a red pigment in the eyes of both Pilobolus and Volvox ;
but, whereas that of Pilobolus is situated in the sensitive protoplasm
and is relatively diffuse, that of Volvox is situated below the sensitive
protoplasm and is aggregated into a dense and opaque cup-like

1 Pilobolus and Volvox may be compared to those mythical monsters of antiquity
Cyclops and Argus : for Cyclops, like Pilobolus, looked out on the world with a single
median eye ; while Argus, like Volvox, had many eyes. It is said that Argus
had one hundred eyes some of which were always open and on the watch, and that
they were so splendid that, when he was killed, Juno transferred them to the Peacock's
tail ; but a Volvox globator, although not mentioned in the annals of Olympus, may
have more than twenty thousand eyes which never close and are ever ready for
service.

VOL. VI. J

114

RESEARCHES ON FUNGI

Fig. 55. — Diagrammatic representation of orientation during a positively heliotactic
response in Volvox. A, B, C, and D, four zooids at the anterior end of the
colony ; l-a, longitudinal axis ; large arrows, direction of illumination ; curved
arrows, direction of rotation ; the colony is moving forward and turning so as
to face the light with its anterior end ; /, flagella : e, eyes, containing a pigment-
cup (represented bj^ a heavy black line) and photosensitive tissue in the concavity
of the cup. Note tliat, when the colony is laterally illuminated, the photo-
sensitive tissue in the eyes on the side facing the light is fully exposed to the
light and the flagella on this side beat laterally, while the photosensitive tissue
in the eyes on the ojjposite side is shaded by the pigment-cup and the flagella
on this side beat directly backwards. The difference in the direction of the beat
of tlie flagella on these two sides is due to alternate decrease and increase in the
luminous intensity to which the photosensitive tissue in the eyes is exposed
owing to the rotation of the colony on its longitudinal axis, an increase causing,
in photopositive colonies, a change in the direction of the stroke of the flagella
from backward or diagonal to lateral, and a decrease a change frorn lateral or
diagonal to backward. In photonegative colonies precisely the opposite obtains.
In photopositive colonies this results in turning toward and in photonegative
colonies in turning from the source of light. In both the turning continues
until opposite sides are equally illuminated, when changes in intensity on the
photosensitive tissue are no longer produced by rotation and the orienting
stimulus ceases. Reproduced from Fig. 7 of Mast's Reactions to Light in
Volvox with Special Reference to the Process of Orientation.

THE PILOBOLUS GUN AND ITS PROJECTILE 115

mass. In Pilobolus the absorption of light by the red pigment may
possibly increase the photosensitivity of the protoplasm in which
it lies, while in Volvox it seems clear that the red pigment functions
by shading the sensitive protoplasm of those eyes which happen
temporarily to be turned away from the light.

The Ocellus of Pilobolus and the Human Eye. — The simple
ocellus of a Pilobolus and the complex eye of a human being, in
their heliotropic response to light, behave in essentially the same
manner ; for they are both in photic equilibrium only when the
spot of light formed in their interior by a luminous object, such as
a candle flame, is symmetrically placed in the middle of their back
wall or retina. If a man and a Pilobolus fruit-body were to be
kept for some time in a dark room and then a candle flame were to
be suddenly exposed in one corner of it : the man, immediately
and instinctively, would turn his head until he faced the candle
flame directly and, in so doing, he would unconsciously place the
spot of light in each eye in the middle of the retina, i.e. in the region
of the blind-spot ; while the Pilobolus fruit- body, very slowly (in
the course of an hour or so), would turn its sporangium and sub-
sporangial swelling until they faced the light directly and, in so
doing, it would automatically place the spot of light in the subspor-
angial swelling in the middle of the red protoplasm at the back of
the swelling, i.e. so that the centre of the spot of light would rest on
the centre of the protoplasmic septum at the top of the stipe ; and
the movement of the Pilobolus fruit-body, accomplished simply
by the unequal growth of the stipe, and the movement of the human
being, accomplished by means of a highly complex nerve-brain-
nerve-muscle mechanism, would both be caused by the same physio-
logical condition, namely, the asymmetry of a spot of light at the
back of a photically sensitive optical organ or eye. Thus, in
respect to their behaviour in the presence of incident rays of light,
the lowly cryptogam Pilobolus and Man, the lord and master of
the organic world, have much in common.

A Heliotropic Experiment made on Pilobolus longipes. — The
heliotropic experiment about to be described was made on a fruit-
body of Pilobolus longipes for the following purposes : ( 1) to determine
how long it takes for a fruit-body which is illuminated by direct

ii6 RESEARCHES ON FUNGI

sunlight to bend heliotropically through a right angle ; (2) to
determine the length of the latent period, i.e. the time which elapses
from the beginning of continuous heliotropic stimulation to the
beginning of heliotropic reaction as indicated by the curvature of
the sporangiophore ; and (3) to observe the spot of light formed
on the back wall of the subsporangial swelling move down the wall
of the swelling, as the stipe bends, and finally come to rest on the
perforate protoplasmic septum at the top of the stipe.

The apparatus used in the experiment was a glass-ring chamber.
A glass ring 3 cm. in diameter was placed on a slide and covered with
a cover-glass in the manner shown in Fig. 56. To cut off undesirable
light, black paper was attached : to the outer and inner surfaces
of the glass ring, except for a window-slit 2 mm. wide, as shown at
A, B, and C ; to the upper and lateral sides of the slide, as shown
at B and C ; and to the upper surface of the cover-glass, except for
a peep-hole, as shown at B and C.

One morning, a large well-developed fruit-body of Pilobolus
longipes which had been directed toward the source of strongest
light for some hours, together with a piece of horse dung on which
it was growing, was removed from a culture dish and was placed
in the experimental chamber in the manner shown in Fig. 56 ; and
two other pieces of horse dung were also placed in the chamber to
assist in keeping its air moist ; whereupon the ring was covered
with the special cover-glass which had been prepared for it. The
chamber was then set on the stage of a microscope and was attached
there by clips. The microscope was turned on its axis and its stage
tilted until the upper surface of the stage and of the glass slide were
parallel to the direct rays of the morning sun and a beam of sunlight
entered the window-slit of the chamber and impinged on the sub-
sporangial swelling, as indicated by the arrow in Fig. 56, A. Under
these conditions, the beam of sunlight struck the subsporangial
swelling transversely, and the sporangiophore was so directed that,
in order to make a complete heliotropic reaction, it was obliged to
bend through a right angle. After the beginning of the experiment,
in order to keep the beam of sunlight on the subsporangial swelling,
it was necessary (owing to the movement of the sun relatively to
the earth) to revolve the microscope slightly on its axis at frequent

THE PILOBOLUS GUN AND ITS PROJECTILE 117

intervals of time. The mirror of the microscope was so turned that
it could not reflect any light upwards. From the beginning to the

Fig. 56. — A glass-ring chamber, as used for observing the heliotropic curvature
of the stipe of Pilobolus longipes. A, a plan of the chamber with the
cover-glass removed, as seen from above : a, a glass slide covered with
black paper ; b, a glass ring covered with black paper c within and with-
out except for a slit in the front where, as indicated by the arrow, direct
sunlight is entering the chamber ; d, a piece of horse dimg bearing a
Pilobolus fruit-body which has just been arranged so that the axis of the
subsporangial .swelling is horizontal and perpendicular to the direction of
the rays of light which strike it ; the two other masses of horse dung assist
in keeping the air of the chamber moist. B, a median vertical section of
the chamber with the cover-glass on : a, the glass slide ; b, tlie glass ring ;
c c, black paper ; d, the horse dung bearing the Pilobolus fruit -body ; e, tlie
cover-glass, covered with black paper except at the very centre where there
is a window through which, as indicated by the arrow, the observer watched
with the low power of the microscope the heliotropic bending of the stipe of
the fruit-body ; sufficient light came up from below to enable these observa-
tions to be made without the use of the mirror. C, the whole apparatusseen
from in front where the direct rays of sunlight are entering through the slit
of glass not covered by black paper : the illuminated subsporangial swelling
in the middle of the chamber can readily be observed. Enlarged to 1 ' 33
the actual size.

ii8 RESEARCHES ON FUNGI

end of the experiment the upper part of the fruit-body, i.e. the
sporangium, the subsporangial swelling, and the top of the stipe,
was observed by looking downwards upon it through the peep-hole
of the cover-glass, as indicated by the arrow shown in Fig. 56, B.

The experiment began on May 3 at 9 o'clock in the morning.
For the first ten minutes, the fruit-body remained in its original
position, as shown in Fig. 56 at A ; but, three minutes later, its
stipe was observed to have turned very slightly toward the light,
so that the presentation time was estimated to have been about
ten minutes. Half an hour later, i.e. forty minutes after the begin-
ning of the experiment, the stipe had bent toward the light through
an angle of 45° ; and at the end of eighteen further minutes, i.e.
approximately one hour after the beginning of the experiment,
the stipe had bent through a complete right angle and had turned
the subsporangial swelling and sporangium through 90° so that they
now faced the sunlight head on. Immediately after the heliotropic
movement had been completed, the top of the fruit-body was drawn
with the camera lucida. A study of this drawing, which is reproduced
in Fig. 57, shows that the motor region of the stipe, to which the
turning movement of the sporangiophore was due, was situated
almost at the top of the stipe, i.e. immediately under the topmost
region of the stipe which is distinguished by the presence of the
incomplete protoplasmic septum.

A few minutes after the drawing shown in Fig. 57 had been made,
the sporangiophore shot away its sporangium, and the sporangium
struck and stuck to the narrow window-slit shown in Fig. 56 at
A and C.

At the beginning of the experiment, a beam of sunlight which
fell on the subsporangial swelling formed a spot of colourless light
on the colourless protoplasm lining the inner side of the back wall
of the swelling. This spot of light could be observed with the
microscope. As the subsporangial swelling was gradually being
turned through a right angle by the growth-movement of the stipe,
the spot of light was seen travelling slowly down the side of the
swelling until at last it settled on the perforate protoplasmic
septum at the top of the stipe. For the first twenty minutes or
so of the turning movement of the stipe, the spot of light travelled

THE PILOBOLUS GUN AND ITS PROJECTILE 119

on colourless protoplasm. Then it approached and travelled
on the reddish protoplasm
situated within and around
the base of the swelling ; and,
finally, about five minutes before
the end of the experiment, it
could be seen leaving the red-
dish protoplasm on the interior
of the swelling and passing on
to the very red protoplasm of
the protoplasmic septum at the
top of the stipe. Fifty-eight
minutes, or approximately one
hour, after the beginning of
the experiment when the spor-
angium and subsporangial swell-
ing had come to face the sun-
light head on, the spot of
light was seen resting sym-
metrically on the protoplasmic .
septum which, in consequence,
glowed with a reddish light (cf.
Fig. 46, p. 91). These obser-
vations show that, in the spor-
angiophore of Pilobolus, the
cessation of heliotropic move-
ment, or in other words the
establishment of photochemical
equilibrium, is correlated with
the passage of a spot of bright
light from one side of the
subsporangial swelling to a
radially symmetrical position
on the red protoplasm at the
base of the swelling and at
the top of the stipe ; and

nn

Fig. 57. — Pilobolus longipes. The fruit-
body shown in Fig. 56, drawn with
the aid of a camera lucida one hour
after the beginning of the heliotropic
experiment. The subsporangial
swelling s and the sporangium with
its black outer cell-wall c and its
bulging basal gelatinous band g,
through which the spores can be seen,
have been turned through a right
angle owing to the unilateral growth
of the motor region of the stipe, m, in
response to the heliotropic stimulus.
The light coming from the sun (c/. A
in Fig. 56) is now refracted through
the subsporangial swelling and is
thereby focussed on the red bicon-
cave perforate protoplasmic septum
situated at p. A few minutes after
this drawing was made the spor-
angium was shot away toward the
sun, and it struck and stuck to
the 2-mm.-wide window shown in
Fig. 56, A and C. The size of every
part is indicated by the scale. Mag-
nification, 37.

they may be accepted as giving strong support to the explanation

120

RESEARCHES ON FUNGI

of the mechanism of the heliotropic reaction of Pilobolus already
set forth in the previous Section.

A Solution of the Problem of the Reaction of the Sporangiophore
of Pilobolus to Two Equal Beams of White Light. — Allen and Joli-
vette ^ made a study of the reactions of Pilobolus to light, in the
course of which they exposed cultures of Pilobolus at one and the
same time to two equal beams of light which passed through two
holes (c/. Fig. 59, A) in the wall of a dark culture chamber. They

Fig. 58. — Pilobolus Kleitiii. Diagram to show the reaction of a
fruit-body to two equal beams of light making a considerable
angle with one another. The directions of the two beams of light
are indicated by the arrows a and b. A, the beginning of the ex-
periment. B and C, alternative end-results of the experiment :
the stipe of the fruit-body has turned the sporangium and sub-
sporangial swelling so that these have come to face either the
beam-of-light a (as in B) or the beam-of-light b (as in C).
Magnification, 14.

observed that, when a culture is exposed to two equal beams of white
light coming from two sufficiently different directions (angle between
the rays converging on the fruit-bodies greater than about 10° and
up to 36° and more), the sporangium of each Pilobolus fruit-body
is aimed at one or the other source of light (c/. Figs. 15, p. 42, and
58) and the aim is as accurate at the source of light chosen as if the
other source did not exist ; and they ^ commented upon this curious
experimental result as follows : " Light rays from both sources
reach the sensitive sporangiophore. Apparently there is nothing

1 Ruth F. Allen and Hally D. M. Jolivette, " A Study of the Light Reactions
of Pilobolus," Trans. Wisconsin Acad., Vol. XVII, 1914, pp. 561-569, 593-594.

2 Loc. cit., p. 593.

THE PILOBOT.US GUN AND ITS PROJECTILE 121

to prevent each set of rays — or each individual light ray for that
matter — from setting up those changes in the protoplasm which
constitute the perception of a stimulus, and nothing to prevent
these simultaneous stimuli from acting together to produce a
resultant reaction. But this does not occur. The visible reaction
of each sporangiophore is to one and one only of the two possible
sources of stimulation."

The fact that a Pilobolus fruit-body, when illuminated by two
equal beams of white light having sufficiently different directions,
reacts apparently to one source of light and not the other, which so
much puzzled Allen and Jolivette in 1914, can readily be explained
on the theory already set forth : that the spot of light formed by
the subsporangial swelling on the protoplasm on the wall of the
swelhng farthest away from the source of light gives the illuminated
patch of protoplasm a photochemical stimulus ; that the stimulus
(by diffusion of a growth-promoting substance through the proto-
plasm or otherwise) is conducted to the motor region of the stipe ;
and that the motor region of the stipe reacts to the stimulus by
growing faster on the side nearest to the source of the stimulus
than on the opposite side and thus bends heliotropically. An
endeavour will now be made to apply this theory to the problem
in hand.^

Let us suppose that a Pilobolus fruit-body, like that shown in
Fig. 47 (p. 92), is pointing vertically upwards and that it is illu-
minated from above by two equal beams of white light which cross
one another on their way to the fruit-body at an angle of 38° and
each of which makes an angle of 19° with the axis of the subsporangial
swelling. One of these beams is shown in Fig. 47 striking the
right-hand side of the swelling, and the other beam which strikes
the left-hand side of the swelling and is like the first but reversed
in direction can be readily imagined.

By reference to Fig. 47 (p. 92), it can be seen that the right-
hand beam forms a spot of light st on the left-hand side of the sub-
sporangial swelling at a distance of about 0- 25 mm. above the median

1 For an account ot Van der Wey's solution of this problem'and for the reason
which induced me to give here my own solution, which is in conformity with his,
vide Chapter I, pp. 44-45.

122 RESEARCHES ON FUNGI

plane of the protoplasmic septum. A similar spot of light must be
formed by the left-hand beam, also at a distance of 0* 25 mm. above
the median plane of the protoplasmic septum, but on the right-hand
side of the swelling exactly opposite to the first spot. Thus we
have two spots of light on opposite sides of the swelling and, accord-
ing to our theory, each of the spots affects the patch of protoplasm
on which it rests photochemically and causes it to send a stimulus
down to the motor region of the stipe. The stimulus arriving from
the patch of protoplasm illuminated by the spot of light on the
left-hand side of the swelling will tend to cause the motor region of
the stipe to grow faster on its left-hand side than on its right-hand
side ; and the stimulus arriving from the patch of protoplasm
illuminated by the spot of light on the right-hand side of the swelling
will tend to cause the motor region of the stipe to grow faster on
its right-hand side than on its left-hand side. Now it is very un-
likely that, under natural conditions, the two stimuli given by the
two spots of light falling on opposite sides of the subsporangial
swelling will be absolutely equal. Let us therefore suppose that
one of the stimuli, say that given by the spot of light on the left-
hand side of the swelling, is very slightly greater than the other
stimulus produced on the right-hand side of the swelling. The
two stimuli will travel downwards on opposite sides of the swelHng
to the motor region of the stipe. Since, according to our assumption,
the left-hand stimulus is very slightly greater than the right-hand
stimulus, the left-hand side of the motor region of the stipe will be
stimulated to grow a little faster than the right-hand side, with the
result that the stipe will bend slowly to the right and, in so doing,
turn the subsporangial swelling and sporangium to the right. As
the subsporangial swelling is being bent round to the right, the
left-hand spot of light must move down the side of the subsporangial
swelling, while the right-hand spot of light must move up the side
of the swelling ; and, doubtless, the left-hand spot of light, as it
goes farther and farther down the left-hand side of the sweUing,
gives a greater and greater stimulus to the left-hand side of the
motor region of the stipe which it is approaching, while the right-
hand spot of light, as it goes farther and farther up the right-hand
side of the sweUing, gives a weaker and weaker stimulus to the

THE PILOBOI.US GUN AND ITS PROJECTILE 123

right-hand side of the motor region of the stipe from which it is
retreating. Thus, in the end, the stimulus given by the descending
left-hand spot of light prevails over and completely dominates the
stimulus given by the ascending right-hand spot of light, with the
inevitable result that the motor region of the stipe bends the sub-
sporangial swelling round to the right until it comes to be directed
head on to the right-hand beam of light. When this position of
heliotropic equilibrium has been established, what was the left-hand
spot of light now rests symmetrically on the protoplasmic septum
at the top of the stipe, while the right-hand spot of light rests on
the right-hand side of the swelling at a distance of about 0*5 mm.
from the median plane of the protoplasmic septum which is about
equal to twice its original distance from the septum. If the right-
hand spot of light when in its fixed position 0-5 mm. from the
septum continues to cause a stimulus to be sent down to the right-
hand side of the motor region of the stipe, we must suppose that
this stimulus is so feeble, relatively to the powerful stimulus sent
down equally to all sides of the motor region of the stipe from the
septum illuminated by the other spot of light, that its effect on the
stipe, so far as causing it to bend is concerned, is negligible.

Thus, by taking into account the special structure and optical
behaviour of a typical Pilobolus fruit-body, it has been possible to
explain why it is that a Pilobolus fruit-body, when stimulated by
two beams of light coming from sufficiently different directions,
reacts by turning to one of the sources of light and pointing to it
with as much precision as it would exhibit were the other source
of hght non-existent.

So far we have considered the heliotropic response of the Pilo-
bolus fruit-body to two sources of light the rays of which make a
relatively large angle, 10°-36° or more, where they meet at the
fruit-body's surface. To complete our enquiry, we shall now
consider the heliotropic response of the fruit-body to two sources
of hght the rays of which make a relatively small angle, say 5° or
less, where they meet at the fruit-body's surface.

Let us assume that the angle between the two equal beams of
white light which fall on a Pilobolus fruit-body is 5°, as shown at B
in Fig. 59, and that at first the two beams fall upon one side of the

124

RESEARCHES ON FUNGI

Cb

CL_

Ob

sq

J

V yv

zS

/

Cb

oc

2d

B

Fig. 59. — A diagram to illustrate the reaction of a fruit-body of Pilobolus Kleinii to
light coming from two equal sources at the same time.

A, part of the wall of a dark chamber in which are two windows, a and b,
with their centres 4 cm. apart. Through these windows two beams of light

THE PILOBOLUS GUN AND ITS PROJECTIT.E 125

fruit-body. Each beam, after refraction of its rays at the surface
of the subsporangial swelUng, will foriu a spot of light on the proto-
plasm lining the back wall of the swelling, and the two spots will
overlap one another to some extent, as shown diagrammatically
at D in Fig. 59. The two heho tropic stimuli produced by the over-
lapping spots of light must travel down one and the same side of
the swelling to the motor region of the stipe and there combine in
causing the stipe to bend heliotropically in the direction of the two
sources of light. As the bending of the stipe takes place, the two
overlapping spots of light will descend the wall of the swelhng and
take up a position on the protoplasmic septum where there is room
for both of them. There are two possibilities with respect to the
exact position of the two spots relatively to the septum : either
(1) the spot which first comes into contact with the septum takes
up an exactly symmetrical position over the septum, its centre

Fig. 59 — cont.

of equal intensity came and struck a Pilobolus fruit-body 42 cm. distant. The
fruit-body reacted in such a way that it pointed its gun at a spot midway between
the two sources of light, as indicated at B where the two outer arrows a and b
show the direction of the two beams of hght and the middle arrow x the final direc-
tion of the axis of the subsporangial swelling and sporangium. C shows the
final position of the fruit-body. The rays a and 6 in C have all come through
the window a in A and are therefore drawn parallel to a in B. They are refracted
into the subsporangial swelling and fall on the protoplasmic septum at p where
they form a spot of light {cf. 6 in D) slightly to the right of the centre of the
septum. The corresponding rays of light coming through the window b in
A, and therefore in a direction parallel with b in B, ha^'e not been represented
in constructing C ; but, if they had, it would be seen that they would form
a spot of light slightly to the left of the centre of the septum p, as shown at
a in D. The two spots of light (cf. a and fe in D) overlap and they can and do
both rest on the septmn at the same time, so that the septum is symmetrically
illuminated. Hence, finally, the axis of the gim is directed, as shown at x in B,
at a spot midway between the two sources of light.

When the two windows in A are far apart, so that the beams of light striking
the Pilobolus fruit-body are inclined to one another at a large angle, say 40°,
instead of a small one, say 5°, as in the case already discussed, if the fruit-body
is at first pointing at a spot midway between the two sources of light, the two
spots of light formed by the two beams on the wall of the subsporangial swelling
must be far apart (cf. a and 6 in E) and cannot overlap, one spot being on one
side of the swelling and the other opposite to it on the other side of the swelling.
Unstable physiological equilibrium must result : one spot of light will stimulate
the motor region of the stipe more than the other with the result that the fruit-
body will turn towacd the source of light which gives the stronger stimulus,
i.e. it will come to jyoint toward one of the windows and not to a spot midway
between them. At the end of the reaction, one spot of light will have moved
downwards on the wall of the swelling and will have taken up a symmetrical
position on the septum whilst the other will have moved upwards and have
become much farther removed from the septum than it was originally. The
scale F indicates the size of each part of C, D, and E : magnification, 69. In A
the vertical lines divide the wall into centimetres.

126 RESEARCHES ON FUNGI

coinciding with the septum's centre, in consequence of which the
other spot hes excentrically over the septum ; or (2) the two spots
as a whole take up a symmetrical position over the septum, so that
their common centre (situated in their overlapping parts, cf. Fig.
59, D) concides with the septum's centre. If one spot only comes
to lie symmetrically on the septum, the fruit-body must point to
but one of the two sources of light ; whereas, if the two spots act
as one and, as a whole, lie symmetrically over the septum, the
fruit-body must point in a direction which bisects the directions of
the two sources of light.

A fruit-body which, in accordance with the possibility (2) as
just described, is supposed to be directed between the two equal
sources of light has been represented in Fig. 59. At B, the two
beams of light which make an angle of 5° with one another are
indicated by the lines a and b and the axis of the fruit-body, which
bisects the angle, is indicated by the line x. At C is a construction
diagram of the fruit-body having its axis x parallel to a; in B and
being illuminated by one of the two beams of light, namely, the
one shown by a in B. The rays of this beam, which make an angle
of 2*5° with the axis of the subsporangial swelling, are shown in
C in the air at a and b and, after refraction, in the swelling where
they converge and form a spot of light on the septum excentrically
on its right-hand side. To avoid confusion, the other beam of
light with rays parallel to 6 in B has not been represented in C, but
it can be readily imagined as it would be just like the beam actually
represented, but reversed in position, The spot of light formed by
this unrepresented right-hand beam, like the other spot, falls on
the septum excentrically, but with its centre a little to the left of
the septum's centre instead of a little to the right. The con-
struction diagram C indicates quite clearly that the two spots
of hght must overlap to some extent in the manner shown at
D and that, as a whole, they can lie symmetrically on the
septum with their common centre resting upon the centre of the
septum.

If the angle between the two beams of light were to be decreased
gradually from 5° to 1° the overlapping of the two spots of hght in
the subsporangial swelling would increase from that indicated in

THE PILOBOLUS GUN AND ITS PROJECTILE 127

Fig. 59 at D until it was very considerable indeed. If the angle
were to be further decreased from 1° to 0°, the two spots finally
would coincide with one another.

Allen and Jolivette ^ investigated the response of Pilobolus
sporangiophores to two equal sources of light which were very close
together and whose rays formed angles from about 13° to about 3°
with one another and, in discussing the results of their observations,
they 2 say : " When the two openings which serve as sources of
illumination are close together, there are, to be sure, a small number
01 sporanges which land about midway between the openings "
and " It is possible that the sporanges which fell between and below
the openings came from sporangiophores which perceived and
reacted to both lights at once, thus aiming at a point between the
tw^o openings." Evidently they suspected that with very small
angles at least some of the projectiles were aimed midway between
the two sources of light although, as they intimate, to admit this
as a fact would conflict with their results obtained with large angles
and make the explanation of the heliotropic reaction of Pilobolus
very difficult. "Why," they ^ ask, " should the resultant reaction
to two simultaneous stinmli appear only when the openings are
close together ? "

In connexion with Fig. 50 it was shown above that, when the
angles between the incident rays of light from two equal sources of
light are very small, the two spots of light partly overlap and, as a
whole, can take up a symmetrical position on the protoplasmic
septum of the subsporangial swelling. Theoretically, therefore,
when the angle between the two beams of incident light is very
small, it is possible for the two stimuli produced by the two beams
of light to act together and produce a resultant reaction in the
motor region of the stipe. It seems to me probable that, under
test conditions, such a resultant reaction would be often observed
or, in other words, that with small angles between equal or almost
equal beams of light the sporangiophores would be found to point
more or less between the sources of light rather than at one or the

1 Ruth F. Allen and Hally D. M. Jolivette, he. cit., pp. 566-569.

2 Ibid., p. 593.

3 Ibid., pp. 593-594.

128 RESEARCHES ON FUNGI

other of them ; but whether or not this supposition is a good one
can only be decided by further investigation. ^

According to Haberlandt,^ as we have seen, the reaction of the
leaves of the higher plants to heliotropic stimuli can be explained by
assuming that the epidermal cells of the lamina act as ocelli and that
heliotropic equilibrium is only attained when the spot of light formed
in each cell has come to lie symmetrically on the protoplasm
covering the cell's inner wall. If this theory is true, a lamina when
subjected to two equal beams of white light making a wide angle
with one another, say of 40°, should, like the sporangiophores of
Pilobolus, turn so as to face either one or the other source of light
and not show a resultant reaction by turning so as to face a point
midway between the two sources of light. It will be of much
interest to know what happens when such a test of Haberlandt's
ocellar theory is actually made.

A Model for illustrating the Pilobolus Fruit-body in its Relations
with Light. — A model for illustrating the fruit-body of Pilobolus in
its relations with light can be made for demonstrations to an
audience as follows. Take a Florence flask or a measuring flask
with a somewhat pear-shaped base and of 500 cc. capacity, fill it
with water, stuff a smooth wet plug of cotton wool (free from air-
bubbles) down the neck as far as the base of the neck, and then close
the mouth of the neck with a cork (Fig. 60). The neck of the flask
then corresponds to the stipe of Pilobolus, the bulb of the flask to
the subsporangial swelling, and the cotton-wool plug to the proto-
plasmic septum at the top of the stipe. To represent the opaque
sporangium, stick a plano-convex mass of moulding clay covered
with black tissue paper over the flat surface of the flask's base, so as
just to cover it. As a source of light, use direct sunlight or a beam
from the arc of a projection lantern.

1 Since this was written, Van der Wey, in a paper referred to at tlie end of
the last chapter (p. 43), has shown that, with small angles between the two beams
of light, both beams influence the direction in which the sporangiophores point,
with the result that most of the sporangia are shot in directions between the centres
of the two beams. Evidence of this fact is to be seen in one of his photographs
reproduced in my Fig. 16 (p. 44).

2 G. Haberlandt, Die Lichtsinnesorgane der LaubhlitUer, Leipzig, 1905 ; also
Physiological Plant Anatomy, translated by M. Drummond, London, 1914, p. 614
et seq.

THE PILOBOLUS GUN AND ITS PROJECTILE 129

(1) To imitate the condition of the Pilobolus fruit-body when in
a state of heUotropic eqiiihbrium. Hold
the flask by its neck in the beam of Hght
with its long axis parallel to the direction
of the incident rays and its black basal
ball facing the rays. It will now be found
that the rays of light falling on that part
of the flask's bulb which bulges out beyond
the black ball are refracted so that they
converge within the bulb and brilliantly
illuminate the cotton-wool plug at the
junction of the flask's bulb and neck.

(2) To imitate the condition of the
Pilobolus fruit-body when not in a state
of heliotropic equilibrium. Hold the
flask in the beam of light M'ith its long
axis making a considerable angle with
the direction of the incident rays, so that
the rays fall obliquely on the flask's bulb
and basal ball. It will now be found
that the cotton- wool plug is no longer
brilliantly illuminated, but that a spot of
light is formed by the refracted light rays
upon the side of the bulb. The spot of
light can be made evident by j^lacing a
sheet of white paper against it or near it.

(3) To imitate the movement of the
spot of light down the side of the sub-
sporangial swelling of the Pilobolus fruit-
body when the stipe, responding to a
heliotropic stimulus, is turning the sub-
sporangial swelling and sporangium
through an angle. Hold the flask as
just described in (2), so that the spot
of light is upon one side of the bulb.
Now turn the flask so that its axis
gradually assumes a direction parallel

VOL. VI.

Fig.

60. — Diagrammatic
longitudinal median sec-
tion through a model used
to illustrate the ocellus
function of the subspor-
angial swelling of Pilo-
bolus Kleinii : a, a
Florence flask ; b, mould-
ing clay adhering to the
base of the flask ; c, black
tissue paper covering the
ball of clay ; d d, water ;
e, cotton wool ; /, a cork.
When the model is pointed
toward the sun or toward
an artificial source of light
a few feet away, the raya
of light are refracted
through the bulb of the
flask on to the plug of
cotton wool, so that this
becomes brightly lighted.
About one-half the natural
size.

130 RESEARCHES ON FUNGI

to, and its basal ball comes to face, the incident rays. During the
progress of the turning movement, one can observe that the spot of
light gradually moves down the side of the bulb (this can be made
evident by applying a sheet of white paper to it) until finally it
takes up a perfectly symmetrical position on the cotton- wool plug
which, in consequence, becomes brilliantly lighted.

(4) To show that, if the cell-sap in the subsporangial swelling
were replaced by air, the swelling would not act as a lens. Hold the
flask in the beam of light so that its basal ball faces the light, as in
the first experiment. The light is refracted on to the cotton- wool
plug. Remove the water from the flask without removing the plug.
Now hold the flask in the beam of light in the same position as
before. The light is no longer refracted on to the plug.

The Periodicity in the Development of Pilobolus Fruit-bodies. —
As we have seen, in a good natural horse-dung culture of Pilobolus,
a crop of fruit-bodies is produced daily for several days in succession,
and each crop takes about 24 hours to complete its development.
An individual fruit-body consists : at mid-day, of a tuber (tropho-
cyst) or swollen plasma-filled cell which becomes the basal swelhng
(Fig. 24, A, p. 60) ; in the afternoon, of a basal swelhng and stipe
which is growing in length (B and C) ; in the late evening, i.e. 11-12
P.M., of a basal swelhng. a stipe, and a sporangium (D) ;
early next morning, i.e. about 6 a.m., of a basal swelhng, a stipe, a
subsporangial swelling and a sporangium (G) ; and, finally, at or
before noon, of a collapsed sporangiophore and a discharged
sporangium (H). Normally the discharge of the sporangium, which
marks the climax in the development of the fruit-body, takes place
between 10 a.m. and early afternoon.

The naked stipe, whilst growing in length during the afternoon, is
positively hehotropic and always points with great precision to the
source of the strongest incident rays of light (Fig. 24, B and C,
p. 60). It contains a mass of colourless protoplasm at its apex,
dense red protoplasm just below its apex, and less red protoplasm
farther down its shaft. Doubtless, when the stipe is growing
toward the Ught, the rays are refracted at its apical surface,
converge, and concentrate themselves in the sub- apical dense red
protoplasm ; and it may well be that this red protoplasm is

THE PILOBOLUS GUN AND ITS PROJECTILE 131

photically sensitive and directs the growth of the stipe towards
the Hght.

The stipe is positively heHotropic so long as it is growing in
length ; but, as soon as it ceases to elongate and begins to develop
a sporangium at its free end, it ceases to respond to unilateral
illumination. Even when it is exposed to the direct rays of the
sinking sun, so that its axis is at right angles to the rays, it shows no
heliotropic reaction whatever. The inability of the stipe to make
heliotropic curvatures coincides roughly with the hours of darkness
and lasts from about 7 o'clock in the evening until early next morning,
by which time the subsporangial swelling has been developed.

What advantage to Pilobolus, if any, is its periodical develop-
ment which results in the production of diurnal crops of fruit-bodies
and in the discharge of the sporangia between about 10 a.m. and
early afternoon ? The answer to this question is not far to seek.
Pilobolus uses light to direct its guns toward open spaces, with the
result that its projectiles are shot away from dung-plats in pastures
on to the surrounding herbage where they remain until they are
swallowed by herbivorous animals. If the guns were to be developed
and discharged during the night, light could not be used to lay them
and the sporangia would not be scattered nearly as effectively as
they actually are ; but the periodicity in the development of a single
fruit-body is such that the diminishing afternoon light can be
employed for directing the growth of the naked sti])e and the strong
late-morning hght for the precise orientation of the mature gun just
before it shoots away its sporangium. We may conclude, therefore,
that the periodicity in the development of the fruit-body of a
Pilobolus indirectly favours the dispersion of its sporangia and thus
assists the species in maintaining its place in nature.

The Subsporangial Swelling and the Discharge of the Pilobolus
Gun. — The first special function of the subsporangial swelling — that
of acting as an ocellus for perceiving the direction of the strongest
incident rays of light and for assisting in the heliotropic laying of
the Pilobolus gun — has been fully treated of in previous pages.
The second special function of the subsporangial swelhng — that of
acting as part of a squirting mechanism for the discharge of the
sporangium — will be discussed in what follows.

132

RESEARCHES ON FUNGI

The Pilobolus gun, as pointed out in an earlier Section, ^ is
discharged explosively : the wall of the sporangiophore breaks
across transversely just beneath the sporangium and columella
[vide the dotted line a in Fig. 28, p. 70) ; the elastic wall of the
subsporangial swelling, stipe, and basal swelling, which has been
distended by the pressure of the cell-sap in the great vacuole,
suddenly contracts ; the cell-sap is violently squirted out of the
open mouth of the subsporangial swelling ; and a spherical drop of

cell-sap carries away the sporangium
at a speed ^ of 10-20 feet per second
through the air. A contracted spor-
angiophore seen in water immediately
after the sporangium has been dis-
charged is shown in Fig. 61.

In the process of squirting away the
sporangium, the subsporangial swelhng,
on account of its position just beneath
the sporangium, its large size, and the
great elasticity of its cell-wall, plays a
chief part. Its external appearance just
before the discharge of the sporangium,
immediately after, and during the next
few minutes, is illustrated in Fig. 62.

The subsporangial swelhng, as may
be realised by a glance at Fig. 28 (p. 70),
contains a large amount of cell-sap.

Fig. 61. — Pilobolus Kleinii. The sporangiophore
after the discharge of the sporangium ; seen
in water with the basal swelling embedded in
part of the substratum : s, the substratum ;
a b c, the sporangiophore, shrunken and
collapsed ; a, the basal swelling with a turgid
apophysis below ; b, the stipe ; c, the sub-
sporangial swelling with its open mouth to-
wards the observer ; and d, the contracted
collar of the subsporangial swelling now
forming a lip to the mouth of the swelling.
Upper half drawn with the help of the camera
lucida, the lower half somewhat diagram-
matic. Magnification, 53.

1 Vide p. 62.

2 Fide p. 67.

THE PILOBOLUS GUN AND ITS PROJFXTILE 133

When the sporangiophore contracts during the discharge of the spor-
angium, the volume of the sporangiophore decreases to at least one-
half of what it was originally (c/. A and B in Fig. 62), with the result

Fig. 62. — Pilobolus Klein it. Changes in the upper part of the sporangiophore
immediately after the sporangium has been shot away, represented somewhat
diagrammatically. A, a fruit-body just before discharge : a, the stipe ; 6, the
subsporangial sweUing, crowned above the upper broken hne by a dehisced
sporangium in wliicli, between tlie two parts of the sporangium-wall, can be
seen tlie swollen gelatinous ring and some of the spores ; the top part of the
wall of the subsporangial swelling between the two broken lines contracts at
the moment of discharge and becomes the lip or collar of the swelling shown at
c in B. B, the contracted sporangiophore a fraction of a second after the
sporangium and a jet of cell-sap have been shot away ; the jet broke up into
droplets of which the last is shown above the arrow '; a, the stipe, now contracted
and bent ; b, the subsporangial swelling, contracted to about one-half its
original volume and now showing the lip or collar c which appears dark owing
to crystals being present on its exterior ; at the mouth of the swelling is seen
a drop of cell-sap d which is growing in size owing to continued contraction of
the wall of the swelling and stipe. C, about half a minute after B ; the drop
has become much larger and has attained its maximum size. D, a minute or
two after C ; the drop is evaporating and has almost disappeared. E, a minute
or two after D ; the drop has disappeared and the stipe and swelling have
collapsed irregularly ; c, the lip or collar now slightly tilted. F and G, respec-
tively, an oblique and a top view of the upper half of a collapsed swelling ;
c, the lip or collar still rounded and comparatively rigid. Magnification, 38.

that most of, or perhaps all of, the cell-sap held in the subsporangial
swelhng is shot out into the air. At the same tmie, something like
one-half of the cell-sap held in the basal swelhng and stipe is forced
upwards into the subsporangial swelling, so that the subsporangial

134 RESEARCHES ON FUNGI

swelling, after its contraction, is filled with sap and not with air.
Even after the sporangium has been shot away and the sporangio-
phore has been thrown backwards on to the substratum, the wall
of the sporangiophore continues to contract, although slightly, with
the result that cell-sap slowly issues from the open mouth of the
sporangiophore and there forms a rounded globule (Fig. 62, B andC).
As soon as the contraction ceases, the globule, owing to evaporation,
begins to diminish in size (D), and soon it disappears completely.
As more and more of the water of the cell-sap in the contracted
subsporangial chamber evaporates, the sides of the chamber fall
inwards and become irregularly folded (Fig. 62, E, F, and G).

The length and breadth of a subsporangial swelling of Pilobolus
longipes were measured (1) when the swelling was fully turgid and
(2) after the swelling had been made to contract symmetrically by
rupturing the stipe below it ; and it was found that, as a result of
contraction, the length of the swelling had decreased from 1-17 mm.
to 0-8 mm. or by approximately 30 per cent, and that the breadth
of the swelling had decreased from 0-875 mm. to 0-65 mm. or by
approximately 26 per cent. These figures indicate that the cell-
wall of the subsporangial swelling is highly elastic and contracts
very considerably when the sporangium is discharged.

The cell-wall of the subsporangial swelling, when distended by
the pressure of the cell-sap, is uniformly thin right up to the
columella. As it contracts and drives the cell-sap away at the
moment when the sporangium is discharged, it thickens, but not
uniformly : it thickens most just around the mouth of the swelhng
and in a zone which stretches a short way below the mouth (c/.
B with A in Fig. 63). From this differential thickening of the cell-
wall on contracting and also from the external appearance of the
top of a contracted swelling (Fig. 62, B-G), it may be safely inferred
that the most contractile part of the wall of the swelling is that
which lies immediately below the sporangium and eventually forms
the lip or collar of its open mouth.

The collar of the contracted subsporangial swelling is shown
externally in Fig. 62 and in vertical section in Fig. 63. It is covered
externally by numerous small crystals of calcium oxalate which,
when it is immersed in water, give it a dark appearance, apparently

THE PILOBOLUS GUN AND ITS PROJECTILE 135

by imprisoning air and thus preventing the water from coming
directly into contact with its surface.

The level at which the wall of the subsporangial sweUing splits
across when the sporangium is discharged (called by de Bary the
Riss-stelle) is indicated by a dotted hne in Figs. 28 (p. 70) and 32
(p. 76), and by the upper dotted line in Fig. ^62. The splitting is
perfectly accomphshed, so that the edge of the mouth of the con-
tracted subsporangial swelling is always smooth and circular (Fig. 62,
B-G). Doubtless, therefore, the wall at the abscission level is

Fig. 63. — Pilobolus Kleinii. Vertical median section through the top part of a sub-
sporangial swelling : A, just before the discharge of the sporangium ; and B,
a fraction of a second after discharge when the cell-wall has contracted. A : the
upper broken line indicates the level of absci-ssion just beneath the sporangium
(c/. Fig. 32) ; a, the cell-wall stretched by the pressure of the cell-contents b.
B, the wall has contracted and that part between the two broken lines in A
has thickened and formed the lip or collar c c (c/. c in Fig. 62). Magnification,
300.

prepared for breaking whilst the wall is being formed and long
before the discharge of the sporangium. Some evidence in support
of this view will now be given. If one strokes a ripe sporangium off
its columella (c/. Fig. 31, p. 75) and examines the wall of the turgid
subsporangial swelling and columella with the microscope, the wall
appears everywhere about equally thin (c/. Fig. 30, B, p. 73). If
now one ruptures the stipe, so that the turgidity of the whole
sporangiophore is lost, the wall of the subsporangial swelling and
columella contract. It is then seen that the wall is fully twice as
thick immediately under the abscission level as it is immediately
above. Also, when a subsporangial swelUng and attached columella
are treated with chlor-zinc iodine, the upper part of the wall of the
subsporangial swelhng swells greatly except at the abscission level.

136

RESEARCHES ON FUNGI

Here, as shown at e in Fig. 64, the wall remains relatively thin. It
seems not unhkely that, just before abscission actually takes place,

0)

o

<E -*^ ;— •^J .„ ^

- O O Is ^ ^ ^

the wall at the level of abscission is weakened by the action of
an enzyme apphed to it through the activity of the adjacent

THE PILOBOLUS GUN AND ITS PROJECTILE 137

u

protoplasm. Since, when maturing fruit-bodies are placed in

the dark, the discharge of the sporangia is delayed for several

hours, it may well be that the weakening of the wall along

the splitting line is

controlled by Hght,

and it is possible that

the shallow heap of red

protoplasm which lies

in the subsporangial

swelling just below the

sporangium and is

fully exposed to the

light(/inFig. 28,p. 70)

is concerned with the

control mechanism.

The columella,
which is carried away
with the sporangium
when this is discharged,
has a wall which, except
for gelatinous swelling
at the peak,^ remains
very thin even after
the sporangium has
been discharged and it
is no longer pressed
against by the cell- sap
of the subsporangial
swelling. Evidently,
the wall of the colu-
mella differs from that
of the subsporangial swelling in being but slightly contractile.

Occasionally, when a fruit-body of Pilobolus is placed in water on a
slide under the microscope, it explodes in such a way that the wall of the
subsporangial swelhng is torn into several fragments some of which
at once become curled up spirally like a roll of paper (Fig. 65, A-C).

1 C/.p. 81.

Fig. (55. — Pilobolus Kleinii. A, one of the fragments
of a subsporangial wall which burst when the
fruit-body was placed in water : when set free it
at once became spirally rolled. B, the same,
represented in transverse section. C, the same,
represented as flattened out. D, vertical section
of a fruit-body at the junction of the stipe and
subsporangial swelling, to show the perforate
protoplasmic septiun in situ. E, a protoplasmic
septum which was expelled from the spor-
angiophore as the sporangiophore contracted and
discharged its sporangium under water. F, a
similar septum. Magnification, A-C, 293 ;
D F, 67.

138

RESEARCHES ON FUNGI

This phenomenon is due in part to the enormous pressure to which
the cell-wall is subjected by the cell-sap and in part to the cell- wall's
wonderful elasticity.

The cell-sap which is expelled from the sporangiophore, when this

contracts., issues from the circular
mouth of the subsporangial swell-
ing as a continuous jet which
immediately breaks up into several
separate drops. All these drops,
which are shot some distance, can
be readily caught on a sheet of
glass placed a few inches in front
of a fruit-body just before it dis-
charges its sporangium (Fig. 66).
The largest drop is formed at the
top of the jet, has the greatest
momentum, travels farthest, from
the first adheres to the under
wettable gelatinous side of the
sporangium, and carries off the
sporangium through the air in the
manner shownin Fig. 74, A (p. 151).
The other smaller drops are formed
from the jet in succession under
the first drop, are not so violently
expelled as the first drop, have
less momentum, and fall much
nearer to the sporangiophore which
has discharged them. Direct
evidence that the range for the
smaller drops is not nearly so
great as for the larger drop is afforded by the fact that, when fruit-
bodies look upwards and a glass plate is placed above them at
greater and greater heights as in a set of experiments aheady re-
corded,! after a certain height the only drops which strike the plate
are those which bear sporangia.

1 Vide pp. 63-66.

f¥:''h

0k
o

m

l^'c/

o

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<iy

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o

0

Oo°'

E

0

o

^ 1

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0

/^ ■^'X

n o

oQ

(:'-.'■■' -J

Q

o

o

\^

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o

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D

Fig. 66. — Pilobolus longipes. A-E,five
sporangia and the cell -sap shot
away from five fruit-bodies, after
they had struck a sheet of glass
held obliquely a few inches in front
of the fruit-bodies and after the
sap had dried up. The jet of cell-
.sap, on being squirted out from the
top of the subsporangial swelling,
broke up under the influence of
surface tension into a series of
drops. The largest drop travelled
with the sporangium to the greatest
distance. The smaller drops trailed
behind the drop attached to the
sporangium. Magnification, 2 • 6.

THE PILOBOLUS GUN AND ITS PROJECTILE 139

The contracting sporangiophore, in addition to expelling from its
interior a large quantity of cell-sap, sometimes also expels the proto-
plasmic septum from the top of the stipe ; for, immediately after
observing the discharge of a ripe fruit-body in water on a sHde under
the microscope, I have occasionally found the septum, which is
easily recognised by its annular shape and its red colour, lying in the
water at some distance from the mouth of the collapsed sub-

FiG. 67. — niobalu.s Kleiiiii. Three sporangia which were
shot away with the subsporangial swelling attached to
them. Magnification, 50.

sporangial swelhng (Fig. 65, D-F). Furthermore, on examining
the drops which have carried away sporangia through the air,
immediately after they have settled on white paper placed on a table
to receive them, I have sometimes observed that the drops contain
a little mass of red protoplasm. There is therefore reason to suppose
that, when the Pilobolus gun is discharged, the sap rushes up the
stipe with such violence that it is apt to tear the protoi)lasmic
septum away from the cell-wall, thus making it possible for the
septum to be included in the large drop of sap which is expelled
from the subsporangial swelling and carries the sporangium through
the air.

140 RESEARCHES ON FUNGI

In a culture of Pilobolus Kleinii about twenty among several
hundred fruit-bodies that came up on fresh horse-dung balls dis-
charged their sporangia abnormally ; for, as was inferred from an
examination of their projectiles (Fig. 67), abscission in the spor-
angiophores took place not immediately under the sporangium but at
the base of the subsporangial swelHng or across the top of the stipe.
The sporangia with the subsporangial swellings attached were found
sticking to the under side of a glass cover situated several inches
above the horse dung on which the fruit-bodies had been growing.
Spores derived from the abnormal projectiles were sown and a new
generation of fruit-bodies was obtained, but none of the new fruit-
bodies in their mode of discharging their sporangia exhibited the
abnormality of their parents.

The Osmotic Pressure of the Cell-sap of Pilobolus. — The force
which expands the highly elastic cell-wall of the Pilobolus gun and
is primarily responsible for the explosion of the gun and for the
discharge of the projectile is the osmotic pressure (turgor pressure)
of the cell-sap of the sporangiophore. It is therefore of considerable
interest to determine what this pressure is and how it compares
with osmotic pressures known to exist in the cells of higher plants.

In an endeavour to determine the osmotic pressure of the sap of
Pilobolus, three methods were tried: (1) the classical plasmolytic
method of NageH, Pfeffer, and de Vries ; (2) extracting the sap of
Pilobolus and using it in an attempt to plasmolyse cells having a
known or determinable osmotic pressure ; and (3) Barger's capillary-
tube method. The freezing-point method was not employed owing
to the difficulty of collecting an amount of cell-sap sufficient for the
requirements of the Beckmann apparatus.

(1) The plasmolytic method for determining osmotic pressures
was found unsuitable in its appHcation to Pilobolus : firstly, because
the sporangiophore is large and has a peculiar rounded form ;
secondly, because the sporangiophore wall is highly elastic and
contracts much more than the cell-walls of higher plants ; and,
thirdly, because there is an optical difficulty in observing the
primordial utricle just beginning to separate itself from the cell-wall.

(2) Cell-sap was extracted from a number of Pilobolus fruit-
bodies and then small strips of a leaf of Elodea canadensis, cut with

THE PILOBOLUS GUN AND ITS PROJECTILE 141

a pair of scissors, were immersed in it. No plasmolysis took place.
The Elodea cells could be plasmolysed slightly with a solution of
sucrose having an osmotic pressure of 10 atmospheres but not with
one having an osmotic pressure of 8 atmospheres. It therefore
seemed reasonable to suppose that the osmotic pressure of the
Pilobolus sap is less than 10 atmospheres, a supposition confirmed
later by results obtained with the Barger method. No further work
with method (2) was attempted.

(3) Barger's capillary-tube method, which was described in
1904, has the merit of being applicable to cell-sap which can be

z a k
» M. n

IT ■ H

H 1 II

nx:

Fig. 68. — Part of the apparatus used for determining the
osmotic pressure of the cell-sap of Pilobolus longipes
by the Barger method. Three capillary tubes attached
to a glass slide by Canada balsam. Each tube
contains 7 drops : those shown in black, Nos. 1, 3,
5, and 7, are drops of sugar solution of known osmotic
strength ; those lightly shaded, Nos. 2, 4, and 6, are
drops of Pilobolus cell-sap. The tubes are closed at
both ends. The whole was kept immersed in water in
a Petri dish. Natural size.

obtained only in small quantities.^ Its essence is the comparison
of a solution of unknown osmotic pressure with standard solutions
of known osmotic pressures made from a substance of known
molecular weight, a series of drops taken alternately from the
solution of unknown osmotic pressure and from a solution of known
osmotic pressure being introduced into a capillary tube. The
vapour pressure of the drops with the lower osmotic pressure is
greater than that of the drops with the higher osmotic pressure, in
consequence of which water vapour passes from the drops with the
lower osmotic pressure and condenses on the drops with the higher
osmotic pressure, with the result that the drops with the higher

^ G. Barger, " A Microscopical Method of Determining Molecular Weights,"
Journal of the Chemical Society, Transactions, Vol. LXXXV, 1904, pp. 286-324.

142

RESEARCHES ON FUNGI

osmotic pressure increase in length while those with the lower
osmotic pressure decrease in length.

In accordance with the details of Barger's technique : the
capillary tubes were made about 6-8 cm. long and with a bore about
1-0 mm. in diameter ; seven alternating drops separated by short
air-spaces were introduced into each capillary tube (Fig. 68) ; the
ends of the filled tubes were sealed up in a flame ; two or three tubes
with like contents were attached with Canada balsam to a glass
slide ; the slide was immersed in water at room temperature, the
water being contained in a Petri dish ; the lengths of the five central

Fig. 69. — Optical section tlirougli part of a capillary tube used for determining
the osmotic pressure of the cell-sap of Pilobolus longipes by the Barger
method, showing the appearance of a drop when its length is being
measured with the scale of the eye-piece inicrometer of the microscope.
The length of the drop here shown is 28*2 units of the scale. Magnifi-
cation, 27.

shorter drops (two of the standard solution, sucrose, and three of the
ceU-sap of Pilobolus) were measured (Fig. 69) under the microscope
with the help of an eye-piece micrometer shortly after the tubes had
been placed in the water ; and the drops were measured again next
day after a lapse of 30-36 hours.

The sap was obtained as follows. Fresh dung from a stable was
spread out on the floor of a large glass case. On the fourth day
thereafter, many thousands of fruit-bodies of Pilobolus longix>es
(Fig. 70) came to maturity without any admixture of Mucor, etc.
When the fruit-bodies were beginning to discharge their sporangia,
they were caused to burst by pressing their subsporangial swellings
(c/. Fig. 18, p. 50) against a glass slide. As soon as the sap thereby
set free amounted to about two drops, it was allowed to run off the
slide into a test-tube. When a sufficient quantity of the sap had

THE PILOBOLUS GUN AND ITS PROJECTILE 143

been harvested in this way, the sap was poured into a watch-glass
and covered with a sheet of glass to check evaporation.

The microscope employed had a mechanical and revolving stage
and a micrometer in its eye-piece ;
and it was fitted with lenses which
gave a magnification of 40. The Petri
dishes containing slides, tubes, and
water were set on the stage of the
microscope and the lengths of the
five central drops in each tube were
read and recorded in succession. With
very little practice it was found possible
to measure the lengths of the drops
with accuracy and rapidity. The appear-
ance of the scale of the micrometer,
when applied to a drop for its measure-
ment, is shown in Fig. 69.

In carrying out the experiment
with the Pilo bolus cell-sap, I received,
and here wish to acknowledge with
my best thanks, valuable assistance
from my friend and former pupil.
Dr. W. F. Hanna. He prepared the
standard solutions of sugar and filled
the capillary tubes, etc. ; I harvested
the cell-sap just before it was re-
quired for use and kept the watch-
glass which contained it covered
except when a drop was being drawn
from it ; and we both took part in
measuring and recording the lengths
of the drops after the tubes had been
sealed and placed in water.

The standard solution employed for comparing with the sap
was sucrose. Of this substance a stock solution of 34-2 grams
in 100 cc. distilled water, i.e. a weight-normal solution, was
prepared. This solution, at a temperature of 20° C, has an

Fig. 70. — FUobolus longipes on
horse dung. The dung,
taken fresh from a stable,
was placed in a covered
crystallising di.sh. The
pliotograph shows part of
the culture four days later.
There are about 500 fruit-
bodies in view. Magnifica-
tion, 1 • 3.

144 RESEARCHES ON FUNGI

osmotic pressure of approximately 24 atmospheres,^ and from it
a series of other solutions was made, these solutions having
osmotic pressures of approximately 12, 10, 9, 8, 7, 6, 5, 4, and 3
atmospheres.

As a result of making five sets of experiments on five different
occasions, the sugar solutions having been freshly made and the sap
freshly collected on each occasion, it was found that the osmotic
pressure of the cell-sap of Pilobolus longipes is less than 24, 12,
10, 9, 8, 7, and 6 atmospheres and greater than 3, 4, and 5 atmo-
spheres. We may therefore take it that the osmotic pressure of
the cell-sap of P. longipes is approximately equivalent to 5-5
atmospheres.

The collective work of various investigators has shown that the
osmotic pressure of the cell-sap of the higher plants varies from about
3-5 atmospheres in the leaves of Aloe americana grown in a green-
house to upwards of 100 atmospheres in the leaves of plants growing
in the rocky desert of the Sahara ^ and to a maximum of about 170
atmospheres in the leaves of Atriplex nuUallii growing in the desert
areas of Utah (U.S.A. ).2 For the sake of comparison with Pilobolus,
a series of osmotic pressures determined by Dixon and Atkins
will now be cited. Dixon and Atkins * treated the leaves of a
number of different kinds of plants with liquid air, pressed out
the sap, measured the freezing point of the sap, and then calcu-
lated the osmotic pressure of the sap. Their findings, showing
the range of the osmotic pressures, have been embodied in the
adjoining Table.

Tjrp

^ This pressure was calculated from the equation : P = — — , where P is the

osmotic pressure in atmospheres, R the gas constant (0-082), T the absolute
temperature (293° C), g the grams of sucrose per litre of solvent (342), and M the
molecular weight of sucrose (342). Vide J. C. Phillip, Physical Chemistry, Its
Bearing on Biology and Medicine, London, 1925, p. 55.

^ Hans Fitting, " Die Wasserversorgung und die osmotischen Druckverhaltnisse
der Wiistenpflanzen," Zeitschrift fiir Botanik; Bd. Ill, 1911, pp. 270-271.

^ J. A. Harris, R. A. Gortner, W. F. Hoffman, J. V. Lawrence and A. T,
Valentine, " The Osmotic Concentration, Specific Electrical Conductivity, and
Chloride Content of the Tissue Fluids of the Indicator Plants of Tooele Valley,
Utah," Journal of Agricultural Research, Vol. XXVII, 1924, p. 909.

* W. R. G. Atkins, Some Recent Researches in Plant Physiology, London, 1916,
pp. 154-155.

THE PILOBOLUS GUN AND ITS PROJECTILE 145

Osmotic Pressure of Leaves as determined by Dixon and Atkins

Species and Dates

Aloe americana,* Jan. 11
Saccharum officinale * Dec. 10
Monstera deliciosa* Dec. 10 .
Anthiiriuin andreanum,* Jan

27 .
Platyceriuni alcicorne,* Jan. 2
Wistaria sinensis, Sept. 30
Anthurium crystallinum* J an

27 .
Vitis Veitchii, Oct. 2
Heliantlius multiflorus, Oct. 2
Equisetum tdmateia, lateral

branch, Aug. 14
Musa sapietdum* Dec. 10
Equisetumtelmateia, main stem

Aug. 14 .
Agave americana * Jan. 11
Selaginella mertensii,* leaves

and aerial stems, Jan. 27
Poll/podium iriodes* Jan. 27
Eucalyptus globulus, Nov. 29
Cordyline australis, Nov. 28
Passiflora quadrangular is, Dec

10

O.P.

3

52

5

83

6

64

7

49

7

51

' 8

52

8

73

9

18

9

18

9

28

9

44

9

64

10

11

10

16

10

65

11

68

13

43

13

98

Species and Dates

Ilex aquifolium, new, ultimate,

Dec. 4
Uhmis campestris, Oct. 2
Fraxinus oxyphylla, Oct. 3
Ilex aquifolium, antepenult!

mate, Dec. 4 . .

Pinus laricio, leaves one year

old, Nov. 30
Apium graveolens (etiolated

bases), Dec. 5
Populus alba, spring leaves

Aug. 28 . . ,

Chamaerops humilis, mature

Nov. 28 .
Hedera Helix, Nov. 29 .
Populus alba, summer leaves

Aug. 28 ,
Magnolia acuminata, Sept. 30
Cerasus laurocerasus, Nov. 28
Chamaerops humilis, just ex

panded, Nov. 29
Fraxinus excelsior, Sept. 30
Syringa vulgaris, Aug. 13
Syringa vulgaris, Aug. 22

O.P.

14-65

14-88
15-06

15-14

15-50

15-66

15-95

1713
17-29

17-88
18-07
18-31

19-22
19-52
24.10
25-50

Growing in greenhouses.

By reference to the Table it will be seen that in only one species,
namely, Aloe americana, was the leaf sap found to have an osmotic
pressure less than 5-5, i.e. less than that of Pilobolus. It is there-
fore evident that the osmotic pressure of the cell-sap of Pilobolus,
relatively to the osmotic pressure of the cell-sap of the leaves of most
of the higher plants, is low.

Factors in the Efficient Working of the Pilobolus Gun.— It may
be asked : how is it that the Pilobolus gun, notwithstanding that
its cell-sap has a relatively low osmotic (turgor) pressure, can shoot
its projectile to a maximum measured height of six feet and a
maximum measured horizontal distance of eight and a half feet ?
The answer is : firstly, an osmotic pressure of 5 - 5 atmospheres is,
after all, a strong pressure, for it is equal to about 82 lbs. to the
square inch ; and, secondly, the action of the Pilobolus gun is

VOL. VI.

146

RESEARCHES ON FUNGI

dependent on several different factors of which osmotic pressure is
only one, and among which we may recognise (1) the osmotic
pressure of the cell-sap, (2) the great elasticity of the cell-wall, (3) the
suddenness with which the aperture in the end of the sporangio-
phore is formed when the explosion takes place, (4) the control of

the explosion, in that
the wall of the sporan-
giophore breaks open
not irregularly but at a
single prepared place —
a circular subterminal
line or ring, and (5) the
opening at the end
of the sporangiophore
having a smooth rim
and being just of the
right size (not too large
and not too small) for
permitting the cell-sap
to be forced through
it in sufficient quantity
and with a sufficiently
high initial velocity
to carry off the projec-
tile advantageously. It
is the combination of
all these factors which
makes the Pilobolus
gun so wonderfully

Fig

71. — Pilobolus longipes. Pliotomicrograpli of
the upper side of a dischaiged sporangium and
of the drop of cell-sap (now dried) which
accompanied it ; No. 1, the precipitate of the
cell-sap, consisting of both organic and inorganic
matter, in part in the form of branched crystals ;
No. 2, a broad clear ring-layer of jelly in contact
with the glass on which the projectile came to
rest ; No. 3, the couve.x, very black, sporangium-
wall covering many thousands of spores ; No. 4,
a few spores lying under the jelly, they were
forced out of the sporangium when this struck
the glass. Magnification, 51.

effective.

An Analysis of the Cell-sap of Pilobolus longipes.— An inspection
of a vertical section through a fruit-body of Pilobolus longipes {cf.
Figs. 27 and 28, pp. 69 and 70) suggests that at least nine-tenths of
the fruit-body consists of cell-sap. When the sap is in situ in the
subsporangial swelling and stipe, it is a very clear fluid. Dissolved
within it, however, are various crystalloidal substances ; for, when
a few drops of the sap are extracted from a number of fruit-bodies

THE PILOBOLUS GUN AND ITS PROJECTILE 147

and are allowed to dry up in a watch-glass, a moderately heavy
white deposit is left behind. This deposit, when seen with the
microscope, is found to consist of a fine flocculent precipitate through
which run numerous, long, fairly thick, branched needles. A
similar deposit forms the halo around a discharged sporangium
(Figs. 71, 72, and 73). It is, of course, the substances dissolved in

^^^W^ ' •

H- • m ^

^% Is

■K ^ 9

■ *t ' ' * *' .

t

•

■ ' *

«» . .-

%

., . *-"

m " ' ' ' ' '

,

• ' *

' ,

* {|^ A

,

• «*f

• K

^^ *

^^•* "^ #

m^ f- *• ^

# **

«, •

?•*

«• •- <

®

A

»

•'

*

«

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*

«

•

•

•

•

*.

!,

®

,

'

'. -•

Fiu. 72. — Filohulwi lomjipes. Sporangia whicli were shot vertically up-
wards for a distance of 4 feet 7 inches on to the under surface of a
horizontal glass plate. Each sporangium is surrounded by a halo made
up of a precipitate of salts, etc., which were dissolved in the large
drop of cell-sap which accompanied the sporangium in its flight.
Photographed dry in transmitted light. Natural size.

the cell-sap which enable the sap to exercise its osmotic (turgor)
pressure.

Since the discharge of the projectile is in large measure due to the
osmotic (turgor) pressure of the cell-sap, and since this pressure is
due to the sap's content of dissolved substances, it is of interest to
determine what these substances are.

Employing the slide-crusher method already described, and
working on four cultures of Pilobolus longlpes which came to maxi-
mum fruition on four different mornings, I succeeded in harvesting

148 RESEARCHES ON FUNGI

about 8 cc. of cell-sap ; ^ and I gave the sap to my colleague Dr. H. P.
Armes, who very kindly undertook the task of analysing it chemically
in so far as that was possible with the limited amount supplied.

Dr. Amies' analysis of the cell-sap of Piloholus longipes yielded
the following results :

Total solids (dried at 150° C.) . . .1-84 grams in 100 cc.

Inorganic matter after ignition . . 1-14 grams per 100 cc.

The cell-sap contains : potassium, sodium, chloride, sulphate, phosphate,
and oxalate.

100 cc. contains 0-26 grams ^ phosphate ion (PO4).

100 cc. contains 0 • 14 grams ^ oxalate ion (CgO^).

There are indications of a carbohydrate, as shown by the Molisch
test. This carbohydrate is not a reducing sugar. Seliwanoff's
test is not given, so that sucrose is not present. Boiling with
dilute hydrochloric acid gives a solution which reduces Fehling's
solution. This might indicate a non-reducing sugar ( ? trehalose) .

From this analysis we may conclude that the osmotic (turgor)
pressure of the cell-sap of Piloholus longipes is largely due to phos-
phate and oxalate ions, but is also due in part to potassium, sodium,
chloride, and sulphate ions, and in part to some as yet unrecognised
carbohydrate, possibly a non-reducing sugar such as trehalose.*

The Landing of the Pilobolus Projectile and the Attachment of
the Sporangium to Herbage.— A sporangium, immediately after
being squirted of! the top of its sporangiophore, is in reality a concavo-
convex body which in side view (Fig. 74) has the appearance of a
plano-convex disc. As may be seen by reference to Fig. 30, C
(p. 73), it is bounded : (1) on its rounded upper and lateral sides by
the convex cap-like portion of the sporangium-wall, which is in-
tensely black except near its free margin where it is paler ; and
(2) on its under side, in part by the annular mass of transparent jelly
which on swelling split the sporangium-wall into two parts and thus
forced its way to the exterior of the sporangium, and in part by the
obtusely conical wall of the columella. To the lower margin of the

1 The harvesting process is a tedious one ; only about 1 cc. of sap was collected
per hour.

2 and ^ These amounts can be regarded as approximate only.

* When this Section was written Lepeschkin's analysis of the cell-sap of
P. longipes, recorded in Chapter I, p. 25, was unknown to me.

THE PILOBOLUS GUN AND ITS PROJECTILE 149

wall of the columella is attached, as shown in Figs. 35 (p. 79), 36
(p. 80), and 37 (p. 81), a very narrow circular collar-like band of the
sporangium-wall, which was separated from the convex cap-like
portion of the sporangium-wall when the pressure of the annular
mass of jelly caused the sporangium to dehisce. Within the
sporangium are enclosed many thousands of orange-yellow spores

• • • ^

WW

^

' •• •

• • •

• • ••

• m 1

^•••^•••i*« •

1

• • V •• •

• •

1

•^ ft ^ •

• . • t •
? A - • :

Fig. 73. — Pilobolus longipcs. The projectiles, eacli consisting of a spor-
angium and a large drop of cell-sap, were shot vertically upwards
for a distance of 4 feet 7 inches on to the under surface of a horizontal
glass plate. The drops then dried up and thus formed arovuid each
sporangiimi a white lialo of ])recipitated salts, etc. The photograph
is similar to tliat shown in Fig. 72, except that it was taken, not in
transmitted liglit, but against a black background in reflected ligiit.
Natural size.

(Fig. 30, C). As we shall see shortly, the fate of the spores is in a
high degree dependent on the peculiar physical properties of the
membranes which bound the siDorangium at the moment of its
discharge.

A Pilobolus projectile, as may be ascertained by examining it
immediately after it has struck a sheet of glass or paper, consists of
a sporangium and a large drop of cell-sap (Fig. 33, p. 77). When
the projectile strikes any object, e.g. a blade of grass, the drop of
cell-sap, owing to the force of impact, flattens out, and the sporan-

150 RESEARCHES ON FUNGI

gium takes up a position at or near the centre of the drop with its
gelatinous side turned toward the object struck as shown in Fig. 74, B.
The water in the drop and in the sporangium then evaporates, in
consequence of which the sporangium becomes fixed to its sub-
stratum by its gelatinous band and surrounded by a halo of tiny
particles precipitated from the drop of cell-sap (Figs. 72 and 73).
As the sporangium dries up, its content of spores and its band of
jelly shrink to such an extent that the free pale edge of the black
sporangial w^all comes into contact with the surface of the substratum.
Therefore, after a sporangium has landed on a blade of grass or
other herbage and has dried up, it is very firmly attached to its
substratum and, at the same time, its spores are all protected
from the light and from mechanical displacement by its tough
black wall.

The rule for the mode of landing of a sporangium, already briefly
stated, may be re-stated more precisely as follows : a sporangium
lands on any object which it happens to strike — no matter what may
be the velocity of the sporangium when it strikes and no matter
whether the surface of the object looks upwards or downwards or
is vertical — so that, with rare exceptions, its under gelatinous side
is turned toivard the surface of the object and its upper black convex
side away from the surface of the object. This remarkable rule has
long been known, for it was enunciated by Coemans^ in 18G1 and
discussed by Grove ^ in 1884. Coemans examined 413 sporangia
which had fallen on to a sheet of white paper set out to receive
them and he found that all but three of them had their gelatinous
sides turned downwards toward the paper. The three exceptional
sporangia were upside down and rested on their black sporangial
walls. Some observations of my own on the landing of sporangia
on the under side of sheets of glass, when the sporangia were travel-
ling at various speeds, will now be recorded.

Some fruit-bodies of Pilobolus longipes, attached to a small
mass of dung on which they were growing, were placed upright in
a compressor cell, so that their sporangia were only about 5 mm.

^ E. Coemans, "Monographic du genre Pilobolus," Mem. cour. et des Sav. etrang.
Acad. roy. de Belgique, T. XXX, 1861, p. 59.
2 W. B. Grove, loc. cit., j). 17.

THE PILOBOLUS GUN AND ITS PROJECTILE 151

[~

Fig. 74. — Diagram to illustrate tlie manner in which a projectile of Pilobolus Kleinii
strikes and adheres to an object in the path of its trajectory. A, a projectile
which is being shot upwards in the direction shown by the arrow and is about
to strike the cover-glass d. The projectile consists of : (1) a sporangium, filled
with spores, covered in part by a black unwettable sporangium-wall a and in
part by a basal gelatinous ring b and the wall of the columella (not here shown),
both of which are readily wetted ; and (2) a large drop of cell-sap c which has
been shot out of the subsporangial swelling of the Pilobolus gun concerned and
which adheres to the wettable structures just mentioned. A point on the left
side of the sporangium just below the arrow will strike the cover-glass first.
There will be a moment of momentum about tliis point and the drop of cell-sap will
quickly move upwards about the point, strike the cover-glass, and flatten out
upon it. As the drop flattens, it must inevitably push the unwettable black
wall of the sporangium away from itself and the cover-glass and drag the wettable
gelatinovis cell-wall and the wall of the columella toward itself and the cover-
glass. The result of all this, when the projectile has come to rest, is represented
at B. In B there are shown: a, the unwettable black sporangium-wall; b, the
wettable gelatinous ring surrounding the spores e ; and the drop of cell-sap c, which
is now flattened out on the cover-glass d. As the whole dries up, the sporangium
shrinks imtil the broken edge of the black wall touches the cover-glass, the drop c
becomes a halo of precipitated particles, and the gelatinous layer causes the
sporangium to adhere very firmly to the cover-glass. Magnification, G3.

152 RESEARCHES ON FUNGI

away from the under surface of the cover-glass. The sporangia
in due course were discharged. Although their initial velocity must
have been 10-20 feet per second ^ and they must have struck the
cover-glass within less than one five-hundredth of a second after
leaving their sporangiophores, yet, when they landed on the cover-
glass, they settled there with their gelatinous lower surfaces turned
upwards and in contact with the under surface of the glass (c/.
Fig. 74, B). The results of this experiment and of others ^ made
when determining the vertical range of the Pilobolus gun prove that,
whatever may be the speed at which it is travelling, a sporangium
normally lands on any object it may strike so that its basal gelatinous
surface is next to the surface of the object.

An attempt to explain why a sporangium lands'with its gelatinous
side toward the surface of the object struck was made by Grove ^
who says : " The upper surface of the sporangium is round and
practically smooth (though not actually so), and the lower edge and
face are occupied by the gelatinous substance. Now, when a
sporange is thrown upwards it will certainly rotate as it flies ; if
the smooth top only comes in contact with the glass (or other vertical
surface) it will not adhere, and the sporange will fall down again.
But, if any portion of the gelatinous substance touches the glass,
the force of progressive attraction between it and the thin film of
moisture which will usually cover the glass * must invariably bring
the lower, somewhat plane, surface of the sporangium in close
contact with the glass. In the case of the paper, the sporangia
would naturally roll over, if they fell on the convex surface, and
settle on their lower face." This explanation is unsatisfactory
because it fails to take into account the fact that a discharged
sporangium is accompanied by a large drop of cell-sap and also
involves two unsound assumptions : (1) that, if a sporangium
strikes a vertical surface by its smooth rounded black surface only,
it will fall to the ground ; and (2) that a vertical surface must be
covered by a film of moisture to enable the sporangium to stick to

1 Vide supra, p. 67. ^ Vide supra, pp. 65-66.

3 W. B. Grove, loc. cit., p. 17.

* Grove covered his culture with a bell-jar, on the inner surface of which
moisture was condensed.

THE PILOBOLUS GUN AND ITS PROJECTILE 153

it. The assumptions are not justified : for there is no evidence to
show that a sporangium ever strikes an object without sticking to
it, and there is plenty of evidence to show that a sporangium will
stick to the vertical surface of any object when the surface is
perfectly dry.

Ingold ^ has supposed that, from the moment the sporangium
is discharged, it trails behind the drop which carries it forward, so
that the drop always strikes the obstacle first and causes the spor-
angium to settle with its gelatinous side toward the obstacle. As
already pointed out in Chapter 1,2 it seems most unlikely that the
projectile, on leaving the sporangiophore, should rotate through
exactly 180° and no further.

A satisfactory explanation of the mode of landing of a sporan-
gium, as we shall see, can be made if one takes into account the
fact — hitherto noticed only by Ingold — that water can adhere to
the under side but not to the upper side of the sporangium or, in
other words, that the lower gelatinous side of the sporangium can he
wetted by water, whereas the upper convex side covered by the sporangial
wall is unwettable. The resistance to being wetted offered by the
sporangial wall may be due in part to the crystals of calcium oxalate
which protrude in such large numbers from its surface. Some
evidence to show that the sporangial wall actually is unwettable
will now be brought forward.

If one brings some freshly-discharged sporangia into contact
with water contained in a crystallising dish, they at once float (c/.
Fig. 76, B) at the surface wdth their lower gelatinous side immersed
in the water and their upper black convex side standing out of the
water, looking upwards, and appearing to be perfectly dry. The
sporangia will float in this way for several days. If one tries to
submerge the floating sporangia with a glass rod, it is difficult to
drive any of them below the surface of the water, and one perceives
that this is due to the resistance of the black sporangial wall to
being wetted and the consequent action of the force of surface
tension. When a sporangium has been submerged, one can see

1 C. T. Ingold, "The Sporangiophore of Pilobolus," The New Phylologist,
Vol. XXXI, 1932, pp. 58-63.

2 This volume, p. 46.

154

RESEARCHES ON FUNGI

that the surface of the black sporangial wall shines with a white
light owing to its being covered by a thin film of air.^

A wide test-tube was almost filled with water and then covered

with a dung-ball which bore a number
of Pilobolus fruit-bodies in such a way
that the fruit-bodies pointed directly
downwards to the water. After a time,
a number of the fruit-bodies discharged
their sporangia which were shot down-
wards at the surface of the water
which was only one centimetre or so
distant (c/. Fig. 75 in which the water
is 3 cm. from the sporangia). The
velocity of the sporangia was probably
not less than 10-20 feet per second.
Most of the sporangia were shot through
the surface film of the water, descended
through the water for a short distance,
and then slowly rose until they again
reached the surface film under which
they remained without breaking through
into the air. However, some of the
sporangia, when shot downwards, failed
to penetrate through the surface film of
water. This failure was evidently due
to the sporangium- wall being unwettable

Fig. 75. — The discharge of Pilobolus projectiles
into water. A wide test-tube was half filled
with water. A piece of horse dung bearing
fruit-bodies of Pilobolus longipes was then re-
moved from a culture dish and placed in the
mouth of the tube so that the sporangia
looked downwards. When the sporangia
were shot away, many of them failed to
penetrate the surface film of the water, owing
to the sporangial wall being unwettable.
Natural size.

1 A submerged sporangium may sink to the bottom of the water or slowly rise
and come to the surface, where it may either break through the surface film and
resume its old position with its black wall protruding clear above the water or it
may fail to break through the surface film and lie just beneath it.

THE PILOBOLUS GUN AND ITS PROJECTILE 155

and to the resistance consequently offered to the j)assage of the
sporangia by surface tension.

A number of sporangia were floating at the surface of some water
contained in a crystallising dish. With a pipette some of the water
and some of the sporangia were removed from the dish, and a drop
of the water bearing a sporangium was caused to hang at the end
of the pipette, as shown in Fig. 76, A. The sporangium remained
at the surface of the hanging drop in an inverted position, with

Fig. H\.- Piloboluv loiKjipes. Diagrams sliowing sporangia in water. The
vvettable annular naass of jelly of each sporangium is immer.sed in
tlio surface film of water, while the black vmwettable sporangial
wall protrudes into the air. A, a sporangium attached to a drop of
water hanging from a pipette. B, a test-tube partly filled with water,
and C another test-tube overfilled with water. Some sporangia have
been placed in the water film. As indicated by the arrows, the
sporangia in B move toward the centre of the surface film of water,
while those in C move toward the edge. If the black sporangial
wall were wettable instead of unwettable, the movements would be
in directions opposite to those indicated. Somewhat enlarged.

its gelatinous side submerged in the surface film of water and its
unwettable black convex side protruding into the air.

As is well known, glass is wettable by water and, when water
is set in a glass dish, the water film bends upwards against the glass.
If now tiny wettable objects which float, such as hollow glass beads,
are set in a small glass vessel containing water, they move to the
sides ; whereas, if similar objects but unwettable, such as hollow
glass beads coated with paraffin wax, are set in the water, they move
away from the sides of the vessel toward the middle of the film of
water. ^ Some sporangia of Pilobolus were placed in water contained

1 C. V. Boys, Soap Bubbles and the Forces which Mould them, The Romance
of Science Series, S.P.C.K., London, 1895, pp. 33-34.

156 RESEARCHES ON FUNGI

in a test-tube one inch in diameter. They behaved like paraffined
beads, i.e. they at once moved away from the sides of the test-tube
and collected in the middle of the surface film of water (Fig. 76, B).

If a small glass vessel is over-filled with water so that the surface
film of water bends downwards to the glass rim, tiny wettable
floating objects, such as unparaffined hollow glass beads, move from
the sides of the vessel to the centre of the film of water, whereas
tiny un wettable floating objects, such as paraffined hollow glass
beads, move from the centre of the water film to the sides of the
vessel. 1 Some sporangia of Pilobolus were placed in water which
overfilled a wide test-tube one inch in diameter. They behaved
like paraffined glass beads, i.e. they at once moved away from the
centre of the surface film of water and came into contact with the
rim of the test-tube (Fig. 76, C).

The two physical experiments just described afford further
evidence that the black convex sporangial wall of Pilobolus is
unwettable.

In the light of the observations just recorded, an attempt will
now be made to explain how it is that a discharged sporangium
always settles on any object it strikes so that its basal gelatinous
side is turned toward the surface of the object.

The Pilobolus projectile consists not of a sporangium only as
Grove and others have supposed but, as we have seen, of a sporangium
and a large drop of cell-sap. Owing to the fact that the gelatinous
under side of the sporangium is wettable while the black convex
upper side is unwettable, it is clear that, as the sporangium is
travelling through the air, the drop of sap must be attached to the
gelatinous side of the drop, as shown in Fig. 74, A (p. 151) ; and
this view is supported by the pipette-drop observations described
above. It may well be, as Grove supposed, that the projectile
rotates as it travels forward, but whether it rotates or not does not
make any difference to the explanation of the mode of settling of
the sporangium, which is now about to be given.

Let us suppose that a Pilobolus projectile is travelling vertically
upwards toward a sheet of glass. As it is about to strike the surface

1 C. V. Boys, Soap Bubbles and the Forces which Mould them, The Romance
of Science Series, S.P.C.K., London, 1895, pp. 33-34.

THE PILOBOLUS GUN AND ITS PROJECTILE 157

of the glass there are five possible ways in which its two elements
may be arranged : (1) the drop of cell-sap may be directly in front
of the sporangium, so that the axis of the projectile is perpendicular
to the surface of the glass ; (2) the drop of cell-sap may be more or
less in front of the sporangium, so that the axis of the projectile is
inclined to the surface of the glass ; (3) the sporangium and the drop
of cell-sap may be side by side, so that they strike the glass simul-
taneously ; (4) the sporangium may be more or less in front of the
drop of cell-sap, so that the axis of the projectile is inclined to the
surface of the glass ; and (5) the sporangium may be directly in
front of the drop of cell-sap, so that the axis of the projectile is
perpendicular to the surface of the glass. All these possible arrange-
ments must now be considered and, for the sake of convenience,
they will be considered in the following order: (1) and (2), (4),
(3), and (5).

(1) and (2). If the dro2J of cell-sap is either directly or more or
less in front of the sporangium, the drop will strike the surface of
the glass first, flatten out there, and so cause the sporangium, which
owing to adhesion cannot leave its surface, to take up a position at
or near its centre, so that the gelatinous side of the sporangium will
be turned toward the surface of the glass and the unwettable convex
side will be turned away from the surface of the glass and will project
freely into the air, as shown in Fig. 74, B.

(4). If the sporangium is more or less in front of the drop of the
cell-sap, but not directly in front as in case (5), as shown in Fig. 74, A,
the sporangium will strike the surface of the glass first and a moment
of momentum about the point of first contact of the sporangium
with the glass (to which the arrow in Fig. 74, A, points) will rotate
the projectile (to the left in Fig. 74, A), with the result that the
drop of cell-sap will strike the surface of the glass, spread out owing
to the force of impact and, in spreading out, drag the sporangium
round by its adhesive wettable side at the same time pushing away
its non-adhesive unwettable side, thus forcing the sporangium to
take up a position at or near the centre of the drop with its gelatinous
under side toward the glass and still in contact with the water and
with its black convex side projecting into the air.

(3). If the sjjora7igium and the drop of cell-sap strike the surface

158 RESEARCHES ON FUNGI

of the glass simultaneously, the drop will flatten out on the surface
of the glass and force the sporangium to take up its characteristic
position on the glass by the same means as described under (4).

(5). If the sporangium is directly in front of the drojJ of cell-sap
so that the axis of the projectile is perpendicular to the surface of
the glass, the sporangium will strike the surface of the glass first
and be momentarily overwhelmed and imprisoned between the
glass and the drop ; but, immediately thereafter, owing to the
lateral spreading of the drop and to the unwettability of the spor-
angium-wall, it is probable that the thin water-film covering the
sporangium will break in such a way as to cause the drop to pull

Fig. 77. — Pilobolus longipes. Diagram showing in lateral view the
position of a discharged sporangium after landing on a sub-
stratum. A, normal position ; sporangium attached to the sub-
stratum by its gelatinous ring. B and C, abnormal positions.
B, sporangium resting on its side, gelatinous ring and spores partly
displaced from their normal position. C, sporangium upside
down ; it has no gelatinous ring. Magnification, about 44.

the sporangium round through an angle of 180° and so cause the
sporangium to reverse its former position, and take up the nor-
mal position for a discharged sporangium, namely, that shown in
Fig. 74, B.

Summing up the explanation given above, it may be said in
general terms that a sporangium settles on any object it may strike
by its gelatinous side because its gelatinous side is wettable and its
convex side covered by the black sporangial wall is unwettable.
and because the sporangium is accompanied to its destination by
a large drop of cell-sap.

Very occasionally, a sporangium lands on the side of a glass
plate or other object so that it comes to rest in an abnormal manner,
i.e. so that its gelatinous side is not flattened out against the object
struck and so that it rests on its side (Figs. 77, B, and 78, A) or on

THE PILOBOLUS GUN AND ITS PROJECTILE 159

its apex (Figs. 77, C, and 78, B) or in some intermediate position.
I have observed that two sporangia which had landed upside-down
had lost their gelatinous ring (Figs. 77, C, and 78, B). It seems
likely that the loss of this wettable substance was the cause of the
sporangia coming to rest upside-down. The sporangium which
had landed in such a way as to rest on its side (Figs. 77, B, and 78, A)

Fig. 78. — Pilobolus longipen. Two projectiles which landed on a glas.s glide abnor-
mally ; seen from above under the low power of the microscope. A, the sporangium
is resting on its side : a, the sporangium -wall ; b, spores, outside the
sporangium ; c, the gelatinous ring, abnormally torn and displaced ; d, pre-
cipitate from the drop of sap which accompanied the sporangium. B, the
sporangium is resting upside down ; it lacks its gelatinous ring : a, the
sporangium-wall incurved over the spores ; b, spores inside tlie sporangium ;
c, the columella through which spores can be seen ; d, precipitate of crystals
and amorphous particles from the drop of sap which accompanied the
sporangium ; e, the surface of the glass slide. Magnification, lUU.

had its gelatinous ring broken and displaced. Here, again, the
abnormal position taken up by the sporangium appears to have
been caused by an accident to the gelatinous ring, in this case its
displacement from its usual position.

It has been shown (1) that the sporangium alights on any object
it strikes so that its gelatinous side is turned toward the object
struck and (2) that the ring of jelly, on drying up, attaches the
sporangium to its substratum. We may now enquire into (3) the
effectiveness of the attachment after it has once been accomi)lished.

i6o RESEARCHES ON FUNGI

The gelatinous ring of a sporangium of Pilobolus Kleinii which
has dried up on a sheet of glass is so strongly attached by its lower
surface to the glass and by its upper surface to the lowest layer of
the spores which make up the spore-mass that, if one scrapes the
sporangium off the glass with a knife, the dried-up gelatinous ring
and the adherent lower halves of the walls of the lowest layer of
spores are left behind together in situ. The broken walls of the
spores are colourless and, in the mass, form a hexagonal pattern
reminding one of honey-comb. When a drop of water is added,
the jelly swells up and each hexagonal half-spore wall separates
from its neighbours and comes to have an oval outline.

Under natural conditions in the open, Pilobolus Kleinii, P.
longipes, etc., grow in pastures on the dung-plats of horses, cows,
and other herbivorous animals, and the sporangia which their guns
shoot away strike and stick to the surface of leaves, stems, and
inflorescences of grasses and other plants making up the surround-
ing herbage (Fig. 80, p. 164) ; and the sporangia, on drying up,
become very firmly attached to their substrata, so firmly indeed
that the wind, however strongly it may blow, cannot dislodge
them.

Sporangia which have dried up are also not easily dislodged from
their places of attachment by falling drops or moving films of water.
Evidence of this fact was obtained from some experiments which will
now be described.

A plate of glass to which a number of sporangia were attached
was set obliquely under a tap in such a way that six of the sporangia
were struck by a rapid stream of large water drops which fell from
the nozzle of the tap for a distance of about one foot. All of the
six sporangia withstood the hammering of the drops unmoved for
half an hour. Then one of them was washed away. The other
five were washed away in the course of the next two and a half hours.
A number of other sporangia which were on the plate and were
washed by the stream of water running down the plate for three
hours were, at the end of this time, still attached to the plate in
their original positions.

In another experiment, a postage stamp was stuck on a glass
plate to which some sporangia were already attached and, as before,

THE PILOBOLUS GUN AND ITS PROJECTILE i6i

drops of water were allowed to fall from a tap on to some of the
sporangia ; and the plate was so arranged that the stream of water,
after leaving the sporangia, ran over the postage stamp. The
postage stamp was washed off the plate in 3 • 5 minutes, whereas
the sporangia withstood the impact of the drops for half an hour.

The effectiveness of the gelatinous ring in enabling the sporangium
to cling to its substratum even when battered by large drops of
water as in the experiments just described appears to be due to the
fact that the jelly, after being dried and placed in water again,
swells up by the absorption of water but only to about its original
volume, so that, unlike the mucilage on a postage stamp, it does
not dissolve in water.

From the observations just recorded we may conclude that,
under natural conditions in pastures, the sporangia are so effectively
attached by their gelatinous bases to the herbage on which they have
alighted that, in dry weather, they cannot be detached from their
substrata by the strongest winds and, in wet weather, they cannot
easily be detached by prolonged rain or even by violent thunder-
storms.

The Relations of Pilobolus with Flowering Plants and with
Herbivorous Animals. — Pilobolus is a highly specialised copro-
philous fungus which is dependent for its existence : firstly, on
flowering plants which provide its sporangia with a temporary but
prospectively favourable lodging-place and, secondly, on herbivorous
animals which swallow the sporangia and herbage together, break
open the sporangia and disperse the spores within their alimentary
canals, and finally extrude the spores undamaged in their solid
faeces. The spores, thus sown in dung-plats in pastures, rapidly
germinate, and the mycelia to which they give rise soon develop
new fruit-bodies which, in their turn, shoot away their sporangia
on to the surrounding herbage (Fig. 79).

The smaller sporangia of Pilobolus Kleinii and of P. longipes are
often shot to a horizontal distance of 3-5 feet whilst the largest ones,
as we have seen, are sometimes shot a horizontal distance of about
8 feet. Therefore, when fruit-bodies of these species are growing on
a dung-plat in a pasture, hundreds of sporangia may be, and often
actually are, shot away so as to dot the leaves and stems of grasses

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THE PILOBOLUS GUN AND ITS PROJECTILE 163

and other plants growing on many square feet in the neighbourhood
of the dung-plat.

The discharge of the Pilobolus guns brings about the dispersion
of the sporangia but not of the spores ; for each sporangium, on its
flight through the air, carries all its spores with it and, after it has
become fixed to the leaf or the stem of a flowering plant (Fig. 80),
its tough black indissoluble sporangial wall prevents the spores from
escaping from its interior. When a sporangium has once become
attached to a flowering plant, neither wind nor rain can dislodge it
or open it, so that clearly wind and rain can have nothing to do with
the dispersion of the spores. The dispersion of the spores can be
effected only through the agency of herbivorous animals.

The greater the horizontal range of the Pilobolus gun, the greater
the number of square feet of herbage surrounding dung-plats which
will become sprinkled with sporangia, and the greater the chance
of the sporangia being swallowed by horses, cows, and other
herbivora. Hence the great violence of discharge of the sporangia
is a factor which, in the end, favours the dispersion of the spores
and the persistence of Pilobolus species.

The heliotropic response of the fruit-bodies of Pilobolus results in
each sporangium being shot toward the source of the strongest inci-
dent rays of light and, therefore, 171 the direction in which there are
fewest obstacles to its flight through the air. In laying the Pilobolus gun,
light is used in the most efficient manner as a directive agent. The
discharge of the sporangia in the direction of least resistance to
their flight favours the scattering of the sporangia on surrounding
herbage and, therefore, ultimately increases the chance of the
sporangia being swallowed by herbivorous animals.

As a rule, only the spores of sjJorangia which are swallowed by a
grazing animal find their way into a dung-plat. Hence the import-
ance of the sporangia becoming firmly fixed to the flowering plants
which they happen to strike and being thereby prevented from
falling to the earth where they would be wasted. Hence therefore,
also, the advantage of the discharged sporangium being provided
with a strongly adhesive gelatinous ring, and of the sporangium
always landing with the ring toward the surface of the flowering
plant. It is the resistance to being wetted offered by the wall of

164

RESEARCHES ON FUNGI

Fig. 80. — Living shoots of a wild grass, bearing numerous, firmly adherent sporangia
of Pilobolufi longipes. The sporangia were shot on to the leaf-blades, leaf-
sheaths, and st^m from fruit-bodies growing on near-by horse-dung balls
contained in a large culture chamber in the laboratory. Photographed through
a green screen. Natural size.

THE PILOBOLUS GUN AND ITS PROJECTIT.E 165

the sporangium which enables the drop of cell-sap accompanying
the discharged sporangium to turn the sporangium round at the
moment of landing so that the gelatinous ring comes into contact
with the surface of the object struck. The unwettability of the
sporangium-wall, in promoting the fixation of the sporangium,
indirectly promotes the dispersion of the spores.

After a sporangium has become attached to the leaf or stem of
a grass or other flowering plant, many weeks or even months must
often go by before it is swallowed by a herbivorous animal. During
this time it may be exposed for a great many hours to brilliant
sunshine and yet (there is every reason to suppose) the spores retain
their vitality unimpaired. The spores of Pilobolus have colourless
spore-walls and therefore, like the colourless spores of Schizophyllum
commune and Daedalea unicolor,^ they might be killed by prolonged
exposure to the sun's direct rays ; but they are protected from any
possibly injurious rays of light by the sporangium-wall which is so
intensely black that it must absorb practically all the light which it
does not reflect or diffuse.^

1 These Researches, Vol. I, 1909, pp. 24-2G.

2 Coprinus, Panaeolus, Anellaria, Sordaria, and certain other genera of copro-
philous fungi have black spores. These spores, like the black sporangia of Pilobolus,
settle on and become firmly fixed to the stems and leaves of grasses and other
flowering plants in pastures, and they must often wait through long periods of
sunny weather before they are swallowed by herbivorous animals (c/. these Researches,
Vol. Ill, pp. 229-230). While exposed to sunlight, these spores are protected
from possibly injurious rays of light by their own light-screens, namely, their rather
thick black walls. In Pilobolus where the spores in a sporangium are protected
by a common light-screen, namely, the black sporangial wall, and the spore-walls
therefore cannot function as light-screens, the spore-walls are colourless. The
presence of a blackish pigment in the wall of the sporangium and the absence of
such a pigment from the walls of the spores are just what might be expected if, as
I think probable, the sporangial wall does actually protect the spores from injurious
rays of light.

While in Coprinus, Panaeolus, etc., as we may suppose, the pigment in the
spore-wall enables the wall to act as a light-screen and is therefore functionally
useful, in other equally coprophilous fungi, e.g. Aleuria vesiculosa, Lachnea stercorea,
and Huinaria granuJata, the spore-walls are colourless. It is possible that, in these
species, owing to the fact that the spore-walls are colourless and therefore cannot
function as a light-screen, the spores, when exposed to sunlight, are more readily
killed than the black spores of Coprinus, etc. An experimental test of this suggestion
is desirable.

The spores of Hypoxylon, Xylaria, Rosellinia, Bulgaria, and certain other
fungi which are not normally coprophilous but live on dead wood or other plant

i66 RESEARCHES ON FUNGI

That the spores contained in sporangia attached to grasses, etc., do
actually retain their vitahty for at least nine months may be inferred
from the fact that at Winnipeg, in March and April, i.e. toward the
end of the long winter, horses fed in stables on hay which has been
gathered in the previous summer yield dung-balls which often produce
fruit-bodies of Pilobolus Kleinii and P. longiiies in great abundance.

The sporangial wall becomes impregnated with its black pigment
long before the sporangium is shot away ; and, therefore, if there
were no subsporangial swelling, the sporangium of an intact fruit-
body would, when the fruit-body was turning toward the light, cut
off light from the stipe and render an accurate heliotropic reaction
to the strongest incident rays impossible. The intercalation of the
subsporangial swelling, which acts as an ocellus, between the black
sporangium and the stipe is an admirable arrangement which
neutralises the shadowing effect of the sporangium, enables the
stipe to turn the subsporangial swelling and sporangium toward the
source of strongest light with a considerable amount of precision
and, therefore, increases the chance of the sporangium being shot to
a distance on to herbage.

substances are as black as those of Ccprinus, Panaeolus, etc., although they are
not of necessity exposed to sunlight for long periods of time. Their black walls
must act as a light-screen to the protoplasm contained in their interior, but it is
possible that the pigment is a mere by-product of the metabolism concerned with
the development of the wall and, for tlie spores in question, is of little or no ecological
significance. The black pigment in the walls of the outer cells of the shoe-string-like
rhizomorpha subterranea of Armillaria mellea and of the cells making up the blocking
layer of the mycelium of Pohjporus squamosals, Fomes applanatus, Armillaria mellea.
and many other wood-destroying fungi (vide /w/ra. Vol. VII),so far as the absorption
of light is concerned, can be of no possible ecological significance since the pigment
is present in structures which normally are developed only in the dark.

In support of the view that the black pigment of the sporangium-wall of Pilobolus
and the black pigment of the spore-walls of Coprinus, etc., do actually protect the
spores from injurious radiation may be cited the recent work of Rabinovitz-Sereni
(" II grado di resistenza di alcuni funghi aU'azione dei raggi ultravioletti," Boll.
R. Staz. Pat. Veg., N.S., XII, 1932, pp. 115-144; cited from Rcrieic of Applied
Mycology, XI, 1932, pp. 737-738) who found that " dark thick-walled conidia such
as those of Helminthosporium gibberosporum, Coniosporium bambusac, and Epicoccum
purpurascens resisted the exposure to ultraviolet light for 180 minutes ; slightly
olivaceous conidia, such as those of Microascus stysanus and Pe)iieiUium crustaeeutn
withstood exposure for 25 minutes, while hyaline conidia, such as those of Clouo-
slachysaravcaria, Fusariv7)i Diartii, und the pycnospores of Deuterophonia tracheiphila
withstood exposure for only 10 minutes."

THE PILOBOLUS GUN AND ITS PROJECTILE 167

Mucor and Pilobohis are closely related genera and it may well
be that Pilobolus, through Pilaira, was evolved from a Mucor. It is
therefore not without interest to compare the sporangial walls of
these two genera. The sporangial wall of Mucor is wettable, non-
persistent in that it is diffluent in water, and more or less colourless ;
whereas the sporangial wall of Pilobolus is unwettable, persistent and
not diffluent in water, and intensely black. The unwettability,
persistency, and high pigmentation of the sporangial wall of
Pilobolus can all be regarded as special adaptations which con-
tribute to the success of Pilobolus as a coprophilous fungus ; for, as
we have seen : (1) the unwettability of the wall is a prime factor in
causing the sporangium to alight on any object with its gelatinous
side turned toward the object : (2) the persistency of the wall
enables the wall, when the sporangium is attached for weeks or
months to a flowering plant, to prevent the spores from escaping
from the sporangium even during rainy weather ; and (3) the
intensely black pigment in the wall enables the wall to absorb sun-
light and thus to act as a light-screen in cutting off injurious rays
of light from the spores which lie beneath it.

After swallowing a sporangium attached to a blade of grass, a
herbivorous animal must often travel many miles before extruding
the faeces in which the spores have become embedded. Hence it is
clear that herbivorous animals are responsible for the geographical
distribution of Pilobolus under natural conditions. It may also be
remarked that, since the sporangia of Pilobolus cling so tenaciously
to dry grass, the commercial transportation of hay must often
involve the spread of Pilobolus species from one country to another.

Often, on a cow dung-plat or a horse dung-plat in a field, one
may observe several hundred fruit-bodies of Pilobolus producing
sporangia at one and the same time. Let us suppose that the fruit-
bodies of Pilobolus Kleinii produced on a single dung-plat in the
course of several days have shot away 1000 sporangia on to the
surrounding grass and that, on the average, each sporangium con-
tains 45,000 spores. Then the total number of spores contained in
the sporangia on the grass will be 45,000,000. When a horse or a
cow comes and grazes near such a dung-plat as the one under con-
sideration, in a few minutes it may take hundreds of sporangia into

i68 RESEARCHES ON FUNGI

its alimentary canal so that, in the end, its faeces— deposited several
days later in various places in the pasture — will be thickly sown with
hundreds of thousands, or even millions, of Pilobolus spores. Owing
to (1) the very efhcient way in which the sporangia are discharged
and fixed to herbage, (2) the large number of the sporangia and still
larger number of the spores often produced ^on a single dung-plat,
and (3) the high probability that sporangia attached to herbage will
be swallowed sooner or later by a herbivorous animal, it is not
surprising that Pilobolus is so successful in maintaining its existence
in pastures and often flourishes there in such great abundance.

Pilobolus gives to flowering plants and herbivorous animals
nothing in return for their services in dispersing its spores. However,
although Pilobolus does not pay for what it receives, it imposes on
the organisms which assist it a burden which is so light as to be
practically negligible.

CHAPTER III

PILOBOLUS UMBONATUS, A NEW SPECIES, WITH
REMARKS ON THE PILOBOLIDAE

Introduction — General Description — Taxonomic Description and Latin Diagnosis —

Remarks on the Pilobolidae.

Introduction. — In the winter of 1931-1932, two species of Pilo-

bolus, P. longipes and P. Kleinii, were being cultivated and studied

in the botanical laboratory of the University of Manitoba. These

fungi commonly appeared on fresh horse

dung, cow dung, etc., brought into the

laboratory. Hans Ritter, a boy eleven years

old, became interested in these cultures and

made many similar ones for himself. His

microscope was provided with a low-power

objective only. With the help of this

instrument he became well acquainted with

P. longipes and P. Klemii. One day he

observed on a horse-dung culture a Pilo-

bolus which he had not previously seen

(Fig. 105, A, B, C, and D, p. 210), and

he at once brought it to my laboratory,

where an examination showed that it was

a new species not yet described by any

mycologist.

The new species is distinguished from all
other species of the genus by its decidedly
umbonate sporangium (Fig. 81) and it is on this account that
I have named it u^nbonatus.

Shortly after becoming acquainted with Pilobolus umhonatus,

109

Fig. 81. — Pilobolus urn-
bona t us. Wild,
small fruit-l)ody, in
air. Magnification,
Gl.

170 RESEARCHES ON FUNGI

I happened to be writing to the late Dr. Roland Thaxter of Harvard
University and, in the course of my letter, hoping to receive from
him some comment on the matter, I mentioned the new Pilobolus
and gave a brief description of it . In his reply he informed me that he
had known my P. uinhonatus for forty years and that its chief sub-
stratum was sheep dung.^ Thus the species occurs not only in central
Canada but also in the eastern part of the United States of America,
General Description. — Pilobolus umbonatus was obtained
upon horse-dung balls taken from the streets of Winnipeg in mid-

'*^.^

Fig. 82. — Pliotomicrogia.pli ot a mass of spores of
Pilobolus umbonatus (small, ellipsoid) together with
five spores of P. longipes (large, rounded-oval).
Magnification, 510.

winter of the years 1931-1932 and 1932-1933. The balls were
brought into the laboratory and were placed in a crystalhsing dish
covered with a glass plate. Soon they thawed and, after a few days,
the fruit-bodies of the new species began to appear upon them.
New crops of fruit-bodies came up each day for four or more days
in succession. Well-grown fruit-bodies are 7-9 mm. in length but
much shorter fruit-bodies have often been seen (c/. A and B in
Fig. 105, p. 210). It was observed on one dung-ball that the length
of the fruit-bodies diminished as successive crops appeared : on the

1 Roland Thaxter : "I have known that ' umbonate ' Pilobolus for many
(40) years. You will find that on its natural substratum, which is more commonly
sheep dung, it varies from a sharply pointed type to one which is quite bluntly
rounded." In litt., Feb. 12, 1932.

PILOBOLUS UMBONATUS

171

first day the length was about 7 mm., on the second day about
5 mm., on each of the next five days 2-3 mm., and on the next day
only about 1-5 mm. The reduction in length of the fruit-bodies
was chiefly due to a shortening of the stipe and, no doubt, was
associated with a gradual diminution of the food supply. The
sporangia were shot away in the usual manner, and sporangium-
deposits were obtained upon glass slides.

As compared with Pilobolus longipes and P. Kleinii, P. umbonatus

Fig. 83. — Photomicrograph of spores of three species of Pilobolus ;
P. umbonatus (very small, pale, ellipsoid) ; P. Kleinii (much
larger, darker, ellipsoid) ; and P. longipes (three only to the
right, rounded-oval, very large and dark). Magnification, 510.

is to be regarded as a smaller and more dehcate species. This may per-
haps be reahzed by comparing Figs. 81, 84, and 88, which respectively
show a rather small, a very large, and a medium-size fruit- body of
P. umbonatus, with Fig. 85, which shows a medium-size fruit-body of
P. longipes, and with Fig. 86, which shows two medium-size fruit-
bodies of P. Kleinii. All these Figures have the same magnification.

The spores are ellipsoid and very small, their dimensions being
5- 0-6-0 X 3 -0-3 -8 \i. Singly they appear quite colourless, but in
the mass they are yellow.

The photomicrograph reproduced in Fig. 82 shows a mass of
Pilobolus umbonatus spores together with five of the rounded-oval.

172

RESEARCHES ON FUNGI

much larger, P. longipes spores ; while the photomicrograph repro-
duced in Fig. 83, with the same magnification as for Fig. 82, shows
spores of P. umbonatus, P. Kleinii, and P. longipes in a single
field of view. In Fig. 83 one can readily distinguish the spores
of P. umbo7iatus by their ellipsoid form, paleness, and very

small size from those of P. Kleinii which,
although also ellipsoid in form, are very
much larger and darker, and from those
of P. longipes (three only, to the right)
which are rounded-oval in form, very
much larger, and darker. Thus Figs. 82
and 83 serve to demonstrate, in respect
to the nature of their spores, how very
distinct from one another are P. umbo-
natus, P. Kleinii, and P. longipes.

At room temperatures, in hanging drops
of cleared dung-agar, in the course of two
days, the spores of Pilobolus umbonatus
swell up greatly and put out germ- tubes
(Fig. 89, A, p. 181). Thereafter the germ-
tubes branch and develop into myceha
(Fig. 89, B-D) with the usual two kinds of
hyphae : (1) main hyphae which become
very thick, contain much orange-yellow
protoplasm, and give rise to basal swellings
(trophocysts) of fruit-bodies ; and (2) much
smaller lateral hyphae which doubtless
send protoplasm and other materials into
the main hyphae.
The basal swellings (trophocysts) of fruit-bodies arise as rounded
or oval swellings in the coarse stolon-like hyphae (Fig. 89, B-D,
p. 181). They may be apparently terminal at the end of a hypha
(Fig. 90, C-E, p. 182) or be obviously intercalary (Figs. 89, D, and
90, A, B). Sometimes they are dispersed at intervals along a single
longer hypha (Fig. 90, G). Each basal swelling gives rise to a stipe
and, as the stipe grows out from it, it usually becomes more or less
turnip-shaped (Figs. 90, C-E, and 105, C, D, and H, pp. 182 and 210).

Fig. 84. — Pilobolus umbo-
natus. Large fruit-body
from pure culture. Mag-
nification, (51.

PILOBOLUS UMBONATUS

^73

The stipe at its base where it adjoins the basal swelling is about
0-065 mm. thick. It increases slightly in thickness upwards until,
just beneath the subsporangial swelling, it is about 0-1 mm. thick.
At the top of the stipe,
just beneath the sub-
sporangial swelling,
there is an orange
band of protoplasm.

The subsporangial
swelling (Figs. 81, 84,
88, and 105, C-E) is
ellipsoid, its greatest
diameter being about the
middle of its length. In
well-grown fruit-bodies
it is about 0-65 mm.
long and 0-46 mm.
wide. Like the stipe, it
exudes numerous colour-
less mucilaginous drops
(Fig. 84). In lateral
view in air, when seen
with a hand-lens, its
base appears very pale,
thus differing from the
subsporangial swellings
of P. longipes and P.
Kleinii in which an
orange tint is readily
observable.

The subsporangial
swelling of Pilobolus um-
bo7iatus resembles that

of P. longipes in being ellipsoidal and having its maximum diameter
about the middle of its length, but differs from that of P. Kleinii
which is distinctly pyriform (c/. Figs. 81, 84, and 88 with Figs. 85
and 86).

Fig. 8.5. — Pilobolus longiprs. Upper part of a wild
fruit-body of medium .size. Drops on sub.spor-
angial swelling drying up, tho.se on sporangium,
already dry. Transparent jelly around base of
dehisced sporangium not visible in the photo-
graph. Magnification, (Jl.

174

RESEARCHES ON FUNGI

Pilobolus umbonatus is unique among Piloboli in having a
sporangium which is more or less conical and decidedly umbonate
(Figs. 81, 84, and 105, C-F). This characteristic enables one to

Fig. SG.^Pilobolus Kleitiii. Two wild fruit-bodies of medium size,
left with drops, right with drops removed or dried up. Trans-
parent jelly around base of each dehisced sporangivim invisible in
the photograph. Subsporangial swellings pyriform. Magnifi-
cation, 61.

recognise the species with certainty even with a hand-lens. Hundreds
of sporangia have been observed and in every one a more sharply-
rounded or less sharply-rounded umbo was present. The width of
the sporangium in well-grown fruit-bodies varies from about 0 • 2 to
0-26 mm., and the height of the sporangium from about 0-14 mm.
to 0-19 mm.

PILOBOLUS UMBONATUS

175

The sporangium-wall is intensely black except below, where it is
very pale-grey or colourless. After a sporangium has dehisced and
just before it is discharged, one can observe the colourless lower
part or fringe of the -sporangium-wall overlying the protruding jelly.

The ratio of the width of the sporangium to the width of the
subsporangial swelling in Pilobolus umbonatus is almost exactly |,
whereas this ratio in P.
longipes is about f and in
P. Kleinii about f. When
one looks at a living fruit-
body of P. umbonatus in
side view with a hand-lens,
one perceives at a glance
that the width of the
sporangium relatively to
the width of the subspor-
angial swelling is much less
in this species than in P.
longipes and P. Kleinii.
An apical view of a fruit-
body showing both sporan-
gium and subsporangial
swelling is reproduced in
Fig. 105, F (p. 210).

A sporangium, after
being discharged, dries
and shrinks and becomes

acutely pointed (Fig. 105, K). When sporangia of P. umbonatus,
P. longipes, and P. Kleinii have been discharged on to the side of
a glass dish and lie mixed near the top and one examines them in
lateral view with a hand-lens, one can readily distinguish those of
P. umbonatus from the two other species by the fact that the former
are conical in shape, whereas the latter are rounded.

When a sporangium which has just been discharged on to a glass
sHde and has dried (Fig. 87) is examined from above with the
microscope, it can be seen : (1) that the main convex portion of the
sporangium-wall, which covers the spores, is intensely black and is

M

Ik

f

!

*

\

«

' i

r

.

•

f

'■'i

i

K

>

i

i-

r

i

J

' fl

■

1

1

2

1

»

1

1

•

P

*

1

*

Fig.

87. — Pilobolus umbonatus. Photomicro-
graph of the upper side of a dried discliarged
sporangium on a glass sHde. No. 1, tlie dried
cell-sap ; No. 2, the broad fiat clear ring-
layer of jelly : No. 3, the narrow transparent
fringe of the sporangium -wall overlying the
jelly ; and No. 4, the convex very black
main portion of the sporangium -wall cover-
ing the spores. Magnification, 120.

176

RESEARCHES ON FUNGI

t

ornamented with minute crystals of calcium oxalate ; (2) that the
fringe of the sporangium-wall which overlies part of the gelatinous
ring, is more or less circular at its free margin (not extended radially
into broad rays),i is transparent, is largely or quite free from crystals
of calcium oxalate, and is colourless or tinged very faintly with
bluish-grey ; and (3) that the gelatinous ring extends radially from
the black portion of the sporangium more than twice the distance
of the fringe of the sporangium-wall.

The fringe of the sporangium-wall of the dried discharged

sporangium of Pilobolus umbonatus is so
characteristic for the species that by this
character alone one can readily distinguish
P. u7nbonatus from P. longvpes and P. Kleinii..
In these two last-named species the fringe :
(1) instead of being circular at the free
margin, is siMt into broad radially-extended
rays (Figs. 33, 34, and 39 ; pp. 77, 78,
and 83) ; (2) instead of being largely or
quite free from crystals, is finely punctate
with evenly-spaced crystals, larger and smaller
crystals usually forming a sort of pattern
(Fig. 44, A, p. 88) ; and (3), instead of being
colourless, is distinctly brownish.

As a sporangium which has been dis-
charged on to a glass slide dries up, the
umbo becomes more prominent (Fig. 105, K)
and at the same time the black part of the
sporangium-wall which covers the spores contracts considerably.
In some sporangia the contraction is uniform or almost so, so
that the dark wall remains smooth and devoid of depressions
(Fig. 105, I) ; whilst in other sporangia it is uneven, so that the
wall becomes dimpled or wrinkled. The wrinkles tend to take a
radial direction, so that the depressions between them are often more
or less triangular in outline (Fig. 105, J).

1 It is possible that the part of the fringe corresponding to the rays of P. longipes
and P. Kleinii is broken away from the fringe at the time the sporangium strikes
an obstacle.

Fig

88. — Pilobolus um-
bonatus, after removal
of sporangium. The
dark, bluntly rounded
coluniella crowns the
subsporangial swell-
ing. Magnification, Gl.

PILOBOLUS UMBONATUS 177

When with the help of the microscope one looks down upon
dried discharged sporangia of Pilobolus umbonatus, P. longipes, and
P. Kleinii attached to a glass slide, one can at once distinguish those
of P. umbonatus from those of the other two species : (1) by the
presence of the umbo which in strong lateral illumination reflects
the light on one side ; (2) by the smoothness or radial wrinkling of
the black sporangium- wall below the umbo ; and (3) by the fringe
of the sporangium- wall which, as already mentioned, is transparent,
practically colourless, circular at its margin, and largely or quite
devoid of crystals (Fig. 105, I and J).

To observe the columella whilst this is still attached to the
subsporangial swelling, one places a fruit- body in a drop of water
on a slide and one then strokes away the sporangium with a needle.
A columella exposed to view in this way (Fig. 88) is very bluntly
conical or rounded in shape, distinctly grey or bluish-grey in colour,
and connected at its base with the usual thin lower band of
sporangium-wall that separated from the rest of the sporangium-
wall when dehiscence of the sporangium took place.

The columella in a dried discharged sporangium attached to a
glass slide can be brought into view by adding water and a cover-
glass, and by then pushing the cover-glass laterally. Columellae
brought into view in this way reveal their grey or bluish-grey colour
and also the narrow band of sporangium-wall attached to their free
margin.

Taxonomic Description and Latin Diagnosis. — An attempt will
now be made to describe Pilobolus umbonatus for taxonomic purposes.

Pilobolus umbonatus, sp. nov. Fruit-body 3-9 mm. high, arising
from an oval to turnip-shaped basal swelling or trophocyst which
may be terminal or intercalary, single or dispersed at intervals
along a coarse stolon-like main hypha. Stipe increasing shghtly in
diameter from below upwards, until just beneath the subsporangial
swelhng it is about 0-1 mm. in diameter. Subsporangial swelling
ellipsoid, in well-grown fruit-bodies about 0-65 mm. long and
0-46 mm. broad ; a pale orange-red band of protoplasm at the
junction of the stipe and the subsporangial swelling. Sporangium
decidedly umbonate and more or less conical, 0-21-0-23 mm. in

VOL. VI. N

178 RESEARCHES ON FUNGI

diameter or about one-half the diameter of the subsporangial
swelHng, shrinking on drying after discharge and becoming acutely
pointed ; columella very bluntly conical or rounded (when removed
from a discharged sporangium its edge is turned inwards toward
the axis), greyish, distinctly darker than the subsporangial swelling.
Spores ellipsoid, singly almost colourless but yellow in mass,
5-0-6-0 X 3-0-3-8 [i..

On horse dung, Winnipeg, Canada, and, according to a communi-
cation from the late Dr. Roland Thaxter (who observed the species
forty years ago but did not describe it), more frequently on sheep
dung, at Boston, U.S.A.

Easily distinguished from all other species of Pilobolus by its
decidedly umbonate sporangium and its minute elhpsoidal spores.
With a hand-lens one can readily make out the acutely-pointed
umbonate shape of the diied discharged sporangia when these are
seen in lateral view,

Latin Diagnosis

Pilobolus umbonatus, sp. no v. Hyphae sporangiiferae 3-9 mm.
altae, e trophocystide terminah v. intercalari ovaU v. napiformi
solitaria v. in hypha crassa repenti sparsa oriundae. Stipes fihformis,
circa 0 • 1 mm. diam., sursum sensim latior. Vesiculum suhsporangiale
elHpsoideum, 0-65 mm. longum, 0-46 mm. latum, circa medianam
partem latissimum. Sporangium eximie umbonatum, plus minusve
conicum, 0-23 mm. diametro, arescendo acutius evadens, columella
obtusissime conica v. convexa, cinerea, quam vesiculum obscuriore.
Sporae minutae, ellipsoideae, dilutissime luteolae, ferme achroae,
5-0-6-0 X 3-0-3-8 [i.

Hab. in stercore equino, Winnipeg, Canada, atque (sec. htt,
Thaxteri) in stercore ovino a.pud Boston America e boreahs.

Remarks on the Pilobolidae. — At my request Mr. W. B. Grove
has prepared for this Volume a systematic account and an arrange-
ment of the Pilobolidae. I have sought to assist him by providing
the necessary illustrations and by placing at his disposal the results
of my studies of Pilobolus longipes, P. Kleinii, P. umbonatus, found

REMARKS ON THE PILOBOLIDAE 179

wild at Winnipeg, and of Pilaira anomala and P. Moreaui sent to
me from Baarn.

Piloboli commonly occur on horse dung, cow dung, etc., and are
so different in appearance from all other fungi and discharge their
black sporangia with such vigour that most mycologists have seen
one or more of them and have recognised them for what they are.
On the other hand, Pilairae are comparatively rare, may easily be
mistaken by the uninitiated for Mucors, and have been less often
found and studied. Hence perhaps it is that Fitzpatrick ^ in his
recent book on the Phycomycetes, after remarking that " at least
four species of Pilaira, all of them from dung, have been described "
adds : " The possibihty that they were based on abnormal material
of Pilobolus leads the writer to regard the genus as somewhat
doubtful." From my own comparative studies of Piloboli and
Pilairae, I have become convinced that the genus Pilaira is a good
one. In the next Chapter the characteristics of Pilobolus and
Pilaira have been set forth in detail.

Anderson ^ has recently taken the trouble to demonstrate the
stabiUty of the genus Pilaira by means of a sj^ecial investigation.
He made monosporous cultures of Pilaira anomala and found that
they remained true and did not give rise to a Pilobolus form.
Further, he fed two rabbits, one with lettuce bearing Pilaira
sporangia and the other with lettuce bearing Pilobolus sporangia.
The dung of each rabbit produced the respective fungus only. As
a result of these experiments Anderson concluded that the genus
Pilaira van T. is a vaUd one.

Our knowledge of the Pilobohdae is not as satisfactory as it
should be. A number of species, more especially of Pilobolus, have
been imperfectly described and illustrated. What is now required
is that some systematist should take up the study of the Pilobolidae
with a view to preparing a monograjih upon them, based on a
comparison of as many species as could be brought together in a long
term of years. The resources of photomicrography, unknown to

^ H. M. Fitzpatrick, The Louver Fungi, Phycomycetes, New York, 1930, p. 253.

^ R. S. Anderson, " Tlie Validit}' of the genus Pilaira," University of loiva
Studies, Vol. XV, 1933, pp. 3-5. Cited from Journ. Roy. 3Iicros. Soc, Ser. Ill,
Vol. LIII, 1933, p. 284.

i8o RESEARCHES ON FUNGI

the older mycologists, are now at our disposal and would facilitate
the task.

To the criteria so far employed by taxonomists for distinguishing
species of Pilobolus should be added : (1) the exact shape of the
subsporangial swelUng, whether elhpsoidal or pyriform, etc. ; (2) the
ratio of the width of the sporangium to the width of the sub-
sporangial swelhng ; (3) the nature of the depressions or wrinkles
on dried discharged sporangia when seen in strong reflected uni-
lateral light ; and (4) the nature of the fringe of the sporangium-
wall of dried discharged sporangia, in respect to form, colour, and
disposition of crystals.

The spores of all the species of Pilobolus and Pilaira contain a
carotinoid pigment which colours oil-drops held within the proto-
plasm. Large spores which contain much of the pigment, e.g. those
of Pilobolus longipes and P. Kleinii, when seen singly in water in
transmitted hght, are orange-yellow, while small spores wliich
contain very little of the pigment, e.g. those of P. umbonatus, when
seen singly are almost colourless and when seen many together are
yellowish.

Van Tieghem ^ remarked that the spores of Pilobolus longipes,
when seen in the mass, appear dull green, and he regarded this as
being due to the slaty-blue colour of the spore- wall combining with
the golden-yellow colour of the spore-protoplasm. When spores of
P. longipes are seen in the mass, they are seen by reflected and not
by transmitted light. I have observed that, if Pilobolus spores are
spread out in a drop of water under a cover-glass and are looked at
with the low-power objective of the microscope, they exhibit
dichroism, in that they are orange-j^ellow or yellowish in transmitted
light and green in reflected hght. This applies to the spores not
only of P. longipes, but also of P. Kleinii ^ and P. umbonatus. It is
therefore clear that a dull green colour for spores in the mass cannot
be regarded as a distinctive character of P. longipes.

The basal swelling (trophocyst) of Pilobolus longipes, as com-
pared with that of other Piloboli, is so much elongated (Fig. 100,

^ P. van Tieghem, " Troisieme memoire sur les Mucorinees," Ann. Sci. Nat.,
6 ser., T. IV, 1876, p. 339.
2 Cf. supra, p. 72.

REMARKS ON THE PILOBOLIDAE

i8i

p. 203) that its form is a valuable aid in identifying this species.
In the other Piloboli, the basal swelling as a rule is rounded, turnip-
shaped, or oval.

In all the species of Pilobolus, the basal swelling together with
the fruit-body which grows out of it may be and usually is solitary ;
but in some species, e.g. P. roridus (Fig. 101, F, p. 204) and P. nanus

Fig. 89. — Pilobolus umbonatus. Gennination of spores and tlevelopnieiit of a
trophocj'st (which becomes the basal swelhng of a fruit-body). Culture medium,
cleared horse-dung agar. A : a, spores placed in culture medium ; b, c, and
d, two days later ; b, a spore swelling ; c, two spores putting out germ-tubes ;
d, a spore with a long germ-tube. B : a main hypha of a mycelium, with
numerous slender brandies (secondary hyphae). C : a main hypha which has
become swollen at 6 as a step toward the formation of a trophocyst. D : a main
hypha in which a local swelling has become divided by two septa, so as to form
a trophocyst b and two apophyses a a. Drawn by A. H. R. BuUer and E. S.
Dowding. Magnification : A, 350 ; B-D, 80.

(Fig. 106, C, p. 212), two or three or possibly more basal swellings,
which become extended into fruit-bodies, may occur in short chains.
A single basal swelling in any Pilobolus species usually arises in
the middle of one of the stouter hyphae in an intercalary manner
and becomes cut off from the rest of the hypha in which it has
originated by two septa (Fig. 89, also Figs. 21 and 27, pp. 52
and 69). One or both of the adjacent portions of the hypha may
then become swollen to form one or two so-called apophyses (Figs. 89
and 90). When one examines a mature fruit-body, if only one
apophysis has been developed (Fig. 90, C-E ; also Figs. 27 and 101,

l82

RESEARCHES ON FUNGI

B, pp. 69 and 204), one gains the impression that the basal swelhng
is terminal, whereas, if two apophyses have been developed (Figs. 80,

Fig. 9U. — Pilobolus umbonatus. Variations in tlie basal swelling and its apophyses.
Fruit-bodies removed from a horse-dung culture and examined in water.
Outlines made with the help of the camera lucida ; protoplasm added semi-
diagrammatically. In all the drawings : a is an apophysis ; b, a basal swelling ;
and c, part of the stipe of a fruit-body. A : the basal swelling is evidently
intercalary ; there are two apophy.ses. B : a much larger basal swelling,
again evidently intercalary ; the apopliy.sis at d is smaller and less typical
than that at a. C : the basal swelling lias only one apophj'sis, a ; it is not
terminal bvit intercalary, as it and its apophysis were developed from a local
enlargement on the hypha d e. D : a basal swelling with one apophysis ; it
is apparently terminal, but at e a slender continuation of the hypha d may
have been torn away in removing the basal swelling from the sul)stratum ; if
such a continuation existed, the basal swelling nuist have dexelojied in an
intercalary manner ; at / and g are two hyphae with club-shaped ends which
possibly might have given rise to truly terminal basal swellings. E : a slightly
elongated basal swelling without airy typical apo]ihysos ; it is possible that a
continuation of the hypha a was broken away at e when tlie fruit-body was
removed from the substratum ; if such a continuation existed, the basal
swelling was intercalary and not terminal in its mode of origin. F : a basal
swelling with three apophyses. C. : two basal swellings which have arisen
on the same main hypha, d e f ; each has a single apophysis on one side of it
and an imswollen part of the main hypha on the other side. Drawn by A. H. R.
Duller and E. S. Dowding. INIagnification, 62.

D, and 90, A and B ; also Fig. 101. G). one readily perceives that
the basal swelling at its origin was intercalary. Although most

REMARKS ON THE PILOBOLIDAE 183

apparently terminal basal swellings in reality have originated in
an intercalary manner (Fig. 90, C ; also Fig. 21, E-G, p. 52), yet
it may well be that now and again some basal swellings originate
in a truly terminal manner, for Cohn ^ (1851) observed in Pilobolus
oedipus certain club-shaped hyphae coming off from stout hyphae,
which he considered to be the possible beginnings of new fruit-
bodies, and I have observed exactly similar club-shaped hyphae in
the mycelium of P. umbonatus (Fig. 90, D, / and g).

The ratio of the width of the sporangium to the width of the
subsporangial swelling in the fruit-body of a Pilobolus may be called
the width-ratio. To obtain the data for this ratio, all that one needs
to do is to remove a fruit-body from a culture, to lay it horizontally
in a drop of water on a glass slide, and then to measure in succession
the width of the sporangium and the width of the subsporangial
swelling.

A preliminary study of the width-ratio of three species of Pilo-
bolus wac^ made under my direction by Dr. Dowding, and the results
of it are embodied in the diagram reproduced in Fig. 91. The upper
five drawings at A show in top view the sporangia of five wild fruit-
bodies of Pilobolus longipes ; their average width-ratio was found
to be approximately f . The lower five drawings at B show five
sporangia obtained from a pure culture of P. Kleinii ; their average
width-ratio was found to be approximately f. The drawing C
shows a single sporangium of a wild fruit-body of P. umbonatus ;
its ratio was found to be — as in other fruit-bodies of this species —
approximately J. Thus the average ratio of the width of the
sporangium to the width of the subsporangial swelling appears to
differ appreciably in the three species of Pilobolus which have been
investigated.

Lepeschkin ^ found that the width of the subsporangial swelling
in a Pilobolus is determined in part by the osmotic value of the
substances dissolved in the water permeating the substratum. On

^ F. Cohn, " Die Entwicklungsgeschichte des Pilobolus crystallinus," Nova Acta
Acad. Cues. Leop., Bd. XXIII, 1851, Plate LII, Figs. 14 and 16. His P. crystallinus
was in reality P. oedipus.

2 W. W. Lepeschkin, " Zur Kenntnis des Mechanismus der aktiven Wasseraus-
scheidung der Pflanzen," Beihefte z. Bot. Centralb., Bd. XIX, 1906, p. 423. Also
vide supra, p. 34.

1 84

RESEARCHES ON FUNGI

this account, in determining the width-ratio of fruit-bodies of any
species of Pilobolus, it is advisable to use wild fruit-bodies obtained
from their natural substratum. Unfortunately, the sporangia of
Pilobolus Kleinii shown at B in Fig. 91 were obtained from a pure
culture. Had they been obtained from a wild culture, it is possible
that their average width-ratio would have been slightly smaller,
perhaps f instead of f , as wild fruit-bodies of P. Kleinii with a
width-ratio of about f have been observed.

In concluding this Section, we may enquire to what extent, if

Fig. 91. — Diagram illustrating a study of the ratio of the width of the sporangium
to the width of the subsporangial swelHng in three species of Pilobolus. Each
fruit-body is shown in top view ; the black area represents the sporangium, the
pale area the subsporangial swelUng. A, five wild fruit-bodies of Pilobolus
longipes (average width-ratio approx. f). B, five fruit-bodies from a pure
culture of P. Kleinii (average width-ratio approx. |). C, a wild fruit-body of
P. umbonatus (width-ratio ^). Magnification, 30.

any, the patterns that can be found on the dried discharged sporangia
of certain Piloboli are of diagnostic value.

Coemans,! in 1861, observed some curious markings on the
sporangium of Pilobolus crystallinus (Fig. 92). He says : " In
Pilobolus oedipus the tint of the coloration is uniform, but in P.
crystallinus it sometimes exhibits beautiful hexagonal patterns
which have a close analogy with the hexagonal cells of the choroid

^ E. Coemans, " Monographic du genre Pilobolus Tode, specialement etudie au
point de vue anatomique et physiologique," Mem. cour. et des Sav. etrang. Acad. roy.
de Belgique, T. XXX, 1861, pp. 23-24.

REMARKS ON THE PILOBOLIDAE 185

of the higher animals. These patterns are very regular ; a chief
alveolus occupies the centre at the top of the globule (sporangium)
and six other exactly similar cells are placed around the sides of the
principal polyhedron. These alveoli have shades of coloration,
their centre is usually pale, and a colourless or paler streak separates
them from one another. I have noticed similar patterns, but ovoid
in form, on the sporangium of Ascophora Cesatii ^' {= Pilaira
anomala).

" It is remarkable that these patterns are not produced regularly
each year. In 1859, in a hot summer, they ornamented all the
globules of Pilobolus crystallinus that I
observed ; in 1860, the summer being cold
and wet, I found them very rarely and
always faintly indicated. The cause of
these variations is probably connected with
the effects of light and heat. It may also
be noted that, the irregularity of the appear-
ance of these patterns being proved, they Fig. 92.— Pt/ofco^ws crys-

^ o J. ' »/ talhnus. Sporangium

cannot have any diagnostic value." flattened out and seen

_. . 1 • -n i i • 1 l^ from above. Copied

Coemans m his illustrations shows the by the author from

pattern on a discharged sporangium (Fig. 92), ^^^/raleif Mag!

but not on sporangia still seated on sub- nification increased

,,. rru • A from 220 to 293.

sporangial swellings. Ihere is good reason

to suppose, therefore, that Coemans saw the pattern on discharged

sporangia only.

Van Tieghem,^ in his description of Pilobolus crystallinus, says :
" A white network with the meshes most often hexagonal ornaments
the upper surface of the cuticularised hemisphere (sporangium) ;
there is a hexagon at the top and six other hexagons arranged in
a circle around the first with their free sides rounded below. Some-
times the central polygon has four, five, seven, or eight sides. This
regular system of white lines, left untouched by the coloration which
affects all the rest of the cuticularised hemisphere, is quite charac-
teristic of this species." Van Tieghem, in a foot-note, adds : that
he has found the network in all the sporangia of P. crystallinus

1 P. van Tieghem, " Troisieme m^moire sur les Mucorinees," Ann. Sci. Nat.,
6 ser., T. Ill, 1876, p. 336.

i86 RESEARCHES ON FUNGI

that he has seen both in winter and summer in numerous generations
obtained in cultures ; and that the reason why Coemans did not
always find them in this species was that he, Coemans, had some-
times had P. Kleinii, which has no network, under his eyes instead
of P. crystallinus. Van Tieghem, in a diagrammatic illustration of
the network (Fig. 93), shows the top of a discharged sporangium
in the form of a black disc marked out with white lines.

Still later Zopf,^ in a study of the parasites of Pilobolus, illus-
trated the supposedly normal fruit-bodies of P. crystallinus. He
shows not only a discharged sporangium with polygonal markings

on its upper surface, but also intact fruit-

B bodies bearing undischarged sporangia with

0 ^ similar markings. Subsequently, he repro-

^ 0 duced two of these illustrations in the form

G) of wood-cuts in his text-book of mycology .^

Fig. qz. — Pilobolus My own studies of the patterns on the

crystallinus A, sporangia of p. Kleinii, P. lonqipes, and P.

upper view oi spor- x o -j j.

angiiim showing a umbonatus have led me to the following con-
white network. B, . / 1 \ . u j.i. j.
spores. Copied by clusions : (1) the patterns are never present

the author^ Jrom on sporangia seated on their sporangiophores,
Troisiime Memoire but only on discharged sporangia ; and (2) the

(1876). Magnifi-

cation, not given. patterns develop on discharged sporangia as

these dry up and flatten down. I am there-
fore of the opinion that Zopf was in error in representing a pattern
on the undischarged sporangia of P. crystallinus.

The netted pattern on a dried sporangium is due merely to the
^VTinkling of the hemispherical sporangium-wall as this settles down
on the drying mass of spores. This mass, as it loses water by
evaporation, shrinks to less than one-half of its original volume.
The white Unes represented by Coemans and van Tieghem in their
drawings of Pilobolus crystallinus (Figs. 92 and 93) were doubtless
ridges around depressions. Sometimes, as I have observed in
a large flattened sporangium of P. Kleinii, the sporangium-wall

^ W. Zopf, " Ziir Keiintniss der Infectionskrankheiten niederer Tliiere und
Pflanzen. No. IV. Einfluss von Parasitismus auf Zygosporenbildung bei Pilobolus
crystallinus," Nova Acta Acad. Cues. Leop. Nat. Cur., Bd. LII, 1888, Plate XXII,
Figs. 1-3.

2 W. Zopf, Die Pilze, Breslau, 1890, Fig. 54, Nos. 2 and 3, p. 84.

REMARKS ON THE PILOBOLIDAE

187

becomes cracked along these ridges and then the cracks appear
as Hnes which are whitish when contrasted with the dark sporangium-
wall.

The formation of a jDattern on a discharged sporangium, con-
trary to the view expressed by van Tieghem, is not limited to
Pilobolus crystallinus, for I have observed patterns on the discharged
sporangia of P. Kleinii (Fig. 39, p. 83), P. longipes (Fig. 40, p. 84).
and P. umbonatus (Fig. 105, J, p. 210).

While the existence of a pattern on a discharged and dried
sporangium cannot be held to be a diagnostic character for Pilobolus
crystallinus, yet differences in pattern are displayed by different
species. Thus a well-developed, discharged, and dried sporangium
exhibits : in P. Kleinii a few rounded regular dimples, one of which

Fig. 94. — Pilobolus Kleinii. Diagram showing variations in tlie pattern on dried
discharged sporangia obtained ivom. a pure culture. A and B, sporangia with
a smooth wall. C-G, sporangia with one dimple, two, three, four, and five
dimples respectively. H, a sporangium with six dimples, one central. I, a
sporangium with six dimples in a circle. Magnification, 47.

often holds a central position (Fig. 39) ; in P. longipes numerous
irregular somewhat gyrose depressions (Fig. 40) ; and in P. um-
bonatus, a central umbo with lateral more or less radial depressions
(Fig. 105, J). These differences in sporangial pattern are un-
doubtedly of diagnostic value and I have often used them in the
laboratory for distinguishing P. Kleinii, P. longipes and P. umbonatus
from one another.

The pattern made by the dimples in the sporangial wall of dried
discharged sporangia of Pilobolus Kleinii varies considerably in
detail, as will appear in what follows. A pure culture of P. Kleinii
was obtained by inoculating sterilised horse dung with a single
sporangium. As soon as new sporangia began to be discharged,
they were caught on glass slides and examined under the microscope.
Whilst still wet, their sporangial walls were perfectly smooth ; but,
as they dried up, in the course of about two minutes, it was observed
that certain circular areas of the walls sank inwards and so formed

i88

RESEARCHES ON FUNGI

crater-like depressions. Fifty dried discharged sporangia were
selected at random and were observed under the low power of the
microscope by reflected light, and it was found that the number of
depressions in the sporangial wall varied from none at all to six
(Fig. 94), as indicated in the accompanying Table.

Fifty dried discharged sporangia of Pilobolus Kleinii

No depressions or faint traces

One central depression .

Two depressions ....

Three depressions

Four depressions ....

Five depressions ....

Six depressions, one central .

Six depressions, irregularly arranged

12 sporangia
8 sporangia
5 sporangia
7 sporangia

11 sporangia
4 sporangia
2 sporangia
1 sporangium

Further observation showed that in dried discharged sporangia
of Pilobolus Kleinii, as a general rule, the number of depressions

in the sporangial wall
varies directly with the
diameter of the spor-
angium, the smallest
sporangia having the
fewest depressions and
the largest sporangia
the greatest number
„ Ar D-7 I, 7 t-; ••• rru of dcprcssions. In

Fig. 95. — Pilobolus Kletnii. The upper convex ^

surfaces of two large dried discharged sporangia wild cultures where
produced by wild fruit -bodies, each with a larger

central dimple surrounded by smaller dimoles. the sporangia were

In A there ar3 ten smaller dimples and in j ^^ ^j^ ^^

B nine. Magnincation, 100. &

the artificial pure
culture from which the fifty sporangia were obtained, it was
observed that the number of depressions in a sporangial wall
was often nine or ten and that, as a rule, there was one larger
central polygonal depression surrounded by a ring of small
depressions (Fig. 95).

An investigation similar to that just described was made on

REMARKS ON THE PILOBOLIDAE 189

Piloholus longipes. Of sixty- two sporangia twelve showed no
depressions, whilst in the other fifty the depressions in the form
of elongated, meandering, irregularly arranged furrows (Fig. 96)
varied from ten to twenty in number. Of seventy-five sporangia
derived from a pure culture only three or four small sporangia

Fig. 96. — Pilobolus longipes. A and B, the upper convex surfaces of
two large dried discharged sporangia, produced by wild fruit-
bodie.«, each showing a pattern of irregular depressions or
furrows. Magnification, 100.

could be found which possessed in their walls depressions that more
or less resembled the rounded depressions of P. Kleinii.

From the special investigations on Pilobolus Kleinii and P.
longipes that have just been recorded it is clear that the pattern on
dried discharged sporangia, while fairly constant in its general
aspect for each species, is subject within each species to a large
amount of variation in detail. The typical pattern for any particular
species ought to be sought for in the larger sporangia rather than in
the smaller ones.

CHAPTER IV

A SYSTEMATIC ACCOUNT AND ARRANGEMENT OF

the pilobolidae
Contributed by W. B. Grove

Introductory Remarks — Historical Account — Systematic Arrangement — -

Bibliography

Introductory Remarks. — The section of the Mucorini entitled
Pilobolidae includes only two genera, Pilobolus and Pilaira. In
1884 the writer of this chapter published a Monograph of the Pilo-
bolidae, in which he gave a systematic arrangement of the ten species
which had been up to that time described. This arrangement was
followed by Saccardo in the seventh volume of his Sylloge Fungorum,
pp. 184-189, and has since been revised by Palla and Morini.^

The writer's personal knowledge of the Pilobolidae in England
is based upon the forms called Pilobolus crystallinus, P. Kleinii,
P. sphaerosporus , P. oedipus, and Pilaira anomala, and in addition
he has seen Pilobolus longipes and P. umbonatus, which have been
found in Canada as shown by Professor Buller in preceding chapters
of this volume. The six forms of Pilobolus just mentioned, as well
as Pilaira anomala, P. nigrescens, P. Saccardiana, and P. Moreaui,
may probably be regarded as definitely established species ; in
regard to most of the others there remains a certain doubt which
can only be removed when some one has devoted to the group

^ This account of the Pilobolidae, written at the request of my friend Professor
Buller, may be considered to be a revision of the systematic part of the Monograph
of the Pilobolidae which I published in the Midland Naturalist exactly fifty years ago.
Professor Buller has been good enough to give me the benefit of his assistance in
defining the group and the genera, in revising the descriptions of certain species,
and in preparing the illustrations. — W. B. G.

190

TAXONOMY OF THE PILOBOLIDAE 191

a large amount of time and patience. The account of those species
which I have not seen is of course compiled from the pubhshed
sources.

The drawings of the earlier authors were but free-hand sketches,
inaccurate in certain details. For instance, Bolton's figure of
Pilobolus roridus (Fig. 98) makes the subsporangial swelling appear
nearly twice as broad as it is high (seemingly in an attempt at
perspective) ; Zopf and Klein represent the subsporangial swelling
of P. Kleinii (their P. crystallinus) as hardly or not at all wider
than the sporangium ; van Tieghem makes the same error in his
figure of Pilobolus nanus (Fig. 106, p. 212), while in Pilobolus longipes
(Fig. 100, p. 203) he draws the spores in the sporangium out of all
proportion to the sporangium in which they are enclosed. By
future workers pure cultures of each so-called species should be
obtained and their special characteristics should be fully illustrated
by photographs and carnera-lucida drawings.

The Historical Account which follows is founded, with many
emendations and the necessary later additions, on that given in the
Monograph of 1884.

Historical Account. — The earliest record I have been able to
find of a species belonging to Pilobolus is in the works of the famous
British botanist, John Ray. In his Historia Plantarum (1688)
occurs the following passage which, on account of its importance,
shall be quoted in full : —

"E Catalogo hue tvanfmljfo J nno 1680, quern compojuit eruditi/Ji-
mus Vir et conjummati/jimus Botanicus D. Johannes Banifter Plantarum
a Jeip/o in Virginia objervatarum.

" Fungus (ex /tercore equino) capillaceus capitulo rorido, nigro
punctulo in Jummitate notato. Ex recenti fimo noctu exoritur cauliculis
erectis, vix digitum longis, capillorum injtar tenuibus nee minus denjis
/eu confertis. Singuli Cauliculi parvulo globule aqueo coronantur, qui
in Jumma Jui macula parva nigra Limacis oculi Jimili in/ignitur."

The same species of Pilobolus was then mentioned and figured
by Plukenet (1691) as ^^ Fungus Virginianus ex /tercore equino
capillaceus canus capitulo rorido, nigro punctulo in Jummitate notato,
D. Bani/ter." Plukenet did not merely copy what Ray had

192

RESEARCHES ON FUNGI

" canus,"

published, for he adds the correct descriptive word
of which Ray says nothing, as well as a small but characteristic
figure (Fig. 97). Both these additions he obtained from Banister's
MS. From Ray's description and Plukenet's figure, it is evident
that the species they had in view was similar to that which was
afterwards called Mucor roridus.

These two notices stimulated observation, for a few years later
the first British record was published in Ray's Synopsis (1696),
in a list of plants communicated by Mr. James Petiver, who remarks
" This I have observed on Horse-dung about London," and refers to
Plukenet's figure. This record, therefore, may be considered to

belong to Pilobolus roridus. It is repeated by
Ray in his Historia Plantarum in 1704, and
again in his Synopsis in 1724, and by Petiver in
his Gazophylacium (1711), where he gives a
figure similar to that of Plukenet.

Another mention of a fungus belonging to
this genus (the earliest known to Coemans in
his review, 1861, of the literature of the sub-
ject up to his time) is due to Henry Baker,
who, in his Natural History of the Polype
Insect (1744), described a number of small
vase-like plants, filled with a clear liquid and
crowned by a black ball ; these, which he had found on mud
brought from the river Thames, were undoubtedly a species of
Pilobolus, presumably Pilobolus oedipus.

In 1764 Otto Miiller discovered and afterwards (1782) described
and figured a Pilobolus under the name of " Kristallschwammchen " ;
he imagined it was in part an animal, in part a plant, and even in
part a crystal, thus partaking of all the three kingdoms of nature.
He thought he saw a slender worm-like body residing within the
organism, which, he says, " crawled round in the crystal globe and
seemed to swim at its ease in a tiny ocean." This was no doubt
a species of AnguilluHdae, but outside, not within, the subsporangial
swelling. The singularity of this view accounted for the wide-
spread attention which was given to his discovery.

It was not till 1772 that Scopoli in his Flora Carniolica first

Fig. 97.— The first
illustration of a
Pilobolus. Ban-
ister's drawing,
reproduced by
Plukenet (1691).

TAXONOMY OF THE PILOBOLIDAE

193

gave to the plant a name which showed a recognition of its true
affinities. He called it Mucor obliquus, from the oblique manner in
which the stipe frequently sprang from the side of the basal reservoir,
but his description, though very interesting, is insufficient to enable
us to identify the species.

Withering, in his Botanical Arrangement (1776), quoted Petiver's
plant from Ray's Synopsis and bestowed upon it the name Mvcor
roridulus.

In Wiggers' Primitiae Florae Holsaticae (1780) Scopoli's plant
was placed in a new genus, under the name
Hydrogera crystallina suggested by his tutor
Weber.

But the first good description of the
genus was given by Tode, who imposed
upon his species the name of Pilobolus
crystallinus by which it is now known. The
generic name is a translation of the title
" Hutwerfer," which he used in the Schrifte
der Berlinsche Gesellschaft naturforschenden
Freunde (1784) ; his account was repeated in
his Fungi Mecklenburgenses selecti in 1790.

Species of Pilobolus were then mentioned
successively : by Dickson (1785), who figured
one under the name Mucor urceolatus ; by
Bulhard, under the same name, in his Herbier
de la France (1784), with a figure added in
1789 ; by Bolton (1789), who, besides figuring under that name a
form resembhng a badly grown Pilobolus Kleinii, added another
supposed to be identical with Petiver's as Mucor roridus (Fig. 98) ;
andby Vahl, in the Flora Danica (1792), who figured one as Pilobolus
crystallinus.

Persoon gives an excellent description of P. crystallirius in his
Observationes Mycologicae (1796), accompanied by an imperfect
figure ; and in his Synopsis methodica Fungorum (1801) he mentions
both that and P. roridus, but considers the latter as doubtfully distinct.

Sowerby, in his EngHsh Fungi (1803), gives a figure of Mucor
urceolatus which seems to represent P. crystalli7ius .

Fig. 98. — Pilobolus roridus
(Bolton) Pers. A
cluster of fruit-bodies
on horse dung, about
natural size, and two
fruit-bodies much en-
larged. Reproduced
by photography from
Bolton's History of
Fungusses (1789).

VOL. VI.

194 RESEARCHES ON FUNGI

Link, in his First Dissertation (1809), attributed for the first
time the projection of the sporangium to its true cause, namely the
tension of the swelUng below the sporangium. His words are :
" Explosio fieri mihi videtur, dum suprema pars stipitis bullata,
sporangium inferne ambiens, contrahitur."

Relhan, in his Flora Cantabrigiensis (1820), maintained that
Pilobolus roridus was distinct from P. crystallinus ; but Purton, in
his Midland Flora (1821), recorded both of them under one name
Pilobolus urceolatus, giving detailed reasons from experiment to
show that they are not distinct, and accompanying his account
with " a very beautiful and accurate drawing " by his niece, " taken
from the fresh plant."

In 1823 Ehrenberg pubhshed in Kunze u. Schmidt's Mykologische
Hefte an account of some observations he had made upon P. crys-
tallinus, in which, while searching for Otto Miiller's " worm," he
noticed a curious movement of yellowish particles arranged in a
snake-hke form in a drop of water which occupied the summit of
the sporangium. This, he thought, might be the " worm," because
it moved with a " slow, steady, circling motion " which excited
his wonder.

All the authors mentioned so far correctly placed the genus in
the immediate vicinity of Mucor. Fries, however, in 1 823, considered
it as nearly alUed to Sphaerobolus and placed it in the Gasteromycetes
in the section CarpoboU, but in 1829 he discovered his mistake and
restored it again to the Mucorini. Nevertheless Berkeley, in Smith's
English Flora (1836), incautiously repeated Fries' error, and in
his Outhnes of British Fungology (1860), perhaps by reason of this
confusion, he omitted Pilobolus altogether.

Up to this time only the two species already mentioned, called
P. crystallinus and P. roridus, were generally known, but in 1828
Montague had already described a third, to which he gave the name
of P. oedipus {cf. Fig. 104, p. 209) on account of the swollen basal
reservoir which is so conspicuous a feature in that species. He
repeated this in his Sylloge generum specierumque cryptogamarum
in 1856.

In 1837 Corda instituted in his Icones Fungorum the group
Pilobohdae to contain Pilobolus and Chordostylum ; in 1842 he

TAXONOMY OF THE PILOBOLIDAE 195

added to the group Pycnopodium and Caiilogaster, placing in the
former genus, as Pycnopodium lentigerum, a species which he had
formerly included in Pilobolus and which would seem to be merely
an abnormal state of P. Kleinii. After Corda's lamented early
death, Zobel pubhshed (1854) from his friend's manuscript notes
a sixth volume of the Icones, in which he gives a long account of
Pilobolus crystallinus containing numerous errors. In his drawing
(f. 32) he represents the interior of the subsporangial swelhng as
hned with reticulations of orange-coloured granules such as no
other author has seen, and which are probably only the meridional
streams, occasionally met with but rarely figured,^ disturbed by
the pressure to which the preparation had been subjected.

When Cohn pubhshed, in 1851, his celebrated monograph " Die
Entwicklungsgeschichte des Pilobolus crystallinus," he had before
him, not that species with which he was really unacquainted, but
the species of Montague. He figures the characteristic yellow,
spherical, thick-walled spores of Pilobolus oedipus, and then remarks
with naive surprise that Corda had represented the spores of P.
crystallinus as elhptic and colourless " in contradiction to nature."

Cesati discovered, in 1850, a species which he pubhshed the
next year in Klotzsch's Herbarium vivum mycologicum under the
name Pilobolus anoinalus, now known as Pilaira anomala Schrot.

Bonorden, in his Handbuch (1851), described a species under the
name of P. crystallinus, which on account of its round spores Coemans
referred to P. oedipus, but which I think there is greater reason for
considering as P. Kleinii, forma sphaerospora.

In 1857 Currey wi'ote a note " On a species of Pilobolus " which
he thought to be P. roridus, but his plate and description clearly
show that the species he had in view was P. Kleinii ; according to
van Tieghem, Leveillc in 1826 had fallen into the same error, giving
the name of P. roridus to a form of P. Kleinii. Currey also attri-
buted the projection of the sporangium to the eversion and upward
pressure of the columella, which he believed not to be thrown off
with the sporangium.

In 1861 Coemans issued his " Monographic du genre Pilobolus,"
in which he summarised what he had read about this subject, and
^ I figured them in my Monograph (1884), pi. 4, f. 12.

196 RESEARCHES ON FUNGI

gave a list of all the species referred by other authors to this genus.
He considered P. crystalUnus and P. oedipus (Fig. 104, p. 209) to
be the only certain species ; P. roridus he regarded as doubtful,
P. lentiger he refers, wrongly, to P. oedipus, and P. anomalus he
places in the genus Ascophora by the name of A. Cesatii.

In 1871 Cooke published the Handbook of British Fungi, but,
though he mentions the two conventional species, P. crystalUnus
and P. roridus, it is impossible to recognise exactly what he means
by the names.

It was in 1872 that Klein (after a short note in 1870) gave to the
world his monograph " Zur Kenntniss des Pilobolus," a monument
of patient and minute investigation. In this he describes two
species, " P. crystalUnus " and " P. microsporus " ; under the
former name he says that he unites the P. crystalUnus and P. oedipus
of former authors. But, though he records his painstaking observa-
tions with great accuracy, in respect of the identification of his
specimens Klein was peculiarly unfortunate. His P. microsporus
is identical with P. roridus, and he was unacquainted with either the
true crystalUnus or the true oedipus. He had before his eyes,
without knowing it, another species hitherto undistinguished, to
which van Tieghem afterwards gave in his honour the name of
Pilobolus Kleinii. The spores of P. oedipus are yeUow, nearly
spherical, and surrounded by a thickened epispore ; those of
P. crystalUnus are ellipsoidal and nearly colourless. Now those of
P. Kleinii are also ellipsoidal, but of an orange-yeUow colour and
twice as long as those of P. crystalUnus ; in certain circumstances,
however, P. Kleinii bears sporangia containing nearly spherical
spores of the same colour but without a thickened epispore. It was
this abnormal state, to which I gave in my monograph of the Pilo-
bolidae the name forma sphaerospora, that led Klein erroneously
to imagine that he had met with forms intermediate between
oedipus and crystalUnus. The credit of clearing up this mistake
was due to van Tieghem (1876).

In my own cultures, on many occasions, I found that the first
two or three days' crops of P. Kleinii bore small sporangia, contain-
ing roundish spores, of unequal size in the same sporangium. These,
however, could be distinguished at once by the want of the thickened

TAXONOIMY OF THE PILOBOLIDAE 197

epispore from those of P. oedipus, and, moreover, the fungus agreed
in all other respects but its minuteness with the true Kleinii into
which it gradually passed on the following days. It would seem
likely that the inequality of the spores in the same sporangium,
together with the dwarfed size, was due to the fact that the fungus
had not yet established itself, and was of weak and uncertain growth,
like some of the dwarf forms of Coprinus.

Brefeld, in 1872, in his Untersuchungen iiber Pilze mentions
and figures a species which he assigns to the genus Pilobolus, under
the name P. Mucedo, but afterwards (1881) he discovered this to
be, in part at least, the same as that previously called by Cesati
P. anomalus. In the same work (1881) he gives a short account of
the other species assigned by him to Pilobolus, but not one of the
names he uses is that to which the species is entitled, as will be
seen by the following list : his

P. crystallinus (Fig. 99, A) = P. Kleinii van Tiegh.

P. oedipus (Fig. 102) = P. Kleinii, iovma sphaerospora Gr.

P. microsporus (Fig. 99, B) = P. crystallinus Tode.

P. roridus — P. longipes van Tiegh. (Fig. 100).

Brefeld, however, like van Tieghem, observed zygospores in Pilo-
bolus anomalus ( = Pilaira anomala). He found them on horse dung.
It will be seen that in " this strange eventful history " nearly
every author seemed to be fated to misunderstand in some degree
the opinions of those who had preceded him. It was not until 1875
that van Tieghem succeeded in clearing up the confusion in which
the subject had been plunged, especially in relation to the Mucor
roridus of Bolton. Bolton expressly describes his species (Fig. 98,
p. 193), which he had found in the neighbourhood of Halifax, as
" four lines high, pellucid and white, sustaining a small globular
head, like a minute pearly drop, with a black spot on its upper part,
which gives to the globe the resemblance of an eye in miniature."
No other author but Klein had been able, up to this time, to meet
with a species answering to this description, and hence it was
doubted by some, as by Persoon, Coemans, Greville, and Purton,
whether it was really distinct ; Klein, as has been said, failed to
recognise it in his microsporus, and it was reserved for van Tieghem

198 RESEARCHES ON FUNGI

to describe and figure (Fig. 101, p. 204) a form which possibly is that
which Bolton had found, and which is as similar as may be to Klein's
microsporus. The long slender stem, the rounded subsporangial
swelling, the minute sporangia, and the want of colour of van
Tieghem's species, all point in this direction and agree pretty well
with Bolton's figure. But it must be admitted that, since Bolton
does not describe the spores, a certain amount of doubt must always
attend any identification of his species ; it would, perhaps, be better
to quote P. roridus van T. rather than P. roridus (Bolt.).

In the same memoir (1875) van Tieghem also instituted the new
genus Pilaira for the reception of the old Pilobolus anomalus of
Cesati, and added a new species Pilaira nigrescens (Fig. 108, p. 218).
He also discovered the zygospores of P. anomala (Fig. 107, p. 217).

In 1876 van Tieghem completed his work by publishing the
descriptions of two new species, P. longipes (Fig. 100, p. 203) and
P. nanus (Fig. 106, p. 212), while at the same time he pointed out
the error which Klein had made and bestowed the nam.e of P. Kleinii
on the species with which Klein had worked. He also described
the chlamydospores of P. nanus (Fig. 106, p. 212), a mode of repro-
duction which had already been signalised by Roze and Cornu (1871)
in P. crystallinus.

Bainier, in 1882, published his " ^fitude sur les Mucorinees," in
which he described specimens he had met with of P. longipes,
P. oedipus, P. Kleinii, P. roridus, as well as a supposed new species,
P. exiguus ; he also confirmed van Tieghem's account of Pilaira
nigrescens.

In 1884 my " Monograph of the Pilobolidae " was published in
the Midland Naturalist, Birmingham, in which there was added
to the hitherto known species the curious form of Pilobolus Kleinii
to which, as already mentioned, the name forma sphaeros2)ora was
affixed. A new species of Pilaira was also described, to which the
name P. dimidiata (Fig. 109, p. 218) was given on account of its
possessing an apophysis nearly as large as its sporangium ; unfor-
tunately this has never been met with since, although at the time
of publication such a sequel was not imagined possible.

Dewevre, in 1894, included a good account of the species of
Pilobolus in his " Contribution a I'fitude des Mucorinees." He

TAXONOMY OF THE PII.OBOLIDAE 199

emphasised the distinction of P. crystallinus from P. Kleinii, with
both of which he was personally acquainted.

Palla, after that date, issued a long account " Zur Kenntniss der
Pilobolus-Arten " (1900), in which he classified the known species
in a novel way, but without adding much to what was previously
discovered ; he also invented a new name, Pilobolus heterosporus
(Fig. 103, p. 208), which was my P. Kleinii, forma sphaerospora,
under a different designation.

In the same year (1900), Morini gave a short description, without
a name, of a new species of Pilobolus, to which afterwards (1905)
Saccardo added the name P. Morinii. In 1906, Morini described
another species of Pilobolus, P. Borzianus, of which he also dis-
covered the zygospores, and in 1904 he had figured a new species
of Pilaira, P. Saccardiana (Fig. 110, p. 219). But Pilobolus Morinii
and P. Borzianus seem to be involved in a cloud of doubt, as do
many of the others, hke those of Spegazzini and Massee, which are
placed towards the end of the following systematic hsts.

In 1926 Ling Yong, working in France, described a new species
of Pilaira, which he named P. Moreaui (Fig. 1 1 1, p. 220), distinguished
from P. anomala by its larger spores.

The latest addition to our knowledge of the species of Pilobolus
has been made by Buller who, in the preceding chapter of this
volume, has described P. umbonatus, a new species distinguished by
the possession of a remarkably umbonate sporangium (Fig. 105.
p. 210).

This long story of the observations made on the systematics
of Pilobolus during nearly two hundred and fifty years is deeply
interesting to the mycologist ; it shows how slowly and painfully
a httle accurate knowledge has been accumulated. . From now on,
with the modern technique of pure cultures and the art of photo-
graphy at our disposal, progress should be more rapid. It is to be
hoped that some younger mycologist may be stimulated by this
presentation of the subject to make a life-study of the genus and
give us a comparative description of all the species that can be
gathered together from different parts of the world.

Systematic Arrangement. — An attempt will now be made to
arrange systematically all the species of the PiloboUdae and to give

200 RESEARCHES ON FUNGI

to the group itself and to the two genera Pilobolus and Pilaira
included within it more precise definitions than have yet appeared.

PILOBOLIDAE

A family of the Mucoraceae having a sporangium which contains
a mass of dense jelly around its base between the sporangium-wall
and the spore-mass. At maturity the mass of jelly swells up and
causes the sporangium to dehisce near its base, so that the jelly
protrudes between the sporangium- wall and the columella. The
sporangium-wall is usually intensely black and is persistent when
immersed in water.

Pilobolus Tode, in Schrift. d. Berl. Gesell. naturf. Fr., vol. v,
p. 46 (1784).

Fruit-body consisting of a sporangiophore and a sporangium.
Sporangiophore seated on a main mycehal hypha, from which it is
separated by one or two septa. From below upwards, it is composed
of a basal swelUng or trophocyst, a cyhndrical stipe, and a more or
less ovoid subsporangial swelling, and when young it is generally
ornamented by beads of moisture. Sporangium usually jet-black,
seated on the apex of the subsporangial swelUng, separated from it
by a columella, and having its wall highly cutinised and persistent
when immersed in water. When mature the sporangium and
columella are violently projected. The species usually occur on
the dung of herbivorous animals.

A. Sporangium black when mature ; no apophysis.

1. P. crystalUnus. 5. P. sphaerosporus.

2. P. longipes. 6. P. heterosporus.

3. P. roridus. 7. P. oedipus.

4. P. Kleinii 8. P. umbonatus.

B. Sporangium yellow when projected ; provided with an apophysis.
9. P. nanus.

All these species have been adequately described and figured,
and (whether they are truly distinct from one another or not) may

TAXONOMY OF THE PILOBOLIDAE

201

be recognised with certainty. After them are placed others which
have been insufficiently or negligently described, and which are
possibly nothing but variants of some of the preceding species :

Doubtful Species

10. P. Morinii. 14. P. minutus.

11. P. Borzianus. 15. P. pullus.

12. P. argentinus. 16. P. Schmidtii.

13. P. roseus.

6

Key to the Species of Pilobolus

(Sporangium decidedly umbonate .
(Sporangium rounded above .

[Trophocyst much elongated
[Trophocyst ovoid or turnip-shaped

Spores globose and elhpsoid in the same sporan
gium ......

Spores globose or subglobose only
Spores elhpsoid only ....

(Spores with two coats ....
(Spores with only one coat

Sporangium yellow when projected
Sporangium black when projected.

Spores from 10 (x upwards in length
Spores averaging less than 10 (x in length

[Spores 5-10 x 4-6 [i ; sporangium large
(Spores 6-8 x 3-4 (x ; sporangium small

umbonatus
1

longipes
2

heterosporus

3

5

oedipus
4

nanus
sphaerosporus

Kleinii
6

crystallinus
roridus

(Probably crystallinus and roridus are merely forms of one species.)

A. Sporangium black ivhen mature ; no apophysis.

1. Pilobolus crystallinus Tode, I.e. p. 46, pi. 1 (1784). Van
Tieghem, Trois. Mem. in Ann. Sci. Nat. ser. 6, vol. iv, pp. 335-8,
pi. 10, f. 4, 5, repeated from Bull. Soc. Bot. Fr. vol. xxii, pp. 283-4

202

RESEARCHES ON FUNGI

(1875). Coemans, MonograpMe, pp. 57-8, pi, 2, f. 1-20. Sacc.
Syll. vii. 185. Grove, Pilobolidae, p. 333 (p. 33 of Reprint), pi. 4,
f. 16. Palla, Zur Kenntniss der Pilobolus-Arten, p. 399.

Mucor urceolatus Dickson, Fasc. PI. Crypt, part 1, p. 25, pi. 3,
f. 6 (1785). Sowerby, Evglish Fungi, pi. 300. Bolton's figure under
this name {Fung. Halif. pi. 133, f. 1) is doubtful.

Pilobolus urceolatus Purton, Midland Flora, vol. iii, p. 323, pi. 31
(1821).

P. microsporus Brefeld, Botan. Unter such., -part 4, p. 70, pi. 4, f. 16,
19-22 (1881).

Not P. crystallinus of Bonorden, or of Cohn, or of Klein, or of
Brefeld, or of many others.

Sporangiophore 5-12 mm. high, or even up to 2 cm., rising
usually from a single, more or less erect, terminal, ovate trophocyst,

which is often concealed in the sub-
stratum ; occasionally the trophocyst
may be intercalary. Subsporangial
swelling ovoid or elliptic-ovoid, about
1 mm. high, 600-800 \l broad. Spor-
angium convex above, from half as wide
to nearly as wide as the subsporangial
swelling, usually 350-500 \x in width ;
columella conical, faintly blackish-blue ;
spores ellipsoid, pale yellowish or quite
colourless, 5-10 [j. long (8-10 x 5-6 \x,
vanT. ; 5-12 x 3-6 [ji, Palla ; 6 x4-7pi,
Brefeld; 7-11 x 4-5-7, Dewevre).

Zygospores subglobose, 140-200 ]x
in diameter, nearly smooth, faintly
coloured, filled with oil-drops (Krafczyk.
in Ber. d. D. Bot. GeseU. 1931, p. 145,
f. 2). Apparently not quite mature.

On dung of cows, horses, and the
like. Reputed common. Europe, North
and South America, Porto Rico, etc.
Not seen by Buller at Winnipeg.
The upper cutinised part of the sporangium, when it is dried up,
is sometimes marked with a few polygonal reticulations (one central) ;

Fig. 99.— Ripe fruit-body and
spores : A, Pilobolus Kleinii
(= Brefeld's P . crystallinus) ;
B, Pilobolus crystallinus
(= Brefeld's P. microsporus).
Copied by A. H. R. Buller
from Brefeld's Untersuch-
ungen. Magnification : fruit-
bodies, 20 ; spores, 200.

TAXONOMY OF THE PILOBOLIDAE

203

but the reticulations are not always so geometrical as van
Tieghem represents them, and they can be found also in other species.
Illustration : 99, B.

2. Pilobolus longipes van Tiegh. Trois. Mem. in Ann. Sci. Nat.
ser. 6, vol. iv, pp. 338-340, pi. 10, f. 11-15 (1876), repeated from
Bull. Soc. Bot. Fr. vol. xxii, pp. 283-4 (1875). Grove, Pilobolidae,
p. 335, pi. 6, f. 1. Sacc. Syll. vii. 185. Palla, I.e. p. 399.

P. roridus Brefeld, in Bot. Zeit. 1875, p. 852 ; Botan. Untersuch.
part 4, p. 70, pi. 4, f. 17.

Sporangiophore 2-3 cm. high, sometimes 4-5 cm. or even
6-7 cm. ; trophocyst usually external to the substratum, elongated
horizontally, 1-5-2 mm.
long, golden-yellow,
almost cylindrical or
slightly tapering, giving
rise to the stipe at one
end. Subsporangial swell-
ing oval, rather less than
1 mm. broad. Spor-
angium globose, black,
about 500 [X across ;
columella broadly conical,
tinged with bluish-
black ; spores globose or
ovoid, 12-15 X 10-12 (x,
the wall rather thick
and tinged (often very
faintly) with bluish-
black, contents yellow-
orange.

On dung of horses. Europe, Canada, U.S.A.

Distinguished by its large roundish spores, its elongated tropho-
cyst, and its height.

Illustration : Fig. 100. Other illustrations in this volume :
Figs. 18, 24, 40, 57, 70, 82, 83, 85, 91, and 96.

>^S?^

Fig. 100.- — Pilobolus longipes v. Tiegh. A, whole
fruit-body. B, trophocyst. C, basal swelling
and part of stipe. D, upper part of fruit-
body enlarged. E, spores : n, intact ; b, broken
open. Reproduced by photography from
van Tieghem's Troisieme Memoire.

204

RESEARCHES ON FUNGI

3. Pilobolus roridus (Bolt.) Pers. Syn. meth. p. 118 (1801).
Coemans, Monographie, pp. 61-2, pi. 2, f. B. (copied from

Bolton). VanTiegh. Nouv.
Eech. Nat. in Ann. Sci.
ser. 6, vol. i, pp. 46-50,
pi. 1, f. 7-13. Grove,
Pilobolidae, p. 336. Sacc.
Syll. vii. 185. Palla, I.e.
p. 398.

Mucor roridus Bolton,
Fung. Halif. vol. iii,
pi. 132, f. 4(1789).

Pilobolus microsporus
Klein, Zur Kennlniss
des Pilob. in Jahrb. f.
wiss. Bot. vol. viii,
p. 360, pi. 27, 28, f. 53-67
(1872).

Not P. roridus of
Brefeld, or of Currey,
or of many others.

Sporangiophore 1-2 cm.
high, nearly colourless,
the trophocyst often
intercalary between two
(or even three) mycelial
swellings. Subsporangial
swelling oval or almost
globose, up to 600 or 700 (x
diam. Sporangium very
much less in diameter,
even as little as 200 \x ;
columella flatly convex or

conical, tinged with bluish-black ; spores ellipsoid, nearly colourless,

6-8 X 3-4 IX (van T.).

On dung of herbivorous animals, including rabbits. Not

common. Distribution uncertain.

This species shows generally much less of the yellow colour

Fig. 101. — Pilobolus roridus (Bolt.) Pers. A,
three fruit-bodies. B, whole fruit-body,
shortened. CjUj^per part of fruit-body after
sporangium has dehisced in water ; m,
mucilage. D, spores. E, germinating spore.
F, two basal swellings, a and b, inserted
successively on the same apophysis c. G , an
intercalary basal swelling a formed between
two apophyses, c and c'. Copied by A. H. R.
BuUer from van Tieghem's Nouvelles
Recherches. Magnification : A, natural size ;
B, 25 ; C, (55 ; D and E, 380 ; F and G, 50.

TAXONOMY OF THE PILOBOLIDAE 205

(carotin) than its allies ; but there has been in most cases con-
siderable doubt whether the plants entered under this name were
anything but forms of P. crystallinus. The chief points which are
supposed to characterise the species are the smallness of the spores
and of the sporangium. The " dew-drops " which are implied in
the name roridus are to be found in suitable circumstances in equal
abundance on other species. It tends to excite our suspicions
when we find authors recording the occurrence of P. roridus in
company with P. crystallinus.
Illustration : Fig. 101.

4. Pilobolus Kleinii van Tiegh. Trois. Mem. in Ann. Sci. Nat.
ser. 6, vol. iv, pp. 337-8, pi. 10, f. 6-10 (1876), repeated from Bull.
Soc. Bot. Fr. vol. xxii, pp. 282-3 (1875). Grove, Pilobolidae, p. 335,
pi. 4, f. 1-8, 10-13, and in Journ. Bot. 1884, p. 131, pi. 245, f. 4.
Sacc. Syll. vii. 185. Bainier, Etude, p. 43, pi. 2, f. 14, 15. Palla,
I.e. p. 399.

P. roridus Carrey, in Journ. Linn. Soc. Lend. Bot. vol. i,
pp. 162-7, pi. 2, f. 1-10 (1857). Not M. roridus Bolton.

P. crystallinus Klein, Zur Kenntyiiss des Pilohol. in Jahrb. f. wiss.
Bot. vol. viii, p. 360, pi. 23-7, f. 1-52. Brefekl, Botan. Untersuch.
part 4, p. 70, pi. 4, f. 15. Zopf, Z%ir Kcnntniss der Infectionskrank-
heiten, p. 354. Not of Tode.

P. Kleinii var. minor Dewevre, in Grevillea, vol. xxii, p. 74 (only
1 mm. high).

Sporangiophore 2-5 mm. high^ varying up to 10-12 mm. high,
rising singly from a turnip-shaped trophocyst which is often buried
in the substratum. Subsporangial swelling obovoid or subellipsoid,
400-800 y. high. Sporangium black, more or less depressed or sub-
globose, about two-thirds as wide as the swelling to nearly as
wide ; columella sometimes with a faint blackish tinge, generally
colourless, broadly conical below, but occasionally narrowed in the
middle so that the apex resembles a papilla ; spores in varying
shades of orange-yellow, ellipsoid, 11-20 x 6-10 \j., with a thin
smooth colourless cell- wall.

Zygospores thick-walled, spherical, nearly smooth, about 200 [i
diani. (Zopf, I.e. pi. 6, f. 8-19).

2o6 RESEARCHES ON FUNGI

On all kinds of dung. Very common. Europe, E. Africa,
Canada, U.S.A., etc.

This appears to be the commonest species in Europe, and
perhaps in most countries where Pilobolus occurs. It has often
been confounded with P. crystallinus, but is not so high, is more
tinged with yellow, the thickened band of protoplasm at the top of
the stipe is more brightly orange, and its spores, although of the same
shape, are perceptibly larger. Trophocysts usually with a single
apophysis, rarely with two.

Illustration : Fig. 99, A. Other illustrations in this volume :
Figs. 2, 12, 13, 22, 27, 28, 29, 32, 39, 42, 46, 61, 62, 83, 86, 91, 94,
and 95.

5. Pilobolus sphaerosporus Palla, Zur Kenntniss der Pilobolns-
Arten, in Oesterr. Bot. Zeitschr. vol. 50, p. 400, pi. 10 (1900).

Pilobolus lentiger Corda, Icon. Fung. vol. i, p. 22, pi. 6, f. 286
(1837), including var. macwsporus Berl. & de Toni, in Sacc. Syll.
vii. 188 (1888).

Pycnofodium lentigerum Corda, ibid. vol. v, p. 18 (1842), an
ill-nourished form.

Pilobolus crystallinus Bonord. Handb. p. 128, pi. 10, f. 203 (1851).

P. oedipus, var. iritermedia, Coemans, Spic. Mycol. in Bull.
Acad. Belg. ser. 2, vol. xvi, p. 71 (1863).

P. crystallinus (P. oedipus, forms b and c) Klein, Zur Kenntniss
des PiloboL, p. 360, pi. 26, f. 40 b, 46-8 ; pi. 27, f. 49, 50 (1872).

P. intermedius (Coem.) Karst. Myc. Fenn. part 4, p. 71 (1879).

P. oedipus Brefeld, Botan. Untersuch. part 4, p. 69, pi. 3, f. 1-10 ;
pi. 4, f. 11-14 (1881).

P. exiguus Bainier, Etude, p. 47, pi. 2, f. 17 (1882).

P. Kleinii, forma spluierospora, Grove, in Journ. Bot., vol. xxii,
p. 132, pi. 245, f. 5 (1884) ; Pilobolidae, p. 335, pi. 4, f. 9.

Similar to P. Kleinii, but usually smaller. Spores yellow or
orange, more or less globose, 10-20 u. in diam., varying greatly in
size, often with granular contents, diffusing very easily in water,
and having a thin wall composed of only one coat.

On dung of man, horse, cow, etc. Europe.

The spores vary considerably in size. I have always found this
in company with P. Kleinii at the beginning of its growth in a
culture, but changing and passing gradually into the normal form.

TAXONOMY OF THE PILOBOLIDAE 207

Palla [I.e.) says that this appearance is due to the growth of the two
species in a mixed (impure) culture, but that P. sphaerosporus
produces its fruit-bodies from one to several days before those of
P. Kleinii show themselves. I do not entirely agree with this ;
it does not explain the transition stages, which may always be
found on looking for them, like those represented by Coemans'
intermedia and Klein's variety c of his P. crystallinus, where both
ellipsoid and round spores may be seen
in the same sporangium.

Illustration : Fig. 102. The figure
here given, from Brefeld's Untersuchungen,
is called by him P. oedipus ; it is not
that species, but exactly represents my
P. Kleinii forma sphaerospora.

6. Pilobolus heterosporus Palla, Zur
Kenntniss der Pilobolus-Arten, in Oesterr.
Bot. Zeitschr. vol. 50, p. 349, pi. 10, f. 1-5
(1900) ; a Resume of this article, with
plates and descriptions, is given by R. Ferr}^
in Revue Mycologique, 1904, pp. 19-33.

Sporangiophore 2-3 mm. high ; tropho-
cyst usually buried in the substratum,
ellipsoid, rarely globose, 300-400 fx long.
Subsporangial swelhng ovoid or elhpsoid,
500-600 fx high, provided at the insertion
of the columella with a thin narrow
annular zone. Sporangium shaped hke a convex cap, deep-black,
400 \i broad ; columella more or less deeply constricted in the
middle, rounded at the apex, reaching nearly to the top of the
sporangium ; spores yelloA\ or orange-red, varying in form and
size in the same sporangium, narrow- or roundish-ellipsoid,
with all intermediate forms, 8-20 (or even 25) [x long, and 6-12 [x
broad.

On cow dung, Graz (Styria).

T have drawn up this description from Palla's rambhng
and diffuse account as given in his article. Palla says that he

Fig. 102. — Pilobolus sphae-
rosporus Palla. Fruit-
body and spores.
Copied by A. H. R.
Buller from Brefeld's
Untersuchungen (his P.
oedipus) and enlarged
by one-third. Magnifi-
cation, 40 and 400.

208

RESEARCHES ON FUNGI

cultivated his species, and fo\md that it retained its characters up
to fifteen generations. But it is in no way different from my

forma sphaerosjjora of Pilobolus
Khinii. The irregularity of the
spores is exactly what I found
in my cultivations, and the
retention of the characters
may be due merely to the
persistence of similar conditions
throughout the whole series of
his fifteen generations. If I
am right in my opinion, the
three species here numbered
4, 5, and 6 are all identical,
and the variations in form are
dependent upon the surround-
ing circumstances.

Illustration : Fig. 103.

c

0,

0^g3o0o°0

D

QP
o

Fig. 103.^ — Pilobolus heterosporus Palla.
A, fruit-body, after dehiscence of
the sporangium. B, fruit-body,
after removal of the sporangium,
showing the columella. C and D,
spores. Copied by A. H. R. Buller
from Palla's Zur Kenntniss der
Pilobolus- Arten and reduced to two-
thirds. Magnification : A and B,
30; C, 214; D, 434.

7. Pilobolus oedipus Mont.
Memoire sur le genre Pilobolus,
in Ann. Soc. Linn, de Lyon,
pp. 1-7, f . a-i (1828). Coemans,
Monograjphie, pp. 59-60, pi.
1, f. 1-20. Grove, Pilobo-
lidae, p. 308, pi. 4, f. 14-15;
and in Journ. Bot. vol. xxii,
p. 131, pi. 245, f. 3. Sacc. Syll.
vii. 186. Palla, I.e., p. 400. Bainier, Etude, pp. 43-4, pi. 2,
f. 1-10.

P. crystallinus Cohn, Entwicklungsgeschichte des Pilob. crystal-
linus, with pi. 51, 52 (1851).

P. reticulatus van Tiegh. in Ann. Sci. Nat. ser. 6, vol. iv, p. 336.
Not the P. oedipus of Brefeld or of Klein, nor perhaps that of
van Tieghem {Nouv. Rech. 1875, p. 43).

Sporangiophores yellow or reddish, usually short and thick,
about 2-3 (or even 5) mm. high, rising singly from a roundish

TAXONOMY OF THE PILOBOLIDAE

209

trophocyst which projects somewhat above the substratum, but
several of these are often so closely aggregated together that they
form little tufts. Sporangium about 500 y. broad, not quite so
broad as the ovoid subsporangial swelHng, almost hemispherical,
black ; columella conical or subcyhndrical, slightly narrowed
in the middle, sometimes so high that it reaches almost to the
top of the sporangium ; spores globose, yellowish-red, 9-16 y.
diam. ; with a wall composed of
two distinct layers, of which the
outer (epispore) is thick and often
bluish.

On dung of horses, cows, pigs,
goats, and mules ; it has also been
found on human excrement, and
it often occurs on decaying vege-
table substances such as Algae
(Spirogyra, Conferva, Oscillaria,
and so on), and therefore also on
the mud of river-banks (Thames,
Oder, Red River of Winnipeg,
etc.). It has been suggested that
perhaps its spores do not require
to pass through the alimentary
canal of an animal, but this seems
unlikely, since in a discharged
sporangium they adhere together
just as in other species of Pilobolus
easily in water. The name of this species should be spelled oedipv3
(adjectival), not OEdipus.

Europe, E. Africa, N. America. Its round thick- walled spores
are characteristic, also the deep colour which it displays owing to
the crowded visible trophocysts. Chlamydospores [Mycogone anceps
Coem.), lying in the mycelium, globose or ovoid, orange-yellow,
oily-granular, 20-30 \j. in diameter, are assigned to this species by
Coemans, and by Ellis, North American Fungi (no. 3360) ; these
may be azygospores (cf. Fig. 106, G.).

Illustration : Fig. 104.

Fig.

104. — Pilobolus Oedipus Mon-
tague. A, young fruit-body. B,
mature fruit -body. C, another
mature fruit-body, with the spor-
angium more flattened than
usual. D, spores. Copied by
A. H. R. Buller from Coemans'
Monograph ie and reduceil to two-
thirds. Magnification : A, 53 ;
B and C, 40 ; D, 200.

They germinate, however.

VOL. VI.

210

RESEARCHES ON FUNGI

8. Pilobolus umbonatus Buller, in his Researches on Fungi,
vol. VI, pp. 177-17^, figs. 81-84, 87-91 (1934).

Fruit-body 3-9 mm. high, arising from an oval to turnip-shaped

Fig. 105.- — Pilobolus umbonatus Buller. A, well-grown fruit-bodies 7-8 mm.
high. B, less well-grown fruit-bodies 1- 5-3-0 mm. high. C and D,
whole fruit-bodies, showing sporangium, subsporangial swelling, stipe,
and basal swelling attached to an apophysis ; C was 4 mm. high, and
D 3-5 mm. high. E, the upper part of a fruit-body, showing the um-
bonate sporangium, the barrel-shaped subsporangial swelling, and part
of the stipe. F, the same seen from above ; ratio of width of spor-
angium to width of subsporangial swelling = |. G, the greyish
columella, seen after removal of the sporangium from the top of the
fruit-body. H, a basal swelling a, attached to an apophysis b. I, a dis-
charged sporangium : a, the black sporangium -wall ; b, the colourless
fringe of the sporangium -wall ; and c, adhesive jelly. J, a similar spor-
angium, but jelly is not shown ; the surface of the sporangium-wall in I
was smooth, in J wrinkled. K, three discharged and dried-up sporangia
seen in lateral view. L, spores. M, diagram showing a spore of P.
umbonatus enclosed by a spore of P. Kleinii, in turn enclosed by a spore
of P. longipcs. Drawn by A. H. R. Buller from material obtained at
Winnipeg. The drawings C and D reproduced from pencil drawings
made by Hans Ritter. Magnification : A and B, natural size ; C and
D, 15 ; E-K, 75 ; L and M, 255.

basal swelling or trophocyst which may be terminal or intercalary,
single or dispersed at intervals along a coarse stolon-hke main hypha.

TAXONOMY OF THE PTLOBOLIDAE 211

Stipe increasing slightly in diameter from below upwards, until just
beneath the subsporangial swelhng it is about 0-1 mm. in diameter.
Subsporangial swelling ellipsoid, its maximum diameter being about
midway between the base of the sporangium and the top of the stipe,
0-65 mm. long and 0-4G mm. broad; a pale orange-red band of
protoplasm at the junction of the stipe and the subsporangial
swelling. Sporangium decidedly umbonate and more or less conical,
0-21-0 -23 mm. in diameter or about one-half the diameter of the
subsporangial swelling, shrinking on drying after discharge and
becoming acutely pointed ; columella very bluntly conical or
rounded (when removed from a discharged sporangium its edge is
turned inwards towards the axis), greyish, distinctly darker than the
subsporangial swelling. Spores ellipsoid, singly almost colourless,
but yellow in mass J 5- 0-6-0 x 3-0-3-8 jj^.

On horse dung, Winnipeg, Canada, and, according to a communi-
cation from the late Dr. Roland Thaxter (who observed the species
forty years ago but did not describe it), more frequently on sheep
dung, at Boston, U.S.A.

Easily distinguished from all other species of Pilobolus by its
decidedly umbonate sporangium and its minute ellipsoidal spores.
With a hand-lens one can readily make out the acutely-pointed
umbonate shape of the dried discharged sporangia when these are
seen in lateral view.

Illustration : Fig. 105. Other illustrations in this volume :
Figs. 81, 82, 83, 84, 87, 88, 89, 90, and 91.

B. Siiorangium yelloiv uihen projected ; provided with

an apophysis.^

9. Pilobolus nanus van Tiegh. Trois. Mem. in Ann. Sci. Nat.
ser. 6, vol. iv, pp. 340-2, pi. 10, f. 10-22 (1876). Orove. Pilobolidae,
p. 336, pi. 6, f. 2. Sacc. Syll. vii. 186. Palla, I.e., p. 398.

^ In most Piloboli, the subsporangial swelling is not constricted below the level
of its attachment to the columella and the wall of tlie sporangium. In P. nanus,
according to van Tieghem, the subsporangial swelling is constricted a sliort way
below that level so that it is divided into two unequal parts, a lower globular sub-
sporangial swelling proper and an ujjper shallower swelling — the so-called apophysis.

212

RESEARCHES ON FUNGI

Sporangiophores erect, not more than 1 mm. high, collected into
groups of two or three (even four or five), all rising from contiguous
buried intercalary trophocysts. Subsporangial swelling subglobose,
colourless. Sporangium globular, about as wide as the subsporangial
swelling, with the membrane of the upper part cutinised and

Fig. lOG. — Pilobolus nanus v. Tiegh. A, three fruit-bodies. B, two basal swellings
p p, and C, three basal swellings p p p, between two apophyses a a. D and E,
optical sections through the upper part of a fruit-body, before and after
dehiscence of the sporangium respectively ; c, yellow cuticularised wall of the
sporangium ; d, diffluent region ; /, limiting ring of cuticularisation ; g, jelly ;
k, columella. F, spores : a, resting ; b, swollen ; c, germinating. G, resting
spores (azygospores), with tuberculate membranes, on a mycelium ; o, in
section to show the thick cell-wall. Copied by A. H. R. Buller from van
Tieghem's Troisieme Memoirc. Magnification, not given.

yellow ; columella depressed-convex ; spores globose, colourless,
3-5-4 [X in diameter.

On excrement of rat. France.

Not observed by anyone but van Tieghem. The protoplasm of
the sporangiophores is said by him to be colourless, as is also that
of the mycelium. On the mycelium grew oblong-roundish, faintly
yellow, coarsely verrucose chlamydospores, 15-20 [x in diameter,
resting on short curved pedicels ; these are probably azygospores.
The sporangia were shot off as in other Piloboli and stuck to the
surrounding objects, while still yellow. When the explosion took

TAXONOMY OF THE PILOBOLIDAE 213

place, the rupture occurred at the constriction between the apophysis
and the subsporangial swelling.

There is a possibility that this species is an abnormal form due
to the unfavourable environment in which it was growing. Sporangia
with defective black pigment in their walls have been observed by
van Tieghem himself in his P. oedipns and by Buller in P. longipes
{vide these Researches, vol. iv, p. 9, and this volume, p. 54).

Illustration : Fig. 106.

Insufficiently known Species

10. Pilobolus Morinii Sacc. Syll. xvii. 505 (1905).

Piloholus sp. Morini, in Mem. Accad. Sci. 1st. Bologna, ser. 5,
vol. viii, p. 85, with plate (1899-1900).

Sporangiophores solitary, 600-800 \x high, each rising from an
erect ovoid trophocyst. Subsporangial swelling subglobose or ovoid,
somewhat narrowed above, and attenuated below into the sporangio-
phore, almost colourless when mature. Sporangium globular, some-
what flattened above, black, 130-200 [x in diameter ; columella
obtusely conical, colourless, rounded above ; spores globose, orange-
yellow (not colourless), 4-5-6 /z in diameter.

On dry human excrement. Montese, Bologna, Italy. Resembling
P. nanus van Tiegh., except for its black sporangium and its
sporangiophores not arising in groups.

11. Pilobolus Borzianus Morini, in Mem. Accad. Sci. 1st. Bologna,
ser. 6, vol. iii, p. 126 (or 396), f. 3-10 (1908). Sacc. Syll. xxi. 827.

Sporangiophores 2-4-5 mm. high, growing two or three together
from one trophocyst, which is ovoid and often imperfectly developed.
Subsporangial swelling globose or shortly ovoid, 200-360 [x high,
almost colourless or quite hyaline. Sporangium globose, very
much flattened from above, 160-250 [x wide, intense bluish-black ;
columella hemispherical or shortly conical, without apophysis ;
spores spherical, deep yellow. 16-23 (x in diameter. Oval chlamy-
dospores are developed in the mycelium.

Zygospores black, globose, about 180 ^ across, with a thick and
glabrous epispore (Morini, I.e. f. 3, 9).

214 RESEARCHES ON FUNGI

On dung in the north of Italy.

Morini (in Mem. Accad. Sci. 1st. Bologna, ser. 6, vol. vi, pp. 123-4,
f. 6-8, 1909) describes a var. geminata of this species. He says that
the trophocyst may produce two hyphae at a time or, if one only,
the one may branch into two above. He asserts that these forms
remained constant in repeated artificial cultures. I suspect that the
var. geminata is nothing more than an abnormal form ; for, since
normally a Pilobolus sporangiophore collapses at the moment of
discharging its sporangium, a forked sporangiophore can shoot away
only one of its sporangia and not both. Abnormal branched spor-
angiophores are occasionally met with in other species, and are figured
by Coemans in P. crijstallinus, by Klein in P. Kleinii (his P. crystal-
linus), and have been seen by Zopf and Grove also in P. Kleinii.

12. Pilobolus argentinus Spegazzini, Fung. Argent. I, p. 176
(1880). Sacc. Syll. vii. 187.

Sporangiophores " immersed," here and there densely gregarious,
5-6 mm. high, at first cylindric-clavate, then filiform below, with
a trophocyst and an ellipsoid subsporangial swelling, the whole
plant entirely yellow. Sporangium globose, 100-125 \l diam., ohve-
black above, greenish-yellow below ; spores spherical, 12-15 [x diam.,
thick-walled, filled with a greenish-yellow granular protoplasm.

On horse dung, in grassy places alongside the Rio de la Plata.
Judging by the description, one would consider this only a form of
P. oedipus.

13. Pilobolus roseus Speg. Fung. Argent. I, p. 175 (1880). Sacc.

Syll. vii. 187.

Sporangiophores densely gregarious, 2-4-5 mm. high, at first
clavate, rosy-orange, truncate at the rounded apex, then filiform
below, ellipsoid or ventricose-spheroid above, very beautifully rosy-
hyahne. Sporangium black, hemispherical, 300-400 \i diam. ;
spores ellipsoid, obtusely rounded at the ends, granular within,
rosy-hyaline, 12-16 x 7-8 [x.

On cow dung, near the Rio de la Plata. This species might well
be merely a form of P. Kleinii ; its chief distinction seems to reside
in its colour, but a rosy hue is not unknown in some other species of
Pilobolus.

TAXONOMY OF THE PILOBOLIDAE 215

14. Pilobolus minutus Speg. Fung. Argent. 1, p. 176 (1880).
Sacc. Syll. vii. 186.

Sporangiophores superficial, loosely gregarious, 2-5 mm. high,
at first fiUform-clavate, then ventricose and ellipsoid, above, always
hyaline, more or less elongated and filiform below. Sporangium
black, lenticular, 125-145 [x diam. ; spores spherical or eUipsoid,
granular, hyaline or faintly greenish-yellow, 7-8 [l diam.

On cow dung, in shady places near the Rio de la Plata. This
species may well be only P. Kleinii var. minor Dewevre.

15. Pilobolus pullus Massee, in Kew Bulletin, 1901, p. 160.
Sacc. Syll. xvii. 506.

Sporangiophore about 1 mm. high, nearly colourless, inflated and
ventricose above. Sporangium depressed-hemispherical, black,
smooth, 250-300 \i broad ; columella convex, often constricted
in the middle ; spores ellipsoid, 10-12 x 8-9 [j., with an orange
epispore.

On cow dung. Tasmania (Rodway). Perhaps akin to a form of
P. Kleinii.

Petch, in recording a species under this name in Annals Roy.
Gard. Peradeniya, vol. vii, part 4, p. 297, says : " Scattered ; total
height 0-6-0'8 mm., clavate, expanding almost from the base,
0-3 mm. diameter above. Sporangia oval, black, 0-25 x 0- 15-0-2
mm. ; wall black-brown, smooth, not areolated. Spores oval,
pale-yellow, 8-10 x 5-6 \l.

" On cow dung, Hakgala, Ceylon, December, 1917."

16. Pilobolus Schmidtii Sacc. Syll. xxiv. 11 (1926). Pilobolus
sp. Alf. Schmidt, in Jahresber. d. Schles. Gesell, xc. 19 (1912).

Sporangiophores standing singly ; trophocyst ovoid, yellowish,
560-720 X 340-400 [x. Stipe 4 mm. high ; subsporangial sweUing
ovoid, up to 1 mm. high, 640-800 [x broad ; columella colourless,
250-370 [J. high. Sporangium hemispherical, black, 430-510 [j.
broad ; spores ellipsoid, thin- walled , yellow or yellowish, 6 -5-8 -5 X
5-6 [J., not diffusing readily in water.

On dung of mules. Reared at Breslau, Germany, on mule dung

2i6 RESEARCHES ON FUNGI

brought from Amani, German East Africa. Allied to P. Kleinii,
but differing in the dimensions of its parts.

Pilaira van Tieghem, Nouv. Rech. in Ann. Sci. Nat. ser. 6, vol. i,
p. 51 (1875).

Fruit-body consisting of a sporangiophore and a sporangium.
Sporangiophore arising from the myceUum without a septum at its
base. It is evenly cyHndrical and has no basal or subsporangiai
swelHng. Sporangium black, separated from the sporangiophore by
a columella, and having its wall highly cutinised and persistent when
immersed in water. When mature the sporangiophore collapses and
there is no projection of the sporangium. The species are all
coprophilous.

Pilaira differs from Pilobolus in that its sporangiophore has no
septum at the base, no basal sweUing, and no subsporangiai swelhng,
and in that its sporangium is not violently projected.

In 1930 Fitzpatrick, in his book on the Phycomycetes, suggested
that the genus Pilaira is " based on abnormal material of Pilobolus."
There can be no doubt that this view is erroneous. Not only
van Tieghem and Brefeld but also BuUer, I myseK, and others have
observed and cultivated the type of the genus, Pilaira anomala, and
have found it to be quite distinct from any abnormal form of
Pilobolus.

Five species of Pilaira are known. The key to them, given
below, is founded on that of Ling Yong.

Key to the Species of Pilaira

[Spores round .....

(Spores oval or elongated .

I Sporangiophores branched

1 Sporangiophores simple

( Sporangiophores only about 1 mm. high

(Sporangiophores up to 10 cm. high

(Spores oval, up to 10 [j. long

(Spores elongated, up to 22 (x long . . . Moreaui

nigrescens

1

Saccardiana

2

dimidiata

3

anomala

TAXONOMY OF THE PILOBOLTDAE

217

1 . Pilaira anomala (Ces.) Schroter, Pilze, in Cohn's Kryptogamen-
Flora von Schlesien, vol. iii, p. 211 (1889). Sacc. Syll. vii. 188.

Piloholus anom/ilus Cesati, in Klotzsch, Herh. viv. mycol., no. 1542
(1851). Brefeld, Botan. Untersuch. part 4, pp. 60-5, pi. 4, f . 18, 23-28.

Ascophora Cesatii Coemans, Monoyraphie, p. 63, pi. 2, f. E (1861).

Piloholus Mucedo Brefeld,
Botan. Untersuch. part 1,
p. 27, pi. l,f. 25, 26 (1872).

Pilaira Cesatii vanTiegh.
in Ann. Sci. Nat. ser. 6,
vol. i, p. 52, pi. 1, f. 14-24
(1875). Bainier, Etude,
pp. 29-32, pi. 1, f. 16-18.
Grove, in Journ. Bot.,
vol. xxii, p. 132, pi. 245,
f. 6 ; Pilobolidae, p. 337,
pi. 6, f. 7, 8.

Sporangiophore cylindrical,
colourles.s, at first erect, 1-2 cm.
high, then growing to a height
of 9-12 (or even 20) cm., at
length shrivelling and falUng
down on the substratum.
Sporangium at first yellow,
black when mature, more or
less globular, 120-250 [i diam.,
then hemispherical with a
small granular apophysis be-
low ; columella colourless,
hemispherical, but somewhat
depressed ; spores ovoid,
nearly colourless (but yellow-
ish in mass), 8-12 x 6-7 y..

Zygo.spores black, globose

Fig. 107. — PiUiira anomala (Ces.) Schroter.
A, three fruit -bodies, collapsing. B,
longitudinal optical .section of a spor-
angium. C, upper and lower part of a
fruit-body, after the dehiscence of the
sporangium ; m, protruding mucilage.

D, sporangium in air, before dehiscence.

E, coliunella, seen from below, after the
fall of the sporangium. F, a similar
columella, in lateral view ; there are
crystalloids in both the stipe and
columella. G, spores. H, I, and J,
three successive stages in the formation
of a zygospore. Copied by A. H. R.
Buller from van Tieghem's Xouvelles
Recherches. Magnification : A, natural
size ; B-F, 90 ; G, 380 ; H-J, 200.

or ovoid, up to 115 a diam.,

epispore covered with numerous minute papiUae (Brefeld. I.e. part 4,

f. 26-28).

On dung of sheep, goats, gazelles, hares, rabbits, goose, pig. ass,
and horse. Europe, U.S.A. (Pennsylvania). Rather uncommon.

2l8

RESEARCHES ON FUNGI

The zygospores were found by Brefeld on horse dung which had
borne luxuriant crops of fruit bodies (c/. Fig. 107, H-J).
Illustration : Fig. 107.

Pilaira nigrescens van Tiegh. in

vol. i

Ann. Sci. Nat. ser. 6,
p. 60, pi. 1, f. 25-8 (1875).
Grove, Pilobolidae, p. 337. Sacc.
Syll. vii. 189.

Sporangiophore shorter than in
the preceding species (1-5-2 cm.)
and more slender. Sporangium
also smaller, but having a simi-
lar granular apophysis ; columella
blackish-violaceous or bluish,
hemispherical, and ending in a
conical papilla. Spores globose,
colourless, 5-6 (x in diameter.

On dung of rabbit. France ;
Distinguished by its size, its spores, and its conical and

Fig. 108. — Pilaira nigrescens v. Tiegh.

A, four fruit-bodies, collapsing.

B, upper part of a fruit-body
after dehiscence of the sporangiiun ;
TO, protruding mucilage. C, upper
part of a fruit-body after the fall
of the sporangium. D, spores.
Copied by A. H. R. Buller from
van Tieghem's Nouvelles Re-
cherches. Magnification : A,
natural size; BandC, 90; D, 380.

rare

coloured columella.
Illustration : Fig

108.

3. Pilaira dimidiata Grove, in Journ. Bot. vol. xxii, p. 132,
pi. 245, f. 7 a-d (1884) ; Pilobolidae, p. 338, pi. 6, f. 10 a-c. Sacc.
Syll. vii. 189.

Sporangiophore slender, cylindrical, and while erect not more
than 0 -5-1 -0 mm. high, then bending down towards the substratum
and becoming 3-4 mm. long. Sporangium ^„^

at first yellow, then black, hemispherical, \y

100-120 (J, diam. ; immediately beneath it
the sporangiophore is widened somewhat

Fig. 109.- — Pilaira dimidiata Growe. A, mature fruit-
body. B, columella. C, spores. DrawTi by

A. H. R. Buller from sketches made by W. B. Grove
in 1883 without the use of a camera lucida.
Cf. Plate 245, Fig. 7, a-d, in Grove's New or
Noteworthy Fungi, \%%^. Magnification: A, 116;

B, 240 ; C, 660.

TAXONOMY OF THE PILOBOLIDAE

219

like the apophysis of a moss-capsule (Funaria). Spores ellipsoid,
almost colourless, 12-14 x 5-6 [x.

On dog's dung. England (Worcestershire) ; found only once,
March and April. Distinguished from Pilaira anomala not only by
its much smaller size, but also by its peculiar apophysis, which is
almost as large as the sporangium, but slightly less in diameter, and
not granular. It was growing luxuriantly on a rich substratum.

Illustration : Fig. 109.

4. Pilaira Saccardiana Morini, first mentioned in Rendic. Sess.

Fig. 110. — Pilaira Saccardiana Moriai. A, fruit-bodies, spor-
angiophores branched ; sporangia mature and now hanging
down. B, a branched sporangiopliore bearing two spor-
angia, one in side view and the other seen from above.
C, a sporangium after dehiscence ; g, swollen jelly. D,
optical longitudinal section of a sporangium, showing the
spores and the columella. E, the sporangium has gone ;
the columella remains and, about its base, can be seen a
gelatinous substance derived from the liquefaction of the
inferior zone of the sporangial membrane. F, spores. G,
part of a sporangiopliore whose sporangium had not yet
ripened ; in the protoplasm are numerous crystalloids
of mucorine. Copied by A. H. R. Duller from Morini's
Ricerche intorno ad una nuova forma di Pilaira. Magnifi-
cation : A, natural size ; B-G, not stated.

R. Accad. Sci. 1st. Bologna, 1904, with plate, and then named
P. Saccardiana in Mem. R. Accad. Sci. 1st. Bologna, ser. 6, vol. iii,
p. 128 (1906). Sacc. Syll. xxi. 827.

220

RESEARCHES ON FUNGI

Sporangiophore rarely emerging from a rudimentary trophocyst
(which is usually wanting), slender, simple or branched, with at most
two branches. Sporangium globose, faintly depressed from above,
90-130 [i, in transverse diameter, brown above, then blackish, lower
zone not cutinised and forming a broad annulus of the membrane
by the gelatinisation of which the spores are afterwards set free ;
columella shortly conical, deep-violet in colour ; spores oval,
7-10 [i long, hyaline, but with a smooth pallid violaceous membrane.

On dung, in the north of Italy.

Illustration: Fig. 110.

5. Pilaira Moreaui Ling, in " Etude morphologique, cytologique

ff'^

Fig. 111. — Pilaira Moreaui Ling. No. 1, young sporangium. No. 2,
mature sporangium, seen in moist air. No. 3, the dehiscence of the
sporangium under the influence of water which swells its lower part.
No. 4, columellae after the fall of the sporangium : a, in profile ;
b, from below. No. 5, spores. No. 6, a germinating spore. No. 7,
a germinating chlamydospore. From Ling Yong's Etude. Magnifi-
cation : nos. 1-4, 60 : no. 5, 300 ; nos. 6 and 7, 70.

et microchimique d'une nouvelle Mucorinee, Pilaira Moreaui "
(1926). See also Rev. generale de Botanique, xlii. 743.

Sporangiophores lax, hyaline, not branched, erect, soon de-
cumbent, 10-12 cm. high, 30 y. broad. Sporangia at first yellow,
depressed, when mature globose, intensely bluish-black, 300-400 y.

TAXONOMY OF THE PILOBOLIDAE 221

in diameter (in dwarfed specimens only 80 [x), membrane encrusted,
the upper zone cutinised, persistent, the lower gelatinous, de-
liquescent ; columella flattened, broadly adnate, 150-180 x
90-100 [i.. Spores cylindric-ellipsoid, smooth, hyaline, 18-20 x 8-10[jt,
(sometimes as much as 24 [x long), granular within, agglutinated ;
chlamydospores few, intercalary in the submerged mycelium ;
zygospores not seen.

On dung of horses and rabbits. France. AUied to P. anomala,
from which it differs chiefly in its larger spores. It forms a gall with
Chaetocladium Jonesii.

Illustration : Fig. 111.

Bibliography. — The following list includes all those papers and
books which refer more particularly to the species of the Pilobolidae
and their difterentiation. Some additional works, which treat of the
physiology, ecology, and other aspects of the group, are cited in the
preceding Chapters written by Professor Buller.

BIBLIOGRAPHY OF THE PILOBOLID.E.

Anderson, R. S. — " The Validity of the genus Pilaira," in University of Iowa Studies,

vol. XV, pp. 3-5. pi. 1 (1933).
Bainier, G.— " Etude sur les Mucorinees," Paris (1882) : pp. 33-48, P. oedipus,

f. 1-10, P. longipes, f. 11-13, P. Kleinii, f. 14, 15, P. roridus, f. 16, P. exiguus,

f. 17 ; pp. 29-32, Pilaira Cesatii, f. 16-18 (on another plate).
Baker, Henry—" Natural History of the Polype Insect," chap, xi, pi. 22, f. 9, 10

(1744).
Bary, A. d^-" Vergleich. Morph. u. Biol, der Pilze," p. 77, f. 38, P. oedipus (1884).
Berkeley, Rev. M. J.—" Fungi," in Smith's English Flora, vol. v, part 2, p. 231

(1836).
Bolton, James — " An History of Fungusses growing about Halifax," vol. iii : pi. 132,

f. 4, Mucor roridus ; pi. 133, f. 1, Mxicor urceolatus (1789).
Bonorden, H. F.— " Handbuch der allgemeinen Mykologie," p. 128 (1851). His

figure 203, called Pilobolus cnjstalUnus, represents a form of P. Kleinii.
Brefeld, O.— Mittheilung in Sitzungsber. d. Gesellsch. naturf. Fr. zu Berlin :

" Copulirende Pilze " in Bot. Zeitung, vol. xxxiii, pp. 850-3 (1875).

222 RESEARCHES ON FUNGI

Brefeld, 0. — " Botanische Untersuchungen iiber Schimmelpilze," Heft 1, p. 27,

pi. 1, f. 25-26, Piloholus Mucedo (1872) ; Heft 4, pp. 60-5, pi. 4, f. 18, 23-28,

P. anomalus; pp. 69-70, pi. 3, f. 1-10, pi. 4, f. 11-14, "P. oedipus''; pi. 4,

f. 15, "P. crystallinus'' ; i. 16, 19-22, "P. microsporus'' ; f. 17, "P. roridus"

(1881).
BuDer, A. H. R. — " Piloholus umhonatus, a New Species " in his Researches on

Fungi, London, vol. vi, pp. 169-178 (1934).
BuUiard, P.— " Herbier de la France," vol. i, p. Ill (1784), pi. 480, f. 1, Mucor

urceolatus (1789).
Cesati, V. de — in Klotzsch, " Herbarium vivum mycologicum," Piloholus anomalus,

no. 1542 (1851).
Coemans, E. — " Monographie du genre Pilobolus, Tode, specialement etudie au

point de vue anatomique et physiologique," in Mem. cour. et des Sav. etrang.

Acad. roy. de Belgique, vol. xxx, pp. 1-68 ; pi. 1 and 1 bis, Piloholus oedipus ;

pi. 2, P. crystallinus, with fig. B. of P. roridus copied from Bolton (1861).
Coemans, E. — " Spicilegium Mycologicum," in Bull. Acad. Belg., ser. 2, vol. xvi,

p. 71 (1863).
Cohn, F. — " Die Entwicklungsgeschichte des Pilobolus crystallinus," in Nova Acta

Acad. Caes. L.-C. Nat. Cur., vol. xxiii, pp. 493-535, pi. 51-2 (1851).
Corda, A. C. J. — " Anleitung zum Studium der Mycologie," pp. 71-2, and p. Ixix,

pi. C, f. 25 (1842).
Corda, A. C. J.- — " Icones Fungorum," vol. i, p. 22, Pilobolus lentiger, pi. vi, f. 286

(1837), afterwards placed in a new genus Pycnopodium, vol. v, p. 18 (1842).

Also in vol. vi, p. 12, Pilobolus crystallinus, pi. 2, f. 32 (ed. Zobel, 1854).
Currey, F. — " On a species of Pilobolus," in Journ. Linn. Soc. Lond. Bot., vol. i,

pp. 162-7, pi. 2, f. 1-10 (1857).
Dewevre, A. — " Contribution a I'Etude des Mucorinees : Pilobolees," in Grevillca,

vol. xxii, pp. 69-79 (1894).
Dickson, J.—" Fasciculi Plant. Crypt. Brit.," part 1, p. 25, pi. 3, f. 6 (1785).
Fitzpatrick, H. M.— " The Lower Fungi, Phycomycetes," ed. 1, pp. 251-253 (1930).
Fries, Elias M.— " Syst'ema Mycologicum," vol. ii, pp. 308-9 (1823) ; vol. iii, p. 312

(1829). In both volumes P. crystallinus and P. roridus are marked " v.v.''''
Greville, R. K.— " Flora Edinensis," p. 448, P. crystallinus (1824).
Grove, W. B.— "New or Noteworthy Fungi," in Journ. Bot. (1884), p. 131, pi. 245,

f. 3, P. oedipus ; p. 131, pi. 245, f. 4, P. Khinii ; p. 132, pi. 245, f. 5, P. Kleinii,

forma sphaerospara ; p. 132, pi. 245, f. 6, Pilaira Cesatii ; p. 132, pi. 245, f. 7,

P, dimidiata.
Grove, W. B. — " On the Pilobolidae," a Monograph (reprinted from the Midland

Naturalist, Birmingham, pp. 1^0, with plates IV and VI (1884).
Klein, J. — " Mykologische Mittheilungen, I. Die Formen des Pilobolus," in Verhandl.

Zool.-Bot. Ges. Wien, vol. xx, pp. 547-556 (1870).
Klein, J.— "Zur Kermtniss des Pilobolus," in Jahrb. f. wiss. Bot., vol.viii, pp. 305-

381, pi. 23-30, f. 1-52, P. Kleinii (miscalled "P. crystallinus''); f. 53-67,

P. roridus (miscalled "P. microsporus "), (1872).
Krafczyk, H. — " Die Zygosporenbildung bei Pilobolus cristalltaus," in Ber. d.

Deutsch. Bot. GeseLl., vol. xlix, pp. 141-6, with two figs. (1931).
Kunze u. Schmidt— " Mykologische Hefte," Heft 2, pp. 70-6 (1823).
Ling, Yong. — " Etude morphologique, cytologique et microchimique d'une nouvelle

Mucorinee, Pilaira Moreaui (Clermont-Ferrand, 1926).

TAXONOMY OF THE PILOBOLIDAE 223

Ling, Yong. — " Etude biologique des phenomenes de la sexualite chez les Mucorin^es "

in Revue generale de Botanique, vol. xlii, pp. 742-3 (1930).
Link, H. F. — ^" Observationes in Ordines plantarum naturales," Diss. I, p. 32, pi. 2,

f. 50, P. crystallinus (1809).
Montagne, C. — " Memoire sur le genre Pilobolus," in Ann. Soc. Linn, de Lyon,

pp. l-7,f. a-i(1828).
Morini, F.- — ■" Ricerclie sopra una nuova Pilobolea," in Mem. R. Accad. Sci. 1st.

Bologna, ser. 5, vol. viii, p. 85, with plate (1900).
Morini, F. — " Ricerche intorno ad una nuova forma di Pilaira," in Rendie. Sess. R.

Accad. Sci. 1st. Bologna, with plate (1904).
Morini, F. — " Materiali per una Monografia delle Pilobolee," in Mem. R. Accad. Sci.

1st. Bologna, ser. 6, vol. iii, pjD. 111-129, with plate (1906).
Miiller, Otto F. — "Von einem Kristallschwammchen," in Kleine Schriften aus der

Naturhistorie, p. 122, pi. 7 (1782).
Palla, E. — " Zur Kermtniss der Pilobolus-Arten," in Oesterr. Bot. Zeitschr., vol. 50,

pp. 349-370, 397-401, pi. 10, Pilobolus heterosporus (1900).
Persoon, G. H. — "Observationes Mycologicae," part 1, p. 76, pi. 4, f. 9-11, P.

crystallinus (1796).
Persoon, C. H. — " Synopsis methodica Fungorum," part 1, pp. 117-8, P. crystallinus,

P. roridus (1801).
Petiver, James — " Gazophylacium," pi. 105, f. 14, Fungus virginianus (1711).
Plukenet, L.— " Phytographia," pi. 116, f. 7 (1691). " Abnagestum Botanicum,"

p. 164 (1696).
Purton, Thomas — " A Botanical Description of British Plants," Appendix to the

" Midland Flora," vol. iii, part 1, pp. 323-5, pi. 31, P. urceolatus (1821).
Ray, John—" Historia Plantarum," vol. ii, p. 1928 (1688) ; vol. iii, p. 24 (1704).
Ray, John — ^" Synopsis methodica," ed. 2, Appendix, p. 322, " Fungus ex stercore

. . ." (1696) ; ed. 3, pi. 13 (1724).
Relhan, R.— " Flora Cantabrigiensis," ed. 3, p. 579 (1820).
Roze, E. et Cornu, M. — " Une culture florissante du Pilobolus crystallinus,'" in Bull.

Soc. Bot. France, vol. xviii, pp. 298-9 (1871).
Saccardo, P. A. — " Sylloge Fungorum," vol. vii, pp. 184-9 ; vol. xvii, pp. 505-6 ;

vol. xxi, p. 827 ; vol. xxiv, p. 11.
Schmidt, Alf. — " Beitrag zur Kenntnis der deutsch-ostafrikanischen Mistpilze " in

Jahresber. d. Schles. Gesell., vol. xc, pp. 17-25 (1912).
Scopoli, J. A. — " Flora Carniolica," ed. 2, vol. ii, p. 494, Mucor obliquus (1772).
Sowerby, J.—" English Fungi," pi. 300, Mucor urceolatus (1803).
Spegazzini, C. — " Fungi Argentini," pugiUus primus, in Anal, de la Sociedad Cientif.

Argent., vol. ix, pp. 158-192 (1880).
Tode, H. J.—" Beschreibung des Hutwerfers," in Schrift. der Berlin. Gesell. naturf.

Fr., vol. V, p. 46, pi. I (1784).
Tode, H. J. — " Fungi Mecklenburgenses selecti," part 1, p. 41 (1790).
Vahl, Martin—" Flora Danica," vol. vi, f. 1080, Pilobolus crystallinus (1792).
Van Tieghem, Ph. — " Nouvelles Recherches sur les Mucorinees," in Ann. Sci. Nat.,

ser. 6, vol. i, pp. 41-61, pi. 1, f . 7-13, Pilobolus roridus ; f . 14-24, Pilaira Cesatii ;

f. 25-28, P. nigrescens (1875).
Van Tieghem, Ph. — " Troisieme Memoire sur les Mucorinees," in Ann. Sci. Nat.,

ser. 6, vol. iv, pp. 335-349, pi. 10, f. 4, 5, P. crystallinus ; f. 6-10, P. Kleinii ;

f. 11-15, P. longipes ; f. 16-22, P. nanus (1876).

224 RESEARCHES ON FUNGI

Wiggers, F. H.— " Primitiae Florae Holsaticae," pp. 110-111 (1780). In the preface

the binomial name (Hydrogera crystallina) is said to have been conferred upon

the plant by his tutor, Weber.
Withering, W. — " Botanical Arrangement of all the Vegetables naturally growing

in Great Britain," vol. ii, p. 784, Mucor roridulus, " Ray, Syn. p. 13 " (1776).
Withering, W. — "A Systematic Arrangement of British Plants," ed. 4, vol. iv,

pp. 394-5, Mucor urceolat'us, M. roridus (1801) ; ed. 5, vol. iv, pp. 437-8 (1812).
Zopf, W.-^" Zur Kenntniss der Infectionskrankheiten," in Xova Acta k. L.-C.

Deutsch. Akad. Naturf., vol. Hi, no. 7, pp. 352-8, pi. 6, f . 1-19, " P. crystallinus "

(1888).

PART II

THE PRODUCnON AND LIBERATION OF SPORES
IN THE DISCOMYCETES

VOL. VI.

CHAPTER I

THE PHENOMENON OF PUFFING IN SARCOSCYPHA
PROTRACTA AND OTHER DISCOMYCETES

Introduction — Historical Remarks — Puffing illustrated by Photography — The
Significance of Puffing — The Genus Sarcoscypha — Sarcoscypha prolracta — The
Perennial Pseudorhiza — The Direction of Puffing and the Campanulate Form
of the Apothecium — The Ascus as an Explosive IMechanism — Radial-longi-
tudinal kSections and Surface Views of the Hymenium — Correlations and Fruit-
body Efficiency — What Factor determines the Oblique Position of the Opening
of each Ascus ? — ^Experimental Proof that a Fruit-body, when it puflfs, pro-
duces a Blast of Air — The Cause of the Blast of Air — The Blast of Air and the
Dispersal of the SiX)res — Concluding Remarks.

Introduction. — In all the Basidiomycetes which violently dis-
charge their basidiospores, namely, the Hymenomycetes, the
Uredineae, Tilletia, and the Sporobolomycetes, every basidiospore
is shot away as soon as it has attained maturity ; and, since the
basidiospores ripen in succession, they are discharged in succession.
The result is that the liberation of basidiospores from the fruit-
bodies of the Hymenomycetes, from the teleuto-sori of the Rust
Fungi, from cultures of the myceHum of Tilletia, and from cultures
of Sporobolomycetes is a steady and continuous process, occupying
many hours, days, weeks, or even months, according to the species
or the cultural conditions. Spore-deposits made from any of these
fungi become denser and denser as the hours go by. Of all the
numerous species included in the groups of Basidiomycetes here
under discussion there is not one in which the basidiospores are given
off in sudden dense clouds at intervals determined by internal
organisation or external conditions.

In the Discomycetes, on the other hand, as is well known, there
are many species the fruit-bodies of which exhibit the phenomenon

of puffing, i.e. which, when subjected to certain changed conditions,

227

228 RESEARCHES ON FUNGI

pass from a quiescent to an active state and suddenly liberate a
cloud of spores. Among the larger Discomycetes which puff may
be mentioned such common species as Aleuria vesiculosa, Galactinia
badia, and Peziza aurantia.

Not only do most large Discomycetes puff but also many of the
very small ones. The small ones often occur in large numbers
gregariously on wood, etc., and all the fruit-bodies of a single group
may puff simultaneously either when the log of wood or other sub-
stratum on which they grow is disturbed or when the tin box in
which they have been collected is opened subsequently in the
laboratory. Dr. Jessie S. Bayhss EUiott has kindly informed me
that her record of very small Discomycetes which puff includes the
following species :

Arachnopeziza aurata. Lachnea setosa.

Ascobolus Crouani.i Mollisia cinerea.

Chlorosplenium aeruginosum. OrbiHa xanthostigma.

Dasyscypha virginea. Rhytisma acerinum.^
Helotium scutula.

Historical Remarks. — The first reference to the phenomenon of
puffing appears to be that of MicheU,^ the discoverer of reproduc-
tion in fungi,* who in his celebrated Nova Plantarum Genera pub-
hshed in 1729 says of Fungoides (= Peziza, etc.) : "All the Fun-
goides are provided on the upper surface with very minute round
or oval seeds, which are afterwards ejected upwards hke smoke or

^ The dung upon which this fungus was growing was kept in a large damp-
chamber. The hymenial surface of the discs, at first pale, became black with mature
asci containing the dark spores. When the door of the damp-chamber was suddenly
opened, all the tiny apothecia puffed simultaneously and, in a flash, became pale
again (J. S. B. Elliott in litt.).

2 In the genus Rhytisma the apothecia open by a cleft. In including Rhytisma
in the Discomycetes I have followed Boudier (Histoire et Classification des Discomy-
cetes d'Europe, Paris, 1907, p. 177).

3 P. A. Micheli, Nova Plantarum Genera, Florentiae, 1729, p. 204, Plate 86,
Fig. 17.

^ For a discussion of Micheli's discovery of spores not only in the Discomycetes
but in fungi generally and for a translation into English of the record of the experi-
ments by which he proved that spores are reproductive bodies vide A. H. R. Buller,
" Micheli and the Discovery of Reproduction in Fimgi," Transactions of the Royal
Society of Canada (Presidential Address to Section IV), Series III, Vol. IX, 1915,
pp. 1-25, Plates I-IV.

PUFFING IN THE DISCOMYCETES 229

sparks, either by a contraction of the fibres while the plants are
expanding or by the hghtest shake of even a gentle breeze."
Micheli's illustration of a puffing Discomycete is reproduced in

Fig. 112.

In 1791, Bulhard 1 described the phenomenon of puffing in
Helvella, Peziza, etc., and illustrated it as it occurs in a species of
Otidea. He says : "If you shake these fungi or blow upon them
from above, their seeds ascend like steam ; you may blow strongly
afterwards, you may break the fungus into pieces, but you will not
see a second jet of seeds follow the first one immediately ; to obtain
a second jet there must pass an interval of some
two or three hours, depending on whether the .:•:: •':::■. V'.-

air is more or less free from moisture ; the parts ■.•:•■;.•■■.••;•■::•■

which compose the apparatus of the fructification ■/.'•:••;.•.■.•■:•;•

are as a rule too delicate to allow one to dis-
tinguish the mechanism of discharge, however
carefully one observes them with the best in-
struments." Bulliard's diagram with which he

,T, 1-1 nc J. i 1 Fig. 112. — Micheli's

attempted to explam how puffing takes place illustration of

shows that he knew nothing of the true structure puffing m the

" _ Discomycetes,

of asci, and Tulasne's criticism of Bulliard's views published 1729.

on puffing was quite justified. Tulasne ^ says : ^ ^ Duller.

" Bulliard's ideas on this point are based on an
imaginary structure of the organs and the author's great want of
knowledge. It is indeed doubtful whether he really knew from his
own experience that the smoke rising from Pezizas consists entirely
of their seeds."

In 1801, Persoon^ recorded puffing in Rhytisma salicinum (his
Xyloma salicinum), for he says " In spring-time, the seed-dust was
blowing away from the cracks hke smoke." In 1805, during a rainy
May, Albertini and Schweinitz ^ saw R. salicinum " sending up clouds

1 P. Bulliard, Histoire des Champignons dc la France, Paris, 1791, pp. 51-52,
Plate II, Fig. 6.

2 L.-R. and C. Tulasne, Seleda Fvngorum Carpologia, Paris, Vol. I, 1861, p. 42 ;
also in the English Translation by W. B. Grove, Oxford, Vol. I, 1931, p. 44.

^ C. H. Persoon, Synopsis metJiodica fungorum, Gottingae, Vol. I, 18U1, p. 103.
* J. B. de Albertini et L. D. de Schweinitz, Conspectus fungorum in Lusatiae
superioris agro Niskiensi crescentiuyn, Lipsiae, 1805, p. 62.

230 RESEARCHES ON FUNGI

of smoke through the cracks of the cortex which was broken into
irregular shield-hke pieces." Tulasne,i in 1865, remarked that from
the ascophorous hymenium of Rhytisma acerinum, when it has
dehisced in spring, " the endospores escape hke smoke."

In 1817, Kunze and Schmidt ^ remarked that they had observed
puffing from the apothecia of two very small Discomycetes, by them
included in the genus Phacidium but now regarded as species of
Coccomyces. In their description of Phacidium trigonum ( = Coc-
co7nyces trigonus) they say : "When in damp weather the disc is
fully exposed, there follows after the least touch, just as in P.
coronatum, the ejection of the spores in the form of a fine grey-green
powder."

Desmazieres,^ in 1845, observed puffing in Helvella ephippium
Lev. and stated that the vapour of the seeds was discharged into the
air with a faint report. Tulasne * suggested that Desmazieres had
" been misled. by some error " in supposing that he had heard his
Helvella puff ; but, as we shall see in Chapter III, Desmazieres's
observation has been supported by subsequent investigations.

De Bary,^ in the first edition of his well-known text-book of
mycology pubUshed in 1866, treated of puffing in the Discomycetes
in a modern manner. He showed : that the asci are turgid cells ;
that, when puffing of a fruit-body takes place, a large number of
the asci open apically at one and the same moment ; and that the
spores of each ascus are shot up into the air owing to the contraction
of the elastic ascus wall.

In 1909, I ^ showed that, if a section of a ripe hymenium of
Aleuria vesiculosa is first submerged in water, the subsequent
apphcation to it of solutions of sodium chloride, potassium nitrate,
grape sugar, or glycerine, all of which withdraw water from the cell-
sap of the asci, does not cause the asci to explode, but that the asci

^ L.-R. and C. Tulasne, loc. cit., Vol. Ill, 1865, p. 117 (Eng. Trans., p. 109).

2 G. Kunze und J. C. Schmidt, Mykologische Hefte, Leipzig, 1871, p. 41.

^ J. B. H. J. Desmazieres, Plant, crypt. France, 2nd ed., fasc. XIX, 18-45, No. 914.
Cited from Tulasne.

* L.-R. and C. Tulasne, loc. cit., p. 42 (Eng. Trans., p. 44).

^ A. de Bary, Morphologic und Physiologic der Pilze, Flechten, und Myxomyceten,
Leipzig, 1866, pp. 141-143.

« These Researches, Vol. I, 1909, pp. 238-241, 268.

PUFFING IN THE DISCOMYCETES 231

explode readily when their tips are allowed to come into contact
with iodine or certain other poisonous substances such as mercuric
chloride, silver nitrate, copper sulphate, sulphuric acid, and alcohol ;
and I further showed that asci which have contracted considerably
owing to withdrawal of water from their vacuoles by potassium
nitrate, etc., explode when brought into contact with iodine. As a
result of these experiments I suggested that puffing is caused by a
stimulus given to the protoplasm in contact with the ascus lid.

In 1926, Ziegenspeck ^ reviewed the literature upon, and gave
an account of his own investigations upon, the discharge mechanism
of the asci of Ascomycetes (Discomycetes, Pyrenomycetes, Lichens).
He came to the conclusion that, in fruit-bodies which puff, sudden
slight changes in the environment of the asci, by setting up a sudden
slight increase in the tension of the wall where the wall is weakest,
cause the asci to explode. Ziegenspeck regards the breaking open
of an ascus during the phenomenon of puffing not as being due to
the action of a stimulus but as a |Ji(re/^ mechanical phenomenon
comparable with the breaking of glass in which strains have been
set up by unequal heating or cooling : there is a zone or line of weak-
ness at the end of the wall of each ascus ; when the distension of an
ascus wall has become great, it needs only a slight additional strain
to cause the wall to break ; a very slight shaking, a very slight
warming, a very slight external pressure, or a sudden withdrawal
of water and therewith a reduction of elasticity, can lead to a sudden
increased strain inside the membrane, with the result that the
membrane relieves itself by splitting where its cohesion is least.
Ziegenspeck, by employing a microscope with special optical
arrangements, obtained evidence that strains are actually set up
in the walls of the ends of the asci of Peziza, Ascobolus, etc., just
before the asci explode. On looking down on ripe moist asci, their
ends appeared smooth and shining ; but, as soon as the asci were
blown upon, the ascus tips became iridescent and exhibited Newton's
rings. Immediately after showing these signs of strain, the walls of
the asci broke open and the spores were discharged.

Ziegenspeck's explanation of the cause of the bursting of

^ H. Ziegenspeck, " Schlcuderraechanismen von Ascomyceten," Botanisches
Archiv (Herausgeber, Carl Mcz), Bd. XIII, 1926, pp. 341-381.

232 RESEARCHES ON FUNGI

thousands of asci at the moment when a discomj'cetous fruit-body
puffs either in the field or in the laboratory is simpler than the one
suggested by myself in 1909 and is in good accord with his experi-
mental observations. I am therefore inclined to accept it. How-
ever, that another factor, in addition to that of purely physical
strains in the ascus wall, may have something to do with the bursting
of an ascus seems to be shown by the ah-eady recorded results of my
experiments on hymenia of Aleuria vesiculosa submerged in water.
We can scarcely suppose that non-poisonous substances (sodium
chloride, potassium nitrate, grape sugar, and glycerine) do not set
up strains in the ascus wall whereas poisonous substances (iodine,
mercuric chloride, silver nitrate, copper sulphate, sulphuric acid,
and alcohol) do. The fact that poisonous substances cause sub-
merged asci to burst, whereas non-poisonous substances do not,
seems best explained by assuming that poisonous substances stimu-
late the protoplasm at the end of each ascus to act upon the ascus
wall in such a way as to cause the operculum to open outwards and
that non-poisonous substances do not so stimulate the protoplasm.

In recent years Richard Falck ^ has studied the conditions which
affect the puffing of Discomycetes and permit of the spores escaping
from the fruit-bodies ; and, as a result of his investigations, he has
divided the fruit-bodies of Discomycetes into two groups : (1) the
radiosensitive, i.e. those which emit spores when warmed by radiant
heat given out by a lamp or the sun, etc., e.g. Morchellaceae, Gyro-
mitra, and Verpa. and (2) the tactiosensitive, i.e. those which puff
when touched or blown upon, e.g. Aleuria, Galactinia, Otidea,
Peziza, and Pustularia.

Puffing illustrated by Photography. — The spore-cloud which,
at the moment of puffing, is emitted from the fruit-body of one of
the larger Discomycetes, is made up of tens of thousands or even
millions of spores and can readily be seen A\ith the naked eye.
Dickson and Fisher,- working with Sclerotinia sclerotiorum ( = S,

1 R. Falek, " Ueber die Sporenverbrcitung bei don Asoomyceten. I. Die radio-
sensiblen Discomycctcn," Mycologische Untersuchungen iind Berichte von R. Falck,
Jena, Bd. I, Heft II, lOK),])}). 77-144 ; " Ueber die Sporenverbreitung bei den Asoo-
myceten. II. Die taktiosensiblcn Discomyceten," ibid.. Heft III, 1923, pp. 370^03.

2 L. F. Dickson and W. R. Fisher, " A Method of Photographing Spore Dis-
charge from Apothecia," Phytopathology, Vol. XIII, 1923, pp. 30-32.

PUFFING IN THE DISCOMYCETES

233

libertiana), have succeeded in photographing it in the following
manner. Large numbers of sclerotia were germinated and, as soon
as the stipitate apothecia had attained full size, some scores of the

Fig. 113. — Arrangement ot apparatus in preparation tor photographing a cloud of
spores liberated during the puffing of the apotliecia of Sclerotlnia sclerotiorum
(= S. libertiana). An inverted glass dish, 6 inches wide, on the table, covers a
number of stipitate apothecia developed from sclerotia. Bright sunlight falls on
the fruit-bodies, and behind them is a black back-ground. A pliotographic
camera (not here shown) is focussed on the centre of the dish. By means of
suitable screens, the air around the dish is kept as still as possible. When the
dish was raised a cloud of spores was emitted, as shown in the next illustration.
Photographed by L. V. Dickson and W. R. Fisher at Cornell University. About
one-eighth the actual size.

sclerotia and their apothecia were arranged upon a layer of wet
cotton wool on a glass plate. The plate and fungi were then
covered with an inverted crystallising dish six inches in diameter.
Thereupon the whole was placed out-of-doors in a shaded spot, and
it was left there for three days whilst the ascospores matured.
About two hours before the photograph was to be made, the dish

234

RESEARCHES ON FUNGI

containing the apothecia was taken into a corridor of the laboratory
and placed in the position shown in Fig. 113. A box lined with
black paper was used to provide a black back-ground. The table
was so arranged that direct sunlight illuminated the apothecia
without shining into the box. A small object was then placed on the

Fig. 1 14. — A photograph showing spore-clouds which have been emit-
ted by the puffing of numerous apothecia of Sclerotinia sclerotiorum
( = S. libertiana) grown from sclerotia. It was taken in bright
sunlight with an exposure of about one-hundredth of a second
about one second after tlie dish (shown in Fig. 113) covering the
fruit-bodies liad been raised. The simultaneous discharge of the
contents of millions of asci doubtless produced air currents which
were a factor in raising the spore-clouds above the apothecia.
Photographed by L. F. Dickson and W. R. Fisher at Cornell
University. About two-fifths the natural size.

top of the middle of the dish and focussed with the camera. When
everything was prepared, the photographer stood ready at the
bulb of the camera and, at a given word, the dish was quickly
removed from the apothecia. Nothing happened for about one
second, and then the apothecia suddenly discharged clouds of spores
into the air. At the right instant an exposure of a very rapid
photographic plate was made for one-hundredth of a second, with
the result shown in Fig. 1 14.

PUFFING IN THE DISCOMYCETES 235

The Significance of Puffing.— The puffing of Discomycetes has
excited the wonder of every field mycologist and is frequently
mentioned in mycological literature. Yet, hitherto, no one, except-
ing Richard Falck, seems to have enquired whether or not the
phenomenon is of any benefit to the fruit-bodies from the point of
view of the dispersal of the spores. Conceivably, the asci of a
Peziza might discharge their contents one by one in the order of
ripening. Why then does a Peziza puS ? Can it be that simul-
taneous ascus-discharge in the Discomycetes is more advantageous
to these fungi than successive discharge ; and, if so, wherein does
this advantage lie ?

Falck has supposed that the dependence of Morchella, Gyromitra,
Verpa, etc., on a sufficiently high temperature for the discharge of
their spores causes spore-discharge to be delayed until the heat of
the sun brings into existence air-currents which may assist in spore-
dispersal 1 ; and he also holds that the dependence of many Pezi-
zaceae on the wind for the discharge of their spores causes spore-
discharge to be delayed in these fungi' until the wind is sufficiently
strong to be effective in carrying away the spores. ^ In these ecolo-
gical theories there may well be some truth.

It was in the hope of throwing more hght on the phenomenon of
puffing that the investigation on Sarcoscypha protracta about to be
recorded was undertaken.

The Genus Sarcoscypha. — -The genus Sarcoscypha, according
to Boudier,3 is a very natural one. It includes species remarkable
for their epixylous habit and the brilhant scarlet-red colour of their
hymenium. The receptacles are more or less stipitate, bell-shaped,
and tomentose on their outer side. The asci are very long, thin,
and at their base attenuated and flexuous. The paraphyses are
much branched, rather more pointed than clavate, and they contain
red granules which turn green wdth iodine. The spores are large
and oblong, and may or may not contain oil-drops ; in the latter
case their contents are finely granular.* Boudier includes in

1 R. Falck, loc. cit., I, pp. 124-126, 134. 2 7^,-^.^ n, pp. 402-t03.

^ E!. Boudier, Histoire et Classification des Discomycetes d'Europe, Paris, 1907,
p. 55.

* Ibid.

236 RESEARCHES ON FUNGI

Sarcoscypha nine species, among them being the well-known 8.
coccinea, found on sticks in damp woods in both Europe and North
America, and the much more rare S. jirofracta.

Sarcoscypha protracta. — Sarcoscyj)ha jirotracta Fr. (Fig. 115),
according to Saccardo,^ has various synonyms : Microstoma hiemale
Milde ; Peziza mirabilis Borsz., under which name it is illustrated
in M. C. Cooke's Mycographia ; Sclerotinia baccata Fuck, (the root-
ing base is not a sclerotium, hence the generic name Sclerotinia was
a misnomer) ; and Anthojjeziza Winteri Wettst., under which name
it is illustrated in Kerner von Marilaun's Natural History of Plants.
There is no description or illustration of the fungus in Boudier's
I cones Fung arum.

Sarcoscypha protracta occurs in both Europe and North America,
and appears to be a northern species. In Europe it has been found
in Scandinavia, Finland, Germany, and Austria, ^ and it was observed
by the late Professor J. H. W. Trail ^ in the month of May growing
in clusters of two to six fruit-bodies among grass on the banks of
the Dee near Ballater in Scotland. In Canada it has been found by
myseK in Manitoba and by Dr. E. H. Moss * in Alberta. Miss Hone ^
states that S. protracta is found in the State of Minnesota ; but, since
her specimens were sohtary and had no guttulae in their spores,
the identification seems doubtful. My own specimens agree well
with the descriptions given by Fries, Rehm, and other European
mycologists.

Karsten,<5 in Finland, found fruit-bodies of Sarcoscypha protracta
on Alder branches {Alnus incana) buried in the ground. According
to Rehm,^ the asci are 250-550 [o. long and 18-24 [j. wide ; and in

1 P. A. Saccardo, SyJloge Fungorum, Vol. VIII, 1889, p. 155.

2 For literature vide H. Rehm in Rabenhorst's Kryptogamen-Flora von Deutsch-
land, Oesterreich und der Schu-eiz, Die Pilze, Vol. Ill, 1896, pp. 1072-1073.

3 Vide W. Phillips, " British Discomycetes," Grevillea, Vol. XVIII, 1889-90,
p. 83.

^ I have seen Dr. Moss's specimens, collected 800 miles west of Winnipeg, and they
exactly resemble those found by myself.

5 Daisy S. Hone, " The Pezizales, Phacidiales and Tuberales of Minnesota,"
Minnesota Botanical Studies, Vol. IV, 1909, pp. 96-97.

^ P. A. Karsten, Mycologia Fennica, Helsingfors, Vol. I, 1871, p. 44. I suspect
that the buried branches (ramulos) were in reality roots (f/. my own Fig. 116).

' H. Rehm, " Hysteriaceen und Discomyceten," in Rabenhorsfs Kryptogamen-
Flora, 2 Aufl., Bd. I, Abt. Ill, 1896, p. 1073.

PUFFING IN THE DISCOMYCETES 237

fruit-bodies found by me at Winnipeg some of the asci (Fig. 119,
p. 245) just exceeded 600 [jl in length. In these very large asci are
contained very large spores, so large indeed that they were regarded
by Fuckel ^ as the largest spores in all the Pezizae. The size of the
spores has been recorded : by Fuckel ^ as 52 x 20 [x ; by Karsten ^
as 36-58 (mostly 42-48) x 15-17 [jl ; and by Rehm * (Finnish and
German specimens) as 36-40 x 15-17 [x. The size of the spores in
Canadian fruit-bodies, as measured by myself, was found to agree
with that given for European fruit-bodies by Karsten and Rehm.
While the spores of S. protracta are very large for Pezizae, yet they
are smaller than the spores of a few other Discomycetes, e.g. Ascobolus
immersus in which the spores (Vol. I, Fig. 82, p. 254), exclusive
of their broad gelatinous investment, measure 55-65 x 35-45 [z,
and Ptychoverpa bohemica in which the spores measure 60-80 X
17-22 [JL ^ The large size of the asci and spores in Sarcoscypha jJro-
tracta was a factor in making this fungus favourable material for my
investigation on the phenomenon of puffing.

Fruit-bodies of Sarcoscypha protracta (Fig. 115) come up singly
or in clusters of two to eleven in young Poplar bush {Populus tremu-
loides) at River Heights, a suburb of Winnipeg, in the last weeks of
April and the first weeks of May ; and they were first found there as
follows. One day near the end of April, 1925, when the winter's
snow had just melted but before there were any leaves on the trees,
Charles aged eleven and Dennis aged eight, sons of my former col-
league. Dr. C. H. O'Donoghue, were roaming the bush when their
eyes were attracted by the beautiful scarlet apothecia standing up
in little groups amid the leaf -mould. They very naturally took
pleasure in gathering these firstlings of the spring and in taking
them home to their parents. Dr. O'Donoghue kindly brought me
some of the booty. Then, on April 30, Dr. O'Donoghue, his two
sons as pioneers, and I visited the Poplar woods, and together we
found some hundreds of fruit-bodies scattered here and there
in the leaf-mould under the trees. On this occasion and

1 L. Fuckel, Symbolae Mycologicae. Brifrrige znr Kennlni-ss der rheinischen Pilze,
Wiesbaden, 1869-70, p. 331.

2 Ibid. ^ P. A. Karsten, loc. cil., p. 44.
* H. Rehm, loc. cit., p. 1073. ^ Ibid., p. 1200.

238

RESEARCHES ON FUNGI

subsequently, fresh material was gathered for investigation as it
was required.

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ungathered fruit-bodies of Sarcoscypha protrada, when tickled hghtly
with a little stick, send out a cloud Hke smoke and hiss as they do
so (c/. Fig. 116) ; and Dr. O'Donoghue has informed me that he him-

PUFFING IN THE DISCOMYCETES 239

self saw fruit-bodies puff on several occasions when he was picking
them from the ground. We thus have good evidence that the fungus
may puff under field conditions.^

The Perennial Pseudorhiza. — Investigations made in the bush
convinced me that every fruit-body of Sarcoscypha protracta is
epixylous. The mycehum grows in the wood of roots which are
about 0' 3-1 • 5 cm. thick and buried in the leaf-mould to a depth of
1-10 cm. The roots presumably are those of Poplar. When the my-
cehum in a root has progressed sufficiently, it usually gives rise to a
single sohtary fruit-body which grows upwards through the leaf-mould
as a slender rod or stipe terminated by a rudimentary apothecium.
Tho growth in length of the stipe is intercalary and takes place just
below the cup. In this way the cup is pushed up through the leaf-
mould and raised somewhat above its surface. After being brought
by the intercalary growth of the stipe to the surface of the ground,
the apothecium expands and thus the mature fruit-body comes to
resemble the one shown in Fig. 116 or the one shown on the extreme
left in Fig. 115. The stipe may be considered as having two parts :
(1) a subterranean part which is blackened by the soil, slender,
easily broken, which corresponds exactly to the " rooting base "
of such Hymenomycetes as Collybia radicata and C. fusipes, and
which is best called a pseudorhiza, and (2) an aerial part, whitish
and highly tomentose, which may be referred to as the aerial stipe.

At the end of the first spring, the soHtary fruit-bod}^ just des-
cribed does not entirely disappear. While its apothecium and its
aerial stipe die and rot away, the lower part of the pseudorhiza
persists in the living condition until the second spring. Then it
proliferates at its upper end and gives rise not to one but to several
new fruit-bodies, each of which has a pseudorhiza and aerial stipe
of its own. Thus in the second year there is developed a cluster of
fruit-bodies varying in number up to eleven. Three such clustered
fruit-bodies are shown on the right side of Fig. 115.

At the end of the second spring, the cluster may die away com-
pletely, but investigation shows that sometimes at least, while the

^ An account of the investigations recorded in this Chapter was given at the
International Botanical Congress, held at Ithaca, U.S.A., in August 1926. Vide the
Proceedings of the Congress, Vol. II, 1929, pp. 1627-1628.

240

RESEARCHES ON FUNGI

;;V*;

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ISifc:

P?

secondary apothecia and aerial stipes decay and disappear, the
bases of the secondary pseudorhizae persist until the third spring,
when the ends of some of them proliferate and then give rise to
tertiary fruit-bodies. We thus find that our original pseudorhiza
produced in the first spring is either biennial or perennial. In
CoUybia fusipes we have an exactly similar arrangement. It is a

remarkable fact that a perennial pseudo-
."...:. .:'■■ rhiza should have been developed in two

such diverse fungi as Sarcoscypha pro-
tracta and CoUybia fusipes ; but both
grow on buried roots, and we can only
suppose that, in the course of evolution,
in response to this common condition of
their environment, they have reacted in
a similar manner.

The Direction of Puffing and the
Campanulate Form of the Apothecium.
— When a fruit-body puffs, the spores
are shot straight outwards from the
cup in directions which are parallel to
the cup's longitudinal axis. If the fruit-
body is upright, as shown in Fig. 116,
the spore-cloud is shot up vertically
into the air, but if the fruit-body is
oblique the spore-cloud is shot away
obliquely.

A large number of fruit-bodies which
were gathered at a temperature only
just above the freezing-point of water,
whilst occasional flakes of snow were

Fig. 116. — Sarcoscypha protracta. A vertical
section through leaf -mould in a Poplar wood
at Winnipeg, Manitoba, to show a single fruit-
body attached by its rooting base or pseudo-
rhiza to a buried root. The scarlet hymenium
which covers the conical interior of the cup has
just puffed and the spore-stream is represented
diagrammatically as rising vertically to a
height of about three inches above the top of
the fruit-body. Natural size.

PUFFING IN THE DISCOMYCETES 241

falling, appeared to be mature but could not be caused to puff
in the open, presumably owing to their being too cold. The
fruit-bodies were put into a vasculum and taken to the laboratory
the air of which had a temperature of about 70° F. As soon as
the laboratory had been entered, the fruit-bodies were removed
from the vasculum, separated from one another, and placed in a
series of Petri dishes. During these operations not a single fruit-
body puffed. However, after an hour, when the fruit-bodies had
become warmed up to the temperature of the room, puffing occurred
freely whenever a mature fruit-body was removed from a Petri dish
and exposed to the relatively dry room-air. Advantage was taken
of this fact to observe the direction and distance of discharge of
three particular fruit-bodies. In turn, each was quickly removed
from its Petri dish with the fingers and held horizontally in the air
of the laboratory. Within two seconds from the beginning of this
operation puffing took place. The spore-cloud produced by each
fruit-body travelled forward horizontally (c/. Fig. IIG). One of the
spore-clouds went 8 cm. before dispersing irregularly, another
12 cm., and another 17 cm. ( = 7 inches).

The results yielded by the experiments just described prompted
the following question : the apothecia being campanulate in form,
how comes it that the spores are shot straight out of the cup in a
direction more or less parallel to the cup's axis ? To solve this
problem it was necessary to ascertain : (1) the exact shape of the
apothecium at the moment of puffing, (2) the arrangement of the
asci in the hymenium, and (3) the manner in which the asci
open.

Variations in the shape of the apothecium, nearly three times the
natural size, are shown in Fig. 117. At A is an end-view and at
B a vertical section of a young apothecium which is about to expand.
Its hymenium, as indicated in B, was lining the cavity of the cup,
but the asci had not yet developed any spores. C is a well-expanded
apothecium seen from above. Its dark central cavity was hned by
a deep-scarlet hymenium containing ripe ascospores, whilst the lighter
marginal crenations were orange-yellow and sterile. The six draw-
ings D-I show vertical sections through six apothecia which had
discharged or were about to discharge their spores. The average

VOL. VI. ^

242

RESEARCHES ON FUNGI

angle of aperture of these and of other mature apothecia was about
50°. Within, the apothecia are rather pointed at the base and never
well-rounded hke those of Galactinia badia, Aleuria vesiculosa, etc.

Fig. Ill .—Sarcoscypha protracta. To show the exact forms of the cups in particular
fruit-bodies. A, a yoving unexpanded fruit-body, seen from above. B, the
same, seen in vertical section : the hymenium lining the inner surface of the
cavity contains young asci which as yet have not developed any spores. C, a
mature fruit-body seen from above : the cup is fully expanded and the hymenium
contains asci enclosing ripe spores. D-I, vertical sections through six fully
expanded fruit-bodies which had discharged, or were about to discharge, their
spores. D and G had already shot away all their spores. The angle of aperture
of the cup is smallest in D and largest in I. Several of the fruit-bodies were
observed to puf? in the laboratory. Fruit-bodies obtained in a Poplar wood at
Winnipeg, Manitoba. Magnification, 2- 6 natural size.

Moreover, they never open out in such a manner as to flatten the
hymenium.

At A and B in Fig. 118, enlarged six times, is shown a diagram-
matic drawing of a vertical section through an average cup. The
cup is 8 mm. deep and has an angle of aperture of 50°. The asci in
the hymenium have straight shafts and are arranged perpendicularly
to the surface of the hymenium. The arrows indicate in A the

PUFFING IN THE DISCO]\IYCETES

243

direction in which one might expect the asci to shoot their spores,
and in B the direction in which the asci actually shoot their spores.
How comes it that the asci do not discharge their spores in the direc-

FiG. 118. — Sarcoscypha protmctn. Two diagrammatic drawings of a vertical section
through a cup, 8 mm. deep, sliowing tlie average slof)e of the liymenium and the
direction of tlie long axes of tlie asci. Tiie angle of aperture of the cup is .50".
The arrows indicate trajectories of tlie spores shot out by single asci. In .\ the
arrows show the direction in which twenty sets of spores would be shot, if they
were discharged from the ends of the asci, in the direction in which the asci
point, in still air : the asci in the lower two-thirds of the cup would shoot their
spores against the opposite walls of the cup ; and the spores which escaped
from the cup, as shown by the arrows, would travel obliquely and not vertically
upwards. In B the arrows show the general direction in which twenty sets of
spores are actually shot. Owing to each ascus having its operculum on the
upward-looking side of its end, all the spores escape from the cup and are shot
vertically upwards. Magnificatiou, U times the natural size.

tion in which their ends point 1 The answer must be sought for in
a minute study of the individual ascus.

The Ascus as an Explosive Mechanism. — The hymenium of
Sarcoscypha protracta, like that of other Discomycetes, consists of
sterile paraphyses and of asci, each ascus containing eight ascospores.

244 RESEARCHES ON FUNGI

A single paraphysis (Fig. 119, d) is a thin, much branched,
septate structure, the cells of which contain deep-red particles.
It is these particles which give to the hymenium as a whole its fine
scarlet colour. The paraphyses constitute more than one-half of
the hymenium and, as shown in Figs. 120, A, and 121, A, they he
between the asci and isolate them from one another. The branches
of the same paraphysis or of adjacent paraphyses are closely packed
together and become anastomosed with one another. Although the
paraphyses tightly ensheathe each individual ascus, their walls and
the ascus-wall, where they come into contact, are never fused
together but are free to move over one another. This freedom is
important, for it permits a young ascus to grow in length and an
exploding ascus to contract in length and slide downwards in the
hymenium between the paraphyses without any serious disturbance
to the hymenium as a whole {cf. A and B in Fig. 120). With iodine
the red particles in the paraphysal cells turn green.

The ascus is a long thin cylinder with a narrower, often undulating
base and a straight shaft. In Fig. 119 there are shown : at a an
almost ripe ascus which as yet does not protrude beyond the general
level of the hymenium as determined by the tips of the paraphyses d ;
at 6 a mature, fully protuberant ascus ; and at c an ascus just after
it has exploded and shot away its spores. In both a and b the cell-
walls are very thin and are hned internally by an equally thin layer
of cytoplasm. This cytoplasmic layer encloses a single large central
vacuole, filled with colourless cell-sap, and eight spores. The spores
are situated in the upper end of each ascus. They adhere to one
another and to the top of the ascus, so that they cannot fall down
to the bottom of the vacuole, from which position they could
not be discharged when the ascus exploded. It seems probable
that they are held together and are attached to the ascus-apex
by cytoplasm. In any case the adhesive substance is weak ;
for, when an ascus explodes, the top spore is freed from the
top of the ascus and all eight spores are separated from one
another.

The eight spores in each ascus (Fig. 119, a, b) are long and oval
or almost fusiform, and they all slope obliquely in the same direc-
tion. The upper end of the top spore rests against the operculum

PUFFING IN THE DISCOMYCETES

245

that is to make its ajipearance when the ascus explodes. Now

since, as we shall see, each

operculum is situated so

that it looks toward the

opening of the mouth

of the apothecium, the

Fig. 1 1 9. — Sarcoscypha protracta.
The elements of the liyme-
nium. The transverse clotted
line indicates the general sur-
face of the hymenium as
defined by the outer ends of
the paraphyses. a, a young
and, as yet, non-protuberant
ascus showing : a thin cell-
wall lined by a thin layer of
cytoplasm, a large vacuole
filled with cell-sap, and eiglit
spores. The wall is slightly
thickened at the end of the
ascus, and all the eiglit spores
are sloped in the same direc-
tion, the uppermost being-
directed towards the future
operculum. b, an older
ascus with maximiun pro-
tuberancy above the general
level of the hymenium ; it
is ripe and ready to discharge
its spores, c, an exploded
ascus which shot out its eight
spores and niuch of its cell-
sap through an obliquely
situated operculate ostiole.
The direction of spore-dis-
charge, shown by the arrow,
was parallel to the vertical
axis of the cup. A compari-
son of b and c shows that,
owing to the elasticity of
the cell-wall, the volume of
the ascus c, during the ex-
plosion, contracted to about
one-half, e, some isolated
spores shot out from an
ascus : their contents include
several oil-drops. </, a
branched paraplij'sis, with
its upper divisions anasto-
mosing and densely com-
pacted. The dots in the
cells represent the red part-
icles which make the hy-
menium a deep scarlet. The
magnification of every part,
as shown by the scale, is 26U.

246 RESEARCHES ON FUNGI

ascospores in a mature upright apothecium (Fig. 116, p. 240) are
all inclined slightly upwards. This is well shown in Fig. 120, A.

A mature ascus, such as the one shown in Fig. 119 at b, is turgid
owing to the high osmotic pressure of the cell-sap contained within
its great central vacuole, and its thin elastic cell-wall is stretched
like that of a toy balloon blown up with air. When the ascus
explodes, it opens at its apex by means of a hinged operculum
(Fig. 119, c), but the aperture is formed not symmetrically about the
longitudinal axis of the ascus as in most other Ascomycetes, but
obliquely on one side of it. Moreover, as shown in Fig. 120, B, the
aperture so formed always looks upwards toward the mouth of the
apothecium. In the light of these facts, we can readily perceive
why it is that the ascus does not shoot its spores in the direction of
its long axis and why, when puffing takes place, the spore-cloud is
projected straight forward from the mouth of the apothecium in a
direction parallel to the apothecium-axis. A comparison of Figs. 116,
118, B, and 120 will make all this clear.

When an ascus explodes, the elastic cell-wall wliich has been
distended by the osmotic pressure of the cell-sap contracts with
considerable force and great rapidity, in consequence of which the
ascus shortens and becomes thinner. The ascus-apex is di'awn down
to the level of the paraphyses (Figs. 119, c, and 120, B) and no
further, so that the total shortening of the ascus as a whole is only
to the extent of about one-sixteenth of its original length or about
6* 3 per centl An ascus, when shooting out its eight spores one after
the other, is continuously contracting in length. If, before all its
spores had been discharged, its apex were to be drawn down below
the external surface of the hymenium as defined by the paraphyses,
it is clear that the remaining spores could not be discharged properly ;
they would strike against the paraphyses and so never get into the
air. It is thus seen that the shortening of an exploding ascus by
an amount just equal to what at first protruded and no more is a factor
in the organisation of the apothecium which makes for success in
the dispersion of the spores. When an ascus explodes, its diameter
becomes reduced to about three-quarters of what it was originally.
Therefore the ratio of the circumference of a turgid ascus to that of
the same ascus after explosion is about 100 : 75 ; or, in other words,

PUFFING IN THE DISCOMYCETES 247

the ascus-wall, when an ascus explodes, contracts circumferentially
to the extent of 25 per cent, of its original measure. As we have
seen, an ascus on exploding contracts in length only about 6 • 3 per
cent. It is clear therefore that, 'per linear unit, an ascus-wall con-
tracts about four times as much in the circumferential direction as
in the longitudinal.

From the fact that the ascus-wall is four times as elastic in the
circumferential direction as in the longitudinal we may infer that
the physical structure of the ascus-wall is not homogeneous, but
is different in the one direction from what it is in the other. This
difference in structure makes for efficiency in the working of the
ascus when the ascus is considered as a mechanism for squirting
away ascospores ; for it is important : (1) for the ascus to contract
longitudinally as little as possible, so that before discharge it will
not be obhged to project much beyond the paraphyses ; and (2) for
the ascus to contract as much as possible circumferentially (and
therefore radially), so that the eight spores and the sap-drops shall
be shot out of the ascus-mouth with as great a velocity as possible.

Owing to the contraction of the cell-wall, an ascus, on exploding,
reduces its volume to about one-half. Therefore an exploding ascus
must discharge about one-half its contents through its apical aper-
ture. The half of the contents which becomes discharged must be
the apical half, and this includes all the eight spores and a mass of
cell-sap having a volume perhaps equal to that of the spores.

The ascus, as a gun, is a squirt from which a jet of watery fluid
containing eight spores is ejected by the pressure of a contracting
elastic cell- wall. The hydi'ostatic pressure of the cell-sap within Is
transmitted equally in all directions through the fluid and thus acts
upon the cell- wall equally at all points. So long therefore as the
ascus-gun during discharge is held firmly fixed in one position by
the paraphyses which surround it, it makes little or no difference, so
far as the range of the gun is concerned, whether the ascus- jet is
shot through a terminal opening in the ascus-wall, as in most Dis-
comycetes, or through an obhque subterminal opening, such as that
which is present in Sarcoscypha protracta. Thus we obtain a physical
explanation for the success of a gun which has the strange pecuharity
of not firing its projectiles in the dii'ection of its long axis but obhquely

248 RESEARCHES ON FUNGI

thereto. Action and reaction being equal and opposite, the asci of
S. protracta, since they have an obhque direction of discharge, might
well fail in effectiveness were it not for the well-developed para-
physes which prevent the end of each ascus from moving in a direc-
tion opposite to that of the projectiles (spores and drops of cell-sap)
whilst the discharge is actually taking place.

That the discharge of the spores from each ascus takes place in a
hne which is very obhque to the ascus-axis can be well demonstrated
by two experiments, one made in the air and the other in water, as
follows :

(1) Using a sharp scalpel and working rapidly, one cuts through
a fruit-body which has been lying in a Petri dish and is ready to
puff, so as to isolate a piece of the apothecium extending from the
rim to the base. This fragment is taken in the fingers and held
horizontally with the hymenium looking upwards. Pufhng then
takes place, and one can observe that the spores are shot away not
perpendicularly to the hymenial surface but obliquely upwards
towards the rim-end of the fragment. For an illustration of what
one sees, one may imagine that the surface of the hymenium shown
on the right-hand side of Fig. 120, A, has been placed in a horizontal
position and that the direction in which the spores are shot is shown
by the arrows in their new positions.

(2) With a hand-razor one cuts a longitudinal-radial section
through one side of an apothecium containing almost ripe asci and
mounts it in water under a cover-glass. It has the appearance of
the right or the left half of Fig. 120, A. One then places a drop of
iodine at the edge of the cover-glass so that it gradually diffuses over
the hymenium beginning at one end and passing slowly to the other
end. As the iodine acts on the asci, they explode one by one in
succession, and one can readily observe that the eight spores of each
ascus are shot obliquely through the water toward the rim-end of
the hymenium. One sees each ascus explode and contract {cf. A
and B in Fig. 120), but the spores are shot away with such speed
that one does not see them passing through the water until they have
almost been brought to rest by the resistance of the water. As the
iodine continues to diffuse over the section, hundreds of asci explode
and the spores accumulate on the surface of the slide as a thick

A

jh Cb V- C Uf

B

Fig. 120. — Sarcoscypha -protracta. A semi-diagrammatic vertical section through the two sides of a cup
to show the appearance of the hymenium before and after spore-discharge. The two sides of the cup
have been approximated to bring them both within the same drawing. A, just before tlie fruit-body
puffed. The hymenium consists of : p p, paraphyses containing the red particles which give the
hymenium its scarlet colour ; a a, asci, each bounded by a thin elastic cell-wall iv, and containing a
lining layer of cytoplasna c, a large vacuole v, and eight spores enclosing oil-drops. The asci are fully
protuberant and the spores are all ripe and ready for discharge. The uppermost spore in each ascus has
its upper end resting against the part of the ascus-wall which is to become the operculum. All the
spores in each ascus look obliquely upwards. The arrows show the direction in which the ascospores
and part of the ascus-sap will be shot. B, the same section as A, one second after puffing has taken
place. The spores and part of the ascus-sap have been shot upwards in the directions shown by the
arrows through operculate ostioles which look upwards to the mouth of the cup. Each operculum has
its hinge on the side of the ostiole farthest from the end of the ascus. In eacli ascus tliere lias been a
reduction of the diameter to about three-quarters, and of the length by an amount equal to the part
of the ascus that formerly was protuberant. Magnification, 200.

250 RESEARCHES ON FUNGI

spore-deposit in front of the hymenium.^ The eight spores of any
one ascus come to rest at a distance of about 1 mm. from the
hymenium, but the discharges of neighbouring asci set up momentary
currents which gradually carry these eight spores farther from the
hymenium, and thus the final spore-deposit comes to be situated at
a distance of 1-2 mm. from the hymenium. If one examines the
exploded and empty asci, one observes : (1) that their openings are
all obUquely situated, as shown in Fig. 120, B, and look in the direc-
tion in which the spores have been shot ; and (2) that their opercula
are all hinged on that edge of the opening which is toward the ascus-
base (Fig. 120, B).

Radial-longitudinal Sections and Surface Views of the Hyme-
nium.— The key to understanding the fruit-body of Sarcoscypha
protracta as an organ for the production and Uberation of spores is a
thorough study of the hymenium in radial-longitudinal sections and
in surface views. Only by such a study can one obtain satisfactory
evidence of the spatial relations of the asci and paraphyses, and of
the relation of the asci with the mouth of the apothecium. Hitherto,
so far as I know, no one has ever studied Discomycetes in this way,
so that Figs. 1 20, 121, and 1 22 af e the first of their kind in mycological
hterature.

A radial-longitudinal section of an apothecium is, of course, one
which, if continued, would pass through the apothecium's longi-
tudinal axis ; and, if complete, it would resemble the section shown
in Fig. 118 (p. 243). Pieces from each side of such a section are
shown in Fig. 120, but, for convenience of illustration, the two pieces
have been brought nearer together than they would usually be in an
actual section. At A is shown the appearance of the hymenium
just before puffing and at B the appearance of the same hymenium
one second after puffing.

In Fig. 120, A, the following points may be observed : (1) the
only elements in the hymenium are asci and paraphyses ; (2) ad-
jacent asci which He nearly or exactly in the same vertical plane
are separated by relatively thick masses of paraphysal branches ;

1 For a discussion of the mode of action of iodine and of other poisonous sub-
stances in causing the explosion of ripe and nearly ripe asci of Aleuria vesiculosa
(there misnamed Peziza repanda) vide these Researches, Vol. I, 1909, pp. 238-240.

PUFFING IN THE DISCOMYCETES

251

(3) the eight ascospores are all situated in the outer halves of the
asci ; (4) the terminal spore of each ascus has its upper end against
the operculum that will make its appearance when the ascus explodes;
(5) the spores in each and every ascus are all inchned upwards so
that the asci have a remarkably uniform appearance ; (6) the asci
are fully protuberant ; (7) the cells of the paraphyses contain dark
particles (these are red in hving sections) ; and (8) the asci do not

B

^

a
0

Fig. 121. — Sarcoscypha protracta. Surface views of tlie hymenimn before
and after spore-discharge. A and B correspond respectively with A
and B in Fig. 120. A, just before the fruit-body puffed : a, asci ; s,
ascospores, all obliquely situated with their upper ends pressing against
the future operculum ; c, the area of contact of a spore with the future
operculum ; p, the paraphyses. B, another surface view, similar to A,
but one second after puffing has taken place : p, the unaltered para-
physes ; a, the empty asci shrunken to three-quarters of their
original diameters ; o, the upward -looking openings of the asci (the oper-
cula attached to the upper rims of the openings are not here shown on
account of the small scale of the drawing). The positions of the asci
in both A and B, and also the ostioles in the asci of B, were drawn with
the camera lucida, while the spores and the areas c in A, as well as the
paraphyses in A and B, have been represented semi-diagrammatically.
Magnification, 267.

contain any dark particles, but their spores enclose characteristic
oil-drops.

In Fig. 120, B, the following points may be observed : (1) the asci
have contracted in length so that they are no longer protuberant ; { 2 ) the
asci have contracted to about three-quarters of their former diameter ;
(3) the ends of the asci are at the level, and not below the level, of the
ends of the paraphyses ; (4) the openings of the asci are all obhquely
situated and look upwards in the directions shown by the arrows ;
and (5) the opercula are all hinged in the same manner, i.e. each hinge
is on that side of the opening which is toward the base of the ascus.

252

RESEARCHES ON FUNGI

In Fig. 121, A, is shown a surf ace view of a hymenium just be ore
pufl&ng and therefore corresponding with the radial- longitudinal
section shown in Fig. 120, A. In Fig. 121, A, the following points
may be observed : (1) the only elements in the hymenium are asci

Fig. 122. — Sarcoscypha protracta. Semi-diagrammatic surface view of the hymen-
ium, about one second after puffing has taken place and all the asci have
exploded : p p, the paraphyses in which the asci are embedded ; e e, the empty
asci ; a a, the apertures of the asci, through which the ascus-jets consisting of
spores and drops of cell-sap were discharged ; o o, the opercula, each one
hinged to the upper edge of the ascus-wall. Magnification, 1143.

and paraphyses ; (2) the paraphyses occupy at least one-half of the
hymenium ; (3) the uppermost spore in each ascus is pointing
obliquely upwards and is resting against the opercuhmi that will be
formed when the ascus explodes ; and (4) there is a large amount
of cell-sap surrounding the spores.

In Fig. 121, B, is shown a surface view of a hymenium just after

PUFFING IN THE DISCOMYCETES 253

puffing and therefore corresponding with the radial-longitudinal
section shown in Fig. 120, B. In Fig. 121, B, the following points
may be observed : (1) the asci have contracted so that their dia-
meters are about three-quarters of what they were before spore-
discharge took place ; and (2) the openings of the asci (the opercula
are not shown) are all obliquely situated on the upper side of the
end of each ascus.

In Fig. 122, which supplements Fig. 121, B, an exhausted
hymenium in surface view is shown on a larger scale. In Fig. 122
one may again notice : (1) the wide separation of the asci by the
paraphyses, and (2) the upper obhque positions of the ascus-aper-
tures ; but, in addition, one may observe (3) that the opercula are
all hinged in the same manner, i.e. on the side of the openings nearest
the bases of the asci.

Figs. 120, 121, and 122 taken together provide data which allow
us to form a clear conception of the spatial relations of the elements
of the hymenium to one another and to the cup-shaped apothecium
as a whole.

Correlations and Fruit-body Efficiency. — It is evident that the
hymenium is wonderfully well fitted for producing and Hberating
spores from an apothecium with a more or less obconical interior.
Correlated with this form is the upward-looking opening of each
ascus, made when discharge of the spores takes place. If the ascus-
openings did not look upwards toward the mouth of the apothecium,
but looked sideways or were terminal, the spores could not be ejected
efficiently from the apothecial cavity. The upward inchnation of
the top spore of each ascus and of the other seven spores in the spore-
chain is correlated with the position of the opening that will be formed
when the ascus explodes. If the ascospores were inclined down-
wards instead of upwards, when an ascus opened the exit of the
spores through the opening would be rendered much more difficult
if not impossible.

The area taken up by the paraphyses in the hymenium is some-
what greater than that taken up by the asci. Why should there not
be fewer paraphyses and more asci ? Would not this make for
greater efficiency ? Let us attempt to answer these questions.
Firstly, it is to be remarked that paraphyses form an essential part

254 RESEARCHES ON FUNGI

of the hymenium : they protect the young asci when they are
developing and pushing upwards, and they support the mature asci
mechanically, preventing them from having their apices forced
down\\ards when they are firing their jet of spores and sap upwards.
If the paraphyses were reduced to such a minimum that the asci
were in lateral contact with one another, many of the asci would
not be able to discharge their spores properly. To make this clear,
let us imagine that on the right-hand side of Fig. 120, A, the five
asci most in view were in contact one below the other. Then to
secure the aerial dispersion of all the spores it would be necessary
for the five asci to be discharged in succession from above down-
wards and in no other order ; for, if of any two adjacent asci in the
row of five the lower one discharged before the upper one, since the
opening of the exploding ascus looks upwards and since an exploding
ascus contracts in length, most of the eight spores of the lower ascus
would be shot against the lower side of the upper ascus and so would
not escape from the mouth of the apothecium. From these con-
siderations it is seen that it is best in Sarcoscyi^lia protracta for the
asci to be well separated from one another, especially in the vertical
direction. If one regards the right-hand side of Fig. 120, A, one
can see that, if one of the middle asci explodes, as it contracts in
length and ceases to be protuberant all the spores can be shot away
without any of them hitting the lower side of the ascus which is
above it. Evidently, the number of the paraphyses is correlated
with the spatial arrangement of the asci necessary to secure that all
the spores from each ascus shall be efficiently discharged through
the cavity of the apothecium into the outer air. A reduction in
the number of paraphyses in the hymenium would therefore be
disadvantageous .

Summing up, we may say that correlated with the conical form
of the cavity of the apothecium in Sarcoscypha protracta, and making
for efficiency in the production and Uberation of spores by the
hymenium, are the following arrangements : (1) the obHque upward-
looking openings of the asci formed at the moment of spore-dis-
charge ; (2) the obUquely upward inchnation of the spores in each
ascus ; and (3) the relatively distant separation of adjacent asci
by paraphyses, particularly in respect to vertical planes.

PUFFING IN THE DISCOMYCETES 255

What Factor determines the Oblique Position of the Opening
of each Ascus ? — It is known that the asci of many Ascobolaceae
and, as we shall see in the next Chapter, of many other Discomycetes
belonging to the Humariaceae, the Pezizaceae, and the Morchel-
laceae are positively heHotropic so that, during their development,
they bend their ends toward the Hght. The length of the part of
the ascus which may bend, relatively to the length of the ascus as
a whole, varies considerably in different species. Thus bending of
an ascus through 45° is effected in Aleuria vesiculosa by the outer
half of the ascus (Fig. 140, p. 293 ; cf. Fig. 123, A), but, in Ciliaria
scutellata, by no more than the last sixth of the ascus (Fig. 135,
p. 284 ; cf. Fig. 123, B). In all probabihty the ascus of Sarcoscypha
protracta, like that of so many other Discomycetes, is positively
heliotropic ; but, if so, its bending is confined to its extreme apex.
We have only to suppose that the operculum originates in the first
place in a radially symmetrical position at the end of the ascus and
that, subsequently, the end of the ascus, after it has emerged at
the surface of the hymenium and has received unilateral light from
the mouth of the cup, makes a positively hehotropic curvature by
growing in length on its darker side just sufficiently to swing the
operculum round through an angle of about 45° until the operculum
comes to face the strongest incident rays of light directly (Fig. 123, C).
The assumption that such a heliotropic reaction takes place serves
to explain not only why the opercula of all the asci in the hymenium
look upwards toward the mouth of the cup {cf. Fig. 120, A and B,
p. 249) but also why they are obliquely situated on the ends of the
asci . Granted that the heliotropic reaction j ust suggested takes place,
then, in a ripe ascus, while the apparent axis is straight, the axis of
organisation is in reality curved at its extreme end (Fig. 123, C).

Seaver ^ has supposed that the oblique position of the opening

1 r. J. Seaver, The North American Cup-fungi, New York, 1928, pp. 17-18.
Seaver states that the apothecia of Phillipsia Chardoniana " are as flat as a pancake
yet, so far as observed, the ascostomes are always eccentric, or, at least, are con-
spicuously and predominantly so." However, he does not inform us whether or not
the apothecia under investigation were unilaterally lighted during their develop-
ment and whether or not the opercula all faced the source of greatest light. As will
be shown in the next Chapter, when the flat apothecium of Ciliaria scutellata is uni-
laterally lighted, the tips of all the asci bend toward the light, and the exploded asci
have opercula which are sub-oblique {cf. Fig. 135, 1 1, p. 284).

256

RESEARCHES ON FUNGI

/

/

n\

Fig. 123. — Diagram illustrating variations in helio-
tropic curvature in tlie asci of different species
of Discomycetes. The arrows indicate the
direction in which the asci were illuminated
during their development. All the asCi, at first,
were straight, and their appearance (including
an indication of the position of origin of the
rudiment of each operculum), just before they
began to bend, is indicated in part by brokeii
lines. Heliotropic curvature toward the source
of liglit began : in A (as in Aleuria vesiculosa)
when the ascus was only half -grown in length ;
in B (as in Ciliaria scutelhttd) when the ascus
was about five-sixths grown in lengtli ; and
in C (as in Sarcoscypha protrnctn) when the
ascus was almost full-grown in length. The
cvirvature of the central broken line which
represents the morphological axis of each ascus
indicates that even in C, which externally has
the appearance of a straight cylinder, the lateral
position of the operculum has been attained, as
in A and B, by a heliotropic curvature.

1 In litt., 1927 and 1928.

/ of the ascus, which he
calls the ascostome, in a
number of tropical Dis-
comycetes, e.g. species of
Phillipsia and Cookeina,
is a purely ''morpho-
logical character " not
influenced by the ex-
ternal stimulus of light,
but he admits ^ that he
has not observed the
fruit-bodies in the living
condition and has no ex-
perimental basis for his
assumption. In view of
my own investigations
on the obliquely situated
ascostomata of Sarco-
scypha protracta which
always look toward the
strongest incident rays
of light, supported by
other investigations on
the position of the asco-
stomata of the asci of the
discoid fruit-bodies of
Ciliaria scutellata, etc.,
recorded in the next
Chapter, I am unable to
accept Seaver's assump-
tion. It is my opinion
that the internal tend-
ency of every ascus is to
produce itsascostomain
a radially symmetrical
position at the ascus

PUFFING IN THE DISCOMYCETES 257

apex and that the ascostoma subsequently takes up its oblique position
owing to a response of the ascus end to a heliotropic stimulus. Thus
the oblique position of an ascostoma at the end of any ascus is regarded
by me not as a purely " morphological character " depending for
its origin on internal growth stimuli only, but as a physiological
character depending on an external stimulus, namely, that of light.
Experimental Proof that a Fruit-body, when it puffs, produces
a Blast of Air. — When a fruit-body of Sarcoscypha jyrotrada is held
horizontally in the still air of the laboratory and it puffs, the cloud
of spores set free travels horizontally to a distance varying from
about 8 to 17 cm. (7 inches), according to the intensity of the puff.
The greater the number of spores set free at one time, the louder is
the hiss made by them as they pass through the air and the farther
do they travel before becoming dispersed irregularly. As I watched
the puffing of a number of fruit-bodies tested one by one in the
laboratory, it seemed that the spore-cJoud — at any rate in the latter
part of its journey — w^as being borne along as if by a blast of air.
I therefore decided to test this idea by means of experiment. On
May 9, 1925, I went to the Poplar wood where Sarcoscypha protracta
grew and gathered a considerable number of fruit-bodies. As the
temperature of the air in the wood w^as only a few degrees above the
freezing point of water, the fruit-bodies would not puff ; but, after
being brought into the laboratory and left in closed Petri dishes at
a temperature of about 70° F. for about an hour, many of them puffed
freely when they were removed from their Petri dishes and were
held in the fingers in the relatively dry air of the laboratory.

The apparatus employed for demonstrating that a fruit- body of
Sarcoscypha protracta, when it puffs, produces a blast of air is shown
in Fig. 124. What is represented was spread out in a horizontal
plane, and the observer is supposed to be looking down on it from
above. A test-tube a with an open side-pipe b (shown in section at c)
is held in a horizontal plane by the clamp e which is attached by
the clamp d to the vertical rod of an iron stand. The position of a
card- board screen is shown at / and g. The apparatus was set up
on a laboratory table near a window, so that strong daylight fell
upon it. In front of the mouth of the side-pipe 6, as shown around i.
there was a black back-ground.

VOL. VI.

258

RESEARCHES ON FUNGI

PUFFING IN THE DISCOMYCETES 259

When the apparatus was set up, fruit-bodies were removed one
by one from the Petri dishes with the fingers as required and were
held at the mouth of the test-tube as shown in Pig. 124 at h. It was
necessary to carry out each of these operations as rapidly as possible
because, if a fruit-body was in a condition to puff, it usually puffed
within three seconds of raising the Petri-dish lid. With the pro-
cedure just described some of the fruit-bodies were caused to puff
into the mouth of the test-tube a.

Immediately after placing a fruit-body at the mouth of the test-
tube a, I looked towards the black back-ground shown at i and then,
within a second, if the fruit-body puffed strongly, I heard the fungus
hiss for about two seconds and saw a cloud of spores shoot out from
the side-pipe b. In the most successful experiments the spore-cloud
was carried horizontally, as shown at i in Fig. 124, a distance of
about three inches beyond the mouth of the side-pipe b before
irregular dispersion took place ; but in several other experiments
the distance was not more than about 1-1*5 inches. Since the
spores cannot be shot by any ascus around a corner, it seems clear
from these experiments that the fruit-bodies, on puffing, must create
a blast of air which can carry the spores passively with it.

To vary the experiment just described, I suspended a strip of
thin tissue-paper four inches long, one-tenth of an inch wide at the
top, and six-tenths of an inch wide at the bottom, so that its lower
end was just in front of and touching the mouth of the side-pipe 6
in Fig. 124. As before, several fruit-bodies in succession were
caused to puff into the mouth of the test-tube a. As each puff took
place, I heard the hiss and saw the lower end of the strip of tissue-

FiG. 124. — Apparatus, seen from above, as used for demonstrating that a fruit-bodj'
of Sarcoscypha prolracta, when it puffs, produces a blast of air : a, a test-tube
with an open side-pipe b (shown in section at c), held in a horizontal plane by the
clamp e which is attached by the clamp d to the vertical rod of an iron stand ;
/ gr, a cardboard screen ; h, a fruit-body removed from a Petri dish and placed
at the mouth of the test-tube about three seconds ago. The fruit-body has
just puffed. The million or more spores and sap-droplets which were shot into
the tube have impinged upon the air and set it in motion, thus producing a blast
of air which is now emerging horizontally through the mouth of the pipe b and
bearing the spores with it, as shown at i. The cup of the fruit-body is some-
what smaller than the mouth of the test-tube ; so that, as the air is driven
forward in the body of the tube a, more air enters at the mouth of the tube near
h. The column of spore smoke, i, was observed in bright daylight against
a black back-ground. Natural size.

26o RESEARCHES ON FUNGI

paper blown away from the mouth of the side-pipe. As the blast
of air subsided, the tissue-paper returned to its former position and
again covered the mouth of the side-pipe. In some of the experi-
ments the tissue-paper was blown a distance of 1 cm. and, in the
most successful experiment, made with a fruit-body which puffed
with great vigour, the tissue-paper was blown a distance of 2 cm.
The blast of air in each experiment carried spores with it and the
spore-cloud could be seen being deflected laterally by the obstacle
of the tissue-paper.

When a fruit-body puffs, it not only shoots away many tens of
thousands of spores but also vast numbers of drops of ascus-sap.
When about twelve fruit-bodies had puffed into the test-tube, so
much ascus-sap in the form of extremely fine droplets had fallen
to the bottom of the test-tube in the region lettered a in Fig. 124
that, when the tube was tilted, the hquid could just be caused to
run in the form of a shallow drop. A microscopic study of asci
before and after explosion goes to show that, in all probabihty, the
volume of ascus-sap shot out from any ascus is at least equal to the
volume of the eight spores and may possibly be greater, so that the
gathering of moisture on the base of the tube a was in accordance
with theoretical expectation.

The Cause of the Blast of Air. — When an apothecium puffs, it
does not contract its rim or alter its general shape, and there is no
reason to suppose that the blast of air emerges from the apothecial
cavity. It seems most probable that the blast of air is brought into
existence by the forward movement of the spores and drops of ascus-
sap. It was calculated that from one fruit-body, which was found
to have all its asci empty after it had puffed, a milhon spores had
been discharged. Probably these million spores were accompanied
by at least a milhon drops of ascus-sap. From the fruit-body,
therefore, there were shot forward in the same direction some two
milhon projectiles. At the beginning of their flight from an apothe-
cium each of the projectiles, moving as it does at a high speed, must
drag a certain amount of air forwards. Very quickly the velocity
of each projectile is greatly reduced by the resistance of the air ;
and, by this time, we may suppose, the air has been bombarded by
the projectiles to such an extent that it moves forward en masse

PUFFING IN THE DISCOMYCETES 261

with a speed of several centimetres a second and carries many of
the spores passively forward with it. The rate of fall of the spores
is much less than the speed of the air. Hence it is possible for the
blast of air to carry the spores through the side-pipe 6 and even
some 1-3 inches beyond its mouth.

The forward movement of the air in the test-tube caused by the
bombardment of the air by the projectiles does not create a partial
vacuum in the tube, because the mouth of the cup of the fruit-body
is somewhat smaller than the mouth of the tube to which it is
applied ; so that, as the air is driven forward in the body of the tube
(Fig. 124, a), more air enters at the mouth of the tube (Fig. 124,
near h).

The baUistic phenomenon under discussion may be treated
mathematically as follows :

Let Mj = the mass of the projectiles (the spores and the cell-
sap) shot out from all the ascus-guns,
v^ = the velocity of projection,
M2 = the mass of the air set in motion by the impact of the

projectiles, and
Vc, = the common velocity of the air and projectiles after
impact.

Then, by the principle of the conservation of energy,

M, v^ = (Ml + M2) v^

i.e. the momentum of the blast of air and of the projectiles which
the air carries along with it is equal to the momentum of the pro-
jectiles at the moment when they left the asci. It therefore follows
that the blast of air is caused by the air being bombarded by the
projectiles.

After a blast of air has been started, its velocity is progressively
diminished by friction with the still air through which it moves-
Hence the blast of air produced by the apothecium, like a smoke-ring
blown from the mouth, does not travel very far.

Since action and reaction are equal and opposite, when puffing
takes place the stalked apothecium of Sarcoscypha protracta must
tend to recoil with a momentum equal to that of the projectiles

262 RESEARCHES ON FUNGI

which are shot away. I have not investigated the recoil in S. pro-
tracta, but Dr. E. C. Stakman has informed me that he has observed
the recoil in the thin-stalked apothecia of Sderotinia sderotiorum :
as puffing took place, the cups containing the asci were visibly-
pressed backwards. Such a recoil gives an indication of the energy
with which the projectiles discharged from the asci bombard the air
and set it in motion .

The Blast of Air and the Dispersal of the Spores. — If the asci of
a Sarcoscypha protracta fruit-body were to explode one after the
other as they ripen, it is probable that the eight spores of each ascus
would not be shot up into the air for more than 3-4 cm., and no
appreciable blast of air could come into existence to raise them still
further. On the other hand, when a hundred thousand asci explode
together, i.e. when puffing takes place, the bombardment of the air
by the spores and ascus-drops collectively is sufficient, as we have
seen, to create a blast of air which can carry the spores with it for
several inches after they have lost the velocity given to them by
the ascus-guns. Consider now a fruit-body under natural conditions
in a Poplar wood. Its stipe is negatively geotropic and its apothe-
cium therefore looks upwards to the sky. If the asci were all to be
discharged in succession as they ripen, none of the spores (we may
suppose) would travel upwards more than an inch or two ; but,
if the asci ripen one by one and then wait before exploding until
some suitable stimulus sets them all off together, then the spores
may be carried upwards by the blast of air. which they bring into
existence, to a height of 5-7 inches. After being carried upwards
into the air, the spores are borne away more or less horizontally by
the wind and are thus dispersed. The nearer to the ground, the less
wind there is ; and every extra inch the spores can be raised into the
air by discharge from the apothecium, the stronger mil be the wind
which they will encounter and the greater the chance that they will
be dispersed widely and find suitable conditions for propagating the
species. Once more we are provided with an instance where union
is strength and where collective action is better than individual
action.

Concluding Remarks. — Oiu- knowledge of the phenomenon of
spore-discharge in the Discomycetes is still very incomplete. With

PUFFING IN THE DISCOMYCETES 263

a view to its extension individual apothecia of a series of typical
species should be observed in the field. Such apothecia should be
left in situ and not be touched by man ; and, for each apothecium,
during the whole spore-discharge period, a continuous record, not
only of the times of spore-discharge, but also of the conditions
of spore-discharge (temperature, moisture, wind-movements, etc.)
should be made.

CHAPTER II

THE HELIOTROPISM OF THE ASCI AND THE DISCHARGE OF THE
SPORES IN ASCOBOLI, CILIARIA SCUTELLATA, ALEURIA
VESICULOSA, THE MORCHELLACEAE, AND OTHER DISCO-
MYCETES

Introduction — The Heliotropism of the Asci of Ascoholus magnifims — Ascoholus
stercorarius — Our Present Knowledge of Ciliaria scuteUata — The Heliotropism of
the Asci of Ciliaria scuteUata — The Heliotropism of the Asci of Melastiza miniata
and Cheilymenia vinacea — Aleuria vesiculosa and its Identification — Results of
a Previous Investigation on Aleuria vesiculosa — The Heliotropism of the Asci
and the Discharge of the Spores in Aleuria vesiculosa — Puffing of Aleuria
vesiculosa under Natural Conditions — The Heliotropism of the Asci and the
Discharge of the Spores in Galnctinia badia — JJrnula Craterium — Otidea onotica
and O. leporina — The Heliotropism of the Asci and the Discharge of the Spores
in the Morchellaceae — The Helvellaceae — Concluding Remarks.

'(^

Introduction. — Sarcoscypha inotracta, which was treated of in the
last Chapter, is a rather specialised Discomycete, for : (1) its
hymenium, which lines the inside of the cup, has more or less the
shape of an inverted cone ; (2) its asci are straight ; and (3) the oper-
cula of its asci are not situated symmetrically at the ends of the asci
but obliquely, so that they look upwards toward the mouth of the cup.
Doubtless, there are a number of other Discomycetes which
resemble Sarcoscypha protracta in their general form and their mode
of producing and liberating spores. However, a very large nimiber
of Discomycetes differ from 8. protracta in that : (1) they have a
flat hymenium, e.g. Ciliaria scuteUata, or a more or less hemispherical
hymenium, e.g. Aleuria vesiculosa and Galactinia badia, or a cavernous
hymenium, e.g. MorcheUa crassipes and M . conica ; (2) their asci
are not straight, but are more or less curved at their free ends where
the spores are situated ; and (3) the mouth of each of their asci is
symmetrically situated at the end of the ascus.

The ripe asci of the Ascoboleae protrude considerably above the

204

HELIOTROPISM OF ASCI IN DISCOMYCETES 265

outer surface of the hymenium, so
by their prominent summits, and
it has long been kno^\^l that these
protuberant asci bend toward the
Hght and are therefore positively
heliotropic. Zopf ^ illustrated the
heliotropism of the asci of Asco-
bolus denudatus and of a species of
Saccobolus in his well-known text-
book in 1890 (Figs. 125 and 126).

As a result of my own obser-
vations, I have no doubt that
the asci of Ciliaria scutellata,
Aleuria vesiculosa, Galactinia
badia, Morchella crassijies, and
other similar Discomycetes, like
those of the Ascoboleae, are heho-
tropic, and that the response of
the asci to the directive stimulus
of light serves to explain how it
is that the ascospores discharged
from the interior of hollow cups,
such as those of Aleuria vesiculosa,
Galactinia badia, etc., and from the
interior of cavernous depressions
at the surface of the caps of the
Morchellae are shot out into the
external air without striking op-
posing chamber walls.

In the summer of 1926, at the
International Congress of Plant
Sciences, I gave a paper ^ on the
discharge of spores in the Higher

that the disc is made papillate

Fig. 125. — Ascobolus denudatus. Helio-
tropism of the asci. A, a smaller
and a larger cup-like fruit-body on
a fragment of dung. The asci pro-
truding above the hymenium have
all become heliotropically bent
toward the light, the direction of
which is indicated by the arrow. B,
a vertical section through one of
the fruit-bodies showing the hy-
menium in which are the lieliotropi-
cally bent asci, each containing
eight spores. C, a single ascus
from B ; it is strongly bent toward
the source of the light. The dotted
line indicates the top of the hy-
menium. Drawn by W. Zopf.
From his Die Pilze (1890, p. 205).
Magnification : A, 25 ; B, 80 ;
C, 300.

1 W. Zopf, Die Pike, Breslau, 1890, pp. 205-206, Fig. 64.

2 A. H. R. Buller, " Some Observations on the Di.scharge of Spores in the Higher
Fungi," Proceedings of the International Congress of Plant Sciences, Vol. II, 1929,
pp. 1627-1628,

266

RESEARCHES ON FUNGI

Fungi in which, after treating of Sarcoscypha protracta, I said : "In

most Discomycetes, e.g. Morchella
conica, Aleuria vesiculosa, Galactinia
badia, Lachnea scutellata, and Ascobolus
immersus, the asci are heliotropic, i.e.
their outer ends bend so that they
point toward the direction from which
the strongest light comes, and the
operculum is situated symmetrically
at the apex of each ascus. The result
of these arrangements is that, when
the asci explode, the spores are suc-
cessfully shot away from the fruit-
bodies into the outer air."

In 1927, J. S. B. Elliott,i in a brief
paper on Aleuria repanda, described
the response of the apothecia to uni-
lateral light. Apothecia came up on
an old jute hearth-rug in a garden
tool-shed into which light penetrated
through a hole in the door. She
found that, in preparation for spore-
discharge, each apothecium undergoes
two successive adjustments: (1) a
coarse adjustment concerned with the
apothecium as a whole ; and (2) a

to its long axis. The spores „ t , , i -ji. j.i,

are stuck together to form fin^ adjustment concerned with the
a single projectile B, the individual asci. In the coarse adjust-

spores shown in detail. 0,a "*

single ascus of a Saccoboius ment, the stalk of each young apo-
thecium bends toward the source of

Fig. 126.— Saccoboius. Helio-
tropism of the asci. A, an
ascus of a Saccoboius from
sheep dung ; it is straight, so
the direction of the incident
light may have been parallel

heliotropically bent toward
the source of light. Amass
of jelly surrounds the eight
spores and attaches the
spore-mass to the apex of
the ascus. Drawn by W.
Zopf. From his Die Pilze
(1890, p. 205). Magnifica-
tion : A, 450 ; B, 900 ; C, 540.

light and thus causes the mouth of
the cup to become directed toward
the source of light (Fig. 127) ; while,
in the fine adjustment which follows

1 Jessie S. Bayliss Elliott, ''Aleuria repanda Pers.," Trans. Brit. Myc. Soc,
Vol. XII, June, 1927, pp. 166-169.

HELIOTROPISM OF ASCI IN DISCOMYCETES 267

the coarse one, each ascus bends toward the source of light and thus
causes its free end to become directed toward the source of light.

The coarse and fine heliotropic adjustments which have just been
described take place not only in Aleuria re-panda but, as I have
observed, in other stipitate Discomycetes when grown in unilateral
light ; and they are analogous to the coarse and fine geotropic

Fig. 127. — Aleuria repanda. Heliotropism of fruit-bodie3. The fruit-
bodies were growing on an old jute hearth-rug in a garden tool-shed
and, during their development, were illuminated solely by light com-
ing through a hole in the door. The stipes, which were positively
heliotropic, have turned toward the source of Hght and have thus
caused the upper hymenial surfaces of the cups to face the light.
Photographed at Tanworth-in-Arden, England, by Jessie S. Bayliss
Elliott. About one-lialf the natural size.

adjustments which take place respectively in the stipe and gills of
many agarics, e.g. Psalliota campestris.^ In both the Discomycetes
and the Agaricaceae, by means of these adjustments, the fungus
guns (asci and basidia respectively) come to rest in positions in
which they point toward open spaces, from which spaces the pro-
jectiles (ascospores and basidiospores), immediately or shortly after
their discharge, can be readily carried off by the wind.

1 These Researches, Vol. T, 1909, p. 56.

268 RESEARCHES ON FUNGI

In 1916, Richard Falck ^ published a paper on the discharge of
spores in the Discomycetes in which he pointed out that Morchella
escidenta, Gyromitra esculenta, and other Morchellaceae emit clouds
of spores when they are warmed by heat radiated from a lamp
(Fig. 128), etc. ; and he called the Discomycetes which emit spores
when warmed the radiosensitive Discomycetes. ^ He did not investi-
gate the shape of the asci in the hy menial chambers of Morchella,
etc., and thus failed to observe that they point toward the openings
of the chambers. In the belief that the asci are straight and
directed perpendicularly to the surface of the hymenium, he ^ said :
" In the chambers of the Morchellae the opposing walls are at most
1 cm. and, as a rule, only a few mm. from one another ; so that, if
no secondary forces came into play, these walls would bespatter
one another with spores. Still more unfavourable are the conditions
in the narrow and winding passages of Gyromitra." He * placed
cover-glasses against the sides of some of the fruit-bodies and
noticed that, when clouds of spores were emitted, the spores were
deflected from their courses by the cover-glasses as if they were
being carried by air-currents. He ^ therefore argued that, when a
Morchella or a Gyromitra fruit-body is irradiated by heat from a
lamp, etc., air and water- vapour currents {Luft- unci Wasserdampf-
stromungen) are produced in the hymenial chambers and passages
and these currents bear the spores along and thus enable the spores
to escape from the fruit-body. Thus, according to Falck, not only
the discharge of the spores but also the escape of the spores from
Morchella, Gyromitra. etc., is dependent upon the fruit-bodies being
warmed by radiation.

I am unable to accept Falck's theory of the escape of spores
from the fruit-bodies of the Morchellaceae because it is based on

1 Richard Falck, " Ueber die Sporenverbreitung bei den Ascomyceten. I. Die
radiosensiblen Discomyceten," Myrologinche Untersuchungen und Berichfe von R.
Falck, Bd. I, Heft II, 1916, pp. 77-144.

2 In a second paper, " Ueber die Sporenverbreitung bei den Ascomyceten.
II. Die taktiosensiblen Discomyceten " {ibiJ., Heft III, 1923, pp. 370-403), Falck
treats of spore-discharge in those Discomycetes which puff when touched by a solid
object or blown upon ; and he calls such Discomycetes the tactiosensitive
Discomycetes.

3 R. Falck, " I. Die radiosensiblen Discomyceten," lor. cit., p. 133.
' Ibid., p. 133. ■' Ibid., p. 134.

HELIOTROPISM OF ASCI IN DISCOMYCETES 269

two false assumptions : (1) that the asci in the hymenial chambers
and folds are not heliotropically curved but are straight ; and
(2) that the air-currents produced during puffing are caused by a
difference in temperature between the fruit-body and the outer air.
In the preceding Chapter, I have shown by means of a simple

Fig. 128. — An experiment on spore-discharge in Gyromitra
esculenta. A fruit-body with ripening asci has been kept
in a moist chamber. A pencil of rays from an incandescent
lamp is now suddenly directed on to the fruit-body. The
fruit-body reacts to being heated by emitting spores vigor-
ously. The clouds of spores rise in the chamber and some of
the spores settle on the glass slides suspended therein. Copied
for the author by G. Atkinson in black-and-white from Olga
Falck's half-tone drawing in R. Falck's Mycologische Unter-
suchungen und Berichte, Heft II, 1916, Fig. 1.

experiment that, when a fruit-body of Sarcoscyj^ha frotracta, which has
not been warmed above the temperature of its surroundings, puffs,
the discharged spores which are shot out from the mouth of the
cup impinge upon the air, set the air in motion and, in the end, are
borne along by the air for a much greater distance than they would
go were the air to remain still. ^ The air-currents which Falck
perceived in his experiments with the Morchellaceae are doubtless

^ Vide supra, pp. 257-260.

270 RESEARCHES ON FUNGI

caused by the same means as those of Sarcoscypha 23rotracta, i.e. they
are not warm-air and water-vapour currents, but are produced
mechanically by thousands of spores violently striking the air in
the same general direction and at the same time, and thus setting
the air in motion.

To explain the phenomenon of pufhng in Morchella and Gyro-
mitra, when the fruit-bodies are warmed, we have only to suppose :
(1) that the asci are sensitive to heat and, when ripe, always explode
when their temperature is raised above a certain degree, so that
pufhng may be initiated by warming a fruit-body ; (2) that the
asci are curved heliotropically toward the mouths of the hymenial
cavities instead of being straight ; and (3) that the air-currents
which arise at the moment of puffing are due to the spores and
ascus sap-drops bombarding the air and setting it in motion
mechanically and are not due to the fruit-body sending out blasts
of warm air.

In what follows an attempt will be made to show how spore-
discharge takes place in a number of the commoner Discomycetes
which have heliotropic asci.

The Heliotropism of the Asci of Ascobolus magnificus. — For the
purpose of verifying and extending Zopf's statement that the asci
of certain Ascoboleae are positively heliotropic, I have investigated
the effect of light on the direction of growth of the asci of Ascobolus
magnificus.

Ascobolus magnificus, originally described by B. O. Dodge ^ from
North America, occurs on horse dung and, as its specific name
indicates, is remarkable for the great size of its fruit-bodies.
Dr. Dodge kindly supplied me with cultures of the mycelium.

When spores of Ascobolus magnificus have been sown on sterilised
horse dung in a warm laboratory, the fruit-bodies begin to appear
on the surface of the dung at the end of seven days, are about half-
grown at the end of ten days (Fig. 129), and are fully grown and
expanded at the end of about fourteen days (Fig. 103, Vol. IV,
p. 179). Mature fruit-bodies have a flat pale-greenish-yellow
hymenium which becomes darkened with protuberant asci containing

1 B. O. Dodge, "Artificial Cultures of Ascobolus and Aleuria," Alijcologia,
Vol. IV, 1912, pp. 218-221.

HELIOTROPISM OF ASCI IN DISCOMYCETES 271

violet spores. Dodge gives the diameter of the fruit-bodies as
0-5-2 -7 cm.

Observations made on artificial cultures in the laboratory
showed that the asci of Ascobolus magnificus, like those of other
Ascoboleae, are positively heliotropic. When the hymenium is
illuminated from above, as indicated in Fig. 130, A, the asci grow
perpendicularly upwards and the axis of the apical end of each

Fig. 129. — Ascobolus magnificus. Young fruit-bodies grow-
ing on sterilised horse dung in a glass jar. Spore -
discharge has not yet begun. Photographed by B. O.
Dodge. Natural size.

ascus remains parallel to the incident rays of light ; and, when the
hymenium is obliquely illuminated, as indicated in Fig. 130, B, the
asci make a growth curvature until the axis of the aj)ical end of
each ascus becomes parallel to the incident rays of light.

The asci of Ascobolus magnificus, like those of A. immersus and
other Ascoboleae, are, as compared with typical Pezizaceae such as
Aleuria vesiculosa and Oalactinia badia, remarkably protuberant
(c/. Fig. 130 mth Figs. 140, p. 293, and 147, p. 306). Almost one-
third of a ripe ascus of Ascobolus magnificus projects freely into
the air, and it is this terminal portion of the ascus which bears the

RESEARCHES ON FUNGI

Fig. 130. — A,scobolu.s ituujiiificus. Two vertical .sections tliiough tlie li\-ing hyineaiiim and subh3'menium,
to illustrate the heliotropism of the asci. In A the ripe asci h, i, and ./ point vertically upwards toward
the source of light wliich illuminated them directly from above, as indicated by the arrows. In B the
free ends of the ripe asci h, i, and J are curved toward the source of light which illuminated them
obliquely, as indicated by the arrows. A : a, the subhymenium, the contents of the cells are not
shown ; b. the hymenium, the contents of the cells are shown by shading. The hymenium consists
of slender unbranched paraphyses c, embedded in a yellowish gelatinous matrix d, and of asci : e e,
very young asci containing vacuolated protoplasm ; /, a slightly longer ascus with a nucleus near its
apex ; g, an older ascus, containing 8 young ascospores, pushing up between the paraphyses ; h, i,
and j three ripe asci all pointing in the direction of the source of light and now ready to discharge
tlieir spores ; k, a purple spore with a white longitudinal line in view ; 1 1, spores which happen to show
tlie external gelatinous meniscus which each spore bears on one side ; m, exceptional spores with
roughened walls ; lu a large central vacuole filled with cell-sap ; o, an ascus which has discharged
its spores and has collapsed, its open end still projects slightly beyond the paraphyses and its operculum
is visible at its apex. B, letters with the same significance as in A. Drawn by A. H. R. Buller and
Ruth Macrae. Magnification, 280.

HELIOTROPISM OF ASCI IN DISCOMYCETES 273

eight violet spores and also executes the heliotropic curvature
toward the source of light.

The paraphyses of Ascobolus magnificus are slender and loosely
arranged, and they are embedded along with the asci in a gelatinous
matrix ; moreover, they are not responsive to heliotropic stimuh.
In being anheliotropic they differ from the paraphyses of some
Pezizaceae, such as Aleuria vesiculosa. Whereas in Ascobolus
magnificus the heliotropic curvature of the asci is accomphshed
above the level of the apical ends of the paraphyses, in Aleuria
vesiculosa it is accomplished chiefly below that level (c/. Figs. 130
and 140, p. 293).

Ascobolus stercorarius. — Ascobolus stercorarius {^ A. fur-
furaceus), an apandrous Discomycete, the archicarp (scolecite) of
which was first seen by Tulasne ^ in 1866, has yellowish discoid
fruit-bodies, 0- 5-5-0 mm. in diameter, which in Europe and
North America commonly appear in pastures on the dung of
horses, cows, and other herbivora.

The apothecium of Ascobolus stercorarius, as found by Janczewski 2
in 1871, is at first angiocarpous. The stages in its development
have been represented diagrammatically by Corner ^ (Fig. 131) and
have thus been described by him. An archicarp arises on the
mycelium and one of its cells becomes the ascogonium which
collapses about the time when the asci appear. " In the first stage
(Fig. 131, a) sterile hyphae arise from the stalk of the archicarp or
from adjacent mycelial hyphae and envelop the ascogonium in a
loose weft (6). The hyphae branch profusely, especially to the
inside, which suggests a sympodium, and the branches apparently

^ L.-R. and C. Tulasne, " Note sur les phenomenes de copulation que presentent
quelques champignons," Ann. de Sci. Nat., ser. V, T. 6, 1866, p. 215. A median-
longitudinal section of a young fruit-body of A.furfuraceus, schematically represented
by Sachs on the basis of a drawing by Janczewski {Bot. Zeit., 1871, Taf. IV), is
reproduced in de Bary's Vergleichende Morphologie und Physiologie der Pilze (1884,
pp. 201 and 223). R. A. Harper (Jahrh. /. wiss. Bot., XXIX, 1896) and E. J.
Welsford {New Phytologist, VI, 1912) found that A. furfuraceus lacks antheridia
and is therefore apandrous.

2 E. V. G. Janczewski, " Morphologische Untersuchungen iiber Ascobolus
furfuraceus," Botanische Zeitung, Jahrg. XXIX, 1871, pp. 271-276, Taf. IV, Fig. 21.

^ E. J. H. Corner, " Studies in the Morphology of the Discomycetes. II. The
Structure and Development of the Ascocarp," Trans. Brit. Myc. Soc, Ve»l. XIV,
1929, pp. 277-278.

VOL. VI. T

274

Fig. 131. — Diagram showing stages in the development of an angiocarpic apothecivim,
e.g. that of Ascobolus stercorarius. The hyphae are represented by short hnes
the direction of which indicates the course of the main hyphae in the different
tissues. The ascogenous hyphae are represented by short thick hnes diverging
from the ascogonium which is drawn as a circle near the base of the apothecium
solely for reference ; actually it is obliterated by the growth of the surrounding
tissue at an early stage in development. Asci are drawn in successive stages
at the margin of the hjTnenium in g and h to indicate the radial growth of the
ascogenous hyphae, but no attempt has been made to show similarly their
intercalary growth. The cortical parenchjTna is shown by means of thick
well-spaced lines without special direction except at the margin, for the palisade
arrangement is commonly lost in the mature tissue. Hyphae which grow from
the miderside of the apothecium as excrescent cells into the substratum and
which constitute a secondary mycelium are shown by means of a few longer
lines, a and b, hyphae growing upwards and env-eloping the ascogonium ; c,
a ball of interwoven hyphae surrounding the ascogonium ; d, tissue differentia-
tion has begun, the cortex is distinguishable ; e, a mucilage cavity has formed
in the upper part of the spherical mass internal to the cortex, and a palisade
layer of hyphae is growing upwards into it, also ascogenous hyphae are growing
from the ascogonium toward the palisade layer ; /, the palisade layer can now
be seen not only on the floor but on the sides of the mucilage cavity, and the
hyphae which compose it are being converted into paraphyses ; g, the internal
tissues, by expanding, have now ruptured the cortical sheath which formed the
roof of the mucilage cavity, the hymenium has thus become exposed, and the
ascogenous hyphae have given rise to asci which are pushing upwards among
the paraphyses ; the primary parts of the apothecium have now been com-
pletely formed ; h, the secondary period of development has begun for marginal
growth is now taking place, the marginal hyphao are developing sympodially
giving rise to paraphj'ses above and cortical cells below. Drawni by E. J. H.
Comer and published by him in Trans. Brit. Myc. Soc., Vol. XIV, 1929.

HELIOTROPISM OF ASCI IN DISCOMYCETES 275

grow in all directions so that a ball of interwoven hyphae with the
ascogonium near the centre results (c). Then tissue differentiation
begins {d). The cells of the outer layers enlarge and often become
thick-walled, forming a pseudoparenchymatous cortex, while the
internal hyphae remain thin-walled, and continue to branch, so that
the spaces which would be formed by the expansion of the cortex
are filled. A mucilage cavity then forms in the upper part of the
spherical mass internal to the cortex (e). It originates partly by
the stretching of the internal tissue but mainly by the dissolution
of the internal hyphae. Numerous hyphae grow into the cavity as
a palisade layer which spreads from the floor over the sides to the
roof. Some hyphae are outgrowths from cells lining the cavity, but
others are said to originate from the neighbourhood of the
ascogonium and to grow up with the ascogenous hyphae. The
ascogenous hyphae are produced from the ascogonium after its
envelopment and on reaching the floor of the cavity begin to form
asci. The upgrowth of the palisade hyphae is soon arrested
and they are transformed into paraphyses, which act marks the
beginning of the hymenium (/).

" Subsequently the cortical layer overlying the mucilage cavity
is ruptured by the expanding internal tissue, and about the same
time the first asci are formed {g). The intercalary grow^th of the
hymenium, due to the production of asci and paraphyses, presses
the sides of the apothecium apart, exposing the disc (g), while the
apothecium passes through a characteristic turbinate shape before
becoming lenticular.

" Finally, in stage (h), a marginal growing-point is formed, and
apparently from the hyphae which grew from the sides of the
mucilage cavity and which, on exposure of the disc, form a
sympodium : the outer laterals are converted into cortical hyphae
and the inner ones into paraphyses.

" Evidently primary and secondary parts can be distinguished
in the angiocarpic apothecium. The primary part consists of the
archicarp, the investing hyphae, and the initial part of the
hymenium, and the primary period of development comprises all
stages up to (g) (Fig. 131). The secondary part consists of all
tissues derived from the marginal growing-point, and the secondary

276

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RESEARCHES ON FUNGI

/

HELIOTROPISM OF ASCI IN DISCOMYCETES 277

period of development extends from the initiation of marginal
growth to maturity."

The asci of Ascoholus stercorarius push upwards between the
paraphyses and at first are straight. However, shortly before they
discharge their spores, they protrude considerably beyond the
general level of the hymenium, and their aerial parts bend helio-
tropically toward the source of greatest light. Two such helio-
tropically curved asci are shown in Fig. 132 in which is reproduced
Corner's illustration (arrows added by myself) of a median- vertical
section through the whole of a small fruit-body. 1 As in other

Fig. 132. — Ascobolus stercornriKs, a common copropliilous Discomycete which has
heliotropic asci and which puffs audibly. Median-vertical section of a very
small apothecium. The apothecium is turbinulate in form ; it was angiocarpic
in origin, and tlie primary sheath of cortical cells which overlay a mucilage
cavity and the disc feocame ruptured at e e owing to the expansion of the internal
tissues, and thus the disc was exposed. The apothecium was built up originally
around the archicarp from sympodial clusters of cortical hyphae and paraphyses,
the intercalary parts of which now form the medulla. Details of structure are
shown as follows : the excipuluin, consisting of the cortex n a and the medulla
b b ; c c, the hypothecium (in which the ascogenous hyphae are situated) ; the
hymoiium, consisting of asci and paraphyses, above the hypothecium ; d,
mucilage ; e e, the broken edges of the primary cortical sheath that at first
covered the mucilage cavity and disc ; /, rudimentary paraphyses, evidently
forming part of the sympodial clusters of hyphae from which the apothecium
was constructed ; g, secondary mycelium composed of hyphae which have growii
from the underside of the apothecium as excrescent cortical cells into the sub-
stratum ; /;, the archicarp (scoledte) consisting of a bent chain of cells with
a wide pore in the centre of each septum ; /, the ascogonium, one of the cells of
the archicarp, which gave rise to the ascogenous hyphae ; j, ascogenous
hyphae passing upwards through the hypothecium ; k, hooks and hook-cells
which were formed at the ends of ascogenous hyphae ; /, young asci pushing up
between the paraphyses, each containing a fusion nucleus ; m, an older ascus
containing four nuclei ; ;;, an ascus containing eight young spores ; o, an ascus
containing eight older spores, each surrounded by jelly ; p, an ascus containing
mature or nearly mature spores each of which has a dark-violet cell-wall marked
with interlacing white lines and bears on one side a lenticular mass of jelly ; q
and r, two highly turgid and fully expanded asci, each containing a thin layer
of protoplasm lining the cell-wall, a large central vacuole filled with cell-sap,
and massed at the apex eight ripe spores which are about to be violently dis-
charged ; the asci q and r protrude beyond the layer of mucilage and their
aerial parts are bent heliotropically toward the source of strongest light the
direction of which is indicated by the arrows ; when the operculum of the ascus
q or the ascus r opens, the elastic ascus-wall will contract and drive out through
the operculum not only the eight spores but also a large amount of cell-sap which
will be scattered in the air in the form of a fine spray of spherical droplets;
s, an ascus which has discharged its eight spores and has slirunk to about one-
half of its original volume ; at its apex the hinged operculum can be seen.
Drawn by E. J. H. Corner, originally published by him in Trans. Brit. Myc. Soc,
Vol. XIV, 1929, but now, with his consent, altered slightly, lettered, described,
and reproduced on a larger scale than formerly by A. H. R. Duller. Magnifica-
tion, about 340.

1 E. J. H. Corner, loc. cit., p. 286.

278 RESEARCHES ON FUNGI

Ascoboli, the paraphyses of A. stercorarius are anheliotropic {cf.
Fig. 132).

Our Present Knowledge of Ciliaria scutellata. — This fungus
(Fig. 133), so well-known under its old name Lachnea scutellata, was
transferred to the genus Ciliaria by Boudier,^ in 1885, in his masterly
revision of the classification of the Discomycetes. Ciliaria scutellata
commonly occurs ^ on damp rotten wood in shady places in woods
in the British Islands, Europe, Canada, the United States of
America, Java, Tasmania, and probably many other parts of the
world. I myself find it every autumn in the woods of Manitoba
and of western Ontario.^ Owing to its brilliant red colour and its
dark marginal hairs, it attracted the attention of the early botanical
systematists and its existence is recorded in the works of Ray ^
(1696), Dillenius^ (1718), VaiUant « (1727), and MicheU ' (1729).
Linnaeus ^ described the fungus in the second edition of his Flora
Suecica (1755) and called it Peziza scutellata, under which name it also
appears in his Sjiecies Plantarum ^ (1753). Illustrations of the fruit-
bodies are given in various works on systematic mycology among which
may be mentioned those of Cooke, i" Rehm," Lindau,^^ and Hard.^^

1 E. Boudier, " Nouvelle Classification Naturelle des Discomycetes Charnus,"
Bull. Soc. Myc. France, T. I, 1885, p. 105. Vide also his Histoire et Classification
des Discomycetes d' Europe, Paris, 1907, p. 61.

2 M. C. Cooke, Mycographia seu Iconcs Fimgorum, London, Vol. I. 1879, p. 73.

3 G. R. Bisby and A. H. R. BuUer, " Preliminary List of Manitoba Fungi," Trans.
Brit. Myc. Soc, Vol. VIII, 1922, p. 95.

^ John Ray, Synopsis Methodica Stirpium Britannicarum, ed. II, London, 1696,
p. 29, No. 41.

^ J. J. Dillenius, Catahgus Plantarum sponte circa Gissam nascentium, Franco-
furti, 1718, p. 194.

® S. Vaillant, Botanicon Parisiense, Leide et Amsterdam, 1727, p. 57, No. 8.

' P. A. Micheli, Nora Plantarum Genera, Florentiae, 1729, p. 206, No. 12.

8 C. Linnaeus, Flora Suecica, Stockliolmiae, 1755, p. 458.

^ C. Linnaeus, Species Plantarum, 1753, p. 1181.

10 M. C. Cooke, loc. cit., Plate XXXIV, Fig. 131 (coloured).

11 H. Rchm in Rabenhorst's Kryptogamen-Flora von Deutschland, Oesterreich und
der Schiceiz, Ed. II, Bd. I, Die Pilze, Abt. Ill, Ascomyceten, p. 1034. Figs. 1-4.
Only 1-2 oil drops are shown in each ascospore, instead of a large number as observed
by Boudier and myself.

12 CI. Lindau in Engler und PrantFs Die nat. Pflanzenjamilien, Teil I, Abt. I,
Pezizineae, p. 181, Fig. 147, A and B.

1^ M. E. Hard, The Mushroom, Edible and Otherwise, Columbus, Ohio, U.S.A.,
1908, p. 509, Fig. 433 (a good photograph).

HELIOTROPISM OF ASCI IN DISCOMYCETES 279

The fruit-bodies of Ciliaria scutellata are usually gregarious,
sessile, almost closed and subglobose at first, then expanded and
plane, fixed by a central point, 3-10 mm. varying up to 15 mm. in
diameter, and 1-2 mm. thick. The upper surface of the disc is
deep carmine or almost vermilion but sometimes pallid, while the
lower surface is yellowish-red or brownish. The outer covering of
the fruit-body is furnished with large brown thick-walled septate
hairs (Fig. 134), 300-600 y. long ^ and 15-20 [jl wide, the longest and
last developed ^ ones being at the periphery. At first, when the
fruit-body is small and almost spherical, the marginal hairs are
turned centripetally over the top of the hymenium ; but, later, as

Fig. 133. — Ciliarin scutellata (= Lachnen scutellata). Fruit-bodies
on rotting wood. Part of Fig. 433 in M. E. Hard's The Mushroom,
Edible and Otherwise, published at Columbus, Oliio, U.S.A., 1908.

the fruit-body expands and flattens, they turn outwards centri-
fugally. Thus the mature fruit-body, when seen from above, has
the appearance of a carmine disc fringed with projecting brown-
black hairs. It was this fringe of dark hairs, reminding one of
eye-lashes, that suggested to Quelet the name of the genus, Ciliaria,
to which Boudier has transferred the species under discussion. The
flesh or trama of the fruit-body consists of an upper layer of fine
interwoven hyphae and of a lower layer of pseudoparenchyma.
The hymenium, made up of asci and numerous paraphyses, is
about 0-3 mm. thick. The asci (Fig. 135) are fairly large,

^ J. Lagarde in his " Contribution a I'etude des Discomycetes charnus " {Ann.
Myc, Jahrg. IV, 1906, pp. 207-208), in giving details of the anatomical structure of
Ciliaria scutellata, states that the length of the liairs varies from 150 to 300 (jl and
that those at the margin may attain 700 [x.

2 Vide W. H. Brown, " The Development of the Ascocarp of LachTiea scutellata,''
The Botanical Gazette, Vol. LII, 1911, p. 276.

28o

RESEARCHES ON FUNGI

cylindrical except at the very base, not turning blue with iodine,
271-305 [1 long and 20-22 [j, wide (in the fruit-bodies investigated),
and after explosion shortened to about 265 [j.. The paraphyses
(Fig. 135, d) are simple or branched at the very base, septate,
orange-red, narrowly cylindrical but club-shaped terminally, con-

^^^

^^

Fig. 134. — W. H. Brown's diagram illustrating tiio mode of development of
a fruit-body of CUutria scufelltifa. The penultimate cell of tlie archicarp
has become swollen to form the ascogonium (ascogenous cell) and has
given rise to hyphae which are forming the asci. The vegetative liyphae
at tlie base of the archicarp have grown in length, have branched, and
have produced the paraphyses, the trama, and the outer covering of the
fruit-bod v including the setae.

taining a few granules, and turning green with iodine.^ The spores
(Fig. 135) are colourless, smooth, ovoid-elliptic, furnished within
with numerous oleaginous granules which fill them completely,
20-22 y. long and 11-13 [x wide.

No one has yet grown Ciliaria scuteUata in artificial cultures.
Brefeld ^ tried but did not succeed in germinating the spores.

1 E. Boudier. in his Icoties Mijcologicae (Paris, 1905-1910. T. IV, p. 207), by
inadvertence, states that the paraphyses turn blue with iodine, but he correctly
illustrates them in his Plate CCCVIII as turning green.

2 O. Brefeld, Untersuchungen iibcr Pihc, Heft X, 1891, p. 331.

HELIOTROPISM OF ASCI IN DISCOMYCETES 281

W. H. Brown ^ has given us an interesting account of the develop-
ment of the fruit-body. He discovered that, if fruit- bodies which
are developing on a log of wood are picked off, a new crop of fruit-
bodies soon makes its appearance. Taking advantage of this fact,
he obtained a series of very young fruit-bodies which he was able
to investigate with the help of the microtome. He found that each
fruit-body develops (c/. Fig. 134) from an archicarp,^ the penultimate
cell of which swells up greatly and becomes the ascogonium or
ascogenous cell. This ascogenous cell, which is multinucleate, sends
out ascogenous hyphae which grow upwards, branch and rebranch
and, finally, after hook-formation and conjugate nuclear divisions,
produce the asci. Each ascus contains two nuclei which fuse
together. The fusion nucleus then undergoes the usual sub-
divisions, so that eight nuclei result. The eight nuclei eventually
become enclosed in the eight spores. No antheridium could be
observed, so that there is no evidence that the ascogenous cell
receives any male nuclei. The vegetative hyphae at the base of the
archicarp grow in length, branch freely, and produce the paraphyses,
the trama, and the outer covering of the fruit-body including the
setae. Brown's diagram illustrating the mode of development of
the fruit-body is reproduced in Fig. 134.

The red colouring matter of Ciliaria scutellata, like that of
Pilobolus, the Uredineae, Polystigma rubrum, Nectria cinnabarina,
Peziza aurantia, etc., is held in tiny oil drops and is therefore a
lipochrome.^ The lipochromes are regarded as carotins.^ They are
insoluble in water, but soluble in alcohol, ether, chloroform, etc.
When dry, with concentrated sulphuric acid, they give the typical

^ W. H. Brown, Joe. cit., pp. 275-305, with 51 Figs, in the text and one Plate.

^ M. Woronin was the first to see and illustrate the archicarp of Ciliaria scutellata.
He said that it consisted of a chain of 2-5 cells which soon became surrounded by
vegetative hyphae which obscured its further development. Vide his " Die
Entwicklungsgeschichte des Ascoholus pulcherrimus und einiger Pezizen " in
de Bary and Woronin 's Beitnige zur Morphologie und Physiologie der Pilze, No. II,
1866, pp. 5-6, Plate II, Figs. 1-3.

^ VV. Zopf, '" tjber das mikrochemische Verhalten von Fettfarbstoffen usw.,"
Zeitschr.f. wiss. Mikroscopie, Bd. VI, 1889, p. 172; also Die Pilze, Breslau, 1890,
pp. 146-147.

* Cf. J. Zellner, ('hfrnip der Hohfrni Pilze. Leipzig, 1907, pp. 12, 139-142 ; and
Hans Molisch, Mikrochenric dvr Pflanzen, 1923, p. 221.

282 RESEARCHES ON FUNGI

carotin reaction, i.e. they turn blue ; and, with iodine dissolved in
potassium iodide, they turn blue-green. ^ The pigmented oil-drops
of C. scutellata are contained in large numbers in the protoplasm of
the cells making up the paraphyses and subhymenium. The pig-
ment was obtained by Zopf ^ by extracting with alcohol and forming
an ester with caustic soda. The ester, when treated with petrol-
ether, yielded a yellow substance that, after being dried, turned
blue when moistened with nitric acid. When examined spectro-
scopically by Bachmann,^ the pigment gave two absorption bands
like those of the lipochrome of the Uredineae.

The Heliotropism of the Asci of Ciliaria scutellata. — Since the
disc of Ciliaria scutellata is flat or almost so, it is not difficult to
make heliotropic experiments with its asci. All that is required is
to let the fruit-body develop on the top of a board lying on the
ground in unilateral light and then, by microscopical investigation,
to find out whether or not the tops of the ripe asci have become
curved toward the source of illumination.

The conditions for such a heliotropic experiment as that just
suggested were provided by one of the ice-houses of the Arctic Ice
Company of Winnipeg. This Company, not far from Winnipeg on
the banks of the Red River, has a series of large wooden ice-houses
each of which is 100 feet long, 30 feet wide, and about 50 feet high,
windowless, and provided at one end with a large double door.
The floors are covered with sawdust including bits of planks, etc.,
derived from a saw-mill. The ice-houses are filled during the
winter with great blocks of ice taken from the Red River, and are
gradually emptied in the spring and summer. After the ice has
been removed from an ice-house, the sawdust and pieces of wood
on the floor are left undisturbed for some months, during which time
lignicolous fungi develop upon them in abundance. As after the
removal of the ice from an ice-house the double door is left more
or less open, the fungi which develop on the floor are subjected to
unilateral daylight. Among the flat Discomycetes found growing
in the ice-houses were : Ciliaria scutellata, Melastiza miniata, and
Cheilymenia vinacea.

1 J. Zellner, loc. ciL, p. 139. 2 w. Zopf, Die Pilze, Breslau, 1890, p. 146.

' E. Bachmann, cited from Zopf, loc. cit.

HELIOTROPISM OF ASCI IN DISCOMYCETES 283

Several fruit-bodies of Ciliaria scutellata which were expanded
horizontally on the top of boards in one of the ice-houses were
chosen for investigation. First, the direction in which the light
from the door of the ice-house had illuminated them was clearly
marked upon their upper surfaces, and then they were removed to
the laboratory and studied by means of transverse hand-sections
taken vertically downwards in a direction parallel to the direction
of the rays of light which had illuminated them (c/. Fig. 135). The
sections, after being mounted in water, were still alive.

On observing the sections it was found that, in every fruit-body,
the ripe asci all across the discs were bent at their free ends in the
direction of what had been the source of light. It was thus proved
that the asci of Ciliaria scutellata are heliotropic. Some of the
hehotropically curved asci are shown in Fig. 135. Each of them is
bent terminally through an angle of 45°.

A mature fruit-body of Ciliaria scutellata, which was about
1-25 cm. in diameter, was spread out as a flat disc on a board on
the floor of one of the ice-houses over 50 feet away from the doorway
through which came the light which had illuminated it unilaterally.
I touched the fruit-body and had the satisfaction of seeing that, as
it puffed, it shot away its spores in the direction of the source of
illumination. The direction of puffing could only have been due to
the fact that the asci were positively heliotropic and, during their
development, had bent their free ends toward the light.

The paraphyses of Ciliaria scutellata, as in the Discomycetes
generally, come to maturity before the asci, and the asci push up
between them (c/. Fig. 135). At first, each ascus is quite straight
and the young spores are relatively small with the uppermost one
at some distance from the end of the ascus. As a young ascus
continues its development, the spores grow in size and move
upwards so that the top one of the chain of eight becomes appressed
to the operculum, while the ascus as a whole, through increase in
length, comes to push its apex about 30 [j, above the general level
of the paraphyses. It is during the emergence of the end of the
ascus into the free air that the ascus responds positively to the
hehotropic stimulus of light, and the actual curvature is confined to
the last sixth (40-50 y.) of the ascus length (Fig. 135, h-k).

284 RESEARCHES ON FUNGI

When an ascus of Ciliaria scutellata explodes, it shortens by

Fig. 135. — Ciliaria acutellata (= Lachnea scutellata). Vertical section througli tlie
subliymeuium a and tlie hymeniiini 6 of a fruit-body wliich grew in unilateral
liglit, to illustrate tlie lieliotropism of tlie asci. The arrows indicate the direction
of the incident i-ays of light, and the asci at their extreme free ends have bent
toward the source of the light. In the liymenium the following structures may
be distinguished : c c, young asci pushing upwards among the pai'apliyses d d ;
e e, older asci containing spores ; /, a still older ascus with more mature sjjores ;
the asci e, e, and/ all have a straight axis ; g, an ascus witli mature spores just
pushing up above the paraphyses, its end is becoming heliotropically curved ;
h, i, j, and k\ four ripe asci with their free ends heliotropically curved toward
the source of light, their spores containing oil-drops ; I I, two asci whicli have
just discliarged their spores and liave contracted in length, so tliat their ends
are below the ends of the paraphyses ; in contracting, these two asci, I /, have
straiglitened somewhat so that their openings (each with an operculum laterally
attached) appear to be asynimetrically situated on the side of the end of the
ascus nearest to the source of light. Magnification, 294.

about 30-40 [i, and thus its apex becomes drawn down to just below
the level of the paraphyses. During the contraction in length, the

HELIOTROPISM OF ASCI IN DISCOMYCETES 285

end of the ascus becomes straighter, and then the opercuhim can
be seen occupying a more or less obUque position at the end of the
ascus (Fig. 135, / /). Investigation of fruit-bodies of C. scuieUata
grown under various conditions of hght seems to indicate that the
opercuhim really originates symmetrically at the end of the ascus,
but that, owing to heliotropic curvature of the end of the ascus,
the operculum becomes pushed to one side — the side which is
nearest to the source of light. Thus the more or less oblique
position of the mouth of the ascus of Ciliaria scutellafa and of other
similar Discomycetes is not a purely " morphological character "
as Seaver ^ thought, but is a physiological character caused by the
response of the ascus to the heliotropic stimulus of light.

The Heliotropism of the Asci of Melastiza miniata and Cheily-
menia vinacea. — Fruit-bodies of these species came up in the
ice-house on pieces of planks and on sawdust along with those of
Ciliaria scutellata which they resemble in their flattened discoid form. 2

The fruit-body of Melastiza miniata (Fuck.) Boud.=^ is an orange-
red disc which varies in large specimens from 1 to 2 cm. in diameter.
It is covered on its outer side by short blunt yellowish-brown hairs.
Its paraphyses are club-shaped at their ends. With iodine the
paraphyses turn green ^ but the asci do not turn blue. The spores
are oval-elhptic, colourless, verrucose, and often blunt at the ends.

The fruit-body of Cheilymenia vinacea (Rabenh.) Bond, is a
yellow disc, 0- 5-1 • 0 cm. in diameter (Fig. 136, A and C). It bears
on its outer side numerous long pointed septate hairs or setae (B).
Its paraphyses are cylindrical and not swollen at their free ends (F).
With iodine the asci do not turn blue. The spores are elliptic-
oblong, colourless, smooth, devoid of oil-drops, and about 20 [x long.^

1 F. J. Seavor, vide supra, pp. 255-2.57.

2 The identification of Melastiza miniata and Cheilymenia vinacea wa.s made
with the help of the excellent descriptions and illustrations given by Boudier in
his Icones Mycologicae.

3 According to Seaver {The North American Cup-fmigi, New York, 1928, p. 103),
this is a synonym for Melastiza Chateri (W. G. Smith) Boud.

4 Boudier {Icones Mycologicae, T. IV. p. 218), by inadvertence, states that the
paraphyses do not turn green with iodine, but he correctly illustrates them as
turning green in his Plate C'CCLXXXVI.

•'' The asci of Cheilymenia vinacea are described by Boudier as 270 \x long. In my
specimens they were only 230 \i long.

286

RESEARCHES ON FUNGI

/ / /

Fig

r)

Just as with the fruit-bodies of Ciliaria scutellata, the fruit-bodies
of Melastiza miniafa and Cheilymenia vinacea were marked before
being gathered in the ice-house and then were removed to the
laboratory and sectioned by hand. The investigation of the

hymenia revealed that in both species the asci,
all across each disc, had become slightly curved
at their free ends toward the door of the ice-
house, i.e. toward the source of hght, and were
therefore positively heUotropic (Fig. 136, C, D,
and E ; the arrows in C indicate the directions
in which the asci pointed).

The heliotropic curvature of the asci of
Melastiza miniafa and Cheilymenia vinacea in
unilateral light is confined, as in Ciliaria scutel-
lata, to the free ends of the asci and, in the ice-
house, it resulted in the opercula being pushed
over toward the light, so that the spores were
probably shot out from each ascus obliquely
upwards at an angle of 45° to the vertical, the
inclination being toward the source of hght.
Here, as in Ciliaria scutellata, it was observed
that, as the asci discharge, they straighten them-
selves out somewhat so that the curvature of
their ends almost disappears and the operculum
in an exploded ascus comes to be obliquely set
at the end of the ascus but always on the side
from which the light has come (Fig. 136, cf. D
and E). The oblique position of the operculum in
an exploded ascus in such a fungus as Cheilymenia
vinacea is, as in Ciliaria scutellata, not a purely
"morphological character" but a physiological one.
Aleuria vesiculosa and its Identification. — Aleuria vesiculosa is
one of the largest and best known of the Pezizaceae, and from its
vesicular ajjpearance, it has been called the Bladdery Peziza ^ and

13(5. — Cheily-
rnenia vinacea.
A and C, a
fruit-body. B,
a ni a r g i n a 1
hair. DandE,
heliotropically
curved asci. F,
a paraphysis.
A and C, nat.
size ; B x 150;
D-F X 300.

^ M. E. Hard, The Mushroom, Edible and Otherwise, Columbus, Ohio, U.S.A.,
1908, p. 508.

HELIOTROPISM OF ASCI IN DISCOMYCETES 287

also the Bladder Elf-cup} It commonly occurs on heaps of horse
dung and on manured soil in Europe and North America.

The fruit-bodies of Aleuria vesiculosa are often clustered so that
they more or less distort one another by mutual pressure (Fig. 137)
but, not infrequently, they occur as isolated individuals. A single
fruit-body varies in diameter from 3 to 8 cm. At first, it is globose
and almost closed ; but, later, it expands to form a more or less
hemispherical cup which is brittle, somewhat translucent and, at
the base, about 3 mm. thick. The margin of the cup usually
becomes notched and may either turn outwards to a greater or less
degree or remain incurved. Below, where it enters the substratum,
the flesh of the cup is contracted centrallj^ to form a short stem-hke
base or stipe which breaks up in the substratum into strands of
myceUum (Fig. 138). The inner hymenial surface of the cup is
pale brown or fawn-coloured, while the outer lower surface is
brownish and coarsely granular or furfuraceous from the presence
of minute irregular warts. The flesh or trama is parenchymatous,
the central cells being large and watery. Sometimes the trama
sphts so that a cavernous air-space is formed between the hymenium
and the base of the cup. The hymenium is about 0* 36 mm. thick.
The paraphyses are unbranched and septate, the terminal cell being
slightly club-shaped and coloured yellow with oil-drops and the
shaft-cells at first cylindrical but becoming swollen at their sides
as the fruit-body becomes older. The asci are fairly large, about
360 [x long and 20 [x wide, sUghtly attenuated dowTiwards, turning
blue with iodine, those at the base of the cup straight and those at
the sides heUotropically curved toward the mouth of the cup. The
spores are elliptic, colourless, smooth, without internal oil-globules,
bearing on one side a little lenticular mass of colourless jelly which
swells up after discharge in water, about 20-24 [i long and 11-13 [j,
wide.

The fruit-bodies of Aleuria vesiculosa used in my investigations
were obtained in part from manured ground at the Manitoba
Agricultural College and in part from laboratory cultures. To
procure hving fruit-bodies during the winter months at Winnipeg

^ E. W. Swanton, Fungi and How to Know Them, London, 1909, p. 182.

288

RESEARCHES ON FUNGI

my procedure was as follows. Frozen horse dung from a street or
fresh horse dung from a stable (the dung-balls unbroken) was spread
in a layer about 3 inches thick on the zinc -lined floor of a large

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HELIOTROPISM OF ASCI IN DISCOMYCETES 289

damp-chamber (3'5 X 2 x 2*25 feet) kept on a table in the
laboratory a few feet away from a window. The dung was watered
from time to time to keep it moist. After about a month, on some
of the dung-balls, fruit-bodies of Aleuria vesiculosa began to appear.
Sometimes they were clustered, at other times sohtary. They
were never very large and, owing to the conditions under which
they were grown (excessive moisture and relatively feeble light).

Fig. 138. — Aleuria vesiculosa. Vertical section tlirough a
very large fruit-body. Its cupulate form was developed
by marginal growth. Tlie liymenium a lines the inside
of the fruit-body. The asci in the upper regions of the
fruit-body at b and c would be at a disadvantage in dis-
charging their spores were they not heliotropic and
therefore directed toward the cup's mouth. Outline of
the Jruit-body copied by the author from Boudier's
Icones Mycologicae, PI. 257, c. Natural size.

they tended to be abnormal : firstly, in sometimes having a well-
pronounced stipe and, secondly, in becoming more expanded than
usual (Fig. 167. p. 333). The expansion was due to the paraphyses
swelling laterally prior to the discharge of the spores from the
asci.

In Volume I of these Researches I gave an account of the pro-
duction and hberation of the spores of the fruit-bodies just described
but, unfortunately, misnamed the species Peziza repanda. From
a comparison of my fruit-bodies grown in cultures with the fruit-
bodies of Aleuria vesiculosa growing in the open, I am now

VOL. vr.

290 RESEARCHES ON FUNGI

confident that my culture fruit-bodies are only a form of Aleuria
vesiculosa.^

Results of a Previous Investigation on Aleuria vesiculosa.— The
following is a summary of the results of my investigation on the
production and hberation of spores in Aleuria vesiculosa (erroneously
identified as Peziza repanda) recorded in 1909 in Volume I of these
Researches ^ :

" The spores of Aleuria vesiculosa are shot up into the air to a
height of 2-3 cm. The eight spores from an ascus separate from
one another almost immediately after leaving the ascus mouth, and
are then carried off by the wind. The fact that the ascus jet breaks
up on leaving the ascus was observed by means of the beam-of-light
method.

^ In 1910 I sent some of my culture fruit-bodies to Dr. E. J. Durand, who wrote
to me as foUows regarding them. " The plant does not seem to me to be P. repanda
but to belong more properly in the vicinity of P. vesiculosa as you suggest. It has
seemed to me for some time that the latter species is very variable or that several
species are confused under this name, which can ultimately be separated. Typical
vesiculosa, as I imderstand it, is usually pale in colour, sessile, semitransparent, and
the opening contracted and small. This evidently is not your plant. The so-called
variety cerea comes nearer to it ; but, still nearer, it seems to me is the plant described
by Vuillemin in the Proc. of the French Ass. for the Adv. of Science for 1886 under
the name Aleuria Asterigma, p. 491, pi. 10. This you will notice is stipitate and
repand, and has an Aspergillus-like conidial stage. Rehm {Discomycetes, p. 1018)
mentions Oedocephulum fimetarium as the conidial stage of P. vesiculosa, and this is
very similar to and doubtfully distinct from the conidial stage mentioned by
Vuillemin. To be sure, the conidia of the latter are slightly smaller than in
Oe. fimetarium and the germination of the spores is slightly dift'erent. The last
feature may well be due to difference in culture medium. It seems to me we have
here three very closely related forms which may be regarded as forms of one variable
species, or which cultures may finally show to be distinct in the conidial condition.
Your plant I think belongs to the form now known as Aleuria Asterigma (or Peziza
Asterigma), but cultures will be necessary to determine the nature of the conidial
stage."

In making the remarks just quoted Durand took into account not only the
fruit-bodies sent to him but also my drawings, including the conidial stage, shown
in Vol. I of these Researches, Figs. 77, 78, and 79 (pp. 235, 236, and 241). Boudier
in his Icones Mycologicae illustrates Aleuria Asterigma and shows every fruit-body
with a well-developed stipe. My culture fruit-bodies differ from those shown in
Boudier's illustrations in that while some have well-developed stipes others are
quite sessile like typical A. vesiculosa.

2 These Researches, Vol. I, 1909, pp. 233-250, Figs. 77-79 ; summary on p. 268.
In quoting from the summary, as above, I have substituted the correct name
Aleuria vesiculosa for the erroneous one Peziza repanda.

HELIOTROPISM OF ASCI IN DISCOMYCETES 291

" Puffing is probably not due (as de Bary supposed) to the mere
withdrawal of water from the asci. Solutions of grape sugar,
glycerine, sodium chloride, and potassium nitrate, which merely
withdraw water from the ripe asci of Aleuria vesiculosa, do not cause
their explosion. On the other hand, solutions of many poisonous
substances, e.g. iodine, mercuric chloride, silver nitrate, acetic acid,
and alcohol, give rise to marked puffing. Two alkahes — sodium
hydroxide and sodium carbonate — kill the asci without causing
them to discharge their contents. It seems probable that puffing
is caused by a stimulus given to the protoplasm in contact with the
ascus lid.^

" The physics of the ascus jet in Aleuria vesiculosa has been
discussed. It seems probable that the separation of the eight
spores of an ascus during their upward flight into the air is due
to considerable differences in the initial velocities given to the
individual spores upon their discharge. Surface tension probably
plays but a minor part in breaking up the ascus jet. When an ascus
is regarded as an apparatus for squirting out a jet in such a manner
that the jet immediately breaks up into eight parts so that each
part contains a spore, its structure becomes more inteUigible.

" The eight spores in an ascus of Aleuria vesiculosa are loosely
attached together, and the row of spores is anchored to the ascus
hd by a special protoplasmic bridle. De Bary's hypothesis of
currents is unnecessary in accounting for the means by which the
spores are caused to take up their characteristic positions in the
ascus."

Whilst making the investigation just summarised, I observed
that some of the asci of the fruit-bodies of Aleuria vesiculosa were
curved whilst some were straight ; but I did not then know the
cause of the difference and, in my illustrations (Vol. I, Fig. 79,
p. 241), represented only straight asci, such as are actually found
at the centre of the base of a well-formed fruit-body. The curvature
of the curved asci, as we shall see in the next Section, is not a mere
accident attributable to the kinetics of sUcing the living fruit-bodies
but is due to the developing asci bending heUotropically.

^ For a discussion of the cause of the bursting of asci when a fruit-body puffs
under normal conditions vide supra, pp. 230-232.

292

RESEARCHES ON FUNGI

The Heliotropism of the Asci and the Discharge of the Spores
in Aleuria vesiculosa. — When a fruit-body of Aleuria vesiculosa is
more or less hemispherical in shape, hke those shown in Fig. 137,
the hymenium is illuminated by daylight which comes to it from
above ; so that, in a fruit-body of the shape postulated, if the asci

Fig. 139. — Aleuria vesiculosa [— Peziza vesiculosa). Semi -diagrammatic median
vertical section through a small, fully expanded fruit-body vvliich grew in tlie
open on dunged soil at Winnipeg, Canada. To show the lieliotropic curvatures
of the ends of tlie asci and the general directions in which the asci would dis-
charge their spores : a, dunged soil ; b, tlie receptacle or fruit-body flesh ;
c. the liymenium. Tlie asci are everywhere bent upwards toward the source
of the strongest daylight, and the arrows indicate the direction in which the
spores would be discharged. Magnification, (i.

are heliotropic, they should all point upwards toward the fruit-body's
mouth. Whether or not the asci of a more or less hemispherical
fruit-body do actually point toward the fruit-body's mouth can be
determined : (1) by examining the hymenium in radial-longitudinal
sections ; (2) by examining the hymenium in surface view ; and
(3) by observing the direction of the discharge of the spores in the
air with the naked eye or in water with the help of the microscope.

HELIOTROPISM OF ASCI IN DISCOMYCETES 293

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RESEARCHES ON FUNGI

Some more or less hemispherical fruit-bodies of Aleuria vesiculosa
were obtained from an open garden at the Manitoba Agricultural
College in October, 1925, and they were examined in the manner
just indicated. In each fruit-body, as shown in Figs. 139 and 140,
it was found that the asci at the base were straight and looked
directly upwards and that the asci on the sides were curved in such

Fig. 141. — Aleuria vesiculosa. Semi-diagrammatic surface view of tlie hymenium
half-way up the side of a cupulate fruit-body (c/. Figs. 138 and 139). Asci
a and parapliyses b are turned upwards heliotropically so as to be directed
toward tlie source of the strongest liglit and, therefore, toward tlie fruit-body's
moutli. Magnification, 293.

a way that their apices looked toward the fruit-body's mouth.
Every ascus which, owing to its position of origin, had developed in
unilateral light had, during its development, bent its free end toward
the fruit-body's mouth, i.e. toward the source of light.

Surface views of the hymenium on the sides of more or less
hemispherical fruit-bodies have the appearance represented semi-
diagrammatically in Fig. 141, from which one may conclude once
more that all the asci point in the same general direction, namely,
toward the fruit-body's mouth.

Radial-longitudinal sections from the sides of a more or less

HELIOTROPISM OF ASCI IN DISCOMYCETES 295

hemispherical fruit-body {cf. Fig. 140, A) were mounted in water
and then a drop of iodine was run under the cover-glass so that it
came into contact with the outer surface of the hymenium. The
wall of the free end of each mature and projecting ascus turned
blue as it absorbed the iodine, and then the ascus suddenly shot
out its eight spores into the surrounding fluid. All the asci in
sections of one fruit-body discharged their spores within a few
seconds, so that the iodine caused the phenomenon of puffing to
take place in a watery medium. Whilst the discharge of the spores
was taking place, it was easy to see that each ascus shot away its
spores in the direction in which it was pointing, i.e. at an angle of
about 45° to the outer surface of the hymenium. This direction of
discharge, had the asci been left undisturbed in their fruit-body
under aerial conditions, would have enabled the asci to shoot their
spores upwards and through the fruit-body's mouth.

If a piece of the wall is quickly taken from the side of a mature
fruit-body of Aleuria vesiculosa which has been enclosed for some
time in a glass case, and is held horizontally in the air until it pufEs,
since the asci are inclined in the direction of the rim, the spores
should be discharged into the air in the general direction of the
rim and the cloud of spores should be seen thus travelling with the
naked eye. Unfortunately, when I wished to make this experiment
with Aleuria vesiculosa, no more suitable fruit-bodies of that species
were available ; but the proposed experiment came ofE quite success-
fully with the very similar fruit-bodies of Galactinia badia (Fig. 149,
p. 308) : the spores were shot toward the rim of the piece of fruit-
body in a cloud at an angle of about 45° with the outer horizontally-
placed surface of the hymenium.

A fruit-body which developed in the large damp-chamber in the
laboratory was abnormally wrinkled and flattened out in the manner
shown in the transverse section in Fig. 142, A ; and it happened to
be so arranged that it faced the incident light. I very carefully
examined the central convex ridge both in radial-longitudinal and
m surface sections, and I found that the asci at the top of the ridge
were straight and faced the light while those on the sides were
curved upwards so that they also faced the light, i.e. that all the
asci on the convex central ridge were pointing toward the light

296

RESEARCHES ON FUNGI

i 1 1 1

(Fig. 142, B). Had the hymenium of the ridge been bent concavely
downwards — as it is in normal fruit-bodies — instead of convexly
upwards, the asci would have looked toward the light in the manner
shown in Figs. 139 and 140 ; but there is this difference between
the arrangement of the asci in the concave and the convex hymenium :
in the concave hymenium (Fig. 140) the asci are turned away from

the centre of the hymenium, whereas in
the convex hymenium (Fig. 142) they are
turned toward the centre of the hymenium.
The arrangement of the asci on the central
convex ridge of our abnormally shaped
fruit-body allows us to draw the conclusion
that the asci in a normal, more or less hemi-
spherical fruit-body do not turn away from
the centre of the hymenium because they
are influenced by the organisation of the
fruit-body as a whole but because they are
stimulated by light which causes them to
curve heliotropically.

Sufficient evidence has now been brought
forward to justify the conclusion that the
asci of Aleuria vesiculosa are positively
heliotropic.

The relations of the heliotropic asci with
the paraphyses will now be discussed. The
asci of Aleuria vesiculosa, when ripe, pro-
trude beyond the paraphyses for a distance
of not more than 30 [x (Fig. 140). Now
the heliotropic curvature of an ascus on the side of a hemispherical
fruit-body of A. vesiculosa is not confined as in Ciliaria scutellata,
Melastiza miniata, and Cheilymenia vinacea to the very end of
the ascus — the part that j^rotrudes beyond the paraphyses — but
begins about the middle of the ascus, i.e. deep down in the
hymenium, and includes the whole of the spore- bearing portion
(Fig. 140). It may therefore be asked : how comes it that
the asci, notwithstanding that they are hemmed in by para-
physes, are able to bend at so great a depth in the hyme-

FiG. 142. — Aleuria vesi-
culosa. A, vertical
section of irregular
fruit-body ; arrows
indicate general
direction of light. B,
diagrammatic repre-
sentation of the
central ridge of A ;
the asci are heliotrop-
ically directed toward
the light. A, 1-3
natiH'alsize ; B,mucli
enlarged.

HELIOTROPISM OF ASCI IN DISCOMYCETES 297

nium ? The answer to this question is provided by a study of the
paraphyses.

As in other Discomycetes, the paraphyses of Aleuria vesiculosa

^;§|

1- • rv>( Y/v,-J V^'^

V

Fig. 143. — Diagram of the developmeut of a gymnocarjiic apothecium, e.g. that
of Ascobolu.s niagnificus or Pyroneina confluen.<i. Tlie hyphae are repre-
sented by short hues the direction of wliich indicates the course of the main
hyphae in the different tissues. The ascogenous hypliae are represented by
short thick hnes diverging from the ascogonium which is drawn as a circle
near the base of the apothecium solely for reference ; actually it is obliter-
ated by the growth of the surrounding tissue at an early stage in develop-
ment. Asci are drawn in successive stages at the margin of the hymenium
in e and/ to indicate the growth of tlie ascogenous hypliae ; but no attempt
has been made to show similarly their intercalary growth. The cortical
parenchyma is shown by means of thick well -spaced lines without special
direction except at the margin, for the palisade arrangement is commonly
lost in the mature tissue. Hyphae wliich grow from the underside of the
apothecium as excrescent cells into the substratum and which constitute
a secondary mycelium are shown by means of a few longer lines. « and b,
hyphae growing upwards and enveloping the ascogonium ; these investing
hyphae do not form a closed sheath as they do in an angiocarpic apothecium
(cf. Fig. 131) ; they continue to grow upwards as a palisade layer which
becomes better defined as new elements are added from below, as in stages
c and d ; tho- thickness of the apothecium depends primarily upon the
extent of this ujigrowth and, as the upgrowth ceases, first in the centre the
distal parts of the hyjihae mature into paraphyses. Thus the formation cf
the hymenium is started and continues centrifugally until maturity. About
the same time the cells in the lower part of the primordiinn begin to enlarge ;
the process extends outwards and upwards to the margin, forming a pseudo-
parenchymatous cortex. The ascogenous hyphae arise at about stage b and
they grow upwards with the sterile hyphae ; the formation of asci begins
shortly after the appearance of the paraphyses and is shown in e and/; in
/ marginal growth is beginning. Drawn by E. J. H. Corner {Trans. Brit.
Myc. Soc, Vol. XIV, 1929).

attain maturity before the asci {cf. Figs. 143 and 144). The para-
physes soon grow to their maximum length and then the asci push
up between them. Observations on fruit-bodies grown in the
laboratory have taught me that the parajihyses are j^ositively helio-
tropic. As shown in Fig. 145, which represents a section through

298

RESEARCHES ON FUNGI

a young hymenium taken from the side of a fruit-body, the outer
ends of the paraphyses are all turned toward the light. This
heliotropic bending of the paraphyses facilitates the heliotropic
bending of the asci ; and it may therefore be said that in A. vesiculosa
the paraphyses prepare a way for the asci which come after them
and eventually push out beyond them. At first the young asci are
straight, as shown in Fig. 145 ; but, as soon as they become about
half-grown in length, they respond to the stimulus of light and, in

Fig. 144. — Diagram of the construction of a sessile apothecium of one of the
Discomycetes. Marginal growth is taking place. The marginal hj'phae
all around the periphery of the disc are developing sympodially, giving
rise to paraphyses above and cortical cells below. It will be seen that,
at the margin of the hymenium, the paraphy.ses are formed first and that
afterwards asci grow up between tliem. Drawn by E. J. H. Corner
(Trans. Brit. Myc. Soc, Vol. XIV, 1929).

so doing, make their way between the curved paraphyses without
disarranging them (c/. Fig. 140, p. 293).

The paraphyses, at first, are only about 3 (i. in diameter and are
quite cylindrical (Fig. 145) ; but, as the fruit-body ripens, they
undergo a considerable change in form. By the time the first asci
are ripening or are ready for spore-discharge, their terminal cell
has become somewhat clavate and their shaft-cells have increased
considerably in diameter (cf. Fig. 140, p. 293). Finally, by the
time the fruit-body has become fully expanded and all the asci
have ripened and some or many have burst, their terminal cell may
have become markedly clavate and their shaft-cells have become

HELIOTROPISM OF ASCI IN DISCOMYCETES 299

bulged out laterally so as to attain diameters often of 12-16 (jl
(Vol. I, Fig. 79, D, p. 241). The lateral expansion of the shaft-cells
of the paraphyses under moist conditions of development is one of
the factors which cause a fruit-body to open out hemispherically

Fig. 145. — Aleuria vesiculosa. Heliotropism of parapliyses. Median-vertical sec-
tion of the side of a young fruit-body : a, cortex ; b, hypotheciuin ; c, hymenium
made up of long slender paraphyses and of young asci pushing outwards and
upwards between the paraphy.ses. The paraphyses, which developed before
the asci, have become heliotropically turned toward the source of light and
therefore upwards as indicated by the arrows. The asci, which are not yet
half -grown, are straight and have not yet begun to bend toward tlie source of
light. The heliotropic curvatures which the asci will make will coincide in
direction with those already made by the paraphyses. Magnification, 293.

or, in the laboratory, to become flattened and even recurved over
the substratum. The asci do not all begin their development at
the same time nor do they all attain maturity at the same time,
but some have the start of others. In the laboratory, and doubtless
also under natural conditions, the fruit-body may discharge spores
several times in succession by puffing. When the first set of ripe
asci has discharged its spores, the paraphyses swell up laterally and

300 RESEARCHES ON FUNGI

fill up the gaps in the hymenium which the contraction and collapse
of the asci have made and thus they assist in maintaining the
mechanical stability of the hymenium as a whole.

The paraphyses of Aleuria vesiculosa and of the Discomycetes in
general function : (1) by forming the framework of the hymenium
in the young apothecium and thus preparing a place for the asci ;
(2) by protecting the developing asci against mechanical injuries and
loss of moisture ; and (3) by supporting the mature asci in fixed
positions whilst the spores are being discharged.

In the Discomycetes in general, the paraphyses, during the early
stages of their development, grow straight outwards from the
hypothecium (subhymenium) and, when fully grown, they are
either straight, e.g. in Ascobolus stercorarius (Fig. 132, p. 276) and
Ciliaria scutellata (Fig. 135, p. 284), or are straight below and
heliotropically curved at their free ends, e.g. Aleuria vesiculosa
(Fig. 140, p. 293). Moreover, when fully grown, they are, as a rule,
simple and unbranched or, if branched, the branches are bent
forwards so that their long axes are parallel with those of the
parent hyphae (Fig. 119, d, p. 245). Furthermore, as a rule, the
paraphyses in a hymenium do not anastomose with one another.^
The general straightness, the simplicity of structure, and the
separateness of individual paraphyses facilitate mechanically the
outward growth of the asci and the taking up by the asci of positions
that are advantageous for spore-discharge. The slenderness of
paraphyses permits of the paraphyses fitting into and filling up the
spaces between the relatively very thick asci, and the club-shaped
swellings so characteristic of the apical cells of paraphyses serve to close
up the hymenium on its exterior and thus to make it more compact
and better adapted for the protection and support of the asci. In
some Discomycetes, e.g. Ascobolus magnificus (Fig. 130, p. 272),
A. stercorarius (Fig. 132, p. 276), and Rhizina inflata, the outer wall
of the end of each paraphysis becomes mucilaginous and the mucilage
so produced assists in closing up the exterior of the hymenium.

^ To this rule I know of only one exception, Sarcoscypha proiracta. In this
Discomycete the upper part of each paraphysis is much branched and the branches
are packed closely together. I have observed anastomoses between some of the
branches {vide supra, p. 244).

HELIOTROPISM OF ASCI IN DISCOMYCETES 301

In the Discomycetes the asci and usually also the ascospores ^
are colourless, and the coloration exhibited by the hymenium,
e.g. scarlet in Sarcoscypha coccinea, S. protracta, and Ciliaria scutellata,
orange in Peziza aurantia, brown in Aleuria vesiculosa and Galactinia
badia, and yellow in Cheilymenia vinacea, is due to pigments con-
tained within the paraphyses. These pigments may be nothing but
by-products of metabolism. On the other hand, there is the possi-
bility that they may have some significance for the production and
liberation of the spores. It is difficult to avoid the supposition that,
in species where the fruit-bodies are exposed to the sun, a pigment,
by absorbing the sun's rays, must be a factor in raising the tempera-
ture of the hymenium and, therefore, indirectly, a factor in hasten-
ing ascus-development and spore-discharge. Falck has actually
observed that, when quiescent fruit-bodies of Morchella esculenta
which contain a brown pigment are exposed to direct sunlight,
not only is the temperature of the hymenium raised but spore-
discharge is initiated. 2

An ascus, like most hyphae with a free end, increases in length
by apical growth. It therefore seems probable that the part of the
ascus which is sensitive to the heliotropic stimulus of light is its
apex. It may well be that in every ascus the operculum originates
in a radially symmetrical position at the end of the ascus and that
the ascus attains heliotropic equilibrium only when the protoplasm
underlying the operculum is symmetrically lighted. This theory of
heliotropism can be extended to all the Discomycetes with helio-
tropic asci. It has the advantage of simplicity and is in accordance
with the modern view of the nature of heliotropic reactions held by
Blaauw and others. It accounts for the fact that in all Discomycetes
with heliotropic asci the opercula (or the equivalent in the in-
operculate species) at the end of the heliotropic reaction do actually
face the strongest rays of light.

The advantage to the fruit-body as a whole in the opercula facing

1 The Ascoboli are exceptional in having ascospores with pigmented walls. The
colour of the disc of Ascobolus stercorarius is somewhat greenish owing to the yellow
colour of the mucilage (derived from the paraphyses) combining with the violet
colour of the spores. The Bulgariae, e.g. the well-known Bulgaria inquinans, have
brown spores.

2 Vide infra, p. 321.

302 RESEARCHES ON FUNGI

the light Ues of course in this : that it enables the asci to discharge
their spores in the direction of the strongest incident rays of light,
i.e. in the direction most free from obstacles. In the more or less
hemispherical fruit-bodies of Discomycetes like Aleuria vesiculosa,
the direction is toward the mouth of the fruit-body.

The chain of eight spores at the end of an ascus of Aleuria vesi-
culosa, as described in Volume I, is held in position by a protoplasmic
bridle. The terminal spore in the chain in a hehotropically curved
ascus usually has a slope counter to that of the curvature of the
ascus, as shown in Fig. 140 (p. 293), while the other spores of the
chain are not arranged so regularly. All the eight spores are held
together by a string of cytoplasm. The gelatinous meniscus on one
side of each spore (Fig. 140) swells up when the spore is shot into
water (Vol. I, Fig. 79, H, p. 241) and doubtless, like the similar
meniscus on the side of the spores of Ascoholus stercorarius and of
Coprinus sterquilinus (Vol. Ill, Fig. 95, p. 227), serves to fasten the
spore to the herbage on which it may settle and thus to keep it there
until it is swallowed with the herbage by a herbivorous animal such
as a horse. There can be but little doubt that the spores of Aleuria
vesiculosa, hke those of many other coprophilous fungi, e.g. Piloboh
and many Ascoboli and Coprini, are able to pass through the
ahmentary canal of a horse unharmed, so that, when excreted
within the substance of the sohd faeces, they find a suitable medium
in which to germinate. The horse is evidently a very important
factor in the dispersion and the maintenance of Aleuria vesiculosa

as a species.

In Aleuria vesiculosa, as in the Discomycetes already treated of in
this Chapter, an ascus, on discharging its spores, not only contracts
but becomes somewhat straighter. In a contracted ascus the
operculum is usually symmetrically placed at the end of the ascus,
but in a much curved ascus it may be very shghtly inclined toward
the shorter and concave side of the ascus.

In my damp-chamber cultures of Aleuria vesiculosa the cup-shaped
fruit-bodies with incurved edges did not contain any mature asci and
the spores became ready for discharge only as the fruit-bodies opened
out and more or less flattened themselves against the substratum.
I gathered an expanded and mature fruit-body from the horse dung

HELIOTROPISM OF ASCI IN DISCOMYCETES 303

on which it was growing and transferred it to a small crystallising
dish covered with a glass plate. On three successive days thereafter
I removed the plate and quickly took out the fruit-body from the
dish. Each time, on coming into contact with the dryer outer air
of the laboratory, the fruit-body puffed vigorously. The blast of
spores was emitted for 1-2 seconds and could be readily heard.
Falck ^ states that, in Aleuria vesiculosa, puffing cannot be caused
by a rise of temperature but can be caused, at first, by touching the
hymenium with a solid object or by stroking it with a hair-pin and
also, later, by blowing upon it. Whether or not my fruit-body
puffed because it was touched, or because air passed rapidly over
its surface, or because the tips of its asci were exposed suddenly to
dry air was not determined.

PuflRng of Aleuria vesiculosa under Natural Conditions. — Dr.
H. T. Giissow has seen fruit-bodies of Aleuria vesiculosa puff inter-
mittently when growing under purely natural conditions and
untouched by man. His observations, which he kindly communi-
cated to me in litt., were as follows. " Toward the end of August,
1928, 1 sat on the shore of Penlake, Muskoka, in Ontario, underneath
hemlock, spruce and maple. The ground was very moist and the
fungus flora plentiful. Occasionally, with the swaying of the
branches, a sunbeam or two flitted across the ground to disappear
again and throw things into a dense shade. In the light of a
sunbeam something like a sparkling cloud was thrown straight up.
I looked more closely. Perchance it was a falling drop of water
splashing ; but no, there was nothing to see ! Another cloud was
shot up not more than forty inches from my eyes, and then I
perceived that it had come from the Waxy Peziza, Aleuria vesiculosa,
wonderfully camouflaged against the debris of the ground. I watched
the fungi for some minutes. Deep shade, Nothing happened.
There ! A sunbeam momentarily fell upon the cups, and at once
there was a puff of glistening sparks ! Soon the sun began to shine
directly upon the cups and then, twice in succession, more clouds
of spores appeared. Would puffing take place in the shade ? I held

^ R. Falck, " Ueber die Sporenverbreitung bei den Ascomyceten. II. Die
taktiosensiblen Di.scomyceten," in his Mycologinche Untersuchungen unci Berichte,
Cassel, Bd. 1, Heft III, 1923, p. 374.

304 RESEARCHES ON FUNGI

my hat so as to cast a shadow upon the cups, and I waited and
watched for several minutes, but all in vain. Perhaps they had
exhausted their ammunition. Away came my hat. The sun again
struck the cups. At once two puffs, like a pyrotechnic display !
I tried to measure the height to which the spores had been shot but
could only estimate it at 4-6 cm."

Dr. Giissow's observations show that, under natural conditions,
the fruit-bodies of Aleuria vesiculosa not only puff but also shoot
up their spores to some distance above the mouths of the apothecia.
Doubtless the direction of discharge of the clouds of spores which
he saw was in part determined by the hehotropic curvatures of
the asci.

Dr. Giissow's observations also suggest that his Aleuria vesiculosa
fruit-bodies puffed as a result of their becoming suddenly illuminated
or heated by a beam of sunhght. However, it is certain that
sunlight is not necessary for the puffing of A . vesiculosa ; for. in the
laboratory, ripe fruit-bodies of this species puff when removed from
damp air and brought into relatively dry air without any appreciable
change in the conditions of hght or heat.

With a view to throwing further Ught on spore-discharge in the
Discomycetes it is desirable that Dr. Giissow's observations should
be extended, i.e. that particular fruit-bodies of various species
growing under perfectly natural conditions and untouched by man
should be studied throughout their spore-discharge period and that
the number of times they puff and the exact conditions under which
they puff should be recorded.^

The Heliotropism of the Asci and the Discharge of the Spores in

Galactinia hsidia.. ^Galactinia badia is another large, commonly

occurring, more or less hemispherical Discomycete (Fig. 146). It

differs from Aleuria vesiculosa in habitat, for it is not coprophilous

and grows on the ground in open or shady places in woods. I have

gathered specimens at the Royal Gardens, Kew, and also at Minaki

on the Lake of the Woods in central Canada.

1 Among the Discomycetes that I have seen puff in the open as they were bemg
touched or gathered are : a Ciboria that grows on male Birch catkins, Ciliaria
scutellata, Galactinia badia, Rhizina inflata, and Urnula Craterium. Probably, had
these fruit-bodies been watched instead of being touched, sooner or later they would
have been seen to puff.

HELIOTROPISM OF ASCI IN DISCOMYCETES 305

The fruit-bodies of Galactinia badia are often caespitose but
sometimes solitary, 3-8 cm. in diameter, brown, and furfuraceous
externally. A single fruit-body soon becomes cup-shaped and then,
with further expansion, more widely opened until it becomes more
or less bowl-shaped or saucer-shaped, with the margin entire or
nearly so and the sides of the cup wavy. Below, the fruit-body is
contracted into a very short stem-hke base. The upper hymenial
surface is fawn-coloured varied with tints of olive and red,^ while
the under side is paler brown and minutely granular. The paraphyses
are cyhndrical but with the apical
cell somewhat thickened at the top,
septate, and almost colourless. The
asci are cyhndrical, slightly attenu-
ated downwards, eight-spored and the
spores uniseriate, turning blue with
iodine, 320-340 (j. long and 16-18 [a
wide. The spores are elliptic-ovoid,
colourless, minutely warted externally,
containing one or usually two oil-
drops, 17-19 [i, long and 9-10 [j. wide.

Falck 2 found fruit-bodies of Galac-
tinia badia on damp sandy open land
and, on testing them, observed that
they puffed vigorously when blown

upon, but not when their temperature was raised. In younger
specimens puffing could be caused by stroking the hymenium with
a hair-pin, but not by blowing upon it.

I gathered some living fruit-bodies of Galactinia badia from a
wood at Minaki, took them to the laboratory at Winnipeg, and there
studied them by means of radial-longitudinal sections in the manner
already described for Aleuria vesiculosa.

One of the fruit-bodies investigated is illustrated in Fig. 146.
It was found that the asci at the base of the cup were straight and

^ This description of the colour is taken from Boudier's I cones Mycologicae,
Vol. IV, p. 155. Rehm {Discomyceten, p. 1011) states that the discs are lunber-
brown or olive-green, and remarks on the variability of the colour as noted by
Fries and others. My own specimens were decidedly brown.

2 R. Falck, loc cit., p. 273.

VOL. VI. X

Fig.

146. — Galactin in badia.
One-half of a fruit-body.
The arrows indicate the
directions in wliicli tlie asci
point and, therefore, the
directions in whicli the
ascospores are discharged.
Natural size.

3o6

RESEARCHES ON FUNGI

thus pointed directly upwards (Fig. 147, A), and that the asci on
the sides of the cup were all curved upwards toward the central

Fig. 147. — Galactinia badia. Heliotropism of the asci and paraphyses. Semi-
diagrammatic representation of two sections taken in a median -vertical plane
through a cupulate fruit-body. The arrows indicate the directions in which
the asci point. A, part of the hymenium at the base of a fruit-body (c/. Fig.
146) : a, an ascus ready to discharge its spores ; 6, paraphyses ; c, an ascus
which has discharged its spores ; the asci and paraphyses point toward the
source of light and, therefore, straight upwards toward the middle of the fruit-
body's mouth. B, part of the hypothecium (subhymenium) and hymenium on
the left side of a fruit-body (c/. Fig. 146) : a, the hypothecium ; b, two asci
ready to discharge their spores ; c, an ascus which has discharged its spores and
which clearly shows its operculimi attached to the side of its ascostoma ;
d, paraphyses ; the asci and paraphyses are heliotropically bent toward the
source of strongest light and are therefore directed toward the fruit-body's
mouth. The ripe spores have rough outer walls and, as a rule, they each
contain two oil-drops. Magnification, 293.

point of the cup's mouth (Fig. 147, B). The maximum bending of
the asci about half-way down the sides of the cup was through an
angle of about 45°. It thus became clear that all the asci, wdierever
situated in the hymenium, w^ere, as in Aleuria vesiculosa, turned

HELIOTROPISM OF ASCI IN DISCOMYCETES 307

toward the mouth of the cup, i.e. toward the source of light. There
can be but little doubt that this arrangement of the asci was due to
these organs reacting heliotropically during their development.

A piece of a fruit-body taken from the side of a cup, including
a portion of the rim, was laid flat on a slide and its hymenium was
examined in face view with the microscope. The overlapping of the
ends of the asci as they pointed in the general direction of the rim
of the cup could be readily seen
(Fig. 148).

A fruit-body had been kept
in a small closed vessel all
night. In the morning this
vessel was suddenly opened and
a piece of the side of the fruit-
body was quickly cut away,
removed to the outer air of the
laboratory, and held horizon-
tally with the hymenium
looking upwards. Immediately
after this had been accom-
plished, the fruit-body puffed ;
and it was then observed by
both Mr. T. C. Vanterpool and
myself that the cloud of spores
emitted from the hymenium

was not shot vertically upwards but obliquely upwards at an angle
of about 45° toward the rim of the piece of fungus (Fig. 149).
This direction of pufhng was, of course, due to the fact that the
asci had curved toward the mouth of the fruit-body and were
therefore inclined toward the nearest point of the fruit-body's
rim. It may be added that the cloud of spores was seen to travel
obliquely forward for about an inch and that its emission was audible.

Puffing of the fruit-bodies of Galactinia badia takes place not
only after confinement in a laboratory but also in the open. In an
excursion in Kew Gardens Miss E. M. Wakefield and I found some
large brown fruit-bodies of 0. badia amid grass under some young
trees. I picked one of the fruit-bodies from the ground and

Fig. 148. — Galactinia badia. Semi-dia-
grammatic surface view of hymenium
on the side of, and near the top of, a
cup-shaped fruit-body (cf. Fig. 146).
Asci a and paraphyses b turned up-
wards so as to point to the source of
strongest light and, therefore, to the
fruit-body's mouth. Magnification,
345.

3o8

RESEARCHES ON FUNGI

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immediately thereafter it puffed vigorously and, in so doing, gave out
an audible sound. Had the fruit-body been left undisturbed where
it had developed, probably it would have puffed sooner or later owing
to its being touched by a passing animal, blown upon by rising wind,
or partially dried by the loss of water vapour to the surrounding
atmosphere as this became less humid.

Urnula Craterium. — Urnula Craterium, the Burnt-out Crater
Fungus, is somewhat rare in Europe but is common in North

America, and I have met
with it several times in
Canada on the shores of
the Lake of the Woods and
of Lake Winnipeg. It
grows on the ground in
woods and is attached to
buried or partly buried
sticks (Fig. 150) or to saw-
dust, etc. (Figs. 169 and
170, pp. 335 and 336).
The fruit-body is stipitate
and the stipe is continued
upwards into a deep black
cup. A mature fruit-body
in the open, when touched,
puffs vigorously, and the
spore-smoke is shot out of
the mouth of the cup.
Here, as in Aleuria vesi-
culosa and Galactinia badia, the safe exit of the spores from the
cup is due to the ends of the asci being heliotropically turned to
the source of brightest light and therefore to the opening in the
top of the fruit-body.

The paraphyses of Urnula Craterium are thin, septate, much
branched and brown above. Their end-branches are straight and
show no signs of heliotropic curvature, thus contrasting with the
asci. In U. Craterium, therefore, while the asci are heliotropic, the
paraphyses are anheliotropic.

Fig. 149. — Galactinia badia. Diagram to illus-
trate an experiment on the direction of
discharge of the asci. A fruit-body matured
its spores in a damp-chamber. A piece of
its side was then very quickly cut away,
removed from the damp-chamber and, with
the hymenium looking upwards, was laid
flat on a sheet of glass in the laboratory.
About two seconds thereafter, the piece of
fruit-body puffed and the cloud of spores
was shot away irom the liymenium in the
manner shown : a the basal end and b the
apical end of the piece of fruit-body (shown
insection); c, the sheet of glass ; thearrows
indicate the direction in which the asci dis-
charged their spores. Natural size.

HELIOTROPISM OF ASCI IN DISCOMYCETES

309

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shaped but are relatively long and narrow and are characteristically
split down one side. Owing to the split, the light strikes upon the

310

RESEARCHES ON FUNGI

hymenium more from the side of the fruit-body than from the free
end. Probably, therefore, in Otidea onotica and 0. leporina the asci
are bent heliotropically toward the open side of the fruit-body rather
than to the free end. The Otideae puff freely when their mature
fruit-bodies are touched, and then the clouds of spores which they
emit through their asymmetrical openings can be readily observed.

Fig. 151. — Otidea onotica, a Disconiycete witli auriculate fruit-bodies. Tlie long
lateral opening down the side of each fruit-body enabled the light to strike the
hymenium more or less perpendicularly and thus, doubtless, to stimulate the
asci heliotropically, so that the ends of the asci turned themselves toward the open-
ing. \\'hen spore-discharge took place, therefore, the ascospores could readily
be shot away from the fruit-body into the open air. Fruit-bodies shown were
collected at the Experimental Farm, Ottawa, by W. S. Odell. Photographed
by the Photographic Division of the Geological Survey of Canada. Natural size.

The Heliotropism of the Asci and the Discharge of the Spores
in the Morchellaceae. — In the Morchellaceae, which includes the
genera Morchella and Mitrophora : the fruit-body or receptacle is
differentiated into a stipe and a pileus ; the pileus is hollowed out
externally into pits or alveoli ; the hymenium is broken up into
separate portions, each of which lines the interior surface of one of
the alveoli ; and the alveoli are separated from one another by ribs

HELIOTROPISM OF ASCI IN DISCOMYCETES 311

Fig. 152. — Morchella esculeitld. A fruit-l)ody (receptacle) with its stipe and pileus.
The pileus is hollowed out externally into pits (alveoli) each of which is lined
by a hynieniinn. The various hynienia are separated from one another by ribs
which are sterile aloufj their outer edges. The asci of each hynienial pit are helio-
tropically curved toward the pit's mouth and, therefore, tliey shoot their spores
away from the fruit-body. Thotographed in Yorkshire, England, by A. E.
Peck. Natural size.

312

RESEARCHES ON FUNGI

Fig. 153. — Morchella esculentn. Upper left and right-hand fruit-bodies, showing
the external appearance of the hymenial pits or alveoli. Lower left fruit-body
in median vertical section, showing tlie hollow structure of the stipe and pileus-
flesh and the depth of the pits. Lower middle fruit-body, a median transverse
section througli the pileus. Tlie asci are lieliotropically curved toward the
mouths of the pits and, tlierefore, slioot their spores away from the fruit-body.
Photographed by the Geological Survey of Canada. Natural size.

HELIOTROPISM OF ASCI IN DISCOMYCETES 313

which are sterile exter-
nally (Figs. 152 and 153).
The fruit-body of the Mor-
chellaceae, owing to its
possessing a subdivided
hymenium, is said to be
compound.^

The alveoli on the
exterior of the pilei of the
Morchellaceae, as defined by
their exterior sterile ribs,
may be irregularly rounded,
irregularly polygonal, or
more or less longitudin-
ally elongated. When the
alveoli are rounded or
polygonal or but slightly
elongated, they remain
simple, although their in-
ternal lateral walls are
usually plicate (Fig. 152).
On the other hand, when
the alveoli are much
elongated longitudinally
(Figs. 154 and 155), they
are usually broken up by
more or less well developed
transverse hymenium-
covered ridges. Thus a
much elongated primary
alveolus may be subdivided
into secondary alveoli .
Each species has alveoli
of characteristic shape.
Thus the alveoli are : in

Fig. 154. — A fruit-body of Morchella deliciosa.
The pits (alveoli) are much elongated and
are divided transversely into secondary
alveoli. Collected at Ottawa by W. S.
Odeil. Photographed by the Photographic
Division of the Geological Survey of Canada.
Natural size.

^ E. Boudier, Histoire el Classification des Discomycetes d'' Europe, Paris, 1907, p. 30.

314

RESEARCHES ON FUNGI

Morchella crassipes and M. esculenta (Fig. 152), irregularly rounded
and plicate within ; in M. rotunda, irregularly quadrangular ; in
M. conica, M. deliciosa (Fig. 154), M. angusticeps (Fig. 155), M. costata,
M. elata, and Mitrophora hybrida, much elongated and divided
transversely into secondary alveoli.^

Each hymenivfm-lined alveolus of a
Morchella or of a Mitrophora, whether it be
rounded, polygonal, or elongated, is com-
parable with the single hymenium-lined
cavity that is characteristic of cupulate
Pezizeae, e.g. Galactinia hadia and Lachnea
hemispherica ; and we can therefore think of
such a fruit-body as that of Morchella conica
or M. crassipes as being constructed, as it
were, of a series of Peziza-cups which have
coalesced to form a conical-ovate compound
structure. To discover the secret of the
escape of the spores from a Morchella fruit-
body it is necessary to investigate the alveoU
individually and to find out how the asci in
their walls are arranged and in what direction
they point. Such an investigation has been
made on the fruit-bodies of both Morchella
conica and M. crassipes.

In June, 1925, at Winnipeg, at my re-
quest, my colleague Mr. C. W. Lowe obtained
some fruit-bodies of Morchella conica and
investigated them whilst they were still fresh

Fig. 155. — A fruit-body of Morchella angusticeps: The
primary pits (alveoli) of the jiileiis are (livided
transversely into secondary pits. Collected at
Ottawa by W. S. Odell. Photographed by the
Photographic Division of the Geological Survey
of Canada. Natural size.

^ For descriptions and excellent coloured illustrations of these species, except
M. deliciosa which is not illustrated and M. esculenta which he has split up into
M. rotunda and M. vulgaris, vide fi. Boudier's Icones Mycologicae, Tomes II and IV,
Paris, 1905-1910.

HELIOTROPISM OF ASCI IN DISCOMYCETES 315

and in good condition. With a hand-razor he cut transverse sections
through the alveoh, mounted them in water, and studied them under
the microscope ; and he convinced himself that, in each alveolus,
the asci were so arranged that their apices were turned toward the
mouth of the alveolus, i.e. in the direction from which the asci had
been illuminated during their development (Fig. 156). The asci on
the sides of an alveolus were curved outwards often through an
angle of about 45°, whilst those at the base of a chamber were
straight. Subsequently, using dried and pickled material (the former
cut with a hand-razor and the latter with the help of a microtome),
I confirmed Mr. Lowe's observations (Figs. 157 and 158).

The curvatures of the asci in an alveolus of Morchella conica are
strictly comparable to the curvatures of the asci in the cup oiAleuria
vesiculosa or Galactinia badia, and there can be little or no doubt
that they are due to reactions to the hehotropic stimulus of Ught.

A thin median- vertical section of a fruit-body of Morchella conica,
such as that shown in Fig. 157, A, not only permits one to perceive
the disposition of the hymenium within the alveoli, but also reveals
the very light physical framework which serves to support the
hymenium and to hold it in a position favourable for the discharge
of the spores : the flesh of the stipe and of the pileus roughly con-
stitutes a cyhnder, and the interior of the cyhnder is occupied by a
relatively very large air-space. Here, as in the stipes of many
Agaricaceae, e.g. Coprinus sterquilinus (Vol. IV, Fig. 66, p. 116),
and as in the stems of many Phanerogams, e.g. Gramineae and
UmbelHferae, the disposition of the supporting substance in the
form not of a soUd cylinder but of a hollow one increases the power
of the organ to withstand mechanical stresses and strains.

On June 13, 1928, at Victoria Beach on Lake Winnipeg, Dr. G. R.
Bisby and I hunted the woods for Morchellaceae and found several
large fruit-bodies of Morchella crassijjes. With the help of a hand-
razor and a travelling microscope set up in the field-station of the
Manitoba Natural History Society, I examined the alveoh in cross-
section and found that, just as in those of M. conica, the asci were
curved towards the mouths of the alveoh. Apparently they had all
responded to the hehotropic stimulus of hght. Dr. Bisby, who was
good enough to examine my preparations, confirmed my observations.

3i6

RESEARCHES ON FUNGI

Boudier/ in his illustrations of M . crassipes, represents four asci
all of which are curved at their ends. The upper parts of two

Fig. 156. — Photomicrograph of part of a transverse section through a pit (alveohis)
of Morchella conica, to show tlie asci heHotropically curved toward the pit's
mouth. The material was fixed, stained, and cut with a microtome. The
opposing walls of the pit are nearer together than they were before the inaterial
was fixed. The ends of the asci are curved through an angle of about 45°, so
that the spores, if the fruit-body had not been disturbed, would have been shot
away from the fruit-body without hitting any opposing hymenial wall.
Photographed by C. W. Lowe at Winnipeg. Highly magnified.

of the asci (Fig. 159), one containing spores and the other after dis-
charge, enlarged 820 times, are both drawn with their ends curved

1 E. Boudier, loc. cit., Tome II, Plate CXCIV, b, d, e.

HELIOTROPISM OF ASCI IN DISCOMYCETES 317

through an angle of about 45°. Doubtless the curvature of these
asci was heliotropic in origin.

Since, in a fruit-body of a Morchella. the asci in each alveolus

Fig. 157. — Morchelhi conica. A, a thin meJiaii-vertical section tlirough
a receptacle (fruit-body) : a, the stipe ; b, the pileus ; c, a longi-
tudinally elongated alveolus (pit) seimrated from neighbouring alveoli
by dissepiments d d and having transverse ridges e within. The
hymenium / covers the interior surface of each alveolus and is
absent only on the free edges of the dissepiments, which form sterile
ribs g g. The broken line indicates the outermost limits of the alveoli.
B, two alveoli of A, shown on a larger scale : a, the pileus-flesh ; b b,
dissepiments ; c c, transverse ridges ; d, the hymenium covering the
interior of the alveoli, but absent from the exterior edges (ribs) of
the dissepiments ; e, a portion of the hymenium illustrated on a
larger scale in Fig. 158. The asci are all directed toward the source
of strongest light and therefore toward the mouth of each alveolus.
The arrows indicate the general directions in which the spores are
shot, and the clouds of spores outside the mouths of the alveoli have
just been formed in consequence of the receptacle having suddenly
puffed in response to the application of heat from a lamp (c/. Fig. 128).
A, natural size. B, four times the natural size.

point toward the mouth of the alveolus and since the operculum of
each ascus is situated symmetrically at the end of the ascus, it is

ii8

RESEARCHES ON FUNGI

clear that, when spore-discharge takes place, the spores must all be
shot through the mouths of the alveoU into the open air (Fig. 157, B).
Thus, so far as the escape of the spores from a fruit-body of Morchella

is concerned, we have a direct and very
simple explanation, one that is in con-
formity with what is known concerning
the escape of the spores from the fruit-
bodies of simpler Discomycetes, such as
species of Ciharia, Aleuria, and Galactinia,
and one which, clearly, must take the
place of Falck's Temperaturstromungen
theory already discussed and criticised
in the Introduction to this Chapter. ^

The asci on the walls of an alveolus of
a Morchella fruit-body all look toward the
mouth of the alveolus and toward that
part of the mouth from which come the
strongest incident rays of hght. There-
fore, when pufhng takes place, the spores
of any single alveolus are all shot outwards
in great numbers in the same general
direction. This being so, the same re-
sults accrue as those already experiment-
ally investigated in connexion with
puffing from the cup of Sarcoscypha
protracta : the spores discharged from
the alveolus strike the air almost simul-
taneously, in the same general direction,
and very violently ; they set the air in
motion ; and they cause an air-current to
come into existence sufficiently strong to
carry them farther from the fruit-body
than they could travel by their own momentum .2 It was mechanically
produced air-currents of the kind just described which Falck perceived
in his investigations on the discharge of spores in Morchella and its
alhes and which he mistook for his " Temperaturstromungen."
1 Vide supra, pp. 268-270. ^ yide supra, pp. 257-260.

Fig

158. — Morchellci conica.
Semi-diagrammatic verti-
cal section through the
liymeniiim on the upper
side of a liorizontal dis-
sepiment between two
alveoU(c/.einFig. 157, B).
The asci, owing to their
having responded to the
stimulus of liglit, are all
curved at their ends to-
ward the movitli of the
alveolus in which they
grew. The arrows indicate
the directions in which
the sj)ores would be shot.
Magnification, 293.

HELIOTROPISM OF ASCI IN DISCOMYCETES 319

The formation of radially-projecting dissepiments and ridges on
the exterior of a pileiis in the Morchellaceae (Fig. 157) is comparable
with the formation of gills on the under side of the pileus in the
Agaricaceae ; for in both groups of fungi the same mechanical advan-
tage is obtained, namely, a considerable increase in the area of the
spore-bearing layer or hymenium without the hymenophore losing
its compactness as a whole. The gills of the Agaricaceae are often
closely packed : indeed, the
upper part of the interlamellar
space between two adjacent gills
in many agarics, e.g. Psalliota
campestris [videYig. 139 in Vol. II,
p. 390), is often reduced to 1 mm.
or less. On the other hand, in
most of the Morchellaceae, the
alveolar spaces are usually several
mm. in diameter. Correlated
with this difference in the spatial
arrangement of opposing hy menial
walls is the fundamental difference
in the structure and power of the
guns in the two groups of fungi.
The basidia of the Agaricaceae are
relatively small and feeble guns
with a range of only 0 • 1-0-2 mm.,

and the basidia on one gill cannot therefore bespatter with spores
the opposing hymenium of another gill, even when the interlamellar
space is only 0- 5 mm. in width {cf. Fig. 139 in Vol. II, p. 390). In
contrast with such basidia, the asci of the Morchellaceae are rela-
tively large and powerful guns with a range of 1-3 cm., and they
therefore requh'e much more room for discharge than basidia.
The actual space provided for them is what is necessary to permit
of all the asci turning toward, and shooting their spores through,
the mouths of the alveoli.^

1 For other remarks on the manner in whieli the basidium lias influenced the
structure of hymenomycetous fruit-bodies and the ascus has influenced the structure
of discomycetous fruit-bodies vide these Researches, Vol. I, 1909, pp. 22-24 ; also
cf. Vol. II, 1924, pp. 67-68.

Fig. 159. — Morchella crnssipes. Asci
sharply curved at tlieir ends. Mag-
nification, 820. Copied by A. H. R.
Bviller from Boudier's Icone-s Myco-
logicac, T. II, PI. 194.

320 RESEARCHES ON FUNGI

As shown by data embodied in a comparative Table ^ in Volume I,
the spores of the Discomycetes and of the Agaricaceae and
Polyporaceae are of the same order of size, and they therefore have
about an equal chance of being dispersed by the wind when they
come within its sweep. In the Agaricaceae and Polyporaceae, the
spores, after discharge, fall down between the gills or down the
hymenial tubes and thus leave the fruit-body ; but, as if to facilitate
the spores being carried off by the wind, the pilei which produce
them are usually raised up on stipes or project laterally from tree-
trunks, etc., a free subpilear space for the passage of the wind and
the removal of the escaping spores thus being provided. In the
Discomycetes, where the asci look upwards, as in the Pezizaceae,
or more or less upwards or laterally, as in the Morchellaceae, the
chances that the wind will carry off the spores are enhanced :
(1) by the considerable range of the individual ascus guns ; (2) in
Pezizaceae, etc., by the simultaneous discharge of many of the
guns — the phenomenon known as puffing ^ ; and (3), in many species
of Pezizaceae and in all the Morchellaceae and Helvellaceae, by the
raising of the pilei above the surface of the ground by means of
stipes comparable with those of the Agaricaceae and Polyporaceae.

It is characteristic of the Morchellaceae and many Helvellaceae
that the fruit-bodies appear in the spring, from March to May,
i.e. at a period of the year when the night temperatures are relatively
low. Falck's observations in the laboratory have led him to
suppose that, in a Morchella or Gyromitra growing under natural
conditions : (1) at night and during the day when the sky is over-
cast and the temperature is low, ripe asci accumulate in the fruit-
bodies but no spores are discharged ; (2) the discharge of spores
takes place only in the daytime when the fruit-bodies are warmed
by the sun ; and (3), in bright sunshine lasting for some hours, the
fruit-bodies discharge their spores continuously, i.e. in the order in
which the asci ripen and not in intermittent clouds.^ Thus, according
to Falck, normal spore-discharge in a Morchella or Gyromitra does

1 These Researches, Vol. I, 1909, p. 248.

2 Vide supra, p. 262.

^ R. Falck, " Ueber die Sporenverbrcitung bei den Ascomyceten. I. Die radio-
sensiblen Disconiyceten," Mycologische Untersuckungen und Berichte von R. Falck,
Bd. I, Heft II, 1916, pp. 126-127.

HELIOTROPISM OF ASCI IN DISCOMYCETES 321

not take place below a certain temperature (about 10° C.) ^and, when
it does take place, it is accomplished not by a series of vigorous and
intermittent puffs but by the successive bursting of asci which
results in the Hberation of a stream of spores Uke that which escapes
from the pileus of one of the Hymenomycetes.

Falck found that two fruit-bodies of Morchella esculenta lying in
the shade in a cool room had a temperature of 15- 3° C. and were not
discharging spores. He thereupon exposed the fruit-bodies to
direct sunlight. After one minute a thermometer behind the
irradiated hymenium registered 18° C. and spore-discharge had
become active. After five minutes the thermometer registered
19' 8° C. and spore-discharge continued. He then placed the fruit-
bodies in the shade. After four minutes the thermometer registered
16-9° C. and the discharge of the spores had ceased.^ These experi-
ments strongly support Falck's conclusion that the sun, under
natural conditions, must often be a prime factor in causing fruit-
bodies, not only of Morchellae but of Gyromitrae, Verpae, and other
vernal radiosensitive Discomycetes, to discharge their spores.

Falck ^ regards the brown colour of the caps of Morchella, Gyro-
mitra, etc., as an aid to the absorption of the sun's rays and therefore
as advantageous for the working of the spore- discharge mechanism.

The Helvellaceae. — The Helvellaceae, according to Boudier,*
include the following genera : Ptychoverpa, Verpa, Gyiomitra
(Figs. 160 and 161), Physomitra, Helvella (Fig. 163, p. 328), and
Leptopodia. In all the species of this family the fruit- bodies are
stipitate, while the j511eus is attached by its centre to the stipe, is
reflexed in the form of a hood, and is more or less lobed.

Several illustrations of asci of various species of Helvellaceae
drawn by Boudier and reproduced in his Icones Mycologicae
suggest that the asci of the Helvellaceae are heliotropic. Among
these illustrations are: (1) an ascus of Gyromitra gigas ^ with

^ R. Falck, " Ueber die Sporenverbreitung bei den Ascomyceten. I. Die radio-
sensiblen Discomyceten," Mycologische Untersuchungen und Berichie von R. Falck,
Bd. I, Heft IT, 1916, pp. 91-92.

2 Ibid., p. 102. 3 Ibid., pp. 84, 114-115, 125.

* fi. Boudier, Histoire et Classification des Discomycetes d'Europe, Paris, 1907,
pp. 33-38.

* E. Boudier, Icones Mycologicae, Tome II, PI. 221,/.

VOL. VI. ^

322

RESEARCHES ON FUNGI

an operculum tilted at an angle of 45° to the slightly curved
ascus axis ; (2) two asci out of the three of Ptychoverpa

Fig. 160. — A fruit-body of Gyromitra esculenta. The hymenium covering tlie
pilaus is much folded. The escape of the spores from the sides and
crevices of the folds is doubtless aided, here as in the Morchellaceae, by the
heliotropic curvature of the ends of the asci. Photographed in Yorkshire,
England, by A. E. Peck. Natural size.

HELIOTROPISM OF ASCI IN DISCOMYCETES 323

bohemica ^ sharply turned at their ends through an angle of
about 45° ; (3) an enlarged outer part of an ascus of Helvella
sulcata 2 turned at its end through an angle of 40° ; and

Fig. 161. — Anotlier fruit-boiy of Gyromitrd eiculenta. The
folds in tlie hymenium are well developed. If the asci
are heliotropic, as in tlie Morchellaceae, those on the
sides of tlie fokls could readily slioot their spores away
fronri tlie fruit-body. Piiotographed at Ottawa by
W. S. Odell in the spring, 1927. Natural size.

(4) a discharged ascus of Leptopodia elastica ^ with its operculum
in face view very obliquely situated on the ascus end.

The only member of the Helvellaceae which so far I have in-
vestigated is Ptychoverpa bohemica (Corda) Boud., often referred to
as VerjM bohemica. The hymenium differs from that of the species

1 E. Boudier, 1 cones Mycolocjkne, Tome II, PI. 218, d.

2 Ibid., PI. 229, ij. 3 Ibid., PI. 232, h.

324 RESEARCHES ON FUNGI

of Verpa in that it is folded into numerous longitudinal and rather
freely anastomosing ribs, and the asci are remarkable in that they
each contain two very large spores (15-18 X 60-80 y., Seaver i)
instead of the usual eight relatively small spores.

On May 21, 1932, my colleague, Dr. G. R. Bisby, kindly brought
to me from the grounds of the Manitoba Agricultural College several
rather old fruit-bodies of Ptychoverpa bohemica. I cut transverse
sections through their pilei, examined these sections under the
microscope, and at once perceived that in all the hymenial grooves
and depressions the asci were curved outwards so that their oper-
cula must have faced the strongest rays of light to which the
ends of the asci had been subjected in the places where the fruit-
bodies developed. Thus clear evidence was obtained that in the
Helvellaceae, just as in the Morchellaceae, the asci are heliotropic.

Concluding Remarks. — From the investigations which have been
recorded in this Chapter, we may conclude that, in a large number
of Discomycetes belonging to various families : (1) the asci are
positively heliotropic ; and (2) this response to the stimulus of light
is of biological significance in that it permits of a fruit-body pointing
and discharging its asci toward open spaces, thus increasing the
chances that the spores will be carried off and be dispersed by the wind.

It is not without interest to note that, while in the Discomycetes
heliotropism of the asci is a common phenomenon, in the Hymeno-
mycetes heliotropism of the basidia is unknown. The ends of the
basidia on the sides of the gills of the Agaricaceae and on the sides
of the hymenial tubes of the Polyporaceae are of necessity illuminated
from below, and yet they never turn downwards. Owing to the
peculiar organisation of the fruit-bodies in these Hymenomycetes
and to the very short range of the basidial guns, it is easy to see
that a heliotropic response on the part of the basidia would not aid
the escape of the spores from the hymenium into the interlamellar
or tubular spaces but would actually hinder it. Thus, where a
heliotropic response by a fungus gun is advantageous for spore-
dispersal, as it is in the Discomycetes, it takes place ; and, where
it would be disadvantageous for spore-dispersal, as in the
Hymenomycetes, it does not take place.
^ F. J. Seaver, The North American Cup-fungi (Operculates), New York, 1928, p. 244.

CHAPTER III

THE SOUND MADE BY FUNGUS GUNS AND A SIMPLE METHOD
FOR RENDERING AUDIBLE THE PUFFING OF DISCOMYCETES

Fungus Projectiles — Type I : Sphaerobolus — Type II : Pilobolus — Type III :
Ascobolus — Type IV : Peziza — A Simple Method for Rendering Audible the
Puffing of Discomycetes — Type V : Empusa and Entomophthora, Uredineae
and Hymenomycetes — Sounds Made by Fungus Guns are of No Biological
Significance.

Fungus Projectiles. — The various projectiles of fungi, in order of
size, may be classified, as follows :

I. A gleba, containing a great number of sjDores, as in Sphaero-
bolus stellatus,
II. A sporangium, containing about 50,000 spores, with
sporangiophore-sap attached, as in Pilobolus,
III. An aggregation of eight spores forming a single mass,

together with ascus-sap, as in Ascobolus immersus,
IV. A chain of eight spores which breaks up into its eight com-
ponents on leaving the ascus, as in Peziza and Pustularia,
and
V. Single spores, as in the conidia of Empusa and Entomoph-
thora, and as in the basidiospores of the Uredineae and
Hymenomycetes.
Type I : Sphaerobolus. — ^The gleba of Sjihaerobolus stellatus —
the largest known fungus projectile — is a viscid, smooth, dark,
spherical body, 1-1 -25 mm. in diameter (Vol. V, Fig. 145, p. 294),
and it is cast out of the Sphaerobolus gun (Vol. V, Fig. 172, c, p. 361)
by a catapult mechanism which has already been described.^ The
gun, when about to discharge its projectile, is 2-2 • 5 mm. in diameter.
Its maximum horizontal range, as measured by myself, was found

1 These Researches, Vol. V, 1933, pp. 310-325.

325

326 RESEARCHES ON FUNGI

to be 18 feet 7 inches ; and its maximum vertical range, as measured
by Leva B. Walker, was found to be 14 feet 5 inches. For Sphaero-
holus stellatus var. giganteus and for S. iowensis Miss Walker found
the maximum vertical range of the projectiles to be about 11 feet
and about 12 feet respectively. ^

The sound of the discharge of the Sphaerobolus gun is quite
distinct and has long been known. It was heard by E. Fischer ^ in
1884 ; and it was mentioned by de Bary ^ in 1884 and by Zopf * in
1890. I heard it as a little snap when the gun was a foot in front
of my eyes.5 Of all fungus guns the Sphaerobolus gun is not only
the largest and most powerful, but also the loudest. Its sound is
much louder than that of the ascus of Peziza and appreciably louder
than that of the sporangiophore of Pilobolus.

The projectiles cf Sphaerobolus are shot away with considerable
speed and, as they are of the size of very small shot, it is not sur-
prising that, when they strike a hard object near their place of
discharge, the impacts are audible. These impact-sounds were
remarked by Micheli ^ in 1729 and have been noticed by a number
of observers since. Some thirty years ago I had some Sphaerobolus
fruit-bodies in a covered glass dish, and I remember very well
hearing the impact of the glebae as they struck the glass cover and
flattened out upon it. The sound of a glebal projectile striking
against glass in this way is distinctly louder than the sound of the
discharge of the gun which fires the projectile.

Type II : Pilobolus. — The sporangium of the larger species of
Pilobolus (Fig. 27, p. 69) and the sap of the subsporangial swelling
which travels with it make up a projectile (Fig. 74, p. 151) which
is nearly spherical and about 0-6 mm. in diameter. The projectile
can be fired upwards from the sporangiophore a distance of 3-6 feet
and horizontally 4-8 feet.'^ As with Sphaerobolus, two sounds can

1 These Researches, Vol. V, 1933, pp. 325-335.

2 E. Fischer, " Entwickhxngsgeschichte der Gastromyceten," Bot. Zeit., 1884,
Nos. 28-31.

^ A. de Bary, Vergleichende Morphologie und Biologie derPihe, Leipzig, 1884, p. 353.

^ W. Zopf, Die Pilze, Breslau, 1890, p. 375.

^ These Researches, Vol. V, 1933, pp. 325 and 326.

^ P. A. Micheli, Nova Plantarum Genera, Florentiae, 1729, p. 221.

' Vide supra, pp. 66-68.

THE SOUND MADE BY FUNGUS GUNS 327

be heard when a Pilobolus gun goes off : (1) the sound of the ex-
ploding gun and (2) the sound of the projectile striking some object.
W. B. Grove, ^ in 1884, was the first to hear the sound emitted by
the gun, and in 1909 I confirmed his observations. ^ More recently,
in my laboratory, I listened to the shooting away of the sporangia
of Pilobolus longipes and, each time a gun went off, I distinctly
heard a minute snap. I asked my colleague Mr. C. W. Lowe and
my laboratory attendant to listen also, and they both declared that

Fig. 1G2. — Acetabnla vulgaris. Anton de Bary records (1884) that lie
lieard a very perceptible hissing sound when large specimens of
tliis fungus puffed vigorously. Photographed by A. E. Peck at
Scarborougli, Englan(l. Natiu-al size.

the sound of each explosion was unmistakable. In Volume I of
this work, I described a simple experiment which enabled a listener
to hear the striking of a Piloljolus projectile on a drum when he
was 21 feet away from the jilace of impact.^

Type III : Ascobolus. — In a fruit-body of Ascobolus hnmersus
(Vol. I, Fig. 81, p. 252) about half a dozen asci come to maturity
and explode every day about noon. The asci and ascospores are

1 W. B. Grove, " Monograpli of the Pilobolidae," The MidUtnd Naluralist,
Birmingham, England, 1884, p. IT).

2 These Researches, Vol. I, 1909, p. 259. ^ Ibid., pp. 259-200.

328

RESEARCHES ON FUNGI

very large. The eight ascospores of each ascus have thick gelatinous
outer walls, and adhere firmly together both before discharge and

when being shot
through the air. The
projectile — an aggre-
gate of eight spores
surrounded by a film
of ascus-sap — is oval in
form, about 0-3 mm.
long, and 0-15 to
0-2 mm. wide ; and it
can be shot directly
upwards 10 inches or
occasionally 14 inches. ^
In respect to A . immer-
sus no one, as yet, has
heard either the sound
of an ascus exploding
or the sound of the pro-
jectile striking another
object ; but it is prob-
able that both these
sounds might be de-
tected by an attentive
listener.

Type IV : Peziza. —

In Peziza, Aleuria

(Fig. 140, p. 293),

Galactinia (Fig. 147,

p. 306), Pustularia,

etc., the ascus contains

eight spores, as in Asco-

bolus immersus ; but the

eight spores separate

from one another as soon as they are shot out of the ascus (Vol. I,

Fig. 78, p. 236). There are many tens of thousands of asci in each

1 Tliese Researches, Vol. I, 1909, p. 252.

Fk;. 103. — Helvetia crispa. Anton de Bary records
(1884) that he heard a very percejjtible liissing
sound wlien largo specimens of tliis fungus puffed
vigorously. Photograpliod by A. E. Peck at
Scarborougli, England. Natural size.

THE SOUND MADE BY FUNGUS GUNS

329

large fruit-body, and the fruit-body is usually more or less cup-
shaped or wine-glass-shaped. An ascus, when exploding, makes
a faint sound ; but this sound is so faint that, if each ascus were
fired off in a solitary manner, it might have escaped detection.
However, the fruit-bodies of Peziza, Pustularia, Urnula, Otidea,
Rhizina, Helvella, and many other Discomycetes exhibit the curious
phenomenon known as
puffing : when certain
conditions surrounding
a mature fruit-body
are suddenly changed,
thousands of asci may
explode almost simul-
taneously and thus
produce a cloud of
white spores which can
be seen floating away
in the air (Fig. 114,
p. 234).i The puffing
of certain Discomycetes
has been heard. Thus
Desmazieres,2 in 1845,
recorded that the spore-
vapour of Helvella
ephippium is discharged
into the air with a faint
report ; de Bary,^ in
1884, stated that he
had been able to hear " a very perceptible hissing sound produced
by large specimens of Peziza acetabulum (Fig. 162) and Helvella
crispa (Fig. 163) " ; and Stone,* in 1920, announced that in a

Fig. 164. — Some of the ear-like fruit-bodies of Otidea
leporina. Tliis fungus puffs audibly, when
touched. Photographed in England by Somgr-
ville Hastings. Natural size.

1 Vide supra, pp. 227-234.

2 J. B. H. J. Desmazieres, Plant, crypt. France, 2nd ed., fasc. XIX, 1845, No. 914.
Cited from Tulasne.

^ A. de Bary, Vergleichende Morphologie und Biologic der Pilze, Leipzig, 1884,
p. 98. (English Translation, 1887, p. 89.)

* R. E. Stone, " Upon the Audibility of Spore Discharge in Helvella ekislica,''
Trans. Brit. Mycol. Soc, Vol. VI, 1920, p. 294.

zz^

RESEARCHES ON FUNGI

very quiet room at the Ontario Agricultural College at Guelph he
distinctly and repeatedly heard the puffing of Helvella elastica even
when the fruit-bodies were several feet distant.

Observations on the audibility of spore-discharge in Discomycetes
have also been made by R. B. Johnstone. ^ This observer collected
fruit-bodies of Otidea leporina (Fig. 16^) at Perth, Scotland, in
September, 1920, and took to Glasgow half a dozen mature

Fig. 165. — Sarcoscypha coccinea, a large Discomycete wliich comes up in early spring
on sticks and whicli, owing to the very pure and beautiful scarlet colour of its
hymenium, is attractive even to children. The puffing of its fruit-bodies when
handled was heard by the late E. J. Durand. The fruit-bodies shown were
collected near Ottawa by W. S. Odell. Photographed by the Photographic
Division of the Geological Survey of Canada. Natural size.

specimens packed in a box, each one wrapped in paper. The box
remained closed for 24 hours. " On opening the box," says John-
stone, " the specimens were placed on the table, and I attended to
something else. While thus engaged I heard every now and then
a slight hissing sound, but, being busy, paid no attention to it, till
looking by chance at the table I saw one of the Otideae puff, and

^ R. B. Johnstone, " Audibility of the Spore Discharge in Otidea leporiTia,''
Trans. Brit. Mycol. Soc, Vol. VII, 1921, p. 86.

THE SOUND MADE BY FUNGUS GUNS 331

immediately heard a hiss. The hiss was quite distinct, and required
no effort to hear it, although I was fullj^ six feet from the plants.
Mr. Stone's experience occurred to me and, placing my six specimens
in a row, I sat for some time watching my miniature field-battery
at work. First one fired (puffed), followed by the report (hiss),
then another carried on, the others following in their turn at intervals
of not more than two or three minutes. I noticed as the time passed
that the intervals between the puffs increased in length. What
surprised me was the frequency with which the fruit-bodies
puffed."

The late Professor E. J. Durand of the University of Minnesota,
who studied the Discomycetes for many years, informed me that
incidentally, in the course of his work, he had heard the puffing of
the fruit-bodies of several species, among which were :

Aleuria repanda, Sarcoscypha coccinea (Fig. 165),

Aleuria vesiculosa, Sclerotinia tuberosa.

A Simple Method for Rendering Audible the Puffing of
Discomycetes. — I have discovered that the puffing of any Dis-
comycete can be readily heard, if one listens to it in a particular
manner which is now to be described ; and this discovery was com-
municated to the British Mycological Society during the Minehead
Foray in October, 1920.1

On August 7, 1920, in the company of Mr. W. B. Grove, I visited
Queen's Cottage Grounds, Kew Gardens, and there found several
cup-like fruit-bodies of Puslularia catinus (Holms.) Fuck. (Fig. 166).
These were put in a small cardboard box where they remained
during the night. The next morning the box was taken to the Kew
Herbarium and there opened for the purpose of identifying the
fruit-bodies which it contained. At once one of the fruit-bodies
puffed, and a cloud of white spores could be seen escaping from the
hymenium. I heard nothing, but I thought of the sound one hears
when one places a sea-shell against one's ear, and I wondered whether
or not I should be able to hear the puffing of the Pustularia if I put
one of its little cups to my ear. No sooner thought of than done.

1 The Minehead Foray, Trans. Brit. Mycol. Soc, Vol. VIT, 1921, p. 4.

332

RESEARCHES ON FUNGI

I put the fruit-body which had already puffed to my ear ; it puffed
again ; and I distinctly heard the puffing which was like a rush of
steam from a minute jet. I tried some of the other fruit-bodies
with a similar result, and Mr. W. B. Grove who was examining the
fungi with me confirmed my observations. In the course of the
next two days, the puffing of the Pustularia fruit-bodies was dis-
tinctly heard by Miss E. M. Wakefield and by Dr. T. Fetch. The
little cups puffed each morning when the box was opened, for six

consecutive days. If one
puts a Pustularia cup to one's
ear, when it puffs one can not
only hear the sound of the
puffing but also feel the spray
from the asci as though the
ear were being sprayed by
a fine atomiser. When the
fungus is close to an ear, the
puffing can be heard even when
the room is not quiet and
one is talking to friends.
Using the method just described I have succeeded in hearing
the puffing of the following species :

Fig. 166. — Fruit-bodies of Pustularia
catinus. They puff audibly. A, a
whole fruit-body. B, a median-
vertical section ; h, the hymenium.
Copied by A. H. R. Buller from
Boudier's Icones Mycologicae, Tome
II, PI. 336. Natural size.

Aleuria repanda,
Aleuria vesiculosa,
Ascobolus stercorarius,
Caloscypha fulgens,
Ciliaria scutellata,
Galactinia badia,
Peziza aurantia,
Pseudoplectania nigrella,

Pustularia catinus,
Pyronema confluens,
Rhizina inflata,
Sarcoscypha protracta,
Sarcosphaera coronaria,
Urnula Craterium,
Urnula geaster.

Aleuria repanda puffs audibly in the same manner as Pustularia
catinus. I gathered one of its fruit-bodies from an old log in a wood
at Kenora on the Lake of the Woods, took it to Winnipeg, placed
it in a closed glass dish, and kept it there undisturbed for 24 hours.
I then took the cover from the dish, picked up the fruit-body, and
at once placed it close to my ear. Immediately thereafter the fruit-

THE SOUND MADE BY FUNGUS GUNS

333

body puffed vigorously, the puffing continuing for about 2 seconds.
During this time I felt my ear being sprayed with the contents of
many thousands of asci, and I distinctly heard a loud hissing sound.
Then the fruit-body became quite silent.

Aleuria vesiculosa (Fig. 167), which in the first volume of these
Researches I incorrectly called Peziza repanda, puffs audibly like
A. repanda and Pustularia catinus. SomxC horse-dung balls obtained
from the streets of Winnipeg in a frozen condition were kept moist

Fig. 1G7. — Aleuria vesiculosa ( = Peziza repanda of Vol. I), a Discomycete
that puffs audibly. The fruit-bodies came up spontaneously on horse
dung kept in a largo glass case in the laboratory at Winnipeg. They
puffed only whe;i fully expanded. Natural size.

in a large glass damp-chamber in the laboratory. The mycelium of
Aleuria vesiculosa grew spontaneously in the dung-balls and, after
about a month, gave rise to several beautiful clusters of fruit-bodies. ^
These were at first globose and closed, but they soon expanded,
the extreme margins of the cups remaining more or less incurved.
The discs were pallid-brown and the external surface furfuraceous,
i.e. coarsely granular or warted. The discharge of the spores did
not begin until the fruit-bodies had become more or less flattened
out. I placed one of the flattened fruit-bodies in a small glass box.
Next day I removed the lid of the box and at once put the fungus

1 The clusters resembled the one in the photograph reproduced as Fig. 432,
p. 508, in M. E. Hard's The Mushroom, Edible and Otherwise, Ohio, U.S.A., 1908.

334

RESEARCHES ON FUNGI

to my ear. Puffing took place almost instantly, and I distinctly
heard the little blast which lasted for 1-2 seconds. The fruit-body
was then put back in the box. On listening as before, I heard the
fruit-body puff on each of the next two succeeding days.

I found some large fruit-bodies of Peziza aurantia (Fig. 168) in

Fig. 1G8. — Peziza aurantia, a well-known Discomycete with deep orange or
orange-red fruit-bodies. The puffing of individual fruit-bodies when placed
against an ear was heard by the author. The fruit-bodies shown were
obtained from above sand below a stump at Ottawa by W. S. Odell. Photo-
graphed by the Photographic Division of the Geological Survey of Canada.
Natural size.

September, 1921, when at the Worcester Foray of the British
Mycological Society, and kept them in a vasculum for about 24 hours.
During this time they were slowly drying. I then opened the
vasculum and at once put one of the fruit-bodies to my ear. It
puffed loudly for about 1-2 seconds in the same manner as the
species of Pustularia and Aleuria already described. I succeeded
in demonstrating the audibility of puffing for this species to several
of my companions.

During the Worcester Foray just mentioned Miss M. A. Brett

THE SOUND MADE BY FUNGUS GUNS

335

found some of the subferruginous, ear-shaped fruit-bodies of Otidea
leporina (Fig. 164, p. 329) growing on the ground in Ockeridge wood.
When she touched them with her hand, they emitted clouds of
spores. She stooped down and, on placing her ear against one of
them, distinctly heard it puff. Puffing, therefore, can be heard
when fruit-bodies are growing under natural conditions in the open.

On September 5, 1924, in Kew
Gardens, I found a cluster of
fruit-bodies of Galactinia badia.
On ^Jicking a large one and at
once placing it against my ear,
I heard it puff vigorously.

Another large Discomycete
which I have seen puff vigorously
in the open, and have also heard,
is Urnula Craterium (Figs. 169
and 170). The fruit-bodies of
this fungus are black or blackish-
brown and they consist of a stem
3-4 cm. long and of a cup 3-4 cm.
in diameter and 4-6 cm. deep.
They come up in the spring on
buried or partially buried sticks
in woods, and I have met with
them under these conditions
both in western Ontario and in
Manitoba. Some twenty years
ago at Kenora on the Lake of the
Woods I found a group of mature U. Craterium fruit-bodies and was
much impressed by seeing them, as I gathered them, shoot dense
clouds of spores out from the mouths of their deep cups. Had I
put one of them to my ear, doubtless I should have heard it puff
loudly, but at the time I did not think of doing this. On May 8,
1933, I gathered a full-grown fruit-body of U. Craterium at Victoria
Beach, Lake Winnipeg. On examining it in the laboratory I found
that its asci were immature : their ends were already turned up
heliotropically toward the mouth of the cup, but the spores had not

Fig.

1G9. — Two fruit-bodies of Urnula
Craterium growing on sawdust and
chips of wood. The mature frviit-
bodies of this fungus puff vigorously
when touched, and tlie pufKng can
readily be heard if it takes place
close to the ear. Collected near
Ottawa by W. S. Odell. Photo-
graphed by the Photographic
l^ivision of the Geological Survey
of Canada. Natural size.

336

RESEARCHES ON FUNGI

yet been formed. The fruit-body was kej)t moist in a glass dish.
Five days after it had been gathered, I took it out of the dish, put
it to my ear, and distinctly heard it puff. On the next day, by
which time more asci had ripened, it puffed more vigorously and,
in so doing, gave out a loud fizzing sound.

The smallest Discomycetes that I have been able to hear puff

are Ciliariascutellata, Pyronema
confluens, and Ascobolus sterco-
rarius.

A fruit-body of Ciliaria
scutellata, about 1 cm. in
diameter (c/. Fig. 133, p. 279),
was removed from a board and
set in a covered dish. Four
days later I opened the dish,
put the fruit-body to my ear,
and distinctly heard the fruit-
body puff.

Some fruit-bodies of Pyro-
nema confluens, 1-2 mm. in
diameter and more or less con-
fluent (c/. Vol. V, Fig. 61,
p. 112), were growing on steri-
lised soil in a pot covered with
a sheet of glass. On removing
the glass and putting my ear
down to the fruit-bodies, I at
once heard them puff vigorously.
A considerable number of
fruit-bodies of Ascobolus stercorarius each about 2-4 mm. in
diameter, had developed on a sterilised horse-dung ball in the
laboratory. One afternoon between 4 and 5 p.m., on removing
the dung-ball from the culture dish and bringing it close to my
ear, I heard the fruit-bodies puff very clearly.

Urnula geaster is a remarkable Discomycete which grows on
roots of dead Elms in woods in the State of Texas, i.e. in a southern
region of the United States of America. There, on account of the

Fig. 170. — Another fruit-body of Urnula
Crateriuvi. Collected near Ottawa by
W. S. Odell along with the two shown
in Fig. 169. Photograj^hed by the
Photographic Division of the Geo-
logical Survey of Canada. Natural
size.

THE SOUND MADE BY FUNGUS GUNS 337

very noticeable cloud of spore-smoke which its mature fruit-bodies
emit when they are gathered in the open or jarred in the laboratory,
it is popularly known as the DeviVs Cigar. ^ A well-grown fruit-

FiG. 171. — Urnula geaster. To the left, a young fruit-body with the
liymonial cavity still closed. To the right, a mature fruit-body
beginning to expand and forming valves from above downwards.
Found on roots of a dead elm, Ulmus crassijolia, at Denton, Texas,
U.S.A., and photographed by W. H. Long. Natural size.

body, just before opening and expanding, is club-shaped and
resembles in form a stipitate Puff-ball (Fig. 171). It is about 4 inches
high, velvety brown without, and leathery in consistence. The
stipe is stout and about 2 inches long and continuous with it above

^ Fide personal communication by F. McAllister of the University of Texas,
December, 1926.

VOL. VI. z

338 RESEARCHES ON FUNGI

is a hollow thin- walled chamber which is oval, 1-5-2 inches in
diameter, and lined within by the hymenium. At first the hymenial
chamber is quite closed but, at maturity, it becomes slit from the

Fig. 172. — Urnula geaster. A fruit-body with six valves,
almost fully expanded, the hymenium exposed to view.
Found on a root of a dead elm, Ulrnxis crassifolia, at E)en.-
ton, Texas, U.S.A., and photographed by W. H. Long.
Natural size.

apex downwards into about six triangular segments (Fig. 172).
These segments then bend outwards and downwards, reminding
one of the segments of the outer peridium of a Geaster. Hence
the specific name. The puffing stage, according to information sent

THE SOUND MADE BY FUNGUS GUNS

339

me by Dr. W. H. Long, is only attained when the segments have
become well reflexed (Fig. 173). Professor I. M. Lewis, formerly

Fig. 173. — Urnula geaster. Two fruit-bodies fully expanded, seoa from above.
This is the puffing stage. Found on roots of a dead elm, Ulmus crassifolia, at
Denton, Texas, U.S.A., and photographed by W. H. Long. Natural size.

340 RESEARCHES ON FUNGI

of the University of Texas, told me that, when puffing takes place,
vast numbers of spores are liberated and the spores rise above the
hymenium to a height of several inches ; and he kindly sent me
some living fruit-bodies for study. Although these fruit-bodies,
packed in moss, were six days in coming from Austin, Texas, they
were still alive and able to discharge spores on arrival in Winnipeg.
I not only saw the puffing of some of these fruit-bodies but heard
it as well. The spores appeared to me to be shot straight outwards
from the hymenium to a distance of 2-3 cm., and I came to the
conclusion that their further ascent above a fruit-body was simply
due to their being carried upwards by air-currents. The puffing
took place, just as in Aleuria vesiculosa, immediately after a fruit-
body had been removed from a closed chamber where it had lain
undisturbed for some hours. On removing a fruit-body from its
chamber and putting it to my ear, I distinctly heard the blast as
numerous asci discharged themselves during 1-3 seconds.

Rhizina inflata, as is well known, has large, convex, inflated,
chestnut-brown fruit-bodies which appear above the ground about
the roots of certain Coniferae (Fig. 174). On September 27, 1920,
at Rabbit Lake, Kenora, central Canada, I found some of these
fruit-bodies growing on the surface of a sandy deposit above the
roots of some Pines {Pinus Banksiana) which had been burnt and
thus killed a year or two previously. I took several of the fruit-
bodies to Winnipeg and, on September 28, put them in crystallising
dishes covered with glass plates. On September 29, after the fruit-
bodies had been kept in the dishes for about 24 hours, I took one
of them out and held it in a beam of sunUght about 12 inches in
front of my eyes. When thus brought into drier air, the fruit-body
puffed vigorously for a few seconds and it continued to give off a
few spores for more than a minute. So much I observed with my
eyes, but I heard nothing. I then took another fruit-body out of
one of the dishes and held it close to my ear. I distinctly heard it
puff. The sound was not so loud as that made by Pustular ia
catinus and Aleuria vesiculosa but it continued longer. It was
loudest during the first two or three seconds and then gradually
died away in the course of about a minute. It reminded me of
the effervescence of freshly poured champagne or mineral waters.

THE SOUND MADE BY FUNGUS GUNS

341

During the next eight days, with the exception of the seventh, I
tested the fruit-bodies daily and on some days three times a day.
They puffed audibly every time I tested them. Altogether, there-
fore, the fruit-bodies puffed audibly for a period of nine days. The
puffing was heard not only by myself but also by Professor Frank
Allen of the Physics Department of the University of Manitoba,
by Professor Charles H. O'Donoghue of the Zoological Department,

Fig. 174. — Bhizma inflata. Large convex inflated chestnut-brown fruit-
bodies on t}ie ground above t}ie roots of Coniferae. Photographed at
Oxshott, England, by Somerville Hastings. Two-thirds the natural size.

and by the following members of the Botanical Department :
Professor H. F. Roberts, Mr. C. W. Lowe, Miss K. Scott, and Miss
I. Mounce. I also succeeded in demonstrating the audibihty of
the fruit-bodies to several students and to the members of the
Scientific Club of Winnipeg.

To hear a fruit-body of Rhizina iyijlata puff, it is necessary to
place it close against one's ear. I could hear the puffing of a fruit-
body very distinctly when the fruit-body was close against my ear,
only faintly when the fruit-body was removed to a distance of
one inch from my ear, and not at all when the fruit-body was
removed to a distance of three inches from my ear. This is easily

342 RESEARCHES ON FUNGI

accounted for by the smallness of the amount of energy transmitted
by the sound waves coming from the exploding asci and by the
well-known law of inverse squares, namely, that the intensity of
the sound travelling outwards in all directions from a given source
varies, when heard by the ear, inversely as the square of the distance
of the source of sound from the ear.

Taking advantage of the audibility of puffing in Rhizina inflata,
one can tell in the dark, merely by hstening and without using one's
eyes, whether or not spore-discharge is taking place. Thus I kept
some fruit-bodies for three days in a dark room. When, at intervals,
I took them out of their dishes in the dark and put them successively
to my ear, they puffed audibly just as they had done in the light
in the laboratory. I could not see the fruit-bodies, but my ears
assured me that their spore-discharging function was being vigorously
carried out. These experiments in the dark room show incidentally
that puffing is not dependent upon light.

The sound of puffing is a collective sound made up of the indi-
vidual sounds produced by the explosion of the individual asci,
and is comparable to the fizzing sound made by the bursting of the
individual bubbles arising in freshly poured effervescent beverages.
I beUeve that it is possible to hear even the individual asci explode.
I put a fruit-body against my ear in a very quiet closed dark-room,
and Hstened attentively to the later phases of the puffing
phenomenon. The sound, after a short time, became discontinuous
and comparable to the sound made by the first few large rain-drops
faUing at the beginning of a thunderstorm upon a tin roof. Just
as one can hear each individual drop of rain under the conditions
just described, so I thought I could hear each single ascus explode
as puffing was ceasing.

The hissing sound produced by the puffing of Puslularia catinus,
Aleuria vesiculosa, etc., is comparatively loud, but has a duration
of only about two or three seconds. On the other hand, the
effervescent sound produced by the puffing of Rhizina inflata is
comparatively feeble, but has a duration of from about one to
several minutes. Fruit-bodies of the Rhizina, kept in a closed
crystalhsing dish for a day and then taken out and placed close to
the ear, usually puffed audibly for upwards of a minute. One such

THE SOUND MADE BY FUNGUS GUNS 343

fruit-body puffed audibly for 4- 5 minutes and another for 9 minutes.
The puffing is always strongest during the first few seconds and
then gradually becomes feebler and feebler until it ceases to be
heard. The fruit-body which puffed for 9 minutes was hstened
to by myself and Miss I. Mounce. We passed the fruit-body from
one to the other at intervals, and we agreed in our observations as
to the gradual dying away of the sound of the puffing and as to the
approximate length of time during which it was audible.

On October 9, I revisited Rabbit Lake and found some more
Rhizina inflata growing about the roots of the dead Pine trees.
In one place several fruit-bodies had united laterally and had
formed an irregular mass covering about 25 square inches of ground.
The day was remarkably warm for the time of the year (70°-80° F.)
and the sun had been shining directly upon the fruit-bodies for
at least two hours. I broke off a small piece of the outer part of
the fungus-mass. Thereupon, the untouched but slightly shaken
remaining part of the fungus-mass puffed vigorously, and the cloud
of spores floated away in the sunlight. A short time thereafter
I stretched myself at full length upon the ground and jolaced an ear
against the upper surface of the fungus-mass, thereby touching it ;
and I thought I heard the fungus-mass puff for at least two seconds ;
but, unfortunately, the wind was sighing in some trees not very
far off so that conditions were not so still as were desirable, and
there was no opportunity of repeating the observation. However,
I have no doubt, from the observations made in the open with my
eyes and ears, as just recorded, that not merely visible but also
audible puffing sometimes takes place in the fruit-bodies of Rhizina
injiata under natural conditions.

I have but little doubt that, by putting the fruit-bodies close to
one's ear, one could hear the sound of spore-chscharge of most, or
perhaps all, of the Discomycetes which puff strongly. My method for
making explosions of asci audible is as simple as that of Columbus for
making an egg stand on end ; and, now that it has been described, it is
probable that the fact that ascus-guns, when firing together as huge
batteries, produce an audible sound will soon be generally confirmed.

Type V : Empusa and Entomophthora, Uredineae and
Hymenomycetes. — Single conidia, together with conidiophore-sap,

344 RESEARCHES ON FUNGI

are shot away from their conidiophores by Empusa ^ and Ento-
mophthora, often to a distance of 1-2 cm. ; and single basidiospores
are shot away from their sterigmata by Uredineae to a distance of
0- 4-1-0 mm., and by Hymenomycetes to a distance usually of
0- 1-0-2 mm. Up to the present, no sound has ever been heard
when spore-discharge has been taking place from the fruit-bodies
of these fungi ; and the projectiles are so minute and their pro-
pulsion so feeble that, probably, for the unaided human ear, Empusa
and Entomophthora and all Uredineae and Hymenomycetes mil
for ever be silent plants. However, physicists have invented
microphones which magnify sounds very greatly ; and it is possible
that, with the aid of these instruments, the collective sound of the
simultaneous discharge of thousands of spores from a large fruit-
body of one of the Agaricaceae might be made audible. So far as
I know, no one has tested this possibihty as yet. The best fruit-
bodies to use with a microphone in a trial experiment would probably
be a large Coprinus, such as Coprinus comatus or C. sterquilinus,
which has large spores and discharges its spores only in the zones
of spore-discharge bordering upon the autodigesting edges of the
gills. A large fruit-body of Coprinus comatus shoots away from
its gill-edges about 1,000,000 spores a minute or more than 10,000 a
second, and it is just possible that a very sensitive microphone might
make the collective sound of these numerous discharges faintly
audible.

Sounds Made by Fungus Guns are of No Biological Signifi-
cance.— Finally, it may be remarked that the sound given out by
fungus guns as they explode and the sound made when a fungus
projectile strikes some object are merely bye-products of the process
which has to do with the dispersion of the spores ; and, obviously,
they are neither of advantage nor of disadvantage to the fungi
concerned. While sounds are given out by, and are heard by, the
Higher Animals and some Lower Animals, so far as we know plants
never signal to one another by means of sound waves or respond
to sounds of any kind whatsoever.

^ For a photograph sliowing how far the spores of Einpusa muscae are shot,
vide Vol. I, 1909, Fig. 83, p. 255. The magnification there given should have been
1-3 and not f.

PART III

PSEUDORHIZAE AND GEMMIFERS AS ORGANS OF CERTAIN

HYMENOMYCETES

CHAPTER I

THE PSEUDORHIZA

Introductory Remarks — Collybia radicata — Mycena galericulata — Coprinus

mdcrorhizus.

Introductory Remarks. — The stipes of the fruit-bodies of certain
Agaricaceae are prolonged downwards through the soil for several
inches by so-called rooting bases. For rooting base Fayod ^ has
substituted the excellent term pseudorhiza. Among the species
having fruit-bodies with a characteristic pseudorhiza may be
mentioned : Collybia radicata, C. longipes, C. pulla, Tricholoma
macrorhizum, Pleurotus Ruthae, P. citrinatus, Pholiota radicosa,
Flammula inopus, Coprinus macrorhizus, and Collybia fusipes. In
all these species, with the exception of Collybia fusipes, the pseudo-
rhiza is annual and unbranched. In Collybia fusipes, as we shall
see, the pseudorhiza is perennial and branched.

A pseudorhiza forms a link between a mycelium vegetating in
a buried root or other buried nutrient substratum and the aerial part
of the fruit-body which produces and liberates spores. In forming
such a link, it is analogous to certain pseudo-sclerotia, sclerotia,
and mycelial cords, but it differs from these structures in being a
specialised part of a stipe of a fruit-body and not part of a mycelium.

The observations on the pseudorhizae of Collybia radicata and
Coprinus macrorhizus about to be recorded were made for the most
part in England during the years 1910-1915, and a brief account of
them was presented at the Ontario meeting of the American Phyto-
pathological Society in 1919.^

1 V. Fayod, " Prodrome d'une Histoire Naturelle des Agaricines," Ann. Sci.
Nat., T. IX, 1889, p. 214.

2 A. H. R. Buller, "The Pseudorhiza of certain Saprophytic and Parasitic
Agaricineae," Phytapalhology, Vol. X, 1920, p. 316.

347

348 RESEARCHES ON FUNGI

CoUybia radicata. — This species appears in the late summer and
autumn in woods and grassy places under certain trees, especially
Beeches. In England I have found it frequently under Beeches
{Fagits sylvatica) and once under a Horse Chestnut {Aesculus Hippo-
castanum). In central Canada, where no species of Beech grows, it
is absent,^ but it is common in the Beech woods of eastern Canada ^
and the United States.^ It occurs in Japan.* Howitt ^ observed
fruit-bodies coming up annually under an Ironwood tree {Ostrya
virginiana) at Guelph, Ontario, and Grove ® repeatedly has seen
fruit-bodies coming up under an Oak {Quercus Robur), which was
far distant from any Beech at Studley, England. CoUybia radicata,
therefore, is associated not merely with Beeches, but with Oaks,
Ironwoods, Horse Chestnuts and, doubtless, a number of other trees.

The stipe of CoUybia radicata is peculiar in that its aerial part,
which is from four to seven inches in height and somewhat thickened
below, is continued downwards beneath the soil. As it passes
beneath the soil, it becomes much swollen and fusiform, and it
then terminates in a long tapering root-like structure. The subter-
ranean " rooting base " of the stipe is often four or more inches
long (Fig. 175).

Fayod ' investigated the so-balled rooting base of the stipe of
CoUybia radicata and found that it originated solely by intercalary
growth. He discovered that the carpophores come into existence
in the first instance upon roots buried to a depth of 10 cm. beneath
the soil ; and he suggested that the fungus is a root-parasite.
The youngest fruit-bodies which he observed were bulbous and
only 2 to 3 mm. long. A longitudinal section showed him that the
bulbous base of a young fruit-body is composed of large barrel-
shaped cells mixed with fine filamentous hyphae, and that the two

^ G. R. Bisby, A. H. R. Buller, and J. Dearness, The Fungi of Manitoba, London,
1929, p. 32.

2 H. T. Giissow and W. S. Odell, Mushrooms and Toadstools, Ottawa, 1927,
p. 116.

** C. H. Kauftmann, The Agaricaceae of Michigan, Lansing, U.S.A., 1918, Vol. I,
p. 766, and Vol. II, Plate CLXVII.

* M. Shirai and K. Hara, A List of Japanese Fungi, ed. 3, 1927, p. 96.
^ J. E. Howitt, personal communication.

• W. B. Grove, personal communication.
' V. Fayod, loc. cit., pp. 214-215.

THE PSEUDORHIZA OF COLLYBIA RADICATA 349

kinds of elements are disposed parallel to the longitudinal axis of
the primordium. A study of successive stages revealed that the
so-called root arises from the multiplication and elongation of the
two sets of elements just mentioned. Thus, by intercalary growth,
that part of the primordium which is to expand into the aerial stipe
and pileus is gradually carried upwards to the surface of the soil
where alone it attains its full development. Fayod's description
of the development of the fruit-bodies of Collyhia radicata, unfortu-
nately, was not accompanied by any illustrations.

Fayod pointed out that the term root is unsatisfactory in
describing the subterranean part of the stipe of such a fungus as
Collyhia radicata, because the so-called root has neither root-cap
nor vascular bundles and arises exclusively by intercalary growth
and "not from an apical growing point. The so-called root also
differs from a true root in that it grows vertically upwards instead
of more or less downwards. In order to indicate that the basal
subterranean part of the stipe of Collyhia radicata and other similar
Agaricaceae is something different from a true root, Fayod gave
to it the name jpseudorhiza.^

My own observations on Collyhia radicata, so far as th'fey have
gone, confirm those made by Fayod. At Heyshott in England, in
September, 1913, there were several fruit-bodies growing around
the base of an old Beech tree. On carefully excavating the soil
surrounding the pseudorhizae, I ascertained that each of the fruit-
bodies was growing just above a Beech root. I succeeded in
definitely tracing one of the pseudorhizae downwards through the
soil and in making out its attachment to a buried root (Fig. 175, B).
The pseudorhizae of the other fruit-bodies were traced downwards
through the soil for several inches, but they broke off just before
their points of connexion with a root were reached. Owing to the
brittleness of the most slender and deepest part of a pseudorhiza
and to the compactness of the soil, it is often not easy to free a
pseudorhiza from the soil without breaking it or detaching it from
the root upon which it has grown. However, in my father's garden
at Birmingham, by taking more time and care than was possible
at Heyshott, I succeeded in exposing two pseudorhizae 16 cm. long

1 V. Fayod, loc. cit., pp. 214-215.

4
#-

^'ViyS^\fjS««^!*?ji:^'

Fig. 175. — Fruit-bodies of Collybia radicata provided with pseudorhizae attached to
roots of trees, etc., beneath the surface of the soil. A, two fruit-bodies on a
Horse-Chestnut root ; r, the root ; s, the soil, excavated ; each fruit-body con-
sists of an aerial stipe-shaft and pileus and of a long subterranean pseudorhiza ;
the spores falling from the pilei are being carried off by the wind. B, a vertical
section through a fruit-body attached to a thick Beech root near the surface of
the soil ; r, the root ; s, the soil ; the pseudorhiza is solid to the centre. C,
a vertical section through a fruit-body attached to the top of a Beech stump
covered with a thin layer of leaf-mould ; iv, wood ; I, the leaf-mould ; no
pseudorhiza has been developed. D, a piece of the outer surface of a root ;
the ring in its centre shows the very small point of attachment of the pseudo-
rhiza of a large fruit-body. A, observed at Birmingham ; B, at Heyshott; and C,
at Kew. A, B, and C, reduced to one-half the natural size ; D, natural size.

THE PSEUDORHIZA OF COLLYBIA RADICATA 351

and also the root of a Horse Chestnut to which they were attached
without breaking the connexions (Fig. 175, A). In Queen's Cottage
Grounds, Kew Gardens, I found a fruit-body attached to the top
of a Beech stump (Fig. 175, C).

The length of a pseudorhiza varies with the depth of the soil
overlying the infected root, through which the rudiments of the
pileus and aerial part of the stipe must be pushed up. The deeper
the overlying soil, the longer is the pseudorhiza, and vice versa.
If a fruit-body begins to develop 16 cm. below the surface of the
soil, the pseudorhiza becomes 16 cm. long (Fig. 175, A) ; if a fruit-
body begins to develop 7*5 cm. below the surface of the soil, the
pseudorhiza becomes 7-5 cm. long (B) ; while, if a fruit-body
develops on the top of a stump where the soil is very thin, the
pseudorhiza scarcely comes into existence at all (C). It is probable
that here, just as in Coprinus sterquilinus} light regulates the length
of the pseudorhiza by inhibiting the growth in length of the pseudo-
rhiza as soon as this organ has pushed up the rudimentary pileus
and aerial part of the stipe to the surface of the ground and has
thus come into a position to receive a light stimulus.

The pseudorhiza thickens and becomes fusoid just beneath
the surface of the ground. It is this fusoid portion only which
functions mechanically in supporting the weight of the whole of the
subaerial part of the fruit-body. The long tapering extremity of
the pseudorhiza, which is very thin and weak, merely serves for
the conduction of food materials. The principle of economy in
structure is here illustrated once more, for the thickening and
mechanical strengthening of the pseudorhiza is limited to that
part alone which has a mechanical function to perform.

The pseudorhiza and the aerial stipe-shaft are both solid, their
central parts being filled with white fibrils ; and both of these
organs are smooth on the exterior (Fig. 175, B). The pileus has
a somewhat slimy pellicle ; but, as experiment showed, drops of
rain-water are not absorbed through it. The fruit-bodies persist
for some time after their expansion, and the spore-discharge period
probably lasts for a week or ten days. The discharge of the spores
from beneath the pilei is represented in Fig. 175.

1 These Researches, Vol. IV, 1931, pp. 112-117.

352 RESEARCHES ON FUNGI

I have found fruit-bodies of Collybia radicata coming up on
two dead stumps. One of these stumps was at Kew Gardens and
the other at Birmingham. The former was in situ where it grew,
but the latter had been pulled up some two or three years previously
and had been laid upon the soil to support ivy. There can be no
doubt, therefore, that Collybia radicata can live as a pure saprophyte ;
and it may be that, even when it grows upon the roots of living
Beech trees, it is merely destroying roots which have been killed
by some other agency. However, it is not unlikely that the fungus
is a wound-parasite, i.e. a parasite which first invades the dead
tissues exposed at the surface of a wounded root and then slowly
invades and kills the living tissues adjacent to the dead tissues
first entered. The facts which lead one to suspect that Collybia
radicata is a parasite are : (1) the fungus grows on the roots of
living Beeches, Oaks, and Horse Chestnuts, (2) the fungus comes up
year after year beneath trees which have once become infected,
and (3) the fungus has developed a special organ — the pseudorhiza
— by means of which it successfully meets the requirements of its
subterranean mode of vegetation. Whether or not the fungus is
really a parasite, however, can only be decided by exact experiment,

Collybia longipes ^ was found by Fayod above the roots of an
Oak. 2 Its pseudorhiza is doubtless developed in the same manner
as that of Collybia radicata ; and the fungus probably has relations
with the Oak of the same nature as those of C. radicata.

Mycena galericulata. — This species Hves on dead wood. Its
fruit-bodies often develop at the surface of unburied stumps and
sticks, etc. Under these conditions each fruit-body consists of a
pileus and normal stipe only. However, it sometimes happens
that the woody medium in which the mycehum vegetates lies
several inches below the surface of the soil or vegetable mould.
When this is so, the stipe of each fruit-body possesses a pseudorhizal
prolongation similar to that of a stipe of Collybia radicata. The
accompanying illustration. Fig. 176, shows the relation of a group
of fruit-bodies to a block of wood which was buried about 4 inches
below the top of a layer of leaf -mould. The three fruit-bodies

1 Vide Cooke's Illustrations of British Fungi, PI. 201.

2 V. Fayod, loc. cit., p. 215.

THE PSEUDORHIZA OF MYCENA GALERICULATA 353

came into existence, in
and they then grew
upwards through the
overlying leaf-mould.
The youngest fruit-
body (a), at the time
the fruit- bodies were
found, had not yet
emerged but, by means
of a pseudorhiza, was
gradually pushing its
pileus upwards into the
light. Its pseudorhiza
appeared to be increas-
ing in length solely by
intercalary growth just
beneath the pileus and
the enclosed rudiment
of the aerial stipe-
shaft ; and its pileus
was very small, hard,
and conical. The free
end of the fruit-body,
in form and mode of
elongation, thus closely
resembled the root-tip
of a Phanerogam and
was admirably adapted
for pushing aside ob-
stacles in its upward
progress. It differed
from the root-tip of
radicles, however, in
that it was growing
upwards instead of
downwards. We may
conclude from the

the first place, at the surface of the wood,

VOL. VI.

Fig. 176. — Mycerm galericulata. Section through
leaf-mould, e, and a buried stump, d, to show
origin of fruit-bodies from the wood and mode
of development of the pseudorhiza ; a, a
pseudorliiza which is elongating just beneath
the rudimentary pileus ; b and c, f ullj' developed
fruit-bodies shedding spores ; in c, the pseudo-
rhiza and stipe, which are continuous with one
another, are both hollow in the centre.
Reduced to two -thirds natural size.

2 a

354 RESEARCHES ON FUNGI

study of such a set of fruit-bodies as that shown in Fig. 176 that
the pileus of Mycena galericulata remains in a very rudimentary
condition whilst travelUng through the soil and only begins to
expand when it has come to the soil's surface.

At its point of attachment to the woody substratum, a
pseudorhiza of Mycena galericulata consists of a small, firm, yellowish
swelling, and the shaft of the pseudorhiza, as it passes upwards
through the soil, gradually increases in diameter, and thus attains
its maximum diameter just beneath the surface of the ground.
The outer surface of a pseudorhiza is white and covered with fine
hyphae which attach themselves to leaf-debris, etc. ; and the interior
of a pseudorhiza is hollow like that of the aerial stipe-shaft with
which it is continuous (Fig. 176, c).

A pseudorhiza, hke an aerial stipe-shaft, grows upwards because
it is negatively geotropic. Sometimes a pseudorhiza, instead of
being straight, is crooked. When this is so, the crookedness has
been brought about by the pseudorhiza, when pushing upwards,
having encountered mechanical obstacles which could not be pene-
trated and which therefore were avoided by obhque growth hke
that which occurs with true roots under similar conditions.

Mycena galericulata, so far as I am aware, hves only as a sapro-
phyte on dead wood, and I have never seen it in any situation
which would suggest that it is a parasite. The fruit-bodies illus-
trated in Fig. 176 were rather large and more expanded than usual ;
but, after they had been gathered a day or two, the gills turned
pinkish in the usual way.

The fruit-bodies of Mycena galericulata shown in Fig. 176 had
bisporous basidia, which is in accord with the observations of
Patouillard,^ Ricken,^ and Lange.^ Ricken * states that the
bisporous basidia of M. galericulata serve to distinguish this species
from the very similar but four-spored M. tintinnahulum. However,
that there is a four-spored form of M. galericulata as well as a two-

^ N. Patouillard, Tabulae analyticae fungorum , Fasc. Ill, 1884, No. 214, p. 96.
2 A. Ricken, Die Bldtterpihe, Leipzig, Bd. I, 1915, p. 439.

^ J. E. Lange, " Studies in the x\garics of Denmark," Dansh Botanisk Arkiv,
Copenhagen, Bd. I, No. 5, 1914, p. 33.
* A. Ricken, loc. cit.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 355

spored is indicated by Rea ^ who has described the basidia of M.
galericulata as " generally with 2-sterigmata only " and by Bauch ^
who, in his hst of the Hymenomycetes having two-spored forms,
remarks that the fruit-bodies of M. galericulata found at Rostock
were " meist zweisporig." Moreover, Rea has informed me that
he has observed fruit-bodies of M. galericulata with quadrisporous
basidia. It may be that, as Bauch ^ found in Camarophyllu^
virgineus (one of the Hygrophoraceae), the two-spored fruit-bodies
of M. galericulata are haploid, while the four-spored are diploid.
Another possibility is that both forms are diploid, but that two
nuclei migrate into each spore of the two-spored form, while
only one nucleus migrates into each spore of the four-spored
form. The problem here suggested can be solved only by precise
investigation .

Coprinus macrorhizus. — This species has been confounded with
Coprinus lagopus (= C. cinereus = C. fimetarius "*), and in Massee's
British Fungus-Flora it is called Coprinus fimetarius, var. macro-
rhizus. A comparative study of the Coprini has taught me that
Coprinus lagopus and C. macrorhizus are independent species. This
conclusion is based not merely on studies in the field but also on a
comparison of pure cultures. The following are some of the points
by which the two species may be distinguished.

(1) Exterior of thepileus. The pileus of C. macrorhizus (Fig. 177)
is rounded at the top, pale, and brownish-grey, the brown being
particularly marked at the apex. The pileus of C. lagopus (Fig. 133,
Vol. Ill, p. 305) is more conical, and ashy-grey except at the
very apex which is brown. The floccose scale-hairs on the surface
of the pileus of C. macrorhizus are more matted than those of
C. lagopus.

(2) Breadth of gills. The gills of C. macrorhizus are distinctly
broader than those of C. lagopus. The more conical form of the

^ Carleton Rea, British Basidiomycetae, Cambridge, 1922, p. 384.

^ R. Bauch, " Untersuchungen iiber zweisporige Hymenomyceten. I. Haploide
Parthenogenesis bei Camarophyllus virgineus," Zeitschrift f. Botanik, Bd. XVIII,
1925-1926, p. 344.

3 Ibid., pp. 354-382.

^ Cf. these Researches : Vol. Ill, 1924, pp. 301-303 ; and Vol. IV, 1931, pp. 191-
193.

356 RESEARCHES ON FUNGI

pileus of the latter is associated with this fact (c/. Fig. 185, p. 367,
and Fig. 138, Vol. Ill, p. 316).

(3) Opening of the pileus. Before spore- discharge and auto-
digestion begin, the pileus of C. lagopus opens widely and thus
becomes almost flattened. The gills are therefore pulled some
distance apart from one another, with the result that, during spore-
discharge, the cystidia do not connect adjacent gills but simply
appear as free projections or pegs on the gill-sides (Fig. 146, Vol. Ill,
p. 325). On the other hand, the pileus of C. macrorhizus begins to

Fig. 177. — Coprinus macrorhizus. Young fruit-bodies grow-
ing on stable manure. Photographed at Birmingham,
England. Natural size.

shed spores while it is still campanulate, and in this species — as
may be readily observed in the field with a pocket lens or even with
the naked eye — the cystidia bridge the interlamellar spaces and
connect adjacent gills during the whole period of spore-discharge
(c/. Fig. 122, Vol. Ill, p. 287). C. lagopus belongs to the Lagopus
Sub-type of fruit-body organisation, whereas C. macrorhizus belongs
to the Atramentarius Sub- type. ^

(4) Shape of the spores. The spores of C. macrorhizus are dis-
tinctly shorter in proportion to their width than those of C. lagopus.
The spores of C. macrorhizus are oval in form and those of C. lagopus
elongated-oval.

1 Cf. these Researches, Vol. Ill, 1924, pp. 296, 301-302.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 357

(5) Stipe. The aerial part of the stipe of C. macrorhizus is usually
stouter and firmer than that of C. lagopus {cf. Figs. 180 and 185,
pp. 360 and 367, with Fig. 133, Vol. Ill, p. 305). The stipe of
C. macrorhizus frequently ends below in a long conspicuous sub-
terranean " rooting

base " or pseudo-
rhiza. In C. lagopus
such an organ is
usually absent.

( 6 ) Substratum.
C. lagopus is ex-
tremely common on
horse-dung balls, as
is shown by the fact
that fresh balls col-
lected at Vancouver
(British Columbia),
Edmonton (Alberta),
Shellbrook (Saskat-
chewan), Winnipeg
(Manitoba), and in
three different places
near Birmingham,
England, all yielded
fruit-bodies of this
species.^ C. macro-
rhizus, on the other
hand, very rarely
comes up on isolated
dung-balls but is ex-
tremely frequent on

large masses of horse dung, such as are represented by manure
piles, hot-beds, and the like. C. macrorhizus seems to be specially
adapted to flourish in dung well mixed with straw and heated by
the fermentation process.

^ W. F. Hanna, " The Problem of Sex in Coprinus lagopus," Annals of Botany,
Vol. XXXIX, 1925, pp. 433-434.

Fig. 178. — Coprinus macrorhizus. Mature fruit-bodies
shedding spores, growing on stable manure. The
one on the extreme right has its pseudorhiza in
view. Photographed at Birmingham, England.
Natural size.

358 RESEARCHES ON FUNGI

(7) Cultures. C. lagopus grows well on sterilised horse-dung
balls, and on this medium new fruit-bodies can be obtained with
certainty in about fifteen days after the spores have been sown.
On the other hand, C. macrorhizus grows relatively poorly on
sterilised horse-dung balls and takes a longer time to produce fruit-
bodies. Both species retain their structural peculiarities when
grown in parallel cultures side by side in the same laboratory.

(8) Size of fruit-bodies. The fruit-bodies of C. macrorhizus are
as a rule larger and less fragile than those of C. lagopus. Both in

Fig. 179. — Coprinus macrorhizus. Two fully expanded, revo-
lute, and almo.st exhausted fruit-bodies, removed from
stable manure. Some of tlie spores have settled on the
stipes. Photographed at Birmingham, England. Natural
size.

the open and in culture the fruit-bodies of C. macrorhizus, if pro-
duced at all, attain a certain minimum size which is considerable.
On the other hand, the fruit-bodies of C. lagopus, while able to
attain a large size under favourable conditions, yet on exhausted
horse dung or under conditions of competition may be extra-
ordinarily small. The stipes of C. lagopus vary in length from
about 10 cm. down to 1-10 mm. and their expanded f)ilei from about
3 cm. in diameter down to 0- 75-3-0 mm. Thus dwarf fruit-bodies
occur in C. lagopus (Fig. 138, A, B, C, Vol. Ill, p. 316) but not in
C. macrorhizus.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 359

Hitherto, the pseudorhiza or rooting base of the stipe of Coprinus
macrorhizus has nowhere been adequately described. In 1911,
Weir gave an erroneous account of the way in which it arises. He
referred to pseudorhizae definitely as roots {Wiirzeln). Translated
from the German, one of his statements is as follows : " The direction
of growth of the root in a homogeneous substratum is vertically
dowTiwards. Hard bodies are avoided by lateral twisting." ^
Again, in describing the origin of the " roots," he says that at first
a knot of hyphae comes into existence something like that of the
sclerotium of Coprinus stercorarius. " The knot . . . increases in
size, begins to elongate, and behaves itself in its upper and lower
halves in a different manner, in that the hyphae of the under half
become positively geotropic. Soon after the formation of this
rudiment {Anlage), the hyphae on the under side become matted
at one point and grow downwards like a root. It is remarkable
that the hyphae, even in the substratum, go on growing so as to
form a firm unified structure by means of which they remove them-
selves more and more from the light and apparently seek the
optimum conditions of moisture and food-materials." 2 His further
remarks on this matter it is unnecessary to repeat as, like those
just quoted, they are based on the erroneous supposition that the
root-like organ of the fungus grows downwards through the sub-
stratum like the root of a Phanerogam. I shall now endeavour
to show : that the root-like organ is really a pseudorhiza, like that
of Collybia radicata ; that, unlike a root, it comes into existence
not by apical growth, as Weir supposed, but by intercalary growth ;
that it is negatively geotropic and not positively geotropic ; and
that, in consequence, it grows upwards and not downwards through
the substratum. It is the thin lower end of the pseudorhiza which
is first formed and not the thick upper end.

For the purpose of my investigation, I examined a large number
of fruit-bodies of Coprinus macrorhizus which were coming up on
a long flat-topped pile of horse manure which had been removed
from some stables and was well mixed with straw. The manure

1 J. Pv. Wrir, •■ Untersuchungen iiberdicGattung Coprinus," Flora, Bd. CIII. 1911,
p. 313.

- Ibid., pp. 312 313.

360

RESEARCHES ON FUNGI

pile was in a state of fermentation, so that only a few inches from
the surface it was decidedly hot to the hand. On digging down

Fig. 180. — Coprinus macrorhizus. Fruit -l)odies in various stage.-; of development
with short pseudorliizae. A and B, each with a p.seudorhiza capped by a pileiis
growing upwards through the substratum. (', a fruit-body nearing the surface
of the ground with an enlarging pileus. D, E, F. stages in the elongation of the
stipe and the expansion of the pileus. G and H, the stipes have attained full
length ; in G, the gills are disappearing through autodigestion and spores are
being shed ; in H, tlie pileus has been almost completely destroyed through
autodigestion, and spore-discharge has ceased. Natural size.

into the manure, I found that many of the fruit-bodies had very
long rooting bases. Using Fayod's terminology, we shall now

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 361

refer to these rooting bases as j^seudorhizae. Illustrations of some
of the fruit-bodies are shown in Figs. 177-187.

I made excavations in the manure pile and discovered that

Fig. 181.-('o/;///(».v ni'icrurhizits. Fniit-boclies excavated, tkuiiig tlie dovelopiuent
of their pseudorhizae, froin below tlie surface of a horse-dung manure heap.
Tlie position of tlie partit-ular j)iece of the substratum from which each pseutlo-
rhiza was growing is shown in every case. A-F, elongation of the pseutlorhiza
by intercalary growth just below the ru(Hnientary terminal pilous. C! J, pilei
enlarging on being brought up to near the surface of the substratiun l)y their
respective pseudorhizae. K, a pseudorhiza growing through densely matted
straw some inches below the sin-face of the substratum. Natural size.

young fruit-bodies, hke those shown in Fig. 180 at A, B, and C
and in Fig. 181 at A, B, and C, were pushing up to the light a few
inches below the general surface of the manure. From a study of

362

RESEARCHES ON FUNGI

a long series of intermediate fruit-bodies, some of which are shown
in Figs. 181 and 186 (p. 369), it became clear that fruit-bodies which
develop pseudorhizae arise as tiny primordia not at the surface of
the manure as Weir would have us suppose, but at some distance
belotv it. These primordia are at first minute balls about 1 mm.
across (Fig. 181, A). They are attached to more sohd parts of the
substratum and frequently arise at the surface of a single straw

making part of a bundle
of straws. Their subse-
quent growth, no doubt,
is accomplished at the
expense of an extensive
mycelium to which they
are attached by their
bases.

In Fig. 181, A-J,
are shown pseudorhizae
in various stages of de-
velopment , after they had
been excavated from the
m anure pile . In Figs .180
and 185 (p. 367) are
shown a number of fruit-
bodies with shorter or
longer fully developed
pseudorhizae in, situ mth
the surface of the manure pile indicated by means of a broken line.
It was found that, when fruit-bodies arise at the surface of the
manure, as they sometimes do, no pseudorhizae whatever are
formed. In Fig. 182, A to D, are shown stages in the development
of fruit-bodies whose origin in the manure pile was superficial. It
is clear that the production of a pseudorhiza depends simply on the
position of origin of the fruit-body primordium. If the primordium
is developed at the top of the substratum, no pseudorhiza is produced
(Fig. 182) ; if it is developed one or two inches below the surface of
the substratum, the pseudorhiza becomes about one or two inches
long (Fig. 180) ; and, if it is developed about four inches below the

Fig. 182. — Coprinus itmcrorkizus. Fruit-bodies
wliich originated at tlie surface of the sub-
stratum and have therefore not developed
pseudorhizae. A, B, C, E, successive stages
of development. D, a section of E showing
absence of pseudorhiza ; the spores on tlie gills
are ripening from below upwards. Natural
size.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 363

surface of the substratum, the pseudorhiza becomes about four
inches long (Fig. 186, p. 369).

The development of a fruit- body primordium will now be
described in detail. The pseudorhiza of a fruit-body which has
originated a few inches below the surface of the manure and which
has shed its spores and withered away aerially sometimes develops
a large number of primordia ; and, occasionally, some of these
primordia develop into fruit-bodies which produce pseudorhizae of
their own, come above groimd, and open out in the usual manner
(Fig. 187, p. 371). The primordia arising on old pseudorhizae
develop in just the same manner as those produced directly on the
surface of a straw and are easier to procure. Old pseudorhizae
bearing primordia were therefore used for studying the earUest
stages of fruit- body development.

The material was fixed ^ in Fleming's fluid (weaker solution)
for 24 hours, washed for 24 hours in running water, and then placed
in 30 per cent, alcohol. It was then brought up gradually to absolute
alcohol and, after being passed through xylol in the usual manner,
was embedded in paraffin. Sections were cut with the microtome
and double-stained in iron-alum-haematoxylin ^ and Bordeaux red.^

The earliest stages in the development of the fruit-bodies of
Coprinus macrorhizus are very similar to those of Psallio'a campestris
described by Atkinson * in 1906. The primordium of the carpophore
as a whole in its youngest state is a homogeneous body composed
of slender uniform dense hyphae which are woven in a complex
manner into an even meshwork, and surrounded by a thin layer of
hyphae which are looser and less dense in their arrangement. This
outer looser layer can be considered as a universal veil. It is quite
distinct in all the youngest stages (Figs. 183 and 184) and grows
for some time. Finally, it ceases to grow and, as the pileus expands,
splits up and thus gives rise to the hairy scales which are such a

* <'f. Chamberlain, Methods in Plant Histology, Chicaffo, 190."). p. 248.

^ This was the .same as Haidenhain's solution {vide Chamberlain, loc. cit., p. 250)
except for the fact that 1 ■ 5 per cent, aqueous solution of iron alum was used instead
of ferrous ammonium sulphate.

^ A 1 per cent, aqueous solution for 3 minutes.

* ('•. F. Atkinson, " The Development of Agaricus campestris," Botanical Gazette,
Vol. XLII, 190(j, pp. 241-264.

364

RESEARCHES ON FUNGI

marked characteristic of the mature pileus. In a very young
primordium there is no evidence of a differentiation into stipe and
pileus : the inner mass of hyphae surrounded by the universal veil
appears to be homogeneous, just as in Psalliota camjyestris . As a
primordium becomes somewhat larger and older, and before there
is any evidence of an external annular fitiTow differentiating pileus
and stipe from one another from without, stained longitudinal

sections exhibit, near
the upper end of the
young fruit-body and
some distance in from
the surface, two small
deeply stained areas.
These are really part
of an annular area
within the fruit-body,
which is composed of
hyphae which are
densely compacted
and rich in proto-
plasm. These hyphae
make up the primor-
dium of the gills
(Fig. 183). It is to be
noted, therefore, that
the primordium of the
gills arises as in Psalliota campestris,^ i.e. that it comes into existence
internally at a time when the fruit-body is homogeneous and com-
pact except for the looser envelope. After the primordium of the
gills has come into existence, interlamellar spaces arise within it,
and the plates of tissue thus separated from one another develop
into the gills (Fig. 184 and in Vol. Ill, Fig. 140, p. 318). A gill-
chamber apart from these interlamellar spaces was not observed.
The gills in their youngest stage have their long axes directed
perpendicularly to the long axis of the carpophore (Fig. 183) ; but,
with further growth, they become obliquely situated, their inner

1 Cf. G. F. Atkinson, he. cit., p. 249.

Fig. 183. — Copriniis imtcrorhizus. A median-vertical
section of a very young fruit-body with its hymeno-
phore just becoming differentiated. As yet no
pseudorhiza has been developed. Magnifi-
cation, 46.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 365

edges remaining in contact with, and in continuity with, the
primordium of the stipe (Fig. 184).

With the differentiation of the primordium of the gills, the other
parts of the young fruit-body become
delimited. We can now distinguish
the primordium of the pileus-flesh
and the primordium of the stipe.
The universal veil at this stage is
seen to form a continuous layer
which encloses both pileus and stipe
(Fig. 184). Soon after the young
gills have begun to grow downwards,
a very slight annular furrow makes
its appearance on the outside of
the whole fruit-body (Fig. 181, B-D,
p. 361). This furrow, which becomes
more and more pronounced as the
gills grow in size (Fig. 181, G-J),
marks off the pileus which lies above
it.

The annular furrow, just referred
to, may be considered as dividing
the stipe into two parts, an upper
interpilear part which is enclosed
between the gills, and a lower sub-
pilear part which is entirely below
the gills. These two parts are con-
tinuous with each other ; but, as we
shall see, it is convenient to dis-
tinguish between them.

If a fruit-body develops directly
on the surface of the substratum,
as sometimes happens in nature
(Fig. 182, p. 362) and in artificial
cultures, the primordium of the

stipe as a whole becomes differentiated into two parts. The
interpilear part becomes the primordium of the shaft of the

Fig. 184. — Coprinus macrorhizus.
A median-vertical section
through the upper part of a
slender cylindrical fruit-body
which was pushing its way
upwards through manure (c/.
Fig. 181, B and C ; also Fig. 186,
h and c). The pseudorhiza is
pushing up the rudimentary
apical pileus by elongating in an
intercalar J' zone of growth which
is just below the level of the
base of the gills. At this stage
of development, the universal
veil covering the apex of the
fruit-body is compact and func-
tions like a root-cap. Magnifi-
cation, 19.

366

RESEARCHES ON FUNGI

stipe, and the subpilear part the primordium of the base of
the stipe.

The various j)rimordia are then related as follows :

/the primordium of )

the gills together forming the

primordium of the

The primordium of
the fruit-body as a
whole producing :

the primordium of
the pileus-flesh

pileus

, the primordium of

the primordium of | the stipe-shaft

the stipe pro--! , . t e

- . I the primordium of

\ ducmg : , . i

^ \ the stipe- base.

Now, when a fruit-body is produced on the surface of the sub-
stratum, the primordium of the base of the stipe gradually thickens
and elongates a little, the elongation taking place chiefly in its upper
part ; and that is all. The primordium of the shaft of the stipe,
however, elongates after a time enormously, and so carries the pileus
high into the air (Fig. 182, p. 362).

When a fruit-body starts its development not at the surface
of the substratum, but at some distance below it, the primordia
originate in the same manner as that just described. But here the
primordium of the base of the stipe becomes especially important.
In its upper part, just below the annular furrow, the parallel hyphae
of which it is composed grow enormously in length by intercalary
growth. The result of this is that the primordium of the pileus
(flesh, gills, and veil), together with the primordium of the shaft cf
the stipe, is pushed upwards through the manure, and an elongating
root-like structure, the pseudorhiza, comes into existence. The
intercalary growth at the top of the pseudorhiza continues until
the primordia of the pileus and stipe-shaft have been carried up
to, or nearly up to, the surface of the substratum. It then ceases.
As the pileus is carried upwards, the pseudorhiza not only elongates
but, as a rule, gradually thickens, so that the diameter of the
youngest and highest part is often very much greater than that of
the oldest and lowest part {cf. Figs. 180 and 185, pp. 360 and 367).

As the pileus approaches the loosest and uppermost layer of

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 367

manure, it enlarges, and its gills become better differentiated. After
the pseudorhiza has ceased its intercalary growth, the stipe-shaft

Fig. 185. — Coprinus macrorhizus. Sections of finiit-bodies in various
stage3 of development, all with a pseudorhiza. A, the solid
pseudorhiza is capped by a very rudimentary pileus which is sliown
enlarged at G ; the fruit-body had not yet reached the surface of the
ground. B, a fruit-body approaching the surface of the ground : its
pileus is enlarging. C, D, E, F, succei5sive stages in the development
of the pileus and subaerial stipe. The dotted line shows the general
level of the substratum. In C, which lias a hollow pseudorhiza, the
spores have not yet been developed : the gills are white. In D, the
spores are ripening from below upwards : the gills are therefore turning
V)lack from below upwards. In E, black spores are present all the
way vip the gills, the aerial stipe-shaft is elongating, and the pileus
expanding. In F, the stipe-shaft has elongated, the gills are under-
going autodigestion, and spores are being shed. In G, which is the
apex of A magnified, the gills and pileus-flesh can be clearly perceived ;
i, the zone of intercalary growth of the pseudorhiza. A-F, natural
size ; G, magnification, 3.

primordium, which has been enclosed between the gills, begins to
elongate. This results in the pileus being torn away from its base.
The universal veil is broken and a ring-like scar is usually left behind

368 RESEARCHES ON FUNGI

at the base of the stipe {cf. Fig. 180, p. 360). As the stipe elongates,
the pileus continues its development. The dimorphic basidia, the
paraphyses, and the cystidia become differentiated, the cystidia
grow in length, and soon the spores appear on each gill from below
upwards. As the pileus, in opening out, becomes campanulate, the
spores begin to fall down in the interlamellar spaces. With the
production of spore-freed gill-surfaces arising from below upwards,
autodigestion sets in and the gills are then gradually destroyed from
below upwards in the manner which has been described for other
Coprini (Figs. 180, p. 360, and 185). The pileus opens out rela-
tively slowly, much more slowly than in C. lagopus.

The whole of a fruit-body (pseudorhiza, stipe, and pileus) is
produced at the expense of a mycelium which vegetates deep down
in the manure. This mycelium is present in the hard masses of
manure, on the surface of which the primordia arise in the first
instance, as shown in Fig. 186. We really have an arrangement
similar to that already described for CoUybia mdicata and for
Mycena galericiUata, which grow on wood beneath the soil.

The lower end of a pseudorhiza is remarkable for the smallness
of its diameter, but it must be remembered that the only function
which it has to perform, after it has pushed up the primordium of
the pileus through the manure, is that of conduction. There is no
need for it to be mechanically strong, as it has no weight to support.
Only on nearing the surface of the ground does the pseudorhiza
become thickened. There can be little doubt that this thickening
is correlated with the demands for mechanical support which must
subsequently be made upon the pseudorhiza by the weight of the
pileus and stipe.

From the surface of the pseudorhiza fine hyphae arise which
pass out into the substratum and become attached to the manure.
It will be remembered that similar hyphae occur on the pseudorhiza
of Mycena galericulata. In all probability, these hyphae are used
chiefly for fixing the pseudorhiza and thus enabling it to push the
primordium at its end upwards with more ease. They may also
conduct to the fruit-body a certain amount of water, but they are
probably not nutritive in the sense that they collect food materials
other than water. There can be but little doubt that the materials

a

Fig.

186. — C'oprinus macrorhizus. Development of a set of fruit-bodies with very long
pseudorhizae, shown in a vertical section through a pile of stable manure. At the base of
the Figure is more solid manure from which the pseudorhizae are springing ; toward the
top, the manure is looser and the straw more evident. Stages in development, drawn from
actual specimens, are indicated by the letters a to/. In a, b, and c, the blunt upper end
of each pseudorhiza consists of a rudimentary pileus, already with tiny gills within ; ind,
e, and/, tlie pseudorhiza, tlirough intercalary growth, has brought each pileus to the surface
of the substratum. At d, the pileus is swelling ; at e, the pileus is expanding and the
aerial stipe-shaft elongating ; at/, the stipe-shaft is fully elongated and the pileus, which
has shed its spores, is now greatly reduced owing to autodigestion. Natural size.
VOL. vr. 2 B

370

RESEARCHES ON FUNGI

for the construction of the stipe and pileus are conducted upwards
from a hard mass of manure through the base of the pseudorhiza.
In support of this view may be cited the analogous case of Collybia
radicata in which the whole fruit-body is produced at the expense of
a mycelium vegetating in a tree-root buried several inches beneath
the soil (Fig. 175, A and B, p. 350).

In passing upwards through the substratum, the pseudorhiza
is doubtless directed, like the stipe, by the stimulus of gravity.
Harder and softer parts of the substratum must be traversed. The
softer parts are directly penetrated, but the harder ones, such as
dense masses of straw, can only be avoided by oblique or lateral
growth. Sooner or later, often by a very tortuous course of from
three to six inches, the surface of the manure is reached. The
twisted pseudorhizae shown in Figs. 181 (p. 361) and 186 tell a
tale of obstacles which have been encountered during upward
growth and have been grown around. In general, the length of a
pseudorhiza varies with the depth in the manure at which the
primordium of the fruit-body has originated.

The older and thinner parts of a pseudorhiza are quite solid,
but the younger swollen parts, beneath the base of the stipe-shaft,
although often sohd (Fig. 185, D and E, p. 367), are sometimes
hollow in the centre (Fig. 185, C). The hollow space, when present,
is continuous with- that of the stipe.

A pseudorhiza, before the pileus has shed its spores, is usually
unbranched. Occasionally, how^ever, I have observed indications
of the putting out of a branch laterally (Fig. 187, E), but this is
very rare. Also, before a fruit-body at the end of a pseudorhiza
has shed all its spores, primordia — but primordia only — of a number
of new fruit-bodies may be developed on the surface of the
pseudorhiza (Fig. 187, B). Nevertheless, I have never seen any-
thing corresponding to the illustration published by Weir ^ in which
he shows one chief fruit-body as yet unexpanded and four long
branches coming from the pseudorhiza and all bearing secondary
fruit-bodies of considerable size. However, branching not in-
frequently takes place from an old stout pseudorhiza when the
fruit-body at its end has shed its spores and withered to the base

1 J. R. Weir, he. cit., Fig. 21, p. 317.

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 371

of the stipe (Fig. 187, C). I should regard Weir's illustration as
correct, so far as the branching is concerned, had the chief and oldest

Fig. 187. — Coprinus macrorhizus. Branching of the pseudorhiza. The dotted line
indicates the general level of the substratum. A, a young fruit-body with
a very stout pseudorhiza likely to produce new fruit-bodies when the first has
been exhausted. B, fruit-body begiruiing to shed spores, having a pseudorhiza
which has already given rise to the rudiments of a number of new fruit-bodies.
C, a very stout pseudorhiza which gave rise to a large subaerial fruit-body which
shed its spores, died down, and is now represented merely by a stump. The
pseudorhiza subsequently gave rise to numerous rudiments of new fruit-bodies,
four of which are now developing normally. D, the terminal fruit-body was
injured and has ceased to develop, and new fruit-bodies are arising on the
pseudorhiza. E, the pseudorhiza which is springing from a straw, has a terminal
fruit-body and two lateral rudimentary ones. Natural size.

fruit-body been represented as having rotted down to the top of
the pseudorhiza : but this was not done. Weir seems to have
combined two stages of development in a single drawing. From
Weir's illustration, as it stands, one would judge that the main axis

ZT^'

RESEARCHES ON FUNGI

and the four chief branches had all been produced simultaneously
or nearly so ; but I do not think that this happened. Rather, a
single stout pseudorhiza was first produced ; then the large fruit-
body at its end opened, shed its sj^ores, underwent autodigestion,
and withered down to its base ; and, finally, from primordia which
were produced on the pseudorhiza either whilst the first fruit-body
was expanding or after it had shed its spores, new pseudorhizae
and secondary pilei were subsequently developed.

The normal production of a number of secondary fruit-bodies
from an old and large pseudorhiza which bears the stump of a large
primary fruit-body was observed several times (Fig. 187, C). Injury
to a primary fruit-body, so that this withers before it has expanded,
may also lead to the production of secondary fruit-bodies (Fig. 1 87,
D). The development of secondary fruit-bodies upon an old
pseudorhiza is no doubt correlated with the fact that the food
materials contained within the pseudorhiza have not been exhausted
by the formation of the primary fruit-body. New fruit-bodies,
as Weir also observed, are produced until exhaustion is complete.
So far as my observations have gone, it is only the larger and more
vigorous pseudorhizae which jiroduce secondary fruit-bodies. Weak
slender ones often show no trace of them. Doubtless, by injuring
the pilei terminating pseudorhizae, one could cause secondary fruit-
bodies to come into existence at will.

What is the function of the pseudorhiza of Coiwinus macrorhizns ?
The answer is as follows. The primordia of the fruit-bodies of
C. macrorhizus are often produced on a deep-seated mycelium at a
little distance below the surface of the nutrient substratum and,
when this occurs, the pseudorhiza serves as an organ for pushing
upwards to the surface of the substratum those parts of the fruit-
body — the rudimentary pileus and the rudimentary stipe-shaft—
which are destined to complete their development aerially. The
frequent production of hundreds of fruit-bodies of C. macrorhizus
on a manure pile where perhaps no other agaric is to be seen testifies
to the success of this species in the struggle for existence.

When visiting a large mushroom cave near Paris, I observed
that Cojjrinus macrorhizus was growing on some of the beds. The
fruit-bodies had the normal size and were provided with the

THE PSEUDORHIZA OF COPRINUS MACRORHIZUS 373

characteristic pseuclorhiza. Since the beds had been left in utter
darkness from the time when they had been made up, it is clear
that light could have had nothing to do with the development of
the fruit-bodies. In particular, the direction of the growth of the
pseudorhiza could not have been influenced by a heliotropic stimulus.
Among the conclusions to which Weir ^ came in his already
mentioned investigations upon Coprinus macrorhizus was that this
fungus possesses " a positively geotropic, root-like sclerotium {ein
positiv-geotropisches, ivurze'dhnlirlies Sklerotium).''' This descrip-
tion of the pseudorhiza is entirely erroneous. The pseudorhiza,
as we have seen, grows upwards instead of downwards, its mode of
growth is intercalary and therefore not like that of a root, and
there is no ground to justify the view that it is to be regarded as a
sclerotium. A sclerotium is an independent more or less compact
mass of mycelium in which food materials are stored and which,
after resting for a longer or shorter time, gives rise to one or more
sporophores or to a new mycelium. But a pseudorhiza does not
consist of mycelium, for it is part of a sporophore ; nor is it a resting
body ; and the food materials which it contains are not. reserve
food materials but materials in transit to the developing pileus and
stipe-shaft.

1 Weir, lor. cit., p. 319.

CHAPTER II

THE PERENNIAL PSEUDORHIZA OF COLLYBIA FUSIPES

Introduction — Historical Remarks — Fruit-body Clusters and their Pseudorhizae —
The Sujiposed Sclerotium — Evidence that the Pseudorhiza Persists — Mode of
Development of a Compound Pseudorhiza — Lateral Crafting — Healing of
Pseudorhizal Wounds — The Mycelium and the Problem of Parasitism — The
Functions of tiie Pseudorhiza and the Significance of its Persistency — Sarco-
safphd prntracla.

Introduction. — Collybia fusipes, one of the best-know^l of the fleshy
fungi, commonly occurs on the ground near the trunks of trees,
particularly those of Beeches (Fagus) and Oaks (Quercus). The
fruit-bodies are sometimes solitary but they usually come up in
smaller or larger clusters, and two such clusters are shown in a
Beech grove at Kew Gardens in Fig. 188. The pileus, when fully
expanded, is about 1-5-2 -5 inches wide, but larger ones are not
rare and I have seen one six inches wide (the left fruit-body in
Fig. 189). The top of the pileus, when young, is reddish-bay ; but,
in age, it becomes dingy tan-colour and is often speckled with
numerous small dark spots and blotches as if it had been injured
in some way. The stipe varies from about 2 to 6 inches in length
and from about 0 • 25 to 1 inch in thickness ; and it is usually more
or less fusiform (hence the specific name), being thickest in the
centre, tapering somewhat upwards toward the pileus, and tapering
greatly toward its base where it is attached in the soil. Its exterior
w^all is reddish-brown and cartilaginous, and within it is at first
fibrously stuffed, afterwards becoming somewhat hollow. The
spores are colourless, small, and thin- walled ; and each one passes
through all its developmental stages from its first origin to its dis-
charge from the sterigma in about one hour and five minutes.^

1 These Researches, Vol. II, 1924, pp. 44, 49, and 54.

374

THE PERENNIAL PSEUDORHIZA 375

Collybia fusipes, whose clustered fruit-bodies are so often seen
over the roots of Beeches and Oaks in Europe and England, seems
to be somewhat rare in North America. Mcllvaine and Macadam ^
state that in the West Virginia mountains it is frequent, but it is
not recorded as occurring in North America by such experienced
mycologists as Atkinson, 2 Kauffman,^ and Murrill.* Dr. R. E. Stone
has informed me that he saw fruit-bodies of C. fusipes under a
Beech {Fagus grandifolia) at Guelph, Ontario, in 1920 ; but Giissow
and Odell ^ do not mention C. fusipes in their account of the mush-
rooms and toadstools of eastern Canada. My colleague Dr. G. R.
Bisby ^ and I have never found C. fusipes in central Canada.' All
of the aiithor's observations on C. fusipes, about to be recorded,
were made in England.

Historical Remarks. — Bulliard,^ as shown by the illustration
in his Plate 106, appears to have found the fruit-bodies in a cluster
attached to something looking like a small sclerotium. In 1843,
Leveille,^ in his Memoire sur le genre Sclerotium, called attention to
Bulliard's illustration and gave the following account of the sup-
posed sclerotium and of the origin of the fruit-bodies. " Agaricus
fusipes Bull, grows in summer and autumn at the foot of trees,
sometimes in groups and sometimes solitarily. Its structure is
most curious. It is remarkable for its fusiform stipe deeply buried
in the earth. Bulliard (PI. 106) appears to have found it on a
sclerotium : this is a supposition ; but, as we have met with it

^ C. Mf] lvalue and R. K. Macadam, Owe Thousand American Fiuigi, Indianapolis,
1902, p. 116, Plate XXIX, A, No. 4.

2 G. F. Atkinson, Studies of American Fungi. Mushroov},'^, edible, poisoiious,
etc., Ithaca, U.S.A., IfiOO.

^ C. H. Kauffman, The Agaricaceae of Micltigan, Lansing, IT.S.A., 1918.

■* W. A. IMurrill, in "The Agaricaceae," North American Flora, Vol. IX, 1910,
p. 375 ; also Edible and Poisonous Mushrooms, New York, 191G.

^ H. T. CUissoAV and W. S. Odell, Mttshrooms and Toadstools, an Account of the
more Common Edible and Poisonous Fungi of Canada, Ottawa, 1927.

® G. R. Bisby, A. H. R. Buller, and J. Dearness, The Funcji of Manitoba, London,
1929, p. 32.

^ It is possible that Colhjbia fusipes does not occur in Japan, as it is not mentioned
in Shirai and Hara's ^4 List of Japanese Fungi, 1927.

8 P. Bulliard, Herbier de la France, Paris, 1782, Plate CVI.

^ J. H. Leveille, " ■Memoire sur le genre Sclerotium," .4?i?j. (Sri. iVa<., ser. 2, T. XX,
1843, pp. 228-229.

376

RESEARCHES ON FUNGI

Fig. 188. — Collybia fii.slpes. Two clumps of fruit -bodies coming up on grass, each
developing from a subterranean persistent pseudorliiza attached to one of the
roots of the Beech tree. Photographed in Kew Gardens,
natural size.

Much reduced from

THE PERENNIAL PSEUDORHIZA -^.^^

several times in this condition, we can believe that the tubercle
from which Bulliard's fungi are springing is a true sclerotium. The
existence of this sclerotium, however, is not constant ; usually the
stipe is attached directly to dead roots or to old pieces of wood
embedded in the earth. When one has observed the fungus in a
certain place one year and one returns there at about the same time
the following year, one almost always again finds individuals of the
same species : if one then digs up the fungus carefully, so as to
obtain everything that is attached to it, one sees an elongated,
irregular, spongy, black body from which spring the new fruit-
bodies. This body is not a sclerotium, but rather the stipe of the
fruit- body of the previous year, which has served as the root-stock
(souche) for new out-growths and which has fulfilled the functions
of a sclerotium. In the following year, the stipes of the fruit-
bodies of the second year serve in their turn as root-stocks, and so
on, successively giving rise to new fruit-bodies ; in such a manner
that an Agaricus fusipes which three or four years before had its
stipe deejoly buried in the earth ends up by finding itself at the
surface. This is the only example of growth of this kind that we
know in the numerous families of the Mushrooms and Toadstools
{Cham}Agno7is).'''

More than three centuries ago, in 1578, Clusius, who was living
in Hungary, was preparing to write his Brevis Historia — the first
monograph on fungi ever published ; ^ and he conceived the happy
idea of having a series of paintings made of those species which he
wished to describe. He therefore engaged an excellent artist \\ho
produced a series of eighty-seven water-colour drawings which are
now known as the Codex of Clusius. This Codex, after having
been lost for two centuries, was discovered in the library of the
University of Leyden in 1874, and was published by Istvanffi at
Budapest in 1900 as a tercentenary celebration of the publication
of the first monograph on fungi. ^ Plate 78 of the Codex represented

^ Clusius, Fungonnn in Pdnnuuiid obserratoriaii hreris Historia, KiOl.

2 G. Istvanffi, A Clusius-C 'ode.r myJcologiai ineltatasa addtokkdl Clusiu.s ehtrajzahoz.
Etudes et Commentaires sur Ic Code de VEscluse, augynentes de quelques notices bio-
grajMques. Enricliis tie 22 figures et de 91 planches chromolithograpliiees, repro-
ductions du Code de I'Escluse, Budapest, 1900, pp. 1--287, publislied by the Author
in Magyar and French.

378 RESEARCHES ON FUNGI

to Clusius, who had no scientific names for his fungi, the sixth
species of the twenty-second genus of his Fungi perriiciales. As
exactly reproduced by Istvanfifi, it gives us an excellent life-size
coloured illustration of a group of seven Collyhia fusipes fruit-
bodies, all arising from the top of a dark, rod-like, somewhat
obconical body about 1-5 inches long and 0-4 inch wide at the top.
There can be no doubt whatever that this body was dug up from
the ground with the fruit-bodies to which it is shown attached, and
that it was simply a stipe-base which had persisted from the previous
year in the manner described by Leveille. It thus appears that the
persistent stipe-base of Collybia fusipes, although not recognised
as such, was observed and illustrated in its natural size in an
admirable coloured drawing long before the time of BuUiard and
Leveille, some 350 years ago.

Fruit-body Clusters and their Pseudorhizae. — Without knowing
of Leveille's observations, I rediscovered the attachment of the
fruit-bodies of Collybia fusipes to the roots of trees in 1912, and only
subsequently was my attention called to Leveille's paper written
seventy years previously.^ I shall now give an account of my own
observations on Collybia fiisipes which, so far as the persistence of
the stipe is concerned, confirm and extend those of the French
writer. It will be shown, however, that the supposed sclerotium is
only a much modified stipe or combination of stipes, and is not a
structure formed by the mycelium prior to the development of
fruit-bodies.

In the month of July, 1912, fruit-bodies of Collybia fusipes
were found in Queen's Cottage Grounds, Kew Gardens, coming
up in clusters upon the vegetable mould near the trunks of certain
Oaks and Beeches. Under one large Beech were found nine clusters
of fruit-bodies which were distant from the tree-trunk as follows :
one 2 • 5 feet, four about 3 feet, one 5 feet, one 9 feet, and two about
12 feet. In general appearance the tree seemed healthy, for it
bore an abundance of green leaves and no big dead branches. One
or two branches, however, had been cut away, and the largest of
these, which had projected from the trunk ten feet from the ground,

^ I am indebted to Mr. J. Ramsbottom for kindly calling mj' attention to Leveille's
paper.

THE PERENNIAL PSEUDORHIZA 379

was six inches in diameter. There was nothing to be seen at the
time above-ground to indicate that the tree was in a moribund
condition ; yet moribund it actually was. In August, 1914, I
revisited the tree and found that the clusters of Collybia fusipes
fruit-bodies on the ground round about the trunk were even more
numerous than in 1912, for there were fifteen clusters instead of
nine. Ten of these clusters were within 3 feet of the trunk, two
about 5 feet distant from the trunk, and one 9 feet distant. The
distances of the other two groups from the trunk, owing to an over-
sight, were not recorded in my notes. The tree was now evidently
suffering from disease, for the bark on one side of the trunk appeared
to be going rotten and adventitious roots which had grown out
here and there in its cracks were already dead. There were leaves
on all the chief branches, but they seemed to be fewer than on
neighbouring trees of the same size. About two years later (1916 ?),
during my absence from England, the tree, on account of its dying
condition, was cut down and removed. As we shall see, the gradual
death of this tree was accompanied by an extensive destruction of
its roots by the mycelium of Collybia fusipes, and the clusters of
fruit-bodies which appeared above the roots year after year were
nothing but the visible 'subaerial signs of the destruction of the
tree's subterranean root-wood.

When, in 1912, I beheld nine clusters of Collybia fusipes fruit-
bodies scattered in the leaf -mould under the Beech tree as just
described, it at once occurred to me that the fungus might be a
root-parasite. I therefore carefully excavated the leaf-mould and
soil covering the bases of several of the clusters. As a result I
found that every fruit-body cluster was attached to a root. The
mycelium of Collybia fusipes growing in the forest floor, therefore,
is to be sought for not in the leaf-mould but in the wood of buried
roots.

One of the Collybia fusipes clusters which, at a distance of 12 feet
from the Beech trunk, was attached to a stout Beech root, is shown
one- third its natural size in the photograph reproduced in Fig. 189.
The cluster was made up of five large fruit-bodies, the smallest of
which had a pileus two inches in diameter and the largest a pileus
six inches in diameter. The five fruit-bodies were all connected

38o

RESEARCHES ON FUNGI

at their strongly tapering bases with a curious dark swollen stroma-
like fungal strand ; and this strand, in its turn and at a depth of
about six inches below the general surface of the ground, was

Fig. 189. — CoUubia fusipes . A group of fruit-bodie.s resembling those
sliown in Fig. 188, after excavation. The fruit-bodies sjiring
from a bhick, swollen, subterranean, i)ersistont psouilorhiza w liirh
is attac-liocl to a rotten root of a Beeeh tree antl is lUrectod vertically
upwards. The top of the root was about five and a half inches
below the surface of the leaf-mould and soil. I'hotographed at
Kew by Miss E. M. Wakefield and the author. Reduced to one-
third the natural size.

attached to a horizontal Beech root. The root was 1 • 5 inches in
diameter, but was so rotten that, with but little difficulty, I was
able to sever it with my penknife. On examining the root in
transverse section, I could see that it was infected with the mycelium

THE PERENNIAL PSEUDORHIZA 381

of the Collybia. The rotten wood was white. Upon the exterior
of the root, the mycelium had formed a thin black crust which was
continuous with the black outer covering of the stroma-like fungal
strand to which the fruit-bodies were attached. The root was
traced three feet toward the tree-trunk and found to be dead and
rotten throughout this distance ; but it could not be followed any
further owing to difficulties of excavation. Neighbouring roots
interlacing above and below the rotten one were living and quite
sound.

The stroma-like strand connecting the Beech root with the fruit-
bodies in the manner just described (Fig. 189) was, as comparative
observations made upon many similar strands has taught me,
nothing more or less than a swollen sympodium of persistent stipe-
bases or pseudorhizae, representing the remains of two or three
crops of fruit-bodies produced in as many years. In shape it was
irregularly cylindrical-obconic. Its height was about 3 inches, its
diameter at its base where it was attached to the root 0-3 inch, and
its maximum diameter, 2-5 inches above its base, about 2 inches.
From the swollen top of the persistent pseudorhizal strand arose
the newly formed fruit-bodies, all attached to it by black and
remarkably attenuated stipe-bases (pseudorhizae). The extreme
basal parts of the new stipes were only 0 • 1-0 • 2 inch in diameter ;
but, as the stipes passed upwards through some two or three inches
of leaf-mould, they thickened out and finally attained a maximum
diameter of 0-5-0-75 inch. Within each stipe were wavy parallel
strands of fibres. In addition to the five large fruit-bodies, the
cluster contained a number of rudimentary ones, which were attached
to the top of the persistent stipe-strand but which had never pushed
themselves up freely into the air. The upper parts of several of
these rudimentary fruit-bodies appeared to be in a state of decay.

A second fruit-body cluster, younger than that just described,
was situated only 1 - 5 feet from the trunk of the Beech tree (Fig. 190,
to the right). After the soil about its base had been removed, it
was found that the fruit-bodies were all attached by means of a
persistent pseudorhizal strand to a stout root which was oval in
cross-section and which measured 5 • 5 inches from above downwards
and 1 - 75 inches in width. In this instance the root, which was traced

382

RESEARCHES ON FUNGI

right up to the tree-trunk, proved to be a buttress-root. Never-
theless, it was quite dead and rotted to a considerable extent.
Neighbouring buttress-roots were quite sound. The top of the

*^«^

%

Fig. 190. — Collybia fusipes. To the right, a cluster of young fruit-
bodies springing from a massive compound pseudorliiza wliieli was
attached to the top of a large buttress-root of a Beech in Queen's
Cottage Grounds, Kew. To the left (somewhat dried) two fruit-
bodies attached to a long thin root-like pseudorliiza. Natural size.

root to which the persistent pseudorhizal strand was attached was
buried 4 inches below the surface of the leaf-mould. The persistent
pseudorhizal strand much resembled the one already described, for
it was obconic in form, 3 inches high, 2 inches mde above, and
attached to the root by a slender base. Upon its broad top there

THE PERENNIAL PSEUDORHIZA 383

were situated about forty young fruit-bodies, the largest of which
had a stipe that as yet was only 1 • 5 inches long and a pileus as yet
only 0-7 inch wide. Doubtless, if the cluster had been left un-
disturbed, only a few of the forty fruit-bodies would have completed
their development and have shed spores, for I have observed that
in all large mature Collybia fusipes clusters there are a few fully

Fig. 191. — Collybia fusipes. A large fruit-body with a thin
pseudorhiza of its own attached to an irregularly cylindrical
persistent pseudorliiza which resembled a piece of rotten
wood. Obtained above a Beecli root in Queen's Cottage
Grounds, Kew. Natural size.

expanded fiuit-bodies and a considerable number of much smaller,
imperfectly developed, fruit-body rudiments. It is the rule, here
as elsewhere in the Agaricaceae, that the fruit-body rudiments
largely outnumber the fruit-bodies which are destined eventually
to produce spores. In some clusters the bases of those fruit-body
rudiments which are inhibited in their development appear to persist
through the winter and, by undergoing a certain amount of renewed
thickening, to add to the mass of the persistent pseudorhizal strand
from which in the next summer the new fruit-bodies arise.

384

RESEARCHES ON FUNGI

The persistent ftseudorhizal strands of fruit-body clusters
attached to the roots of a number of trees other than the Beech
above described were also examined. Some of them were several
inches long, narrowly cylindrical in shape, and scarcely or not at
all swollen at their tops (Fig. 190, to the left ; also Fig. 191) ; and,
when thus constructed, they usually bore only one, two, or at most

Fif!. 1!)2. — Colh/hiii fusipes. A black, massivo, spongy, compound pseudorhiza
broken into five pieces. It doubtless took several yoais to form. A new
crop of fruit-bodies is springing from its to|i. Found almost at the surface
of the ground above a buttress-root of a Beech in Queen's Cottage (j rounds,
Kew. Natural size.

very few fruit-bodies. These particular strands resembled thin
rotten roots in their form, blackness, and consistence to such a
degree that they might easily have been taken for them. Indeed,
I myself was deceived by the first one I found, but soon discovered
my error.

The Supposed Sclerotium. — Certain other pseudorhizal strands,
instead of being obconic or cylindrical, were massive and irregularly
rounded ; and they were usually seated upon buttress-roots just
below the surface of the ground. One of them, which was seated

THE PERENNIAL PSEUDORHIZA 385

upon the buttress-root of a Beech, was as large as a child's fist,
blackish both without and within, and spongy in texture. After
I had excavated it, I broke it up into five pieces all of which are
shown in Fig. 192. This dark body appeared to be made up of a
great number of irregularly fused, rather brittle, persistent stipe-
bases or pseudorhizae ; and its formation was doubtless due to
several years' growth. As it was black and spongy in texture, it
resembled a sclerotium not a little ; and it was probably such a
large black irregular structure as this that Leveille had in mind
when he stated that the fruit-bodies of Collybia fusipes sometimes
spring from a sclerotium. However, we ought not to regard such
a structure as a sclerotium : firstly, because it is composed of basal
parts of fruit-bodies and not of mycelium ; and, secondly, because
there is no evidence that, if isolated from the root to which it is
attached, it could independently produce any fruit-bodies. Doubt-
less it contains a certain amount of reserve food materials ; but,
in the main, it is not a food reservoir but only a conductor of food
materials from the mycelium in the wood of the root to the new
fruit-bodies which develop at its apex.

Evidence that the Pseudorhiza Persists. — The evidence that
goes to prove that the stroma-like fungal strand connecting a fruit-
body cluster of Collybia fusij)es with the root of a tree is really a
persistent pseudorhiza or sympodium of pseudorhizae is of two
kinds : (1) field observations, which show that a cluster of fruit-
bodies often comes up above a root at exactly the same spot where
a cluster appeared the previous year, and (2) comparative observa-
tions upon the structure of pseudorhizae.

(1) Field observations. In 1916, Miss E. M. Wakefield and I
made careful notes upon the positions of twenty Collybia fusipes
fruit-body clusters which had come up above the roots of Beeches
and Oaks in Queen's Cottage Grounds, Kew Gardens ; and, in order
to find out whether or not new clusters would appear in 1917 at
exactly the same places as clusters had appeared in 1916, we drove
into the ground alongside of each cluster a long metal skewer. In
1917, on account of the war, I was unable to return to Kew, and
Miss Wakefield was able to visit the skewers only once. This
visit, which was made in early autumn, yielded positive results,

VOL. vr. 2 c

386

RESEARCHES ON FUNGI

for Miss Wakefield reported to me that she had found six new fruit-
body clusters coming up close by as many skewers in exactly the
same places as those in which their predecessors had appeared the
previous year. The remaining fourteen skewers, with the exception

of two or three which had
B A

vanished, were also visited,

but no fruit-body clusters
had as yet appeared by
any of them. The six
positive observations,
however, strongly support
the view that the pseudo-
rhizae are persistent from
year to year and give rise
to successive crops of
fruit-bodies.

(2) Comparative obser-
vations on the structure of
pseudorhizae. A consider-
able number of stroma-like
strands connecting fruit-
body clusters with buried
roots were unearthed and
carefully examined. In
every instance their struc-
ture was in harmony with
the view that a stroma-
like strand is either a
simple or compound per-
sistent pseudorhiza.
Mode of Development of a Compound PseTidorhiza.—In order
to follow the steps by which a compound persistent pseudorhiza is
gradually built up, let us assume : (1) that a stout root of a Beech
or an Oak bulled some inches beneath the surface of the ground has
become infected with the mj^celium of Collybia fusipes, and (2) that
the fungus i)lant is fruiting for the first time. The forms of many
old compound pseudorhizae seem to indicate that often, in the first

Fic

. lit:}. — Cullybidjusipes. A, a vertical sect ion
tliioiigli leaf-mould. /, and soil, *•, showing a
small Beech root, r, to which a jiersistent
subterranean [xseudorhiza, p, is attached.
The pseudorhiza and root are rcpiesented
as cut through in a vertical plane. The
substance of the pseudorhiza is continuous
with the sheet of mycelium m in the rotten
root ; n, another very thin sheet of mycelium
in the region of the cambium. B, anotiier
drawing showing the root, r, and pseudo-
rhiza, p, in longitudinal .section (the pseudo-
rhiza for convenience in representation lias
been bent through a right angle from its
natural position shown in A) ; m and )i, .sheets
of mycelium in the rotten root. Found in
Queen's Cottage (i rounds, Kew, by Mi.ss
E. M. Wakefield. Natural size.

THE PERENNIAL PSEUDORHIZA 387

fruiting year, only one large fruit-body is sent upwards from the
root to the surface of the ground. Let us assume that this has
happened in the theoretical case under discussion. The single
fruit-body Nv'ill consist of a pseudorhiza resembling the pseudorhizae
of Collybia radicata, Coprinus macrorhizus, etc., already described
in previous pages, an aerial stipe-shaft, and a pileus (Fig. 194, A).
A first single fruit-body of this kind I have not as yet been fortunate
enough to find. However, Miss Wakefield, when excavating a
large fruit-body cluster attached to a buttress-root of a tree in
Queen's Cottage Grounds in August, came across the solitary, un-
branched, more or less obconic structure shown in Fig. 193. There
can be no doubt that this structure, which was unearthed only
by accident, was nothing more than the persistent jjseudorhiza
of a single fruit-body, which had developed the previous year,
which had persisted in the soil for about twelve months, and the
apex of which had not as yet given rise to any new fruit-bodies.
The pileus and aerial stipe-shaft, which the pseudorhiza had
supported, had rotted away, and the top of the pseudorhiza
itself had become healed over by a protecting surface layer
of tissue.

From the foregoing we may assume that, in the first year of
fruiting, usually or often, one large fruit-body is sent upwards from
a root (Fig. 194, A), and that this fruit-body, after sporulation, dies
and rots away except for its subterranean pseudorhiza which persists
through the ensuing winter (B). In the second year of fruiting, it
often happens that the solitary persistent pseudorhiza of the first
year produces several large fruit-bodies from rudiments which arise
at or near its apex (C). Each of these new fruit-bodies has a
pseudorhiza. These second-year fruit-bodies, after shedding their
spores, die and rot away except for their jjseudorhizae which persist.
Thus, in the second winter, the persistent subterranean structure
consists of a central first-year pseudorhiza bearing a number of
second-year pseudorhizae (D). In the third year of fruiting, some
or all of the second-year pseudorhizae, in their turn, may give rise
to new fruit-bodies (E). These, after sporulation, would die down
leaving their living pseudorhizae behind (F). Thus, in the suc-
ceeding winter, the subterranean structure would consist of a

388

RESEARCHES ON FUNGI

sympodium of the stipes produced during the three preceding
summers. In the fourth year of fruiting, one or more of the per-
sistent third-year pseudorhizae would give rise to new fruit-bodies
(G) ; and then these fruit-bodies and the subterranean sympodium

THE PERENNIAL PSEUDORHIZA 389

of pseudorhizae might have an appearance like that found for the
fruit-body cluster shown in Fig. 195. It is possible that the com-
pound pseudorhiza under favourable conditions might function
for even one or more further years.

When in the first year of fruiting, instead of one fruit-body,
several fruit-bodies are produced, several pseudorhizae persist
through the winter ; and in the next summer several or all of these
pseudorhizae produce new fruit-bodies ; and so on from year to
year (Fig. 196). If, in such a case, the buried root is only about
two inches below the siu-face of the ground, the pseudorhizae are
all very short ; and there may be formed, in the course of several years,
a black agglomeration of very numerous more or less laterally fused
pseudorhizae, which may be more or less rounded peripherally and
sclerotioid in general appearance. Such, doubtless, was the origin
of the massive structure shown in Fig. 192 (p. 384). Its true nature
was made out from vertical and transverse sections, and by com-
parison with a series of persistent pseudorhizae which led by
gi'adations to the simplest and most unmistakable forms.

Lateral Grafting. — In an old compound pseudorhiza, one often
finds that the persistent pseudorliizae of any one year have become
irregular in outline, more or less tuberculate, and fused together
laterally. This natural lateral grafting of pseudorhizae which
were originally distinct appears to be due to a certain amount of
renewed growth taking place in summers subsequent to the one
in w^hich the pseudorhizae were originally developed. It was
doubtless such renewed growth and fusion of many scores of

Fig. 194. — VoUybia fasipes. A diagrammatic representation of the development of
a compound pseudorhiza during a series of years. A, a fruit-body in the
summer of the first year ; r, a Beecli root being rotted by the myceUum ; s,
the general surface of the leaf-mould ; p, tlie simple pseudorhiza passing into a,
tlie aerial stipe-shaft. B, the same fruit-body in the ensuing winter : the
pseudorhiza alone is persistent. C, summer of the second year : the pseudo-
rhiza has given rise to several new fruit-bodies, each of which has its own
pseudorliiza. D, winter condition of C : the persistent pseudorhiza is now com-
pound. E, summer of tlie third year : the compound pseudorhiza has given
rise to several new fruit-bodies, each of which again has its own pseudorhiza.
F, winter condition of E : the persistent pseudorhiza is now made up of the
pseudorhizae of three successive generations of fruit-bodies. G, summer of
the fourth year : new fruit-bodies are again being produced, but only from one
part of the top of the pseudorliiza ; tlie numbers 1, 2, and 3 indicate the
successive annual increments of growth of the compound pseudorhiza c.
About two-thirds natural size.

390

RESEARCHES ON FUNGI

pseudorhizae produced in
successive years that
brought into being the
pseudorhizal mass shown
in Fig. 192 (p. 384).

Healing of Pseudo-
rhizal Wounds. — It was
discovered that, if apseudo-
rhiza which has been
freshly dug up from the
ground is broken across
and kept in a moist place,
the wound heals up within
a few days. The hyphae
at the wound-surface turn
brown and form a dark
smooth layer resembhng
that which one normally
finds on the pseudorhiza's
exterior. Such heaUng,

Fig. 195. Collybia fusipes. A
much elongated compound
perennial pseudorliiza arising
from a deeply -buried root
of a Beech in Kew Gardens.
I, leaf -mould made of Beech
leaves ; s, soil ; r, a deep-
seated root ; a, the pseudo-
rliiza of the first-year fruit-
body ; b, a pseudorliiza of a
second-year fruit-body ; c, a
pseudorhiza of a third-year
fruit-body ; and d, a pseudo-
rliiza of a fourth-year fruit-
body. The root in which the
mycelium was vegetating is
represented here, for the
sake of convenience, as only
about 8 inches below the
surface of the leaf -mould ;
but its actual depth was
about 12 inches. Clouds
of spores are shown escaping
from the pilei and being
carried away by the breeze.
One-half natural size.

THE PERENNIAL PSEUDORHIZA 391

doubtless, also takes place under natural conditions, whenever an

Fig. 19(3. — Collybia fu.sipc.s. (1) On the right, five fruit-bodies develojiing
in 191G from one of several pseudorliizae which liave persisted since
the summer of 1915. The 1915 fruit-bodies arose from the persistent
(and now iriegiUarly swollen) pseudorhiza of a fruit-body wliich
developed in 1914. Tlie pseudorhiza of the 1914 fruit-body is shown
attached to a piece of wood wliich was part of a large decaying Beech
root. (2) On the left, a living fungous mass consisting prol)ably of
a 1914 pseudorhiza and three 1915 p.seudorhizae. It was found in 191(5
beneath the groimd attached to a Beech root. Had it been left undis-
turbed, it would have given rise, doubtless, to a new set of fruit-
bodies. Photographed in August, 191(5, at Kew by Miss K. M.
Wakefield. Natural size.

aerial stipe-shaft dies down and rots away leaving a bare irregular
exposed surface at the top of the subterranean pseudorhiza. The

392 RESEARCHES ON FUNGI

wound-tissue, with which the pseudorhiza heals itself, serves to keep
bacteria and other small organisms from making their way into the
interhyphal air-spaces and to conserve moisture in dry weather.

The Mycelium and the Problem of Parasitism. — ^The continuity
of a persistent pseudorhiza with the mycelium in the root of a Beech
is well shown in Fig. 193 (p. 386) which is reproduced from a sketch
made by Miss E. M. Wakefield. The root contained a paper-thin
sheet of mycelium between the bark and the wood {n), and a thicker
sheet of mycelium in the wood itself (m). With these sheets of
mycelium the base of the pseudorhiza was in direct continuity.
Moreover, Miss Wakefield found long tubes containing a dense
liquid and therefore resembling latex vessels, not only in the
pseudorhiza but also in both of the mycelial sheets. These observa-
tions, as well as others which there is no need to describe, clearly
show that the mycelium of Collybia fusipes inhabits the roots above
which the fruit-bodies are found.

In a few cases I observed that there was a sharp line of demarca-
tion between the dead part of a buttress-root upon which the
mycelium of Collybia fiisipes was feeding and the living sap-filled
part a few inches nearer the tree-trunk. What was observed
suggested that the fungus is parasitic on Beeches and Oaks, and
that its mycelium is able to kill and destroy progressively even their
stoutest roots. On the other hand, it might perhaps be argued that
the fungus is nothing more than a saprophyte, and that it destroys
roots progressively toward the tree-trunk only after they have died
from other causes. To determine mth certainty whether or not
Collybia fusipes. in addition to behaving as a saprophyte, may also
behave as a parasite would require a detailed investigation such as
I have not been able to make. It is possible that, if one inserted
small pieces of Beech wood in which the mycelium was growing
into a large sound root, the mycelium might grow into the wood
of the sound root and kill the root as its hyphae advanced ; and,
in a few successive summers, one might observe fruit-bodies coming
up above the inoculated root and attached to it by pseudorhizae.
If fruit-bodies were thus produced during two or three successive
summers, one wovild doubtless find at the end of this time that the
root had been killed and its wood destroyed for a distance of several

THE PERENNIAL PSEUDORHIZA 393

feet. The rate of progress of the mycelium along the root per
annum might then be calculated. If such a series of positive
observations should one day be made, there would be no alternative
but to regard Collybia fusipes as a destructive root-parasite. On
the other hand, if inoculation experiments were to yield only negative
results, we might be obliged to consider the fungus merely as an
innocent saprophytic scavenger, which rots Beech roots and Oak
roots only after these have been killed by some other agency.
Here, then, is an attractive problem for the phytopathologist.

The Functions of the Pseudorhiza and the Significance of its
Persistency. — The pseudorhiza of Collybia fusipes has the same
chief function as the pseudorhiza of Collybia radicata, Coprinus
macrorhizus, etc., i.e. it serves as an organ for pushing upwards
from the surface of the buried nutrient substratum (here a tree-
root) through a non-nutrient medium (here soil and leaf-mould) to
the surface of the ground the rudimentary stipe-shaft and pileus,
thus enabling these parts of the fruit-body to expand subaerially.
The pseudorhiza also (1) conducts food materials from the mycelium
in the buried root to the stipe-shaft and pileus whilst these are
developing subaerially, and (2) gives a certain amount of mechanical
support to the aerial stipe-shaft and pileus, thus assisting these
organs in taking up and maintaining their proper positions in space.

Just as in Collybia radicata and Coprinus macrorhizus, the
pseudorhiza of Collybia fusipes increases in length bj^ intercalary
growth in a subterminal axial region which lies just below the
rudimentary pileus and stipe-shaft. The upward direction of
growth of the pseudorhiza is doubtless due to negative geotropism ;
and probably the pseudorhiza, while able to grow in length freely
in the dark soil, has its growth in length inhibited by light, so that
the action of light regulates the length of the pseudorhiza and
prevents this organ from emerging above the surface of the ground.

In Collybia radicata and C. longipes the pseudorhiza is strictly
annual and dies shortly after the fruit-body of which it forms a
part has shed its spores, but in Collybia fusipes it is perennial. In
having a perennial pseudorhiza Collybia fusipes, so far as is at
present known, is not only unique in the genus Collybia but also
unique among the Agaricaceae in general.

394 RESEARCHES ON FUNGI

In having a pseudorhiza which is persistent and perennial,
Collybia fusipes gains a distinct advantage, for thereby it economises
fruit-body material and so, in the end, increases its output of
spores. As we have seen, the mycelium lives in a buried root and
produces new stipe-shafts and pilei subaerially each year. If the
new fruit-bodies produced in successive years by a single mycelium
were each to develop a full-length pseudorhiza stretching upwards
from the buried root to the surface of the soil, a great mass of fungus
material would be expended in pseudorhizal production that is
actually saved by the first-formed pseudorhiza and its branches
being persistent and perennial {cf. Fig. 195, p. 390). There can be
but little doubt that the fungus material saved by using the same
pseudorhiza over and over again in successive summers is applied
to the production of additional or of larger fruit-bodies and, there-
fore, to the production and liberation of millions of additional
spores. Thus the persistence of the pseudorhiza of Collybia fusipes
is a factor of considerable importance to the fungus in its struggle
for existence.

The annual pseudorhiza of Collybia radicata and the perennial
pseudorhiza of Collybia fusipes are comparable wdth the annual
fruit-body of Polyjwrus squamosus and the perennial fruit-body
of Fomes applanatus respectively. The perennial pseudorhiza and
the perennial polyporous fruit-body must be considered as having
been derived in the course of evolution from their annual counter-
parts in allied species, and therefore, as representing advances in
specialisation and adaptation of structure to function. There can
be no doubt that the persistence of the fruit-body in Fomes
applanatus is a great economy and enables very many more spores
to be produced than would be possible were it necessary to renew
the fruit-body flesh in its entirety each year. Thus the persistence
of the pseudorhizal portion of the fruit-body of Collybia fusipes
and the persistence of the whole fruit-body in Fomes applanatus both
serve to increase the number of spores produced and liberated, and
therefore make for greater efhciency in the process of reproduction.

Sarcoscypha protracta. — This Discomycete (Fig. 197), as
already set forth in a previous Chapter, ^ resembles Collybia fusipes

1 This volume, pp. 239-240.

THE PERENNIAL PSEUDORHIZA

395

in that its mycelium vegetates in buried roots and its fruit-bodies
develop a perennial pseudorhiza. Now that the mode of origin of
the fruit-bodies of C. fusipes has been described in detail, a

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396 RESEARCHES ON FUNGI

comparison between the fruit-bodies of S. protracta and C. fusijjes
can be made more readily.

A solitary fruit-body of Sarcoscypha protracta attached by a
pseudorhiza to a buried Beech root is shown in Fig. 116 (p. 240)
and is strictly comparable with the solitary fruit-body of Collyhia
fusipe-s attached to a buried Poplar root show^n in Fig. 194, A

(p. 388).

A persistent pseudorhiza which has branched in the second
year is shown for Sarcoscypha protracta in Fig. 197, Nos. 3, 4, 5 and
6 from the left, and a similar persistent pseudorhiza is shown for
Collyhia fusipes in Fig. 194, C (p. 388).

A pseudorhiza in the third year, i.e. with primary, secondary,
and tertiary parts, is shown for Sarcoscypha protracta in Fig. 197,
No. 2 from the left, and a similar pseudorhiza is shown for Collyhia
fusipes in Fig. 194, E (p. 388).

The production of a perennial pseudorhiza in Collyhia fusipes
and Sarcoscypha protracta, both of which have a mycelium which
vegetates in buried roots, affords another example of two very
diverse plants having become adapted in the same way to meet
the requirements of a similar set of external conditions.

Probably there are other Agaricaceae beside Collyhia fusipes,
and other Discomycetes beside Sarcoscijjyha 2^rotracta, which have
a perennial pseudorhiza ; but, if so, they remain to be discovered
by further field investigations.

CHAPTER III

OMPHALIA FLAVIDA, A GEMMIFEROUS AND LUMINOUS

LEAF-SPOT FUNGUS

Introduction — OmpJialia flavida and the American Coffee-leaf Disease — Stilhum
flavidum as a Stage in the Life-history of Omphalia flavida — The Structure
of the so-called Stilbum-hody — The Omphalia flavida Sporophore — The Origin
of the Stilbum-hodies — The Stilbum-hody as a Gemmifer — The Basal Curvature
of the Pedicel and its Significance — The Sigmoid Curvature of the Pedicel and
the Abscission of the Gemma — The Detachment of a Gemma from its Pedicel
— The Attachment of a Gemma to a Leaf — Mode of Germination of a Gemma
— The Effect of Desiccation on the Vitality of a Gemma — Inoculation Experi-
ments with Living Leaves — Omphalia flavida as a Non-specialised Parasite —
Sterility of the Mycelium Induced by Prolonged Cultivation on Artificial Media
— The Effect of Light on the Formation of Gemmifers — Luminescence of the
Mycelium and its Value as a Diagnostic Character of the Coffee-leaf Disease —
The Gemmifers of Sderotium coffeicola.

Introduction. — Oniphalia flavida is a Hymenomycete of peculiar
interest in that : ( 1) it is a parasite which is able to attack the leaves
of a great variety of plants ; (2) it reproduces itself not only by
means of basidiospores but also by means of gemmae of unique
structure (the so-called stilbum-hesids) ; and (3) its mycelium is
luminous.

Omphalia flavida and the American Coflfee-leaf Disease. —
Omphalia flavida first attracted attention owing to the fact that,
under very moist climatic conditions, it causes a serious leaf-spot
disease of the Coffee tree (Figs. 198, 199, and 200). The disease
has been reported from Mexico, Central America, the Antilles,
Trinidad, Venezuela, Brazil, and generally throughout the coffee-
growing region of America, ^ and it has therefore been called the
American Coffee-leaf disease.^

^ G. L. Fawcett, " Fungus Diseases of Coffee in Porto Rico," Porto Rico Agri.
Exp. Station, Bull. No. 17, 1915, p. 11.

2 S. F. Ashby, " The Perfect Form of Stilbum flavidum Cke. in Pure Culture,"
Bulletin of Miscellaneous Information, Royal Botanic Gardens, Kew, 1925, p. 325.

397

398

RESEARCHES ON FUNGI

The American Coffee-leaf disease, as it occurs in Porto Rico, has
been thus described by Fawcett.^ " The disease is characterised by
the occurrence on the leaves of small spots usually circular in outline,
but sometimes ovate along the veins. The newer ones are very

, „ _„ dark, the older ones

•^■-^ light colored. The

"^ spots are usually

^'^ about 6 mm. in

diameter, although
many of the older
ones become 12 to
13 mm. in diameter.
Sometimes they fuse
or give entrance to
other tissue-destroy-
ing fungi which
infect the interven-
ing tissue, producing
spots of considerable
size. The worst
affected leaves have
from 30 to 40 or
even more spots, so
that a large propor-
tion of the leaf tissue
is destroyed. On
the upper surface of
many of the spots
and also to some
extent on the lower
surface may be seen
hair-like projections from 1 to 4 mm. long of a yellowish color, each
bearing at the end a head so that they resemble minute pins. This is
the reproductive or fruiting stage of the fungus [cf. Figs. 201 and 202,
pp. 402 and 403]. Each spot produces a continuous crop of these
hairs so long as weather conditions are favourable. The total

1 G. L. Fawcett, loc. ciL, pp. 11-12.

Fig. 198. — A Coffee tree almost defoliated by Omphalia
fldvida. Only tlie youngest leaves remain on the
twigs. Photographed by G. L. Fawcett at the
Mayagiiez Experiment Station, Porto Rico.

OMPHALIA FLAVIDA 399

number at any time is small and in an entire season but from 20 to

Fig. 199. — Leaf -spots caused by the mycelium of Ompludia flavida on Coffee leaves.
Photographed by G. L. Fawcett at the Mayagiiez Experiment Station, Porto
Rico. Reduced to about one-half the natural size.

50 are produced in each spot, judging from the number of old
filament bases. The largest number observed was 70 in a spot of

400

RESEARCHES ON FUNGI

7 mm. diameter. As the leaf-spots become older, growth having

stopped for any reason,
such as the advent of the
dry season, the diseased
tissue falls away, leaving
numerous circular open-
ings in the leaf. In other
leaf diseases the dead
tissue remains.

" Sometimes the fun-
gus attacks young stems,
where it causes conspic-
uous scars and so weakens
the points affected that
they are easily broken by
the wind. The berries also
are attacked, a slight dis-
coloration of the grain
being frequently caused."
In Porto Rico the
disease is restricted to the
moister parts of the island,
but there the best coffee
is produced. The trees
with leaf-spots yield fewer
berries. " The injury to
the trees," says Fawcett,
" is not so much in the
actual amount of the leaf
tissue destroyed, although
this may amount to one-
fifth or even more of the
entire amount in the
worst cases, but in the
defoliations which take
place after a time. The
diseased leaves drop

Fig. 200. — A Coffee leaf sliowing leaf-spots
caused by the mycelium of Omphalia flavida.
Each spot has arisen from a gemma, pre-
sumably blown on to the leaf by the wind
or splashed on by the rain. The spots,
apparently, have not yet produced any
gemmifers. They are luminous in the dark.
Photographed by G. L. Fawcett at the
Mayagiiez Experiment Station, Porto Rico.
About the natural size.

OMPHALIA FLAVIDA 401

sooner than those not affected and, owing to the weakened condition
of the tree, are not soon replaced. After the first severe attack,
the base of each tree may be seen surrounded by a pile of green
leaves several inches deep. The disease never kills the trees. They
live on with scanty foliage and are able to put forth new growth
and bear a small amount of berries each year."

The tiny yellow pin-like fruiting structures described by Fawcett
as projecting from the surface of the leaf-spots are the so-called
stilbum-hodies. A stilbum-hody never produces any spores ; but,
when fully formed, its head, often called a stilbum-head, is readily
detachable (c/. Figs. 205, A, p. 408, and 213, C, p. 424). " The
fungus," says Fawcett, " is distributed by the heads at the ends of
the filaments being caught by the wind or rain-drops and carried to
near-by leaves, a process facilitated by the heads becoming loosened
in the older filaments through the formation of cavities or ' lacunae '
near the point of attachment. The head is soon fastened to the
leaf on which it happens to fall by the numerous threads which it
sends out at the point of contact. Within less than a week a dark
circular spot is formed and new filaments appear and new loosely
attached heads are formed on these by means of which the spread of
the disease is continued."

Recently Briton- Jones ^ has attempted to control the Coffee-leaf
disease by heavy pruning followed by the removal of all the re-
maining leaves and by manuring and cultivation to induce the
subsequent production of vigorous new growth.

Stilbum flavidum as a Stage in the Life-history of Omphalia
flavida. — In 1880, some diseased Coffee leaves were sent to M. C.
Cooke 2 from VenezAiela by Dr. Ernst. On some of the coloured
spots Cooke found the perithecia of Sphaerella cojfeicola ^ and on others
the tiny yellow Stilbum-like fruiting structures of another fungus
which he called Stilbum flavidum. In some of the spots the two

1 H. R. Briton-Jones, " Control of the American Leaf Disease {Omphalia flavida)
on Arabian ColTee in Trinidad," Memoirs of the Imperial College of Tropical Agri-
culture, Trinidad, Mycological Series, No. 2, 1930, i^p. 1-8.

2 M. C. Cooke, " The Coffee Disease in South America," Journ. Linn. Soc,
Botany, Vol. XVIII, 1881, pp. 461-467, PI. XVIII, Figs. 1, 5, 6.

^ According to E. J. Butler (Note on Cooke's type specimens at Kevv, 1915)
Sphaerella coffeicola is a Didymella, for its perithecia contain paraphyses.

VOL. VI. 2 D

402

RESEARCHES ON FUNGI

fungi grew together. The heads of the s{ilbum-})od'iQS, as we have
seen, serve to spread the American Coffee-leaf disease.

Fig. 201. — Two Nerium Oleander leaves infecte;! witli tlie mycelium of
0»iph<iliii Jlavida and bearing numerous gemmifers of the fungus.
The leaves were gathered, dipped in 0- 1 per cent, mercuric chloride
for 2 minutes, rinsed in sterilised water, and placed in a large
crystallising di.sh on moist sand. Each leaf was wounded by
scratcliing tlie surface with a sterile needle and tlie wound was
tlien inoculated with three or four gemmae. The gemmifers began
to appear 10 days after inoculation. The photograpli was taken
19 days after inoculation. The fungus strain was of Porto Rican
origin. The divergence of the gemmifers from one anotlier can
bo observed. Natural size.

OIMPIIALIA FLAVIDA

403

Stilbum flavidum Cke., as we
shall see, has nothing to do with
the genus Stilbum but is merely a
stage in the life-history of Om-
])halia flavida (Cke.) Maublanc et
Rangel.

In 1914, Maublanc and Rangel ^
obtained some spotted leaves of
the Loquat, Eriohotrya jajwnica,
at Rio de Janeiro and placed
them in an atmosphere saturated
with water-vapour. On the surface
of the spots there developed first
of all a crop of Stilbum flavidum
fruit-bodies and subsequently the
much larger fruit-bodies of a small
agaric to which they gave the name
Omphalia flavida. Similar results
were obtained with the leaves of
undetermined species of Melasto-
maceae and Compositae. Because

(1) the leaf-spots frequently pro-
duced the Stilbum and the Om-
phalia in succession, and because

(2) the two fungi showed marked
resemblances in colour and general
structure, Maublanc and Rangel
concluded that Stilbum flavidum Cke.

Fig. 202. — Numerous gemmifers on a leaf
of Nerium Oleander artificially inocu-
lated with Omphalia flavida. The
same leaf as the one on the left in
Fig. 201 photographed 10 days later
and 29 days after inoculation with
gemmae. The divergence of the
gemmifers from one another can
again be well seen. Natural size.

^ A. Maublanc ct E. Rangel, " Le Stilbum flavidum Cooke, forme avortee de
V Omphalia fluvida n. sp.," Bull. 80c. Myc. France, T. 30, 1914, pp. 41^7.

404

RESEARCHES ON FUNGI

is nothing more or less than an aborted condition {eUit avorte) of
Omphalia flavida.

In 1925, Ashby,! making use of some diseased Coffee leaves
obtained from a valley in the Northern Range of the island of
Trinidad, proved by the pure-culture method that Cooke's Stilbum
and the Omphalia of Maublanc and Rangel do actually arise from,
one and the same mycelium.

Ashby lifted ripe stilhum-hQa.d^ from a leaf-spot, washed them

in a weak solution of
sulphuric acid for about
a minute, and then
placed them on corn-meal
agar in a Petri dish.
At room temperature
(79° r.), after three days,
a radiately spreading
growth of fine hyphae
had developed from most
of the heads, only two
out of ten mycelia having
become contaminated by
bacteria. Transfers of the
mycelium were made to
sterilised potato blocks,
rice grains, and bread. On
potato and rice there was
fair growth and reproduc-
tive bodies began to develop but remained imperfect and sessile.
On bread, however, development was completed. This substratum
was used by Ashby because Westerdijk ^ had recommended it for the
culture of Basidiomycetes. In a flask containing four parts of water
to one part of fresh crumb of white bread, at room temperature, the
mycelium spread steadily around the inoculum and, after a few
days, became dotted with pale-yellow Stilbum flavidum initials
which completed their development and formed a dense low forest

1 S. F. Ashby, he. cit., pp. 325-328.

2 J. Westerdijk, Report Internal. Conf. Phytopath., Holland, 1923, pp. 165-169.

Fig. 203. — Omj)halia flavida, growing on bread
and water in a conical flask. In front, the
white bread permeated by the mycelium ;
above, a forest of numerous yellow gem-
mifers ; still higher, a group of thirteen
yellow sporophores towering up above the
gemmifers. Photographed by S. F. Ashby.
Slagnification, about 1 ■ 5.

OMPHALIA FLAVIDA

405

ikhii^-

extending from the centre almost to the margin of the colony.
After twelve days a few much larger bodies, having deep-yellow
hemispherical heads, began to push up from
the centre, and in fifteen days some of them
had become perfect Omphalia flavida agarics
of a light sulphur colour, with erect slender
minutely hirsute stipes and membranous sub-
hemispheric or broadly conical pilei (Fig. 203).
As inocula for further subcultures on sterilised
bread, Ashby used either (1) s^iZ6wm-heads or
(2) fragments of the stipes or pilei of the
agarics, with the result that the mycelium
always gave rise to both sh76wr?i-bodies and
Omphalia fruit-bodies. Basidiospores, ob-
tained from the gills of one of the agarics,
were sown ; and the mycelium, after being
transferred to a corn-meal agar sloj)e, yielded
many 5^i/6wm-bodies and a few perfect
agarics. Thus Ashby conclusively proved
that the mycelium of Omphalia flavida
produces fruiting structures of two kinds :
(1) ordinary hymenomycetous sporophores
which liberate basidiospores, and (2) peculiar
pin-shaped stilbum-hodies which are sporeless
but each of which readily sets free its stilbum-
head.

In the autumn of 1925, Mr. Ashby, at the
Imperial Mycological Institute, Kew, kindly
showed me his cultures of Omphalia flavida
and gave me a subculture. I took this to
Winnipeg and, in conjunction with T. C.
Vanterpool, repeated some of Ashby's experi-
ments. The mycelium was transferred to

Fig. 204. — Omphalia fi avid a, growing on an oat-meal agar
slope in a test-tube. The mycelium has produced
numerous gemmifers and a few perfect fruit-bodies.
Culture several weeks old. Natural size.

4o6 RESEARCHES ON FUNGI

sterilised bread (1 part bread, 4 parts water) where, within about
three weeks, it gave rise first to a little forest of stilbum-hodies and
afterwards to a number of the much larger perfect Omphalia agarics
(cf. Fig. 204). Both stilbum-hodiefi and perfect agarics were also
obtained by sowing stilbum-heads (1) on bread sterilised in conical
flasks and (2) on living leaves of Bryophyllum calycinum (for
details vide infra). ^ Thus Ashby's conclusions as to the behaviour
of Omphalia flavida in artificial cultures have been confirmed.

The Structure of the so-called Stilbum-body. — The structure of
the stilbum-hody was first investigated and illustrated by Putte-
mans.2 With the hope of throwing light on the mode of abscission
of the head from the stalk, it has been carefully re-investigated by
Miss Ruth Macrae and the author in the laboratory at Winnipeg.
The description which here follows is based on observations made
by us on living material grown on malt-agar and also on Bryophyllum
and Oleander leaves.

A stilbum-hody is, as we have seen, a minute pin-shaped structure
consisting of a slender cylindrical stalk surmounted by a head which,
when fully developed, can be readily detached (Fig. 205, A, B, C).
Both stalk and head are yellow. The stalk, which tapers gradually
from below upwards, is about 2-0 mm. in length, about 0-12 mm.
in diameter at its base, and about 0-05 mm. in diameter just below
the head, while the head has an average diameter of about 0 • 36 mm,
varying up to 0 • 4 mm. A stilbum,-hody never produces any spores.^

1 A. H. R. BuUer and T. C. Vanterpool, " The Bioluminescence of Omphalia
flavida, a Leaf-spot Fungus," Phytopathology, Vol. XVI, 1926, p. 63.

2 M. A. Puttemans, "Sur la maladie du Cafeier produite par le Stilbella flavida,'^
Bull. Soc. Myc. France, T. XX, 1904, pp. 158-164, PI. XI.

3 M. C. Cooke {Grevillea, Vol. IX, 1880-1881, p. 11) and Kohl {vide infra) thought
that conidia are produced on the exterior of the head ; but the careful researches of
Puttemans (foe. cit., pp. 160-163), which are supported by the observations of
Patouillard, Massee, Spegazzini, Delacroix, Ashby, and myself, lead to the conviction
that Cooke and Kohl were mistaken. Cooke was probably misled by the Stilbum-
like appearance of the fungus and, as Puttemans argues, by an optical illusion in
respect to the appearance of the outer hyphae of the head. Kohl, whose description
of the stilbum-hea,d and its outer hyphae is imperfect and unsatisfactory, states that
for months he sought in vain for conidia before finding any and that many attempts
to infect Coffee leaves with the supposed conidia completely failed. He concluded
that, under natural conditions, the fungus is propagated not by the conidia but by
the detached heads.

OMPHALIA FLAVIDA 407

The head is an oblate spheroid (a flattened globe) with an
apophysis of smaller diameter below (Fig. 205, A, B, C). Its upper
surface is slightly depressed in the centre. The apophysis encloses
and clasps the stalk about 0-1 mm. from its extreme end. The
head is tough and coriaceous, so that, when it dries, it is not appre-
ciably deformed. With moderate magnification one can observe
that the main oblate-spheroidal part of the head, but not the
apophysis, is covered peripherally with a large number of aerial
radiating hyphal filaments (Fig. 205, C, /). It is these filaments
which serve to infect a new host-leaf when a head has fallen upon it
and the weather is sufficiently moist.

The stalk is a solid cylinder (Fig. 205, B, C, D), and not hollow
as described and illustrated by Puttemans.^ When very young, it
is quite straight and perpendicular to the substratum (Fig. 212,
A, B, p. 419) ; but, as it grows in length, it usually becomes more
or less bent or curved (Fig. 205, A and B). At maturity, i.e. when
about 2 mm. long, it is thickest at its base, slightly attenuated
from its base up to the apophysis and then, within the apophysis,
distinctly contracted and always more or less sigmoidally bent
(Fig. 205, B and C). The sigmoid terminal portion of the stalk is
hidden from external view inside the head, but can readily be
observed after the head has been removed from it.

The microscopic structure of a median-longitudinal section of
the head and upper part of the stalk of a mature stilbum-hody is
shoM^n in Fig. 205, C. The head consists of a central mass of
relatively large pseudoparenchymatous cells (m), surrounded above
and at its sides by a thin layer of smaller and more flattened cells
from which radiate outwards a number of slender branched septate
hyphae (n) which, at the sides of the head, terminate in large pear-
shaped cells (k) and, at the top of the head, terminate in more
slender clavate cells {i). A certain number of the swollen cells at
the sides of the head give rise each to a single aerial hypha which is
usually simple (1) but may be branched. The hyphae grow out-
wards from the head and give it the woolly appearance that can be
seen externally with moderate magnification. The clavate cells on

^ Puttemans {loc. cit., p. 159, Plate XI) in his Fig. 4 erroneously shows aerial
hyphae just as thickly present on the top of the head as at the sides.

OMPHALIA FLAVIDA 409

the somewhat depressed upper side of the head (i) are sHghtly
separated from one another by the mucilage of their outer walls (j),
and they do not bear aerial hyphae but remain naked.

The flesh of the whole head is solid ; for the space between the
pseudoparenchymatous cells, the radiating hyphae, the clavate cells,
etc., is filled with transparent mucilage which, doubtless, just as in
the thallus of a Fucus, is derived from swollen outer cell-walls.
When a head on its stalk is placed in water, no air-bubbles can be
seen between any of the cells of the head. The only air-bubble to
be observed is a large one which fills the cavity around the end of the
stalk within the apophysis. The whole head, owing to its solidity
and yellow colour, has a waxy appearance v/hen seen in bright light

Fig. 205. — The structure and orientation of the gemmifers of Otnphalia flavida.
A, a group of four mature gemmifers on the upper side of a leaf-spot of a leaf of
Nerium Oleander. During their development, these gemmifers diverged from
one another and took up the positions here shown. Each gemmifer consists
of : (1) a pedicel which tapers upwards and exhibits a divergence-curvature
below its middle point ; and (2) a terminal gemma. The gemma of the gem-
mifer farthest to the left has just been blown away from its pedicel by the wind
in the direction shown by the arrow. Magnification, 5.

B, a median -longitudinal section of a single gemmifer attached to an Oleander
leaf, shown in its natural position : a, part of the leaf ; b, the pedicel, bearing
hairs at its surface ; c, the gemma, produced peripherally into infection hyphae.
The pedicel b exhibits two curvatures : (1) a divergence-curvature at d, and
(2) a double or sigmoid geotropic curvature terminally at e. The sigmoid
bending of the terminal part of the pedicel resulted in the end of the pedicel
being torn away from the flesh of the gemma. The gemma is now attached to
the pedicel merely by its basal collar or apophysis 'and, in this condition, it is
ready for dislodgment and transportation by the wind. Magnification, 38.

C, the upper part of the gemmifer in B greatly enlarged, to show the histo-
logical structure. In this vertical median-longitudinal section the parts may
be distinguished as follows : a, the pedicel, with a thicker-walled cortex and
a thinner-walled looser medulla (cf. D) ; the terminal part of the pedicel is
sigmoidally curved ; the downward curvature b was made in response to a
positive geotropic stimulus, and the upward curvature c in response to a negative
geotropic stimulus and, when the sigmoid curvature was being formed, the
pedicel broke away from the flesh of the gemma to which it previously had been
attached at d ; e, a large air-space between the terminal part of the pedicel and
the apophysis (collar) of the gemma ; //, the apophysis of the gemma which
holds the gemma on to the pedicel until the wind blows it away ; g g, fimbriate
cells which form the outer layer of cells of the apophysis ; h, the apex of the
gemma, somewhat depressed ; i i, clavate cells separated by a gelatinous
matrix y_;' derived from swollen cell-walls ; h k, more swollen clavate cells at the
periphery of the gemma, which are produced terminally into aerial infection
hyphae II ; mm, pseudoparenchymatous cells embedded in a gelatinous matrix
and forming the core of the flesh of the gemma ; n n, slender branched septate
hyphae forming the cortex of the flesh of the gemma. Magnification, 405.

D, a transverse section of the pedicel a little below a in C ; n, the thicker-
walled cortex ; b, the thinner-walled medulla ; c c, two hairs. Magnification, 410.

E, a surface view of part of the apex of the gemma, as seen at h in C :
a, clavate cells ; b, the gelatinous matrix formed of swollen cell-walls. Mag-
nification, 405.

Drawn by A. H. R. Buller and Ruth Macrae.

410 RESEARCHES ON FUNGI

and, owing to its mucilage, is slippery and difficult to hold in place
for making hand-sections.

The apophysis or under part of the head is formed of hyphae
which arise from the core of the oblate-spheroidal part of the head.
These hyphae (Fig. 205, C,/) are extended outwards and downwards,
so that at first they avoid the contracted upper part of the stalk,
and then inwards and downwards so that finally many of them
come to rest against the stalk, with the result that an annular air-
space is formed between the upper part of the stalk and the apophysis
by which it is surrounded (Figs. 212, D, p. 419, and 205, C, e). The

Fig. 206. — Omphalia flavida. Vertical section through pilaus and upper
part of the stipe of a large expanded fruit-body. The fruit-body was
removed from a Bryophyllum leaf which hafl been inoculated witli
gemmae 38 days previously. Note the umbilicate pileus, the thin
pileus-flesh, the decurrent gills, and the solid stipe. The pileus was
6-7 mm. in diameter. Drawn by A. H. R. Buller and Ruth Macrae.
Magnification, about 15.

outer hyphae of the apophysis end in outwardly curved, swollen,
almost hyaline cells, each of which is extended into a number of
short, slender, simple or bifurcated projections (Fig. 205, C, g).

From the above description it will be seen that the stilbum-hody
produces spores neither externally nor internally, i.e. it is completely
non-sporogenous.

The Omphalia flavida Sporophore.— The external appearance of
the sporophore of Omphalia flavida, which represents the perfect
stage of the fungus and produces and liberates an abundance of
basidiospores, is shown in Figs. 203, 204, and 213 (pp. 404, 405, and
424). It was first observed and described in 1914 by Maublanc and
Rangel.i Their diagnosis, translated from the Latin, is as follows.
1 A. Maublanc et E. Rangel, he. cit., p. 46.

OMPHALIA FLAVIDA

411

" Very minute, yellowish ; pileus thin, membranaceous, hemi-
spheric-campanulate, depressed or subumbilicate in the centre, then
more or less flattened, glabrous, radially striate, 1-5-2 -5 mm. in
diameter, with an acute margin ; stipe setiform, straight, thin, of
the same colour, very minutely velvety, about 1-1-5 cm. long,^

Fig. 207. — Ornphnlia flavida. Plan of under side of the pileus of an
expanded fruit-body, to show the arrangement of the gills. The
fniit-body was removed from a Bryophyllum leaf which had been
inoculated with gemmae 40 days previously. Drawn by A. H. R.
Buller and Ruth Macrae. Magnification, about 15.

0-25 mm. thick, the base not swollen. Gills few, rather distant,
yellowish, somewhat waxy, triangular, attenuated at each end,

1 Maublanc and Range], in their general description of the fungus {loc. cit.,
p. 43), give the height of the fruit-body as about 1 cm. (hautd'environun centimetre),
but in their diagnosis they say the stipe is " circ. 1 • 5-3 mm. longo." This discrepancy
seems to be due to a misprint in the diagnosis, as the authors' illustration shows the
fruit-body a little more than 1 cm. high. Ashby {loc. cit., p. 327) states that the
fruit-body is 1-1 • 5 cm. high, and my experience is the same as his. I have therefore
emended the diagnosis of Maublanc and Rangel by substituting 1-1-5 cm. for
1-5-3 mm. Ashby gives the width of the pileus as 2-3 • 5 mm.

412

RESEARCHES ON FUNGI

more or less decurrent. Basidia clavate, 14-17-4 x 5 (jt, ; spores
minute, ellipsoid or ovoid, apiculate below, hyaline, eguttulate or
with one guttule, 4—5 X 2-5-3 (x.

" On leaves of Eriobotrya japonica, Melastomaceae, Compositae,

and Rubiaceae near
^ ^ ^ RiodeJaneiro(Brazil)

in company with Stil-
hum flavidum Cooke
(its abortive form)."
The sporophore,
as may be seen from
Figs. 203, 204, and
213 (pp. 404,405, and
424), is a much larger
organ than the gem-
mifer. Its height was
found to vary from
0-6 cm., as shown
in one produced on
a Bryophyllum leaf
(Fig. 218, p. 429), to
1 • 5 cm. where growi^h
took place on a
medium of bread
crumbs. The young
stipe is only very
slightly or not at all
heliotropic and soon
becomes negatively
geotropic so that, in the end, the axis of the pileus becomes vertical
(Fig. 213, p. 424). Two illustrations showing a median- vertical
section through a pileus and the appearance of the under side of a
pileus are reproduced respectively in Figs. 206 and 207.

In a gill (Fig. 208, A), the trama consists of large elongated cells,
the subhymenium of smaller much more numerous cells, and the
hymenium of basidia and paraphyses. The hymenium lacks
cystidia (pleurocystidia) but there are numerous fringed cystidia

Fig. 208. — Omphalia flavida. A, vertical section
through a lamella of a perfect fruit-body :
a, the hymenium made up of basidia, each
bearing four spores, and paraphyses ; b, the
subhymenium ; and c, the trama. B, a
cheilocystidium (cystidium on the free edge of
a gill) ; it is fimbriate, like the clavate cells
on the exterior of the pileus. Drawn by
A. H. R. Buller and Ruth Macrae. Magnifi-
cation, 540.

OMPHALIA FLAVIDA 413

(cheilocystidia, Fig. 208, B) along the edge of each gill. Each
basidium bears four spores, and the spores are minute, ovoid,
apiculate below, as a rule eguttulate, 5-6-5 X 2-5-3 jx.

The upper end of the stipe expands obconically and to it are
attached the decurrent gills (Fig. 206, also Fig. 213, p. 424). The

Fig. 209. — Omphalia flavida. Vertical section through the pileus-
flesh above the gills of a large expanded fruit-body grown on
a Bryophyllum leaf in a Petri dish : a, part of a layer of swollen
cells ; b, loose, netted, thin hyphae, terminating on the exterior
of the pileus in irregularly clavate, fimbriate cells c ; d, mucilage,
derived from the outer hyphal walls, filling the spaces between
the hyphae ; e, a clamp-connexion. Drawn by A. H. R. Duller
and Ruth Macrae. Magnification, 467.

thin pileus-flesh above the gills consists below of two or three layers
of swollen elongated cells (Fig. 209, a) and above of slender netted
hyphae (6) terminating on the exterior of the pileus in irregularly
clavate, fimbriate cells (c). Between these loose hyphae and between
the clavate cells the spaces are filled, as in a stilbum-hea,d, with
mucilage (d) derived from the swollen outer cell-walls.

The pileus-fiesh at the top of the stipe and below the umbilicate

414

RESEARCHES ON FUNGI

pilear depression consists of netted gelatinous hyphae which ter-
minate above in a layer of clavate cells (Fig. 210). These clavate
cells are more club-shaped and less fimbriate than those which
bound the flesh above the gills.

The spores are produced in considerable numbers when once the
pileus has begun to liberate them, and fairly thick white spore-
deposits were obtained on cover-glasses placed beneath the pilei
of fruit-bodies growing normally on Oleander leaves.

Newly fallen spores were tested for germination. The spores on
some cover -glasses were covered with sterilised tap-water, those

on other cover-glasses
with malt-agar, and
those on still other
cover-glasses with malt-
extract (2-5 grams malt
to 100 cc. water), and
the cover-glasses, with
their drops hanging
downwards, were set on
van-Tieghem cells con-
taining a little water.
The spores in the tap-
water and in the malt-
agar did not germinate,
but those in the malt-extract put out germ-tubes within 36 hours.
Stages in the germination of some spores are shown in Fig. 211.

A pileus which was actively discharging spores was set in suc-
cession over two fresh wounds scratched in a Bryophyllum leaf, so
that many spores must have fallen into each wound. The leaves
were kept on very wet sand in a Petri dish covered with a bell- jar.
The air in the Petri dish must have been saturated with water
vapour. Nevertheless, the wounds healed up without becoming
infected. Whether or not, therefore, germinating basidiospores can
initiate the Coffee leaf-spot disease is still an open question. Since,
under natural conditions, the perfect fruit-bodies appear to be but
rarely developed, basidiospore infection, if it occurs at all, may be
very infrequent.

Fig. 210. — Ornphalia flavida. A, surface view, and
B, vertical section, of the pileus-fie.sh above the
stipe and below the central umbilicate de-
pression : a, clavate fimbriate cells ; b, muci-
lage ; c, netted hyphae. Drawn by A. H. R.
Buller and Ruth Macrae. Magnification, 467.

OMPIIALIA FLAVIDA

415

The Origin of the Stilbum-bodies. — As first pointed out by
Maublanc and Rangel/ the s/i/6Mm-bodies and the Omphalia sporo-
phores show marked resemblances. Among these resemblances are
the following. (1) The stalk and head of a stilbum-hody correspond

^

A B

J%

Fig. 211. — Omphalia flavida. Basidiospores and their germination in a malt
solution (2-5 per cent.). A: spores freshly immersed, some in lateral
view, others in face view. B : spores after being immersed 36 hours ;
they are now much swollen. C : spores germinating after 42 hours
immersion; the germ-tubes have just been produced. D: other spores
with longer germ-tubes, the seven upper ones after 42 hours immersion,
the two lower ones after six days ; the spores cannot now be distinguished
from the germ-tubes or mycelium ; the hyphae are filled with fine cyto-
plasm, and some of the sporelings have developed one or two septa.
Drawn by A. H. R. BuUer and Ruth Macrae. Magnification, 749.

respectively to the stipe and pileus of the agaric. (2) The stalk of a
stilbum-hody and the stipe of the agaric are both clothed with
short simple hair-like outgrowths. (3) The palisade cells at the
top of the pileus of the agaric correspond to the swollen cells which
surround the oblate-spheroidal part of the head of a stilbum-hody,
but differ from them in being fimbriate and in not producing long
1 A. Maublanc et E. Rangel, loc. ciL, pp. 44-45.

4i6 RESEARCHES ON FUNGI

filiform hyphae. (4) The large clavate palisade cells at the margin
of the pileus of the agaric are fimbriate and thus correspond to the
very similar cells which occur on the exterior of the apophysis of a
stilbum-hody, i.e. on a structure which may be regarded as forming
the outer margin of a stilbum-head. (5) The spaces between the
hyphae in a head of a stilbum-hody and the spaces between
the hyphae of the flesh of a pileus are both filled with mucilage.
(6) The position of the annular air-chamber enclosed between the
apophysis and the upper end of the stalk of a stilbum-hody corre-
sponds to the position of the gills in a young pileus. These re-
semblances and also the occurrence of what Maublanc and Rangel
took to be intermediate forms ^ between the stilbum-hodies and the
perfect sporophores led these authors to the conclusion that the
stilbum-hodies are nothing but aborted Omphalia fruit-bodies.

The view that the stilbum-hodies have been derived from the
rudiments of Omphalia fruit-bodies appears to me to be well based.
Many Hymenomycetes produce far more fruit-body rudiments than
ever come to perfection ; and it seems likely that, in Omphalia
flavida, in the course of evolution, some of the rudiments have become
progressively metamorphosed by means of structural and physio-
logical changes so as to fit them for liberating their aborted pilei
and thus disseminating the species in a novel but very effective
manner.

The Stilbum-body as a Gemmifer. — The stilbum-hody, whatever
its origin in the course of evolution, is to-day an effective organ for
bringing about the dissemination of Omphalia flavida from place to
place, and it performs this function by liberating its tiny head.
This is blown, splashed, or otherwise carried from diseased leaves to
healthy ones, the latter readily becoming infected by means of the
long filiform filaments — which we may call the infection hyphae —
which radiate from the surface of the head and at once renew their
growth when a head becomes attached by its gelatinous envelope to
a new host-leaf.

The name stilbum-hody is a misnomer ; for, as we have seen, a
stilbum-hody has nothing to do with a true Stilbum. A stilbum-

1 Intermediate forms between stilbum-hodies and perfect agarics have not been
observed by either Ashby {loc. cit., p. 328) or myself.

OMPHALIA FLAVIDA 417

body, whatever its origin, cannot now be called a sporophore, for it
produces no basidiospores or conidia ; and to call it an aborted
sporophore is to neglect the fact that it is an active organ with a
definite reproductive function and interesting structural characters
of its own. A stilbum-hody is in reality a gemmifer, and in what
follows it will be thus designated.

The gemmifer of Omphalia fiavida consists of two parts : ( 1 ) the
stalk which we may now call the pedicel, and (2) the head which is
in reality a gemma.

Under natural conditions, according to Maublanc and Rangel,^
the gemmae (their s^i76ww-heads) are the actual means by which
Omphalia flavida is disseminated and reproduced, for the perfect
sporophores were seen by them only in artificial cultures in which
the atmosphere was saturated with water vapour. While it is true
that the leaf-spots on attacked leaves of Coffee, etc., give rise only
to gemmifers, it is possible, as Maublanc and Rangel point out,
that the perfect fruit-bodies are sometimes developed on fallen
leaves in very wet situations on the ground, although, so far,
apparently no one has ever seen them there. It therefore seems
that, in Omphalia flavida, reproduction by gemmae has largely or
wholly taken the place of reproduction by basidiospores. This
suppression and replacement of basidiospores finds analogies else-
where. Thus chlamydospores have completely or almost completely
taken the place of basidiospores in Nyctalis 2 and in Ptychogaster.'

That the gemmifers of Omphalia flavida are well suited to act
as reproductive organs is shown by the following considerations.
(1) The gemmifers are produced in considerable numbers. Each
spot on a Coffee leaf in an entire season may produce 20-50 gemmi-
fers ; but as many as 70 have been observed on a leaf-spot 7 mm. in
diameter .4 (2) A gemma is easily detached from its pedicel by
wind, rain, or other mechanical means. (3) The gemmae are very
small, each being about one-third of a millimeter in diameter.
Owing to their small .size they are readily transported by mechanical

1 A. Maublanc et E. Rangel, loc. cit., p. 45.

2 These Researches, Vol. Ill, 1924, pp. 447-448, 463.

3 O. Brefeld, Untersuchungen iiber Pilze, Heft VIII, 1889, pp. 114-142.
* G. L. Fawcett, loc. cit., p. 11.

VOL. VI. 2 E

4i8 RESEARCHES ON FUNGI

means, e.g. wind, rain-splashes, etc., from one place to another.
(4) The exterior layer of each gemma is mucilaginous, so that a
gemma readily adheres to the upper surface of a leaf on which it may
happen to fall.^ (5) The pear-shaped palisade cells all around the
outer side of the oblate-spheroidal part of each gemma bear more or
less radiately-directed filiform hyphae — the infection hyphae. When
a gemma falls on a leaf, these filiform hyphae grow over the surface
of the leaf (Fig. 212, H), pierce the cuticle, pass through the epidermis,
and soon invade the palisade cells and spongy mesophyll.^ In less
than a week, the mycelium in the leaf -spot begins to form new
gemmifers (Fig. 213, A and B, p. 424).

The Basal Curvature of the Pedicel and its Significance.—
When a gemmifer growing on the upper side of a leaf or a malt-agar
plate is very young, the pedicel projects outwards perpendicularly
or almost perpendicularly from its substratum and the gemma is
always situated symmetrically on the end of the pedicel (Fig. 212,
A and B). As the pedicel increases in length by intercalary growth
just beneath the gemma, its lower or basal half usually becomes
curved, so that the upper half of the pedicel and the gemma are
turned away from the perpendicular at an angle which often varies
from 30° to 45° (c/. Fig. 212, C, D, E. ).

At first it was thought that the basal curvature of the pedicel
just described might be due to the stimulus of gravity, but experi-
ment soon disproved this supposition. Gemmifers were grown on
malt-agar : (1) in upright Petri dishes, (2) in inverted Petri dishes,
(3) in vertically placed Petri dishes, and (4) in Petri dishes rotated
in a vertical plane on a klinostat. Under all these conditions the
gemmifers at first grew out perpendicularly from their substratum,
and then their pedicels became more or less curved in various
directions {cf. Figs. 202, p. 403, and 213, p. 424). In the inverted
and vertical Petri dishes, the pedicels did not all curve
downwards as they should have done had they responded to' a

1 F. G. Kohl, " Untersuchungen liber die von Stilbella flavida hervorgerufene
Kaffeekrankheit mit Angaben der aus den Untersuchungen sich ergebenen Mass-
regeki gegen diese Pilzepidemie," Beihefte zum Tropenpflanzer, Bd. IV, 1903,

pp. 63-64.

2 Kohl shows the infection hyphae growing from a gemma into a leaf in his

Taf. 11, Fig. 7.

OMPHALIA FLAVIDA

419

positive geotropic stimulus, but some turned upwards, some down-
wards, and some sideways. Also, when rotated slowly on the

Fig. 212. — Omphalia flavida. Stages in the development of a gemmifer on a leaf of
Bryophyllum cnlychmm. A, a very young stage in median-vertical section
showing the primordia of the pedicel and the gemma. B, the pedicel, which
is still straight, has elongated by intercalary growth at its upper end, and the
gemma has become swollen. C : the pedicel has become bent (repulsion
curvature) and is still elongating by intercalary growth under the gemma ;
the gemma has developed a circular cavity between the pedicel and the apophy-
sis ; hairs have grown out from the pedicel and infection hyphae from the
periphery of the gemma. D, the circular cavity has enlarged and the pedicel is
still growing in lengtli. E : the pedicel is now full-grown ; its end has become
sigmoidally bent (geotropi(^. curvatures) and has broken away from the gemma
which now has its axis horizontal ; the gemma is holding on to the end of the
pedicel by its apophysis only. F, the gemma is being blown away from its
pedicel by the wind and is travelling in the direction shown by the arrow.
G, the underside of a ripe gemma after leaving the pedicel ; the central opening
came into existence when the gemma slipped of? the stipe. H, a gemma which
has settled on a leaf and is infecting it by means of its infection hyphae which
have grown in length. Drawn by A. H. R. BuUer and Ruth Macrae. Mag-
nification, 47.

klinostat during their development, the pedicels all became more or
less curved, the direction of the curvature being usually away from
the centre of the plate toward the edge of the radiately growing

420 RESEARCHES ON FUNGI

mycelium. There can be no doubt, therefore, that the basal
curvature of the pedicel is not due to a geotropic stimulus.

What, then, does cause the basal curvature of the pedicel ? A
study of the disposition of gemmifers in a single group growing on
agar in upright, inverted, or vertical fixed Petri dishes or in Petri
dishes rotated in a vertical plane on a klinostat, or on a leaf-spot
(Fig. 213), reveals the fact that the gemmifers diverge from one
another. One cause of the general curvature of the stipe, therefore,
is the mutual repulsion of the gemmifers. Where a gemmifer is
growing alone and its pedicel is curved, it may be that the
curvature is due to the mycelium in the substratum which in some
way repels the gemmifer more on one side than on the other.

The bending of the stipe of a sporophore and the basal bending
of the pedicel of a gemmifer are due to different causes and have
different biological advantages. A stipe is negatively geotropic :
as it grows in length, its upper end becomes more and more vertical,
with the result that the median axis of the pileus becomes vertical
and the pileus is given the most favourable orientation for the
successful discharge of the spores (Fig. 213, p. 424). On the other
hand, a pedicel (except at its apex, as we shall see in the next Section)
is ageotropic and the different pedicels in a group of gemmifers bend
away from one another owing to mutual repulsion, with the result
that the gemmae, which are adhesive, avoid coming in contact with
one another during their development and, when the time arrives
for their dispersion, have a better chance of being carried off freely
by the wind (Fig. 213).

The Sigmoid Curvature of the Pedicel and the Abscission of the
Gemma. — A gemma, before being dispersed by the wind, undergoes
abscission from the end of the pedicel whilst still attached to the
pedicel subterminally by means of the clasping collar-like apophysis
(c/. Fig. 212, D and E). The abscission process, which is effected
in a unique manner, has been investigated in detail, and an account
of it will now be given.

The extreme end of a pedicel (the last 0-2 mm.), i.e. the part
within and just below the clasping apophysis, is at first quite
straight (Fig. 212, D) ; but, finally, as shown in Figs. 205, C (p. 408)
and 212, E, it becomes curved sigmoidally. It is whilst the end of

OMPHALIA FLAVIDA 421

the pedicel is becoming sigmoid that the top of the pedicel is torn
away from the gemma, thus bringing about the abscission of the
latter. After abscission of the gemma has been effected, the
attachment of the gemma to the pedicel is maintained merely by
the clasping apophysis (c/. Fig. 212, E).

Until the abscission of the gemma has taken place, the apophysis
firmly clasps the pedicel, and it is this firm attachment which makes
abscission of the gemma from the top of the pedicel mechanically
possible. After abscission has taken place, the attachment of the
apophysis to the pedicel weakens, and then the gemma can readily
be blown off the pedicel by the wind (Fig. 212, F). Thus the apophy-
sis functions in two ways : ( 1 ) it grasps the pedicel subterminally
and thus permits of the abscission of the gemma from the top of the
pedicel, and (2), after abscission, it holds the gemma on to the top
of the pedicel until a blast of wind carries the gemma away and thus
brings about its dispersion.

We have just seen that the sigmoidal growth-curvature of the
end of the pedicel results in the abscission of the gemma from the
top of the pedicel. We may now ask : what causes the end of
the pedicel to assume its sigmoid form ? The answer to this
question is to be found in the response of the pedicel to geotropic
stimuli.

By observing gemmifers growing on malt-agar plates from
surfaces looking upwards, downwards, and sideways, it was found :
(1) that the part of the pedicel in the region of the collar of the
apophysis always bends downwards through an angle, often of 45°,
during the last stages of the development of the gemmifer ; (2) that,
at the same time, the very top of the pedicel, hidden within the
apophysis, always bends upwards (Fig. 212, E) ; and (3) that, whilst
the pedicel is bending sigmoidally, the upper side of the apophysis
elongates slightly more than the lower (Figs. 205, C, p. 408, and
212, E). The simplest explanation of all these growth phenomena
is that they are due to geotropic stimuli : gravity stimulates the
pedicel in the region of the collar of the apophysis to elongate more
on its upper side than on its lower ; gravity stimulates the pedicel
at its very top to elongate more on its lower side than on its upper ;
and, finally, gravity stimulates the apophysis to elongate more on

422 RESEARCHES ON FUNGI

its upper side than on its lower. The opposite geotropic reactions
of the subterminal and terminal parts of the pedicel produce two
opposite curvatures which together give to the last 0-2 mm. of the
pedicel its characteristic sigmoid form. The sigmoid curvature,
since it is due to the positive and negative geotropic stimuli, is
necessarily always in a vertical plane (Figs. 205, C, p. 408, and
212, E, F).

That the stimulus of gravity is the true cause of the sigmoid
curvature of the end of the pedicel and of the asymmetrical growth
of the apophysis of the gemma is strongly supported by an experi-
ment made with the help of a Pfeffer klinostat. A malt-agar plate
upon which the rudiments of gemmifers of Omphaliaflavida were just
beginning to appear was rotated on the klinostat in a vertical plane,
and the rotation was continued for several days until the gemmifers
were full-grown. As a control, another malt-agar plate, prepared in
the same way as the first, was kept in a fixed position (upside down
on a table). In the control, when the experiment came to an end,
all the gemmae were turned slightly downwards on the ends of the
pedicels and, when the gemmae were pulled off their pedicels, the
ends of the pedicels were found to have the characteristic sigmoid
curvature. Moreover, the gemmae had become asymmetrical in
form, the upper side of the apophysis, as usual, having become longer
than the lower. On the other hand, in the culture rotated on the
klinostat, the ends of the pedicels were quite straight and none of them
had developed even a trace of a sigmoid curvature, so that each
gemma occupied a symmetrical position on the end of its pedicel.
Furthermore, each of the gemmae which had been rotated on the
klinostat, instead of displaying the usual asymmetry, was sym-
metrical in form, like a door-knob, the apophysis not having
elongated more on one side of the gemma than on the other.

From the above observations and experiments we may conclude
that the abscission of a gemma from its pedicel is effected by the
end of the pedicel, toward the close of its development, taking on
a sigmoid form, and that the sigmoidal curvature is due to the end
of the pedicel giving a double response to the stimulus of gravity.
It is evident that a gemmifer is beautifully organised as an organ
for the production and liberation of its gemma.

OMPHALIA FLAVIDA 423

The Detachment of a Gemma from its Pedicel. — Ripe gemmae
could be readily blown away from their pedicels as follows. A
hollow glass tube was drawn out to a slight nozzle at one end, the
nozzle was then placed near some gemmifers growing on a Bryo-
phyllum leaf, and then air was blown through the tube from the
mouth. The gemmae upon which the blast of air impinged were
very easily blown away from their pedicels to some distance. There
can be no doubt that a slight wind would also have carried off these
gemmae.

A test-tube containing a malt-agar slope which bore gemmifers
was held horizontally with the gemmifers looking downwards and
was then tapped. Several of the gemmae came off their pedicels
and settled on the side of the tube below, others remained on their
pedicels. This experiment affords further evidence that ripe gemmae
can be detached from their pedicels without much difficulty by
mechanical means.

The gemmae never droj) off their pedicels sjiontaneously and, no
doubt, under natural conditions in the open, they remain in situ
until the wind is sufficiently strong to bear them away. This
resistance to detachment except under conditions favourable for
dispersion must be of no small value to a fungus which is a parasite
on leaves. It finds its parallel in the fruits of the Manitoban Maple,
Acer Negundo, which in Manitoba hang on the trees through the
winter until some violent gale in March or April tears them from
the branches and scatters them far and wide.

The mature gemma of a gemmifer situated on the top of a leaf-
spot, owing to the basal and the sigmoid curvatures of the pedicel,
comes to have its median axis disposed more or less parallel to the
leaf surface (Fig. 213, C). This orientation of a gemma, as we have
seen, is due to the reaction of the pedicel to certain stimuli. The
basal curvature of the pedicel of a gemmifer in a group of gemmifers
serves to remove the gemma from neighbouring gemmae, and the
sigmoid curvature of the pedicel resulting in the turning downwards
of the gemma seems to be significant merely as an incidental factor
in the mechanism of abscission. On the other hand, it may be that
the final orientation of the gemma contributes something to the ease
of detachment of the gemma by the wind. The wind sweeping

Fig. 213. — Omphalia flavida on a leaf of Bryophyllum calycinum. Semi-diagrammatic drawings
(based on laboratory cultures on isolated leaves kept on wet sand), to show the development
of a leaf-spot (which is luminous), the production of gemmifers and of a perfect fruit-body,
and the dissemination of gemmae and basidiospores. A, a cross-section of part of a leaf upon
which a gemma has just settled after being blown from its pedicel by the wind. B, the same,
ten days later : from the gemma which fell on the leaf the infection hyphae grew into the leaf
and the mycelium of the parasite then progressively killed the host-cells there, thus forming
a necrotic lesion in the form of a blackish leaf-spot ; from this spot gemmifers have developed
and are still developing centrifugally ; the younger gemmifers have straight pedicels ; the
older gemmifers have pedicels which are bent basally owing to mutual repulsion and bent
above sigmoidally owing to a double reaction to the stimulus of gravity. The gemmae of the
older gemmifers have nearly horizontal axes. C, the same as B, 3-4 weeks later : the leaf -spot
has increased in size, but is no longer extending ; the gemmifers are all mature and two of
the gemmae have just been blown from their pedicels in the direction shown by the arrows ;
a perfect fruit-body has developed at the edge of the leaf-spot and is now discharging
clouds of spores which are being carried away by the wind. Drawn by A. H. R. Buller and
Ruth Macrae. Magnification, 6-6.

OMPHALIA FLAVIDA

425

over the surface of a leaf must strike many gemmae on their broad
under side instead of laterally and thus, perhaps, it may detach them
from their pedicels more readily than if their axes had been
perpendicular to the leaf surface.

The Attachment of a Gemma to a Leaf. — When a gemma falls
on to a leaf, it usually settles on its slightly concave upper surface
and readily becomes attached to the leaf, presumably by means of
the mucilage in which the clavate palisade cells, which form the

Fig. 214. — OmphaUa flavida (from Trinidad). A, a gemma ripe
and ready for dissemination, seen from above. It grew in
moist air. Short infection hyphae can be seen at its
periphery, but the central disc cells are free from hypliae.
B, part of a longitudinal section of a ripe gemma {cf. Fig.
205), showing clavate peripheral cells a embedded in a
gelatinous matrix, some of them extended into infection
hyphae b. Drawn by A. H. R. BuUer and Ruth Macrae.
Magnification : A, 86 ; B, 406.

exterior layer of cells of the gemma, are embedded (Fig. 213, A).
Gemmae which have fallen on to a leaf are not easily detached from
the leaf ; for, when air was blown at them through the nozzle of the
glass tube already used to blow them from their pedicels, they
remained on the surface of the leaf and were not driven away from
it. It thus appears that the ripe gemmae are well adapted for dis-
persion and for attachment : the wind can easily blow them from
their pedicels and thus transport them from leaf to leaf ; but, when
once they have settled on a leaf, they resist the action of the wind
in removing them. Owing to the manner in which they attach them-
selves to a leaf, their chances of causing new leaf-spots are increased.

426

RESEARCHES ON FUNCxI

Mode of Germination of a Gemma. — Preparations for the ger-
mination of a gemma are made before the gemma is blown away

Fig. 215. — Omphalia flnvida (from Trinidad). A gemma germinating. Drawn
24 hours after it was removed from its pedicel and placed in a hanging-drop
of malt-agar. The upper surface of the gemma, which visually comes into
contact with a leaf, is shown. The radiating hyphae, which are growing
rapidly in length, are prolongations of the short infection hyphae which were
produced by the pear-shaped peripheral cell.3 and were already present on the
gemma before its removal from the pedicel. Drawn by A. H. R. Buller and
Ruth Macrae. Magnification, 88.

from its pedicel ; for, when a gemma is mature and still attached to
its pedicel, there grow outwards into the air from its pear-shaped or
clavate cells all around the outer surface of its oblate-spheroidal
part a large number of what we have called infection hyphae (Figs.

OMPHALIA FLAVIDA

427

205, C, p. 408, and 214, B). These hyphae come to project aerially
from the gemma to a distance of 0-05-0- 1 mm., and then they cease
to elongate.

When a gemma (Fig. 214, A) is placed in tap-water or in malt-
agar, the infection hyphae resume their growth and, in malt-agar,
in the course of about 24 hours, they become 0-4-0-5 mm. long,
thus surrounding the gemma with a radiating mycelium (Fig. 215).
The individual hyphae of this mycelium are evenly
cylindrical in form, 3-4 [x in diameter, septate, and
provided with numerous clamp-connexions (Fig. 216).
It is these hyphae which, under natural conditions,
penetrate through the epidermis of a Coffee leaf,
attack the internal leaf-tissues, and so produce a
leaf-spot.

The Effect of Desiccation on the Vitality of a
Gemma. — It is well known that the spores of many
Hymenomycetes, e.g. species of Coprinus, will with-
stand desiccation for several weeks or months. It
therefore seemed of interest to enquire whether or
not the gemmae, which in Coffee plantations appear
to be the normal reproductive bodies of Omphalia
flavida, can also withstand desiccation.

Some ripe gemmae were taken from the pedicels
of some gemmifers growing on an agar-plate and
they were set on four cover-glasses A, B, C, and D.
The gemmae on A were not allowed to dry up but,
immediately after removal, were covered for two
minutes with a minute drop of water, after which they
were submerged in a drop of malt-agar. The cover-
glass was then set on a van-Tieghem cell with water
at the base and the drop of malt-agar hanging down-
wards. The gemmae on the cover-glasses B, C, and D

Fig. 216. — Omphalia flavida (from Trinidad). Hyphae from the
rswliating mycelium growing from a gemma placed in malt-
agar for 76 hours. As indicated by the clamp-connexions,
the mycelium is in the diploid nuclear condition. A, the
terminal part of a hypha. B, an older part of a hypha.
Drawn by A. H. R. BuUer and Ruth Macrae. Magnification,
466.

428

RESEARCHES ON FUNGI

were exposed to the air of the laboratorj^ for half an hour, one hour,
and 26 hours respectively, after which they were treated in the same
manner as the gemmae on cover-glass A. The air in the laboratory
was remarkably dry and the gemmae on the cover-glasses B, C, and
D, when exposed to it, dried up within about a minute. Whilst

undergoing desiccation,
the gemmae became
much shrunken. When
treated with water,
they rapidly expanded,
and their expansion
was doubtless due in
part to the imbibition
of water by the gela-
tinous matrix in which
all the cells of each
gemma are embedded.
After the gemmae
had been 24 hours in
malt-agar , it was found :
(1) that the gemmae
on the cover-glass A,
which had not been
allowed to dry up,
had all germinated
perfectly, their infec-
tion hyphae having
grown out radially from
the gemma to a dis-
tance equal to the
gemma's diameter ; (2) that the gemmae on the cover-glasses
B and C, which had been dried for half an hour and one hour
respectively, had germinated imperfectly, for only very few of the
infection hyphae of each gemma had grown out radially into the
culture medium ; and (3) that the gemmae on the cover-glass D,
which had been dried for 26 hours, had not germinated at all.

From the above series of experiments it is obvious that exposure

Fig

217. — Omphalia flavida on a leaf of Bryo-
phyllum calycinum, two weeks after inocula-
tion. The leaf was wounded by lightly
scratching it in the centre and also near the
left lower edge ; and then a few gemmae were
sown on the wounds. The mycelium grew
into the leaf-tissues and formed two leaf -spots.
In the central leaf -spot can be seen a number
of gemmifers each bearing terminally a tiny
gemma. Natural size.

OMPHALIA FLAVIDA 429

to very dry air seriously injures the gemmae within 0- 5-1-0 hour
and kills them within 26 hours.

Some gemmae were removed from their pedicels and set on a
cover-glass in a Petri dish in which the air was saturated with water
vapour for 24 hours and, at the end of this time, they were placed
in a hanging drop of malt-agar. They germinated perfectly. From
this we may conclude that gemmae, after being blown from their
pedicels on to other leaves in a Coffee plantation when the weather

Fig. 218. — A leaf of Bryophyllum calycinum infected with the myceliiun of
Omphalia flavida which, in the course of about a month, produced gemmifers
first and then, as here shown, a number of perfect fruit-bodies. The leaf
was isolated, inoculated with gemmae, and kept moist on wet sand. The
fungus has killed most of the leaf which, however, has succeeded in pro-
ducing a few new shoots and roots at its edge. Natural size.

is moist, probably retain their vitality and ability to germinate for
several days.

Inoculation Experiments with Living Leaves. — In 1901, Kohl 1
examined many hundreds of Coffee leaf-spots and observed that
there was a gemma adhering to the epidermis above the middle of
every one of them. With a little practice and under favourable
light conditions, he succeeded in finding the gemmae even with the
naked eye. Thus Kohl obtained strong evidence that, under natural
conditions, Omphalia flavida is propagated by its gemmae. In
80-85 per cent, of the leaf-spots examined the gemmae were attached
to the upper side of the leaf, while in the remaining 15-20 per cent,
they were attached to the lower side of the leaf.

Kohl 2 also carried out some inoculation experiments. He
1 F. G. Kohl, loc. cit., p. 63. 2 /{,j^,^ pp. 64-65.

430

RESEARCHES ON FUNGI

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placed gemmae on living Coffee leaves and observed that a typical
leaf -spot was formed beneath and around each gemma, thus proving

beyond all doubt that the
gemmae serve as sources of
infection. Presumably, Kohl
saw new gemmifers arise on
his experimental leaf-spots,
although he does not mention
them.

In the autumn of 1925,
T. C. Vanterpool and the writer,
working in conjunction at
Winnipeg, succeeded in in-
fecting a number of living
leaves with Omphalia jiavida.
One set of the experiments
will now be described.

Two leaves of each of the
following plants were gathered
from the green-house : Bryo-
phyllum calycinum, Nerium
Oleander, and a species of Ficus.
The leaves were then washed
for about two minutes in
0 • 1 per cent, mercuric chloride,
rinsed in distilled water, and
set on very wet sand in a large
crystallising dish. One leaf of
each kind was then wounded
by scratching it very slightly
with a sterilised needle, and
the other leaf of each kind
was left intact. Then a very
few gemmae were removed from
a bread culture with the help of a sterilised needle and placed in
particular spots on the upper surface of all the six leaves. In the
case of the three wounded leaves the gemmae were placed on the

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6

OMPHALIA FLAVIDA 431

wounds. The crystallising dish was then covered and set in diffuse
daylight on a table in the laboratory. The air within the dish very
soon became saturated with water vapour.

Typical leaf-spots, which rapidly grew in size, were developed
within a week on both the wounded and the unwounded Bryo-
phyllum leaves and on the wounded, but not on the unwounded,
Oleander and Ficus leaves. About ten days after inoculation, a
crop of saffron-yellow gemmifers began to develop at the surface
of the infected areas (Fig. 217, cf. Fig. 201, p. 402) ; and, after
another ten days, at the edges of the same areas, a few typical

Fig. 220. — Omphnlia flavida on an isolated leaf of Nerium
Oleander re.sting on wet sand in a Petri dish. The leaf
was dipped in 0 • 1 per cent, corrosive sublimate, washed
in sterilised water, and placed on sterilised sand moistened
with sterilised water. The surface of the leaf was then
scratched with a needle and a piece of mycelium was laid
over the wound. After about a week, a few gemmifers
came up above the leaf. On the twenty-first day after
inoculation, the sporophores here shown began to make
their appearance. Photographed at Winnipeg twenty-
seven days after inoculation. Natural size.

Omphalia flavida sporophores made their appearance (Figs. 218, 219,
and 220). Thus the mycelium, by producing both kinds of fruiting
structures, behaved in living leaves just as it had done in artificial
bread cultures. ^

In further experiments, Vanterpool and I succeeded in infecting
the leaves of Plumbago capensis ; but, in this species, the leaf-
spots developed gemmifers only, no sporophores ever making their
appearance.

Omphalia flavida as a Non-specialised Parasite. — Many para-
sites, e.g. Uredineae, Ustilagineae, and most Peronosporeae and
Chytridiaceae, are highly specialised, some of them being restricted

1 Cf. Figs. 203 and 204, pp. 404 and 405.

432

RESEARCHES ON FUNGI

to even a single host ; while other parasites, e.g. Fomes pinicola,
Pohfporns squamosus, Peronospora parasitica, and Cyslopus
candidus, are far less specialised and are found on many different
hosts. Omphalia flavida is an extreme example of a non-specialised
parasite ; for, in addition to Coffee, its chief host, it attacks plants
belonging to the most diverse families of Flowering Plants and also
various Ferns. It is probable that there are but few parasites which
can attack Ferns as well as Flowering Plants. i The following list
includes the host-families of Omphalia flavida and the observers by
whom they have been recorded.

DiCOTYLEDONES

Anacardiaceae {Mango)

Apocynaceae

Begoniaceae
Compositae

Crassulaceae
Leguminosae

{Nerium Oleander)
I {Tabernaemontana)
[Begonia)
{unidentifled spp.)

{Bryophyllurn)

[{Bryophyllurn pinnatum)
{ {Inga vera — Guava)
{{Andira inermis — 31 oca)

Fawcett.2

Buller and Vanterpool.^
Puttemans.*
Fawcett.

Maublanc and Rangel.^
(McClelland.6
[ Buller and Vanterpool.
Miiller.7
Fawcett.
McClelland.

1 The species of the Rust genera Hyalopsora, Milesia, and Uredinopsis have
their aecidial stage on a Conifer (Abies) and their uredospore and teleutospore stages
on Ferns (Blechnum, Scolopendrium, Polypodium, etc.).

2 G. L. Fawcett, loc. cit., p. 13.

3 A. H. R. Buller and T. C. Vanterpool, loc. cit.

4 A. Puttemans, " O Stilbella flavida parasita sobre Tabernaemontana," Revista da
Sociedade scientifica de Sao Paulo, 1907, p. 95. Cited from Maublanc and Rangel.

5 A. Maublanc et E. Rangel, loc. cit., pp. 41, 43.

6 T. B. McClelland, " The Coffee Leaf Spot (Stilbella flavida) in Porto Rico,"
Porto Rico Agric. Exp. Station, Bull. No. 28, 1921, p. 7. McClelland, in a badly
affected, almost abandoned plantation in Porto Rico found the following plants
acting as hosts for Omphalia flavida : achiotilla, bilsamo, bejuco de mona, bejuco
de paloma, berugillo, bruja, cadillos, camasey bianco, camasey cimarron, china,
helecho, guasabara, guayaro, guava, higiierillo, lechecillo, lengua de vaca, nioca,
nuez moscada cimarrona, palo de cucubano, palo de hueso, tostado, vinagrera,
yerba hedionda. Owing to uncertainty as to the scientific equivalents of these
local names, I have not added them to my list.

7 A. S. Miiller, at Mayaguez, Porto Rico, in litt., 1928.

OMPHALIA FLAVIDA

433

Melastomaceae {unidentified spp.) .
Moraceae (Ficus)

Plumbaginaceae {Plumbago) .
Rosaceae {Eriobotrya japonica —

Loquat)

{{Coffea)

1 {Cinchona) .

Rubiaceae

Rutaceae

{Orange)

Maublanc and Rangel.
Buller and Vaiiterpool.
Buller and Vanterpool.

Maublanc and Rangel.
Cooke and others.
Kohl.i
Fawcett.

Araceae
Commelinaceae

Musaceae

MONOCOTYLEDONES

( Yautia) . . . Fawcett.

{Commelina spp.) . . Fawcett.

{Zebrina pendula) . . Miiller.^

{Banana)

. Fawcett.

Various Ferns

Ptertdophyta

{unidentified) . . Fawcett.

Sterility of the Mycelium Induced by Prolonged Cultivation on
Artificial Media. — S. F. Ashby isolated his pure culture of Omphalia
flavida in Trinidad in 1925. Subcultures of this culture were used
by Vanterpool and myself in the winter of 1925-1926, during which
time the mycelium fruited well both on artificial media and on living
leaves. Two years later, in the winter of 1927-1928, I procured
another subculture of Ashby 's pure culture from the Centralbureau
voor Schimmel-cultures at Baarn, but found that the mycelium on
bread and agar media, even after many weeks, produced neither
gemmifers nor sporophores. This sterility appeared to be due to
prolonged cultivation of the mycelium on artificial media.

The mycelium which, instead of producing gemmifers, developed
an aerial fluffy hyphal mat was brought back into the fruiting condi-
tion by passing it through living leaves. Some Bryophyllum leaves,
kept on wet sand in Petri dishes, were wounded by scratching with

^ F. G. Kohl, loc. cit., pp. 66-68. Kohl, in Central America, examined 36 different
kinds of plants and found ten of them affected by the leaf-spot disease. One was
a Quinahautn. The others he was unable to identify.

2 A. S. Miiller, at Mayagiiez, Porto Rico, in litt., 1928.

VOL. VI. 2 F

434 RESEARCHES ON FUNGI

a needle, and then the wounds were inoculated with mycehum
attached to bits of agar. Infection took place ; but, in general, the
leaf-spots failed to develop any gemmifers. At length, on one leaf-
spot, two or three gemmifers made their appearance. The gemmae
of these gemmifers were then removed with a needle and used as
inoculum on a new wounded Bryophyllum leaf. The new leaf-spot
produced gemmifers more freely than its predecessor, whereupon
its gemmae were used as inoculum as before. After having been
passed in this way through Bryophyllum leaves several times,
the mycelium fruited freely, and thousands of gemmifers and some
scores of sporophores were obtained from it on bread and malt-agar
media as well as on living leaves of Bryophyllum and Oleander.
Nevertheless, the mycelium did not seem to be in quite so good a
condition as it had been three years before, because (1) it fruited
rather slowly, and (2) it still showed a tendency to develop a fluffy
mycelium at the surface of the culture medium, instead of gemmifers.

In the spring of 1928, through the kindness of Mr. J. A. B. NoUa,
I obtained from Porto Rico a culture of Omjihalia flavida which had
recently been isolated by Professor Albert IMiiller of the Mayagiiez
Agricultural College. When portions of this Porto Rican culture
were transferred to malt-agar plates, the mycelium, unlike that from
Trinidad, did not develop an aerial fluffy layer of hyphae but rapidly
produced gemmifers. Within five days after inoculation of the
plates, which were exposed to light on a table, gemmifer production
was in full progress. A comparison showed that the newly isolated
Porto Rican culture fruited far more rapidly and vigorously than
the Trinidad culture derived from an isolation made three years
previously.

From the above observations we may conclude : (1) that the
mycelium of Ornphalia flavida, when newly obtained from gemmae
developed in the open on Coffee leaves, fruits vigorously ; (2) that,
when the mycelium is grown for several years on artificial media,
it gradually loses its fruiting power ; and (3) that the fruiting power
in an old culture can be restored in a large measure by passing the
mycelium through living leaves.

The Effect of Light on the Formation of Gemmifers.— The
mycelium of the Trinidad strain of Omphalia favida, after it had

OMPHALIA FLAVIDA 435

been brought back into the fruiting condition, was used to inoculate
malt-agar in Petri dishes. The mycelium grew radially outwards
from the centre of each dish. Certain of the cultures which were
exposed to diffuse daylight on a table in the laboratory formed
concentric zones in which broader fluffy sterile rings of mycelium

Fig. 221. — Omphalia flavida. Alternate zones of sterile fluffy myceliixm (white)
and of gemmifer-bearing mycelium (dark) in a malt-agar culture of Omphnlia
jlavida originating from Trinidad. The culture was started by placing
a single gemma in the middle of the agar. The sterile zones of mycelium
were formed during the night and the fertile zones during the day. The last
two dark zones are narrower than the previous ones because, on the days
when they were formed, the plate was exposed to light only from 9.30 a.m.
to 5.30 P.M. Natural size.

alternated regularly with narrower, non-fluffy rings of mycelium
bearing gemmifers (Fig. 221). By marking the plates it was soon
found that the sterile zones were formed during the night and the
fertile zones during the day. These facts indicated that the pro-
duction of gemmifers by the mycelium is initiated by a morphogenic
stimulus of light. Some further observations supporting this
deduction will now be recorded.

The Porto Rican culture, referred to in the last Section, was sent
from Porto Rico in a dark wooden box and, after arrival in Winnipeg,

436 RESEARCHES ON FUNGI

it was kept in the box in the dark. This culture grew well but did
not produce any gemmifers in the dark in the course of several
weeks.

Small pieces of agar bearing mycelium were taken from the Porto
Rican culture and were used to inoculate the centres of three malt-
agar Petri dishes on June 7, 1928. Two of these dishes were then
exposed to daylight on a table, whilst the third was exposed to
daylight for about one hour and was then enveloped in black paper
and placed in a dark cupboard.

On June 13, i.e. six days after the beginning of the experiment,
the condition of the plates was as follows. In the two plates which
had been exposed to daylight numerous gemmifers had appeared
not only on the mycelium on the pieces of Porto Rican agar used as
inoculum but also on the new agar, and on the new agar three
distinct concentric zones of gemmifers could be clearly observed.
On the other hand, on the plate which had been exposed to light
for about an hour and had then been placed in the dark, a certain
number of gemmifers had developed on the old mycelium in the
inoculum which had been exposed to the light for an hour, whilst
no gemmifers whatever had appeared on the new mycelium which
had grown out radially in the fresh agar in the dark. At the end
of another week, the lighted cultures had developed many zones
bearing gemmifers while the darkened culture had developed no
such zones, the mycelium of the darkened culture, excepting that
in the original inoculum which had been exposed to daylight for
about an hour, having remained quite sterile.

From the above observations we may conclude : (1) that the
formation of gemmifers is initiated by the stimulus of light ; and
(2) that the mycelium is stimulated to produce gemmifers by an
exposure to daylight of one hour or less.

Ashby 1 observed that both gemmifers and sporophores devel-
ojied to maturity in bread cultures in flasks kept in the dark. The
production of fruiting structures in this instance may well have been
due to the stimulus of light given during the time when the flasks
were being inoculated or were being examined from day to day. In

1 S. F. Ashby, " The Perfect Form of Stilbum flavidum Cke. in Pure Culture,"
Bulletin of Miscellaneous Information, Royal Botanic Gardens, Kew, 1925, p. 327.

OMPHALIA FLAVIDA

437

the mould Fusarium discolor sulphureum, that shows typical zonation
in Petri-dish cultures exposed to daylight, Bisby ^ observed that an
exposure of the mycelium to bright daylight for only one-fourth to
one-half of a second is sufficient to cause the formation of a ring of
conidia which can be detected
with the naked eye. As we have
seen, exposure of the mycelium
of Omphaliaflavida for one hour
or less stimulates it to produce
gemmifers. Further experi-
ment may show that an ex-
posure of the mycelium to
bright daylight for a very few
minutes, or possibly less than
one minute, is sufficient to
initiate the production of
gemmifers.

Luminescence of the My-
celium and its Value as a
Diagnostic Character of the
Coffee-leaf Disease. — For some
years, in the hope of discover-
ing luminosity in fungi in
which it had not yet been
observed, I examined system-
atically in the dark every
fungus species grown in my
laboratory and also many
isolated agaricaceous fruit-
bodies — but all in vain. One

evening in the autumn of 1925, however, my efforts were at last
rewarded with success ; for, on taking a bread culture of Omphalia
flavida contained in a conical flask into the dark room, I at once
perceived that the mycelium emitted light (c/. Fig. 222). The
glow was pale but quite distinct, and the culture was used to

^ G. R. Bisby, " Zonation in Cultures of Fusarium discolor sulphureum,"
Mycologia, Vol. XVII, 1925, p. 92.

Fig. 222. — The mycelium of Omphalia
finvida growing on either moist bread-
crumbs or corn-meal in a conical flask,
photographed by its own light. Ex-
posure of negative (a panchromatic
plate), 75 hours. Aperture 4-5.
Culture made by S. F. Ashby at the
Imperial Mycological Institute at Kew,
and negative by G. Atkinson, artist at
the Royal Botanic Gardens, Kew.
One-half the natural size.

438

RESEARCHES ON FUNGI

demonstrate the phenomenon of biohiminescence to students and
friends.^

The mycelium appeared to emit light best when grown on bread
(1 part bread, 4 parts water), but it is also luminous when grown on
oatmeal agar or malt agar. The display of luminescence continues
steadily both day and night so long as the mycelium is actively
growing and only ceases when the mycelium has become old and
exhausted. The colour of the light may be described as pale
bluish-white.

As in Panus sfypticus lurninescens,^ shadow photographs can be

OMPHALIA

FLAVIDA

Fiu. 22:{. — A shaciow-photograpli of the black-paper letters of the words om-
rn.\L[.'V FLAVIDA made with tlie light of the mycelium of OmphdUa flavida
growing on an agar medium in a Petri dish 7 cm. in diameter. Tlie negative,
covei'ed by a glass plate bearing the black-paper letters, was exposed for
12 hours at a distance of 10 cm. from the Petri dish. Photograph made for
the author by H. H. Thornbury. Reproduced the original size.

made with the light emitted by the mycelium of Omplialia flavida,
and one such photograph, kindly made for me by Mr. H. H.
Thornbury of the University of Minnesota, is reproduced in Fig. 223.
The mycelium was grown on an agar medium in a Petri dish 7 cm.
wide. The negative, covered by a sheet of glass to which the
black-paper letters OMPHALIA FLAVIDA were attached, was
exposed for 12 hours at a distance of 10 cm. from the Petri dish.

1 In 1927, whilst visiting the Imperial Mycological Institute at Kew, by making
use of some of Mr. Ashby's cultures I was able to demonstrate the bioluminescence
of the mycelium of Omphalia flavida to Mr. Ashby himself.

2 These Researches, Vol. Ill, 1924, pp. 388-390, Figs. 168-169.

OMPHALIA FLAVIDA 439

Vanterpool and I ^ took the leaves of Bryophyllum, Neriiim,
Ficus, and Plumbago which we had artificially infected with Omphalia
flavida into the dark room and there observed that the leaf-spots on
all the four kinds of leaves emitted light.

The observations on luminosity so far recorded were all made
with a strain of Omjjhalia flavida of Trinidad origin. In 15)28,
another strain, of Porto Rican origin, was examined and found to
be equally, or perhaps even more, strongly luminous. The light
emitted by the mycelium of Porto Rican origin, when the mycelium
is growing on bread in a conical flask of 400 cc. capacity, was
sufficiently strong to permit of the reading of large print with letters
6 mm. high.

Four leaves of Nerium Oleander which had been inoculated with
the Porto Rican strain of Om'phaUa flavida showed infected areas
which were irregularly elliptical and about two inches long {cf. Figs.
201 and 202, pp. 402 and 403). On examining these leaves in a
dark-room I was able to detect the leaf-spots by their luminosity
when the leaves were 12 feet distant from my eyes. A nearer view
of the leaves revealed that the leaf-spots were beautifully defined
by the light which they gave out. On examining the leaf-spots
with a hand-lens, I clearly perceived that the luminosity was
not confined to the mycelium in the leaf but extended also to
the gemmae.^ The young gemmae could be seen as bright
spots. Some germinating gemmae which had rested for a few
hours on a fresh Oleander leaf had the appearance of tiny
stars. On the other hand, no luminosity could be detected in
older cultures as coming from the little agarics which produce the
basidiospores.

The discovery that the mycelium of Omphalia flavida growing
in the leaf-spots of living leaves emits light has provided a means of
diagnosing the American C'of[ee-leaf disease in the dark. Unfor-
tunately, owing to my great distance from those parts of America

^ A. H. R. Buller and T. C. Vanterpool, " The Bioluminesoence of Omphalia
flavida, a Leaf-spot Fungus," Phytopathology, Vol. XVI, 1926, p. (33.

2 In the communication of Buller and Vanterpool {loc. cit.) it was stated that the
gemmifers and sporophores " give out no light whatever." This statement, in so
far as it applies to gemmifers, is erroneous ; for, as here recorded, it has been found
that the gemmae are luminous.

440

RESEARCHES ON FUNGI

where Omphalia flavida flourishes, I have not been able to go into
Coffee plantations, pluck spotted leaves, examine them in the dark,
and observe their luminescence ; but Professor Albert Miiller of
the Mayagiiez College, Porto Rico, has recently done this,^ thus
proving beyond doubt that, so far as the emission of light is con-
cerned, the spots on Coffee leaves in the open resemble the spots
on leaves of Bryophyllum, Oleander, etc., in the laboratory at
Winnipeg.

In the spring of 1928 and also on September 3 and December 4
of the same year. Professor Miiller made field observations on the
luminosity of infected leaves in a Coffee plantation in Porto Rico,
and he described his observations to me in two letters, from one
of which the following has been extracted. " My experience A\ith
Omphalia flavida has been very interesting. I saw luminosity for
the first time when I entered my darkened laboratory and picked
up a moist chamber containing leaves bearing the typical spots of
the disease. This led to field expeditions for observing the pheno-
menon in the open. It was found necessary to select nights when
the moon was absent and situations where the brightness of the
tropical stars did not interfere. Another factor of the environment
played a part in the form of fire-flies, large numbers of which flit
about the Coffee trees or rest upon the leaves, giving off a very
bright light. After the fire-fiies had been dispersed, it was easy to
observe luminosity in the numerous spots on the leaves. This
luminosity was quite faint compared with the luminosity of a fire-fl}'
placed on a leaf near the spot, yet quite bright compared with the
himinosity of entire dead leaves of the CJuava shade- trees found
lying on the ground underneath, giving off a dull glow. An attempt
was made to ascertain from what distances the luminosity of Coffee
leaf-spots could be seen. From two to three feet the spots showed
brightest. From six to ten feet one could state positively that
luminosity was visible, but beyond ten feet imagination seemed to
influence the decision of the observer."

It is possible that the luminosity of Omphalia flavida leaf-spots
was actually observed by those engaged in coffee-growing half a
century ago ; for, in 1880, Mr. C. Michelsen, the Commissioner of

1 In lift., 1928.

OMPHALIA FLAVIDA 441

Agriculture at Bogota, wrote a letter to the Vice-consul of New
Granada (Colombia), quoted by Dr. Ernst ^ in another letter to
Nature, in which, after describing the Coffee leaf-spots and the
yellow gemmifers which appear upon them, he adds : " This fungus
is said to be phosphorescent at night ; and in places where it is very
common a phosphoric smell is noted." That the Coffee leaf-spots
should appear to be luminous in plantations after dark is exactly
what might be expected in view of the laboratory observations of
Vanterpool and myself and the Porto Rican observations of Pro-
fessor Miiller, but the idea that the fungus gives out a phosphoric
smell is doubtless an accretion invented by the mythopoeic faculty.
Omphalia flavida, it is true, is odoriferous, but its scent is faint and
pleasant, reminding one of apricots ^ ; and, as stated in the discussion
of bioluminescence in Volume III,^ there is no reason to believe that
the emission of light by fungi has any special relation with the
element phosphorus.

There is another leaf-spot disease of Coffee caused by Sclerotium
cojfeicola which will be treated of in the next Section. Here it is only
necessary to state that a comparison of artificial cultures made in
the Winnipeg laboratory in the dark showed that, whereas the
mycelium of Omphalia flavida is luminous, the mycelium of
Sclerotium cojfeicola is non-luminous. The luminosity criterion,
therefore, should enable a phytopathologist to determine whether
a particular Coffee leaf-spot is or is not caused by Omphalia
flavida.

Omphalia flavida is not the only species of Omphalia which is
luminous, for O. Martensii emits light also. Omphalia Martensii
was described by Hennings * in 1893. This fungus grows on roots
on the ground in Borneo ; and in March, 1863, near Bengkajang,
it was observed to be luminescent by Professor O. Martens, a zoo-
logist who had accompanied a Prussian expedition to eastern Asia.

1 A. Ernst, " Coffee-Disease in New Granada," Nature, Vol. XXII, 1880, p. 292.

^ The scent can be detected when the mycelium has just covered a malt-agar
Petri dish and is producing gemmifers.

3 These Researches, Vol. Ill, 1924, p. 364.

^ P. Hennings, " Einige neue und interessante Pilze aus dem Konigl. Botanischen
Museum in Berlin," Hedivigia, Bd. XXXII, 1893, pp. 63-64, PI. VII, Fig. 3. I am
indebted to Mr. L. C. C. Krieger for calling my attention to this paper.

442 RESEARCHES ON FUNGI

The fungus, on being examined by Hennings, proved to be an
Omphalia, and it was named in honour of Professor Martens, its
discoverer. The fruit-body has a stipe 2-2-5 cm. high and
0-5-1 mm. thick, while the pileus is 5-9 mm. in diameter.
Evidently, the fruit-bodies of 0. Martensii are more than double
as large as those of 0. flavida. The two fungi also differ in
their luminescence, for the light is emitted by 0. Martensii
from the sporophore and by 0. flavida from the mycelium and
gemmifers.

The full description given by Hennings for Omphalia Martensii,
translated from the Latin, is as follows : " Pileus membranaceous,
campanulate, umbilicate in the centre, radiately striate, dirty yellow-
ish, 5-9 mm. in diameter ; stipe thin, hollow, smooth and glabrous,
yellowish, subfuscous at the base, 2-2-5 cm. long, 0-5-1 mm.
thick ; gills subtriangular, broad, subdistant, pallid, decurrent ;
spores not seen. Habitat : west Borneo, near Bengkajang, on
roots."

In view of the fact that the mycelium of Omphalia flavida makes
Coffee and other kinds of leaves luminous, one may well ask whether
or not the mycelium of similar fungi is the cause of the luminosit}'
which may be observed in dead leaves of Beech, Oak, Hornbeam,
etc., forming part of the leaf-mould of the broad-leaved forests ^
very generally throughout the world.^ This question has recently
been answered in the affirmative by Bothe.

Bothe 3 has discovered that the mycelium of the following species
of Mycena emits light : M. jjolygramma Bull, and M. tinUnnabulum

1 Most observers have sought for kiniinous leaves only in broad-leaved forests,
but Bothe (1931, in Planta, p. 753, vide infra) has discovered that they also occur in
coniferous forests. In various places in the neighbourhood of Braunschweig and
in the Harz under Pines, etc., he found needles of conifers, little twigs, and isolated
" Tannen " cones, which gave out light just as strongly as decaying Beech and Oak
leaves.

2 In 1924, in Volume III of these Researches (pp. 421-427), to France, Germany,
and Sumatra I added England, Canada, and the United States as countries in which
luminous leaves occur. In 1926, S. R. Bose {Nature, 1926, p. 156) added India
(Bengal). Here also it may be recorded that in 1929 I observed luminous Beech
and Oak leaves in Scotland (Loch Awe) and in 1931 in Ireland (near Belfast).

3 F. Bothe, " Ein neuer einheimischer Leuchtpilz," Bcr. d. D. lot. Gesell, Bd.
XLVIII, 1930, pp. 394-399 ; also " Uber das Leuchten verwesender Blatter und
seine Erreger," Planta, Bd. XIV, 1931, pp. 752-765.

SCLEROTIUM COFFEICOLA 443

Fr., which grow on wood, and the following six species which grow
on leaves :

M. dilatata Fr. M. sanguinolenta A. et S.

M. epipterygia Scop. M. stylohates Pers.

M. galopus Pers. M. zephira Fr.

The mycelium of these leaf-fungi was obtained from spores and was
then transferred to sterilised Oak and Beech leaves or Pine needles.
The leaves were soon invaded by the fungi and in consequence they
became luminescent. The mycelium of Mycena galericulata proved
to be definitely non-luminous.^ Certain, but not all, fruit-bodies
of M. epipterygia, M. galopus, M. pura, M. sanguinolenta, and M.
zephira collected in woods were found to have luminous gills.
From Bothe's observations we may conclude that the luminescence
of decaying leaves in forests is in part, if not entirely, due to the
mycelium of various species of Mycena.

The Gemmifers of Sclerotium cofifeicola. — Sclerofium coffeicola 2
Stahel is a parasitic fungus, probably of hymenomycetous origin,
which is similar to Omphalia flavida in that it attacks Coffee plants
and produces large numbers of gemmifers. A gemmifer of Sclerotium
coffeicola, although differing in form, resembles in function a gemmifer
of Omphalia flavida.

Our knowledge of Sclerotium coffeicola and of the disease which
it causes is chiefly due to Stahel ^ who published his researches in
1921. I myself know the fungus only from spirit specimens on
diseased Coffee berries and from a culture kindly sent to me by
IVIr. S. F. Ashby.

With a view to extending our knowledge of gemmifers in general,

1 F. Bothe, Joe. cit., 1931, p. 764. The mycelium of the following Mycenae, as
so far cultivated, also appeared to Bothe to be non-luminous : M. alkalina, M.
crocata, M. haematopus, M. janthina, M. metata, M. vulgaris, and four other undeter-
mined wood-destroyers.

2 Stahel wTote the specific name coffeicolum, but I have changed this to coffeicola
in accordance with the Latin rule that the inhabitant of a place is denoted by a
word ending in cola. Here the specific name is not an adjective but a noun in
apposition. Cf. Sclerotium lichenicola Svendsen.

^ G. Stahel,." De Sclerotium-ziekte van de Liberiakoffie in Suriname," Departe-
ment van der Landbouw in Suriname, Bull. No. 2, 1921, pp. 1-34, Plates I-XI.

444

RESEARCHES ON FUNGI

an account of the life-history of Sclerotium coffeicola, based on
Stahel's investigations, will now be given.

Sclerotium coffeicola is the cause of the Sclerotium disease of the
Coffee plant. The fungus, so far, is known to occur only in Dutch
Guiana ( Surinam ),i British Guiana, ^ the island of Trinidad,^ and
Sierra Leone in west Africa.^

Martyn ^ has observed that in British Guiana Sclerotium coffeicola
occurs as a leaf-parasite not only on Coffea liberica and one or two
other Coffee varieties, but also on an ornamental shrub, Gardenia

■m

1^

Fig. 224. — Sclerotium coffeicola. Leaf-spots caused by the
fungus, seen from the upper side of pieces of two
laminae of Coffea excelsa. Each spot is composed of
a series of concentric rings. Gemmifers are absent,
since they are produced only on the lower side of the
spots. Photographed by G. Stahel. Natural size.

jasminoides, and on certain weeds growing in and about Coffee
plantations, namely Cecropia peltata, Commelina nudiflora, Vitis
sicyoides, an unidentified Melastomaceous plant, and a fern, Blechnum
serrulatum. He also found the unmistakable bristles (gemmae) on
the leaves of a shrub or young tree far removed from cultivation
and, below the tree, on decaying leaves and fruits, the orange

^ G. Stahel, " De Sclerotium-ziekte van de Liberiakoffie in Suriname," Departe-
ment van der Landbouw in Suriname, Bull. No. 2, 1921, pp. 1-34, Plates I-XI.

2 E. B. Martyn, "The Sclerotium Disease of Coffee and its Occurrence in this
Colony," Agric. Journ. Brit. Guiana, Vol. II, 1929, pp. 7-10 ; also " The Sclerotium
Disease of Coffee," ibid.. Vol. Ill, 1930, pp. 28-34.

■* In Trinidad S. coffeicola has been observed on excelsa Coffee leaves and fruits.
Information communicated by S. F. Ashby.

* S. F. Ashby, personal communication.

5 E. B. Martyn, lac. cil.. Vol. Ill, pp. 28-29.

SCLEROTIUM COFFEICOLA

445

sclerotia and the white feathery mycelium. The sclerotia and
mycelium of S. cojfeicola were observed by Martyn on decaying
leaves not only in Coffee plantations but also in native forests. As
a result of his observations Martyn is inclined to believe that S.
cojfeicola is to be regarded as a saprophyte on decaying leaf-tissues
and, at the same time, as a potential parasite which, under suitable
weather conditions, obtains a foot-hold on living plants. In being

Fig. 225. — Sclerotiuni cqffeicola. Leaf-spots caused by the fungus, seen from the
under side of a leaf of Coffea liberica. The two large spots have produced
numerous gemmifers which are arranged in concentric rings. The needle-like
gemmae and the knob-like pedicels from which they break away can be easily
recognised. The fungiLs progresses fastest along the larger veins of the leaf.
Photographed by G. Stahel. Natural size.

able to attack the living leaves of various kinds of plants, including
Ferns, S. cojfeicola resembles Omphalia jiavida.

The disease caused by Sclerotium cojfeicola on the Coffee plant
was first described by Kuyper ^ in 1913. He called it the Coremium
disease because the little white needles (gemmae) which are produced
on the leaf-spots and Coffee berries reminded him of coremia.
However, these " coremia " do not produce any conidia and the
presence of clamp-connexions in the mycelium affords evidence
that the fungus is a Basidiomycete. Clearly, therefore, the name

1 J. Kuyper, " Overzicht van de Koffieziekten in Suriname," Departement van
der Landbouw in Suriname, Bull. No. 31, 1913, p. 58.

446 RESEARCHES ON FUNGI

Coremium disease is a misnomer. Since the fungus produces
characteristic sclerotia, it is better to follow Stahel and call the
disease the Sclerotiuni disease.

Sderotium coffeicola attacks both the leaves and the berries of
the Coffee plant, and its ravages, in very moist weather, may even
extend to the inflorescences and flower-buds. The berries are affected
only when they are about three-quarters grown and are beginning
to ripen. On the leaves, like Omjjhalia flavida, Sderotium, coffeicola
causes the formation of brown leaf-spots (Figs. 224 and 225). These
spots are characterised by the presence of concentric rings and by
the production of gemmifers. The rings are due to the alternation
of narrower lighter brown zones of dead tissue with broader darker
brown zones. So long as the diseased leaves are hanging on the tree,
the gemmifers are produced only on the under side of the leaf -spots.
In the morning, after a dewy night, they can be seen on the lower
surface of each spot standing uJD in large numbers and more or less
in concentric circles (Fig. 225). The gemmifers are also produced
in dense crowds on diseased berries and sometimes on the peduncles
(Fig. 226).

On fallen leaves, in moist weather, the mycelium often grows
out centrifugally from the leaf-spots over the surface of the
leaves in the form of feathery branching strands which pro-
duce numerous gemmae (Fig. 227) ; and, in continuously moist
weather, this may happen even on leaves still hanging on the
trees.

Each gemmifer consists of a little white knob-like pedicel,
attached to the substratum, and of an apical gemma. The gemma
takes the form of a slender white cylindrical needle which ends in
a blunt point. The gemmae on the leaf-spots are 1 • 5-4 • 0 mm. long
and 0- 05-0-1 mm. thick, i.e. about forty times as long as broad,
while those on the fruits are shorter and thicker — about 1-2 mm.
long and 0-08-0 -2 mm. thick.

There can be no doubt that the gemmifer of Sderotium coffeicola,
like that of Om2)halia flavida, is entirely sporeless, so that, whatever
its evolutionary origin, at the present day it does not serve as a
sporophore. Since it is an active organ, obviously functioning by
producing a multicellular body which is able to propagate the

SCLEROTIUM COFFEICOLA

447

species, we are justified, as in the analogous case of Omphalia flavida,
in calling it a gem7nifer.

When examined with the microscope, a gemma of Sclerotium

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448

RESEARCHES ON FUNGI

cojfeicola is seen to be composed of a bundle of hyphae, each 5-8 [x
thick, united with one another by numerous anastomoses. Further-
more, the outer surface of each hypha in a ripe gemma is verru-
culose oudng to the presence of crystals of calcium oxalate. Owing
to these structural features, a gemma is a very stiff rod, in conse-
quence of which under slight pressure it readily breaks off just
above the knob-like pedicel on which it stands. By the time a
gemma is ready to be set free, its hyphae contain a rich store of
glycogen.

Even a slight wind is sufficient to break off the gemmae from

Fio. 227. — Sclerolium coffeicola. Infected leaves of Coffea liberici which had fallen
iipon the ground. The mycelium has grown out from the leaf -spots centri-
f ugally over the surface of the leaf in the fonn of strands. The mycelial strands
on the left-hand leaf liave produced a number of gemmifers. Photographed by
G. Stahel. Natural size.

their bases and carry them away. In plantations which are badly
affected with the disease, a number of gemmae can be seen lying on
every leaf, chiefly on the upper surface (Fig. 228), but not infrequently
also on the lower surface. In damp weather it is possible to observe
the gemmae infecting the leaves and forming new leaf-spots.

When a gemma which has been blown on to a leaf begins to
develop, it first of all forms an appressorium, or sometimes two or
more. An appressorium is a solid mass of hyphae which assumes a
hemispherical shape and flattens itself out upon the epidermis.
When full-grown, it has a diameter of 0-05-0 -5 mm. The appres-

SCLEROTIUM COFFEICOLA 449

soria formed on the under side of leaves are usually smaller than

Fig. 228. — Sclerotium coffeicola. Upper side of pieces of leaves of Goffea excelsa
with about thirty gemmae lying on the epidermis. Several of the gemmae
have germinated and have penetrated into the leaf-tissue. The appres-
sorium of some of the gemmae can just be seen. Photographed by G.
Stahel. Natural size.

those on the upper side. Each appressorium becomes firmly
attached to the cuticle by means of mucilage. In the middle of the

VOL. VI.

2q

450 RESEARCHES ON FUNGI

appressorium, on the upper side of a leaf, the hyphae converge to
a point. The hyphae at this central point then press against the
cuticle, force their way through it, and at once kill the epidermal
cells with which they come into contact. The invading hyphae, in
a compact mass, then force their way in between the cuticle and the
epidermis, kill more epidermal cells, press against and flatten the
dead epidermal cells, kill the subjacent palisade cells, and break
through the epidermis into the intercellular spaces of the palisade
layer. The palisade cells become compressed by the advancing
wedge of hyphae. The hyphae now kill the spongy parenchy-
matous cells below them. Then, still in a compact mass, they grow
downwards through the spongy parenchyma as far as the lower
epidermis. Already by this time a small brown leaf-spot has been
formed. Hyphae now grow out laterally through the intercellular
spaces of the mesophyll, and thus the leaf-spot, so long as the weather
is sufficiently moist, continues to enlarge centrifugally. The leaf-
cells a short distance in front of the advancing hyphae die before
the hyphae reach them, a fact which indicates that the mycelium
excretes a toxic substance. Since the hjrphae of the gemmae and
of the mycelial fibrillae which spring from the sclerotia are coated
with calcium oxalate, Stahel has suggested that the toxic substance
is oxalic acid. If this supposition is correct, the leaf-spots ought
to give a pronounced acid reaction. Whatever the nature of the
toxic substance, its effect upon the leaf is such that the hyphae
which excrete it grow only in dead tissue.

The lower epidermis, unlike the upper, contains numerous
stomata, and here the invading hyphae which grow out from an
appressorium enter the leaf via the stomatic clefts. Stahel proved
by experiment that the gemmae on the under side of a leaf infect
the leaf more quickly and more easily than gemmae on the upper
side. Nevertheless, under natural conditions, as might be expected
from the fact that the gemmae settle more easily on the upper
side of leaves than on the under side, most infections take place
from the upper side. Stahel investigated 213 leaf-spots and found
that 175 (82 per cent.) had the infecting gemma on the upper side
of the leaf-spot and 38 (18 per cent.) on the lower side.

In his infection experiments, Stahel observed that the leaf-spots

SCLEROTIUM COFFEICOLA

451

began to produce gemmifers 10-12 days after the leaves had been
inoculated with gemmae. A single leaf-spot may produce several
scores of gemmae.

In dry weather the gemmae dry up, but they retain their vitality
for some time even in the dried condition. Stahel placed a number
of gemmae in a desiccator for varying periods of time and then tested
them for germination. He found that they retained their vitality
after two weeks in the desiccator, but not after three or four weeks
except for a single gemma which germinated weakly.

Dry weather checks the progress of the Sclerotium disease ;

Fig. 22j. — Sclerotium cqffeicola. Dead Coffee berries covered with sclerotia, lying
on the ground. Photographed by G. Stahel. Natural size.

for, under these conditions, not only can new infections not take
place, but the leaf-spots already in existence cease to grow in size
and dry up. With the advent of dry weather, the leaf-tissues form
a callus around each spot which effectually prevents the spots from
increasing in size again when wet weather comes on. Stahel suggests
that the callus sets a limit to the growth of the mycelium by pre-
venting the toxic substance produced by the hyphae in the leaf-spot
from diffusing centrifugally.

The sclerotia of Sclerotium coffeicola were discovered by Kuyper.
They develop in considerable numbers on the outside of infected
leaves and berries as these lie upon the ground under Coffee trees

452 RESEARCHES ON FUNGI

(Figs. 229 and 230). Occasionally they arise within the tissues of
a leaf between the two layers of epidermis. They are orange-yellow
or brown in colour, 2-15 mm. broad, and mostly somewhat flattened.
In continuously rainy weather sclerotia may be formed on the
berries and more rarely on the under side of leaves, even before
these organs fall to the ground.

The sclerotia, as observed by both Kuyper and Stahel, never
give rise to any sporophores. In moist surroundings, e.g. under
trees and in cultures, they send out feathery branching mycelial

Fig. 230. — Sclerotium cojjeicola. Germinating sclerotia on green leaves of
Coffea liberica. The mycelial strands have produced numerous appres-
soria. Photographed by G. Stahel. Reduced to three-quarters of the
natural size.

strands which grow over the surface of the dead leaves and fruits
to which they are attached (Fig. 230). These mycelial strands,
which Stahel refers to as rhizomorphs, under favourable weather
conditions form gemmifers, the gemmae of which may be carried
away by the wind and deposited on leaves and fruits, where they
may form disease spots and thus reproduce the species. Some
sclerotia, out in the open, were found by Stahel to have retained
their vitality for one and one-third years. The sclerotia of Sclerotium
cojfeicola are thus well fitted for carrying the fungus over periods
of drought and other adverse weather conditions.

In my laboratory at Winnipeg, a malt- agar plate was inoculated
with the mycelium of Sclerotium cojfeicola. The mycelium spread
radially over the agar and, in the course of two or three weeks,

SCLEROTIUM COFFEICOLA

453

gave rise to three large sclerotia. The appearance of the plate one
month after inoculation is shown in Fig. 231. This experiment
and others make it evident that the sclerotia of S. coffeicola are
readily formed in artificial cultures.

Since clamp-connexions are present in the mycelial strands which
grow out from the sclerotia, it seems very probable that Sclerotium

Fig. 231. — Sclerotium coffeicola growing on 2-5 per cent, malt-agar in a Petri
dish. A montli after inoculation with mycelium. The "mycelium has
spread over the plate and has formed three sclerotia. The thickest
mycelial cords lead to the sclerotia. Natural size.

coffeicola belongs to the Basidiomycetes and, in particular, to the
Hymenomycetes. In the Hymenomycetes sclerotia are known in
Typhula and other Clavariaceae, Hypochnus, Coprinus, Collybia,
Lentinus, and Polyporus. Stahel is inclined to regard Sclerotium
coffeicola as most like a Typhula. In this genus not only are sclerotia

454 RESEARCHES ON FUNGI

known to be formed, but several species, e.g. T. variabilis on Sugar-
beet, T. varians on Beet leaves, and T. gyrans on Cabbage, are
parasitic. The gemmifers of Sclerotium cojfeicola are rod-shaped
in form and thus remind one of the fruit-bodies of Clavariaceae and
particularly of the sterile branched structures of Anthina, a pseudo-
genus placed among the Clavariaceae by de Bary.

It therefore seems not unlikely that the gemmifers of Sclerotium
cojfeicola, like those of Oywphalia flavida, have been derived from
sporophores or sporophore-rudiments which have become meta-
morphosed and adapted to reproduce the species by means of gemmae
instead of by basidiospores.

It is indeed a remarkable fact that there should be two unrelated
gemmiferous species of Basidiomycetes, both of which form leaf-
spots on the leaves and attack the berries of the Coffee plant, and
in which the perfect sporophore has been either almost wholly or
wholly suppressed. It may well be that, in the tropics, in the course
of time, yet other gemmiferous Basidiomycetes will be discovered.

GENERAL SUMMARY

THE FOLLOWING IS A SUMMARY OF THE MORE IMPORTANT
RESULTS OBTAINED DURING THE INVESTIGATIONS

PART I

Chapter I. — The history of our knowledge of the discovery, develop-
ment, general structure, sexuality, cytology, pigmentation, parasites,
drop-excretion, reactions to light, and balHstics of Pilobolus has been
reviewed.

The relation of larval Roundworms (Nematoda) to the fruit-bodies of
Pilobolus has been discussed. These animals often swarm up the sides
of the sporangiophore but do not penetrate into the subsporangial swelling.
Sometimes they travel with a sporangium when this is shot away through
the air.

Syncephalis nodosa van Tiegh., as a parasite on Pilobolus longipes
and P. Kleinii, has been described and illustrated.

Chapter II. — The germination of the spores, the growth of the
mycelium, and the formation of fruit- bodies of Pilobolus longipes have
been described.

Spores of P. longipes were sown on fresh sterilised horse-dung balls
in a closed crystallising dish, and many of the fruit-bodies which came up
on the dung had colourless, instead of black, sporangial walls. This
abnormality appears to have been caused by gaseous emanations given
off by the horse dung.

Species of Pilobolus observed at Winnipeg were : P. longipes, P.
Kleinii, P. oedipus, and P. umbonatus.

A series of successive stages in the development of a diurnal crop of
fruit-bodies of P. longipes, as affected by external conditions, particu-
larly light and darkness, has been represented diagrammatically.

The maximum vertical height to which sporangia of P. longipes and
P. Kleinii were shot was 6 feet 0-5 inch.

The maximum horizontal range of the fruit-body gun was found to
be : for P. longipes, 8 feet 7 -5 inches ; and for P. Kleinii, 8 feet 0-5 inch.

The structure of the sporangiophore and of the sporangium of P.
Kleinii and P. longipes has been described in detail as a preliminary to a

455

456 RESEARCHES ON FUNGI

discussion of the factors which permit of the successful operation of the
Pilobolus gun.

The sporangium-wall dehisces by splitting horizontally into two parts,
a lower narrow band which remains attached to the base of the columella
and an upper, much larger, cap-like portion which covers the spores.
The escape of the spores from a sporangium which has just dehisced is
prevented by a ring of jelly. This jelly, after the sporangium has been
discharged, serves to stick the sporangium to the surface of a grass-leaf,
etc.

The number of "spores in a sporangium of P. Kleinii was estimated to
be 30,000-90,000, varying with the sporangium's size.

The level of abscission in the sporangiophore when the sporangium is
shot away is at the top of the subsporangial swelling just beneath the
junction of the sporangium- wall with the wall of the columella.

The structure of a discharged sporangium has been described and
illustrated in detail. As a discharged sporangium dries, the sporangium-
wall becomes locally depressed above and circularly tucked-in beneath
the spores below, while the spores contract in size and become polygonal.

A sporangium-wall, before the sporangium has been shot away, is
always smooth and rounded. The more or less regular pattern of dim-
ples, hexagonal areas, etc., which can often be seen on a dried discharged
sporangium is formed as the sporangium dries up and contracts. The
pattern on a dried discharged sporangium of P. longipes differs from that
on a dried discharged sporangium of P. Kleinii ; and, in general, the
patterns are an aid in distinguishing these two species of Pilobolus from
one another.

The drops excreted by the sporangium and subsporangial swelhng of a
Pilobolus fruit-body contain a colloidal mucilaginous substance, for they
dry up with an irregular surface. The drops on the sporangium usually
dry up before the sporangium is discharged ; and, as they do so, they
become darkly pigmented like the sporangium- wall. The drops on the
upper part of the subsporangial wall tend to dry up sooner than those on
the lower part, and their interference with the light rays which cause
heliotropic response is thus diminished.

The wall of a Pilobolus fruit-body bears numerous very minute crystals
of calcium oxalate. In P. lo7igipes these crystals are arranged : most
densely on the sporangium-wall, less densely on the wall of the subspor-
angial swelling, and far less densely on the wall of the stipe. The un-
wettability of the sporangium-wall may be due to the numerous close-set
crystals imprisoning air and thus preventing water from coming into
contact with the wall's surface.

The subsporangial swelling of the Pilobolus gun functions in two
different ways : ( I ) as an ocellus which receives the heliotropic stimulus
which causes the stipe to direct the free end of the gun toward the source
of brightest light ; and (2) as part of a squirting apparatus which,

GENERAL SUMMARY 457

by violently expelling cell-sap, shoots away the sporangium from the
sporangiophore.

A subsporangial swelling is transparent and refracts light like the bulb
of a Florence flask filled with water ; and its diameter is always greater
than that of the black sporangium which it supports. The lens action
of a subsporangial swelling has been investigated directly and also by
means of construction diagrams.

When the sunhght strikes upon one side of a subsporangial swelling,
the light rays are refracted through it and converge so as to form a spot
of light on the other side. When the incident rays of light strike the
sporangium head on and are exactly parallel to the long axis of the swelling,
the spot of light which is formed by the rays entering that part of the
swelling which bulges out beyond and around the sporangium is symmetri-
cally placed at the base of the swelling. Under these conditions there is
physiological equilibrium and no heliotropic response takes place. When,
however, the incident rays of light strike a swelling obliquely, the spot of
light is placed on one side of the wall of the swelling in a manner which is
asymmetrical for the swelling as a whole. Under these conditions, the
protoplasm which is lighted by the spot of light sends a heliotropic
stimulus down to the protoplasm at the top of the stipe just beneath the
base of the swelling. The top of the stipe then reacts by growing in
length most rapidly on the side nearest to the spot of light and thus
bending as a whole. As a result of this reaction, the swelling is moved
about its base through an angle and the spot of light passes downwards
on the wall of the swelling until it comes to be symmetrically placed at
the base of the swelling. As soon as the spot of light arrives at this
terminal position, a physiological state of equilibrium becomes established
in the sporangiophore and the heliotropic reaction ceases. At the end
of the turning movement the gun is directed toward the source of the
brightest light.

In Pilobolus Kleinii and other Piloboli the protoplasm in the lower
part of the subsporangial swelling and at the top of the stipe contains a
red pigment (carotin) ; and, at the top of the stipe just above the stipe's
motor region, the protoplasm is heaped up so as to form a strongly bi-
concave, very red, centrally perforated septum. As shown by direct
observations and by theoretical diagrams, this protoplasmic septum is
admirably shaped and situated for receiving the light rays converging
on it when the gun is in a position of complete or almost complete physio-
logical equilibrium. Its concave upper surface, its position in respect
to the subsporangial lens, and its strong pigmentation suggest a com-
parison in function with the retina of the eyes (ocelli) of certain Mollusca.

The diameters of the sporangium, the subsporangial swelling, and the
motor region of the stipe below the swelling in a well-grown fruit-body of
P. Kleinii were observed to be 0-43 mm., 0-76 mm., and 0-16 mm.
respectively. A simple calculation based on these data shows that the

458 RESEARCHES ON FUNGI

sporangium, when head on to a beam of parallel light rays, casts a shadow
which has an area 7-2 times that of a cross-section of the stipe. If there
were no subsporangial swelling, the shadow of the sporangium would cut
off the light from the top of the stipe before the ortho-hehotropic position
had been completely attained. This would prevent the gun from being
accurately directed toward the source of light. Evidently the difficulty
of supplying the stipe with its required delicate hehotropic stimulus has
been surmounted in the course of evolution by the intercalation between
the sporangium and the stipe of the large light-collecting subsporangial
swelling. That part of the swelling which bulges out beyond the black
sporangium receives the Hght and concentrates it by refraction upon the
base of the sweUing ; and, when the spot of light so produced is asym-
metrical in position, it provides the stimulus to which the motor region
of the stipe can react,

A subsporangial sweUing is capable of producing not only a spot of
light but also a more or less well-defined image of the source of light or
of an illuminated object. Such images have been observed and photo-
graphed.

The mechanism of heUotropic response in Pilobolus has been compared
with that of (1) the leaves of certain Flowering Plants, (2) a free-swimming
Volvox sphere, and (3) Man.

In the heliotropic reaction of Pilobolus, which is caused by the asym-
metrical position of a spot of light in the subsporangial swelUng with a
consequent bending of the stipe, we have clear proof of the theory, first
suggested by Haberlandt, that heliotropic reactions may take place in
plants through oceUus action.

The sporangiophore of Pilobolus is the only ortho-heliotropic organ
known which takes up its positively heliotropic position owing to the
possession of a special light-perceiving cell structure.

Pilobolus may well be described as a fungus with an optical sense
organ or simple eye (ocellus) ; and, in using its eye for laying its gun, it is
unique in the plant world.

In bright sunlight directed perpendicularly to the long axis of the
subsporangial swelling, a stipe of P. longipes was observed to turn the
swelling and the sporangium through an angle of 90'^, and thus to complete
its heliotropic reaction, in about one hour.

A solution of the problem why it is that a Pilobolus fruit-body turns
so as to face directly one of two equal beams of light coming from suffi-
ciently different directions, and does not take up a position of resultant
reaction, has been given. It confirms Van der Wey's solution of the
same problem, published by him in 1929, and is based on the assumption
(1) that the subsporangial swelling acts as an oceUus and (2) that the
pigment zone at the base of the swelHng is the region of protoplasm where
perception of light takes place. Two spots of light are formed by the
two beams of light in the swelling : the spot of light nearer the base of

GENERAL SUMMARY 459

the swelling gives a greater stimulus to the motor region of the stipe
than the spot farther away and, as a consequence, the stipe bends toward
the source of light which has formed the lower spot of light and away
from the source of hght which has formed the higher spot of light. As
this process continues, the lower spot of light moves toward the base of
the swelUng and the upper spot away from it. This results in the lower
spot giving a greater and greater, and the upper spot a lesser and lesser,
heliotropic stimulus to the stipe. Finally, the lower spot of hght comes
to rest directly on the perforate red protoplasmic septum at the top of
the stipe. Thus heliotropic equiUbrium becomes established and the
sporangium faces one of the two beams of light (the one that produced
the lower spot of light in the first instance) and one only.

A model for illustrating the Pilobolus fruit-body in its relations with
light has been described.

The diurnal periodicity in the development of the fruit-body of
Pilobolus enables the fruit-body to use the morning sun for directing its
axis toward the source of strongest light and therefore toward an open
space. Thereby the dispersion of the sporangia, which takes place
during the noon hours, is accomplished under favourable conditions.

The second special function of the subsporangial swelling, that of
acting as part of a squirting mechanism for the discharge of the sporangium,
has been discussed. When a Pilobolus gun explodes, about one-haK of
the volume of the cell-sap in the stipe and subsporangial swelling is
shot out of the opening in the top of the swelling. The cell-wall of the
sweUing is highly elastic, and its most contractile part is a band, called
the collar, situated around what is to become the mouth of the swelling.
The abscission level, i.e. the level at which the swelling is destined to split
across, is indicated before the sporangium is discharged. As a Pilobolus
fruit-body explodes, a jet of cell-sap is shot out of the mouth of the
sweUing. The first and largest drop of this jet carries off the sporangium
and travels with it through the air. The other drops are smaller than
the first one and have shorter trajectories.

Sometimes, when a Pilobolus gun explodes, the sporangiophore
breaks across, not — as normally — just below the sporangium, but across
the top of the stipe. When this happens, the projectile consists of a
sporangium, a subsporangial swelling, and a drop of cell-sap.

By means of Barger's capillary-tube method it was found that the
osmotic pressure of the cell-sap of Pilobolus longipes is approximately
equal to 5 • 5 atmospheres.

The efficient working of the Pilobolus gun is due to a number of
different factors, five of which have been specified.

A chemical analysis of the cell-sap of Pilobolus longipes suggests that
the osmotic (turgor) pressure of the sap is largely due to phosphate and
oxalate ions, but is also due in part to potassium, sodium, chloride, and
sulphate ions, and in part due to some as yet unrecognised carbohydrate.

46o RESEARCHES ON FUNGI

The problem why it is that a discharged sporangium normally lands
on a grass-leaf, etc., so that its under gelatinous side is turned toward
the surface of the substratum and its black upper convex side away
from the surface of the substratum has been solved by taking into account
the fact that (1) the lower gelatinous side of the sporangium can be
wetted by water whereas (2) the upper convex side covered by the black
sporangial wall is unwettable. That the black sporangial wall is un-
wettable has been demonstrated by various experiments. A Pilobolus
projectile, whilst travelling through the air, consists of a sporangium
and a large drop of cell-sap. The drop does not enclose the sporangium
but is attached to the sporangium's wettable gelatinous under side.
The projectile may rotate as it passes through the air. As the projectile
lands on a grass-leaf, etc., the drop spreads out on the surface of the
substratum. As it does so, it drags the gelatinous wettable under side
of the sporangium toward the surface of the substratum and, at the
same time, pushes away from itself and the substratum the black
unwettable convex side of the sporangium.

Very occasionally one observes a sporangium which is attached to
the surface of glass, etc., not by its gelatinous under side, but by its
rounded black upper side. The taking up of this abnormal position by
a sporangium may be due to the gelatinous ring having been torn away
from the sporangium before the projectile struck the surface of the
substratum or at the moment of impact.

The gelatinous material on the under side of a sporangium has
remarkable adhesive properties, as may be shown by attempts to wash
sporangia off sheets of glass, etc., to which they have become attached.
Under natural conditions in pastures, the sporangia of Pilobolus are so
effectively attached by their gelatinous sides to the herbage on which
they have alighted that, in dry weather, they cannot be detached from
their substratum by the strongest winds and, in wet weather, they cannot
easily be detached by prolonged rain or even by violent thunderstorms.

Pilobolus is a highly specialised coprophilous fungus which is dependent
for its existence : (1) on flowering plants which provide its sporangia
with a temporary but prospectively favourable lodging-place ; and (2) on
herbivorous animals which swallow the sporangia and herbage together,
break open the sporangia and disperse the spores within their alimentary
canals, and finally extrude the spores undamaged in their solid faeces.

The sporangial wall of Pilobolus, as opposed to that of Mucor, is
(1) unwettable, (2) persi.stent (non-deliquescent), and (3) intensely black.
The unwettability of the wall is a prime factor in causing the sporangium
to alight on any object with its gelatinous side turned toward the object ;
the persistency of the wall enables the wall, when the sporangium is
attached for weeks or months to a flowering plant, to prevent the spores
escaping from the sporangium even during rainy weather ; and the
intensely black pigment in the wall enables the wall to absorb sunlight

GENERAL SUMMARY 461

and thus to act as a screen in cutting off injurious rays of light from the
spores which lie beneath it.

Pilobolus gives to flowering plants and herbivorous animals nothing
in return for their services in dispersing its spores. However, although
Pilobolus does not pay for what it receives, it imposes on the organisms
which assist it a burden which is so light as to be practically negligible.

Chapter III. — A new species of Pilobolus, Pilobolus umbonatus, has
been described. It occurs on horse dung at Winnipeg and was observed
by the late Dr. Roland Thaxter on sheep dung in the eastern part of the
United States of America.

Pilobolus umbonatus, as compared with P. lo7igipes and P. Kleinii,
is a smaller and more delicate species. It is easily distinguished from
all other species of Pilobolus by its decidedly umbonate sporangium and
its minute ellipsoidal spores. With a hand-lens one can readily make
out the acutely-pointed umbonate shape of the dried discharged sporangia
when these are seen in lateral view.

A series of critical remarks on the Pilobolidae, made with a view to
assisting future workers on this group, has been recorded.

Pilaira is regarded by the author as a good genus and not as " abnormal
material of Pilobolus."

To the criteria so far employed by taxonomists for distinguishing
species of Pilobolus should be added : (1) the exact shape of the sub-
sporangial swelling, whether eUipsoid or pjo-iform, etc. ; (2) the ratio of
the width of the sporangium to the width of the subsporangial swelling ;
(3) the nature of the depressions or wrinkles on dried discharged sporangia
when seen in strong reflected unilateral light ; and (4) the nature of the
fringe of the sporangium-wall of dried discharged sporangia, in respect
to form, colour, and disposition of crystals.

The spores of Piloboli, when seen in water, are dichroic : they are
orange-yellow or yellowish in transmitted light and green in reflected light.

The form and the variability of the basal swelling of the fruit-bodies
of Piloboli have been discussed.

The width-ratio of the sporangium, i.e. the ratio of the width of the
sporangium to the width of the subsporangial swelling, has been measured
in Pilobolus longipes, P. Kleinii, and P. umbonatus.

The pattern on the sporangium of Pilobolus crystallinus, as illustrated
by Coemans, van Tieghem, and Zopf, has been treated of. Patterns
develop on the discharged sporangia of P. Kleinii, P. longipes, and P.
umbonatus as the sporangia dry up and flatten. Studies on the variability
of patterns in P. Kleinii and P. loncjijyes have been made. The pattern
on a dried discharged sporangium, while fairly constant in its general
aspect for each species of Pilobolus, is subject within each species to a
large amount of variation in detail. The typical pattern for any par-
ticular species ought to be sought for in the larger sporangia rather than
in the smaller ones.

462 RESEARCHES ON FUNGI

Chapter IV. — This Chapter contains a systematic account and arrange-
ment of the Pilobohdae, contributed by W. B. Grove, and it may be
considered as a revision of the systematic part of his Monograph of the
Pilobolidae pubhshed in 1884.

A history of our knowledge of the taxonomy of the PiloboHdae during
nearly two hundred and fifty years is recorded. It shows how slowly
and painfully a little accurate knowledge has been accumulated. From
now on, with the modern technique of pure cultures and the art of photo-
graphy at our disposal, progress should be more rapid. It is to be hoped
that some younger mycologist may be stimulated by this presentation
of the subject to make a life- study of the Pilobolidae and give us a com-
parative description of all the species that can be gathered together from
different parts of the world.

The first observations on a Pilobolus, made by John Banister in
Virginia, were recorded by Ray in 1688. The most recently found species,
Pilobolus umbonatus, is described by Buller in this volume (1934).

An attempt has been made to arrange systematically all the known
species of the Pilobolidae and to give to the group itself and to the two
genera, Pilobolus and Pilaira, included within it, more precise definitions
than have yet appeared.

Sixteen species of Pilobolus and five species of Pilaira are Usted and
described.

Of the species of Pilobolus the following are considered to have
been adequately described and illustrated : crystallinus, heterosporus,
Kleinii, longipes, nanus, oedipus, roridus, sphaerosporus, and umbonatus ;
while the following are considered to have been insufficiently or negli-
gently described : argentinus, Borzianus, minutus, Morinii, pullus, roseus,
and Schmidtii.

A key to the species of Pilobolus is presented. It is based on char-
acters of the sporangium, the trophocyst, and the spores.

The five known species of Pilaira are the following : anomala, dimidi-
ata, Moreaui, nigrescens, and Saccardiana. A key to these species is also
provided.

Appended is a bibliography which includes all those papers and books
which refer more particularly to the species of Pilobolidae and their
differentiation. Some additional works which treat of the physiology,
ecology, and other aspects of the group are cited in the preceding Chapters
written by Buller.

PART II

Chapter I. — Most Discomycetes exhibit the phenomenon of puffing, i.e.
when they are subjected to certain changed conditions they pass from a
quiescent to an active state and suddenly liberate a cloud of spores, visible
to the naked eye. The fruit-bodies of Hymenomycetes, on the other

GENERAL SUMMARY 463

hand, never puff but liberate their spores in a steady stream which may-
continue for hours, days, or weeks.

Not only large Discomycetes but also small ones puff, so that puffing
is not correlated with fruit-body size.

Puffing was first described by Micheli in 1729 and has been noticed
by all mycologists since his time. In 1916, Falck divided the Discomy-
cetes into : (1) the radiosensitive which emit spores when warmed by
radiant heat given out by a lamp or the sun, and (2) the tactiosensitive
which puff when touched or blown upon. In 1926, Ziegenspeck came to
the conclusion that the opening of the asci at the moment of puffing is
not due to a stimulus but is a purely mechanical phenomenon caused by
a slight additional strain in the ascus walls at their apices.

Photographs, made by Dickson and Fisher, illustrating the spore-
clouds of Sclerotinia sclerotiorum given off at the moment of puffing have
been reproduced.

Conceivably, the asci of a Peziza might discharge their contents one
by one in the order of ripening. Why then does a Peziza puff ? Falck
has supposed that the dependence of Morchella, Gyromitra, Verpa, etc.,
on a sufficiently high temperature for the discharge of their spores caiises
spore-discharge to be delayed until the heat of the sun brings into ex-
istence air-currents which may assist in spore-dispersal ; and he also holds
that the dependence of many Pezizaceae on the wind for the discharge
of their spores causes spore-discharge to be delayed until the wind is
sufficiently strong to be effective in carrying away the spores. In these
ecological theories there may well be some truth. It was in the hope of
throwing more light on the phenomenon of puffing that an investigation
on Sarcoscypha protracta was undertaken.

Sarcoscypha protracta occurs in young Poplar bush {Populus tremu-
loides) in the suburbs of Winnipeg, and its fruit- bodies appear near the end
of April and at the beginning of May. The cups are scarlet in colour
and conical in form, and they look upwards toward the sky. They are
attached to buried roots by a pseudorhiza ; and the pseudorhiza, like
that of Collyhia fusipes, is perennial.

When a fruit-body of Sarcoscypha protracta puffs, the spores are shot
straight outwards from the conical hymenium in directions which are
parallel to the cup's longitudinal axis. The distance to which the spore-
cloud was shot before dispersing irregularly was found in three fruit- bodies
to be 8 cm., 12 cm., and 17 cm. (= 7 inches) respectively.

Each ascus opens obliquely and the opening faces the mouth of the
cup and consequently the sky. On this account, although the asci are
straight and are obliquely inclined toward the long axis of the cup, the
spores are shot not from one side of the cup to the other, but straight
upwards through the mouth of the cup and parallel to the cup's long
axis.

Owing to the contraction of the cell-wall, an ascus, when discharging

464 RESEARCHES ON FUNGI

its contents, reduces its volume to about one-half. The half of the
contents of the ascus which is discharged is the upper half which includes
the eight spores and a mass of cell-sap.

The ascus, as a gun, is a squirt from which a jet of watery fluid con-
taining eight spores is ejected by the pressure of a contracting elastic
cell- wall. The wall contracts more per unit of distance in the circum-
ferential direction than in the longitudinal direction.

Radial-longitudinal sections through a cup and surface views of the
hymenium, (1) before puffing has taken place and (2) immediately after
puffing has taken place, have been illustrated with a view to showing the
exact positions of the asci, the opercula of the asci, the hinges of the
opercula, the long axes of the spores, and the paraphyses, relatively to
the position of the mouth of the cup as a whole.

Correlated with the conical form of the cavity of the apothecium of
Sarcoscypha protracta and making for efficiency in the production and
liberation of spores by the hymenium are : (1) the oblique upward-
looking openings of the asci formed at the moment of spore-discharge ;

(2) the obliquely upward inclination of the spores in each ascus ; and

(3) the relatively distant separation of adjacent asci by paraphyses.
The paraphyses form at least one-half of the hymenial substance.

They assist the discharge of the spores : (1) by holding the asci fixed in
their positions whilst the asci are shooting away their spores obliquely
through their apices ; and (2) by keeping adjacent asci sufficiently far
apart, thereby preventing the spores of one ascus from hitting the pro-
truding end of another ascus during spore-discharge.

It is probable that, in Sarcoscypha protracta, the mouth of an ascus
comes to look upwards toward the mouth of the apothecium as a result
of the end of the ascus making a heliotropic curvature.

By means of an experiment with a test-tube provided with a lateral
opening, it has been proved that, when an apothecium pufifs, it produces
a blast of air. The blast of air is caused by tens of thousands of spores
and sap-drops, which have been shot in the same general direction,
striking the air and setting it in motion.

The significance of the blast of air in respect to the dispersal of the
spores has been discussed. If the asci of a fruit-body of Sarcoscypha
protracta were to explode one after another as they ripen, it is probable that
the eight spores of each ascus would not be shot up into the air more than
3-4 cm., and no appreciable blast of air could come into existence to
raise them still further. On the other hand, when a hundred thousand
asci explode together, i.e. when puffing takes place, the bombardment
of the air by the spores and sap-drops collectively is sufficient to create
a blast of air which can carry the spores away with it for several inches
after they have lost the velocity given to them by the ascus-guns. Under
natural conditions in a Poplar wood, the stipe of the fruit-body is nega-
tively geotropic and the apothecium looks upward to the sky. If the

GENERAL SUMMARY 465

asci were all to be discharged in succession as they ripen, none of the
spores (we may suppose) would travel upwards more than an inch or
two ; but, if the asci ripen one by one and then wait before exploding
until some suitable stimulus sets them all off together, then the spores
may be carried upwards by the blast of air, which they bring into exis-
tence, to a height of 5-7 inches. After being carried upwards into the
air, the spores are borne away more or less horizontally by the wind and
then dispersed. The nearer the ground, the less wind there is ; and,
every extra inch the spores can be raised into the air by discharge from
the apothecium, the stronger will be the wind which they will encounter
and the greater the chance that they will be dispersed widely and find
suitable conditions for propagating the species.

Our knowledge of the phenomenon of spore-discharge in the Discomy-
cetes is still very incomplete. With a view to its extension individual
apothecia of a series of typical species should be observed in the field.
Such apothecia should be left in situ and not be touched by man ; and,
for each apothecium, during the whole period of spore-discharge, a
continuous record, not only of the times of spore-discharge, but also of
the conditions of spore-discharge (temperature, moisture, wind-move-
ments, etc.) sho^^ld be made.

Chapter II. — In 1890, Zopf observed that the protuberant asci of
Ascobolus denudatus and of a species of Saccobolus are heliotropic and
bend toward the source of strongest light.

As a result of a series of his own observations the author has no
doubt that the asci of Ciliaria scutellata, Aleuria vesiculosa, Galactinia
hadia, Morchella crassipes, and other similar Discomycetes, like those of
the Ascoboleae, are heliotropic, and that the response of the asci to the
directive stimulus of light serves to explain how it is that the ascospores
discharged from the interior of hollow cups, such as those of Aleuria
vesiculosa, Galactinia hadia, etc., and from the interior of cavernous
depressions at the surface of the caps of Morchellae are shot outwards
into the external air without striking opposing chamber walls.

Richard Falck expressed the view that, when a Morchella or a Gyro-
mitra fruit-body is caused to puff by irradiating it with heat from a lamp,
air and water-vapour currents are produced in the hymenial chambers
and passages and that these currents bear the spores along and thus
enable the spores to escape from the fruit-body. The author is unable
to accept this theory.

To explain the phenomenon of puffing in a Morchella or Gyromitra
which has been irradiated by heat from a lamp we have only to suppose :
(1) that the asci are sensitive to heat and, when ripe, always explode when
their temperature is raised above a certain degree, so that puffing may
be initiated by warming a fruit-body ; (2) that the asci are curved
heliotropically toward the mouths of the hymenial cavities instead of
being straight ; and (3) that the air-currents which arise at the moment

VOL. VI. 2 H

466 RESEARCHES ON FUNGI

of puffing are due to the spores and sap-drops bombarding the air and
setting it in motion mechanically and are not due to the fruit-body being
hotter than the surrounding air and sending out blasts of warm air.

In Ascobolus magnificus about one-third of each ripe ascus protrudes
freely into air above the hymenium. This terminal part of the ascus
contains the eight spores and, when young, it executes a heliotropic
curvature toward the source of light. The paraphyses of A. magnificus
are an heliotropic.

On the basis of Corner's work and investigations by the author, the
development and the structure of the apothecium of Ascobolus sterco-
rarius have been described and illustrated. The asci of this species do
not protrude so freely into the air as those of A. magnificus ; but, as
usual in the Ascoboleae, they are heliotropic.

Our present knowledge of the apothecium of Ciliaria sculellata
(= Lachnea scutellata) has been summarised.

The apothecium of Ciliaria scutellata is discoid and its hymenium is
flat or almost so. When an apothecium of C. scutellata develops in
unilateral hght, the asci all across the disc bend their free apical ends
in the direction of the source of light ; and, when puffing takes place, the
spores are all discharged toward the source of light.

In respect to the heliotropism of their asci, the discoid fruit-bodies
of Melastiza miniata and of Cheilymenia vinacea resemble those of Ciliaria
scutellata. In all these three species, when an ascus which is curved at
its end discharges its spores, it straightens considerably and the oper-
culum, which was terminal, comes to occupy a more or less oblique position
on that side of the ascus which is nearest to the source of light.

The fruit-bodies of Aleuria vesiculosa have been described and their
varieties discussed. Previous observations on the discharge of the spores
have been summarised.

In a hemispherical apothecium of Aleuria vesiculosa the asci are
heliotropic, in consequence of which their free ends are all directed toward
the apothecium's mouth. Hence, when puffing takes place, the spores
are all shot out of the mouth of the apothecium and so escape freely into
the air. The outer halves of the asci on the sides of an apothecium may
be bent through an angle of 45°. The asci in the middle of the base of
the apothecium may be quite straight. The amount of bending of an
ascus varies with the position of the ascus in the hymenium and therefore
with the angle at which the light strikes the end of the ascus as it is
developing.

The paraphyses of Aleuria vesiculosa attain maturity before the asci
and, Hke the asci, they are positively heliotropic. They bend toward
the source of hght and so point toward the mouth of the apothecium.
This arrangement assists the asci in pushing their way up between the
paraphyses as they develop.

Observations made by H. T. Giissow in a wood in Ontario, Canada,

GENERAL SUMMARY 467

and communicated to and recorded by the author, prove that apothecia
of Aleuria vesiculosa, growing under purely natural conditions and un-
touched by man, may puff intermittently.

In respect to the heliotropism of their asci the cup-shaped apothecium
of Galactinia hadia resembles that of Aleuria vesiculosa. The asci on the
sides of an apothecium of G. hadia discharge their spores, not in directions
which are perpendicular to the hymenium, but obliquely upwards at an
angle of about 45°.

Each hymenium-lined alveolus of a fruit-body of a Morchella or
Mitrophora is comparable with the single hymenium-lined cavity of one
of the cupulate Pezizeae.

Investigations on fruit-bodies of Morchella conica and M. crassipes
have shown that the asci in each alveolus are curved toward the mouth
of the alveolus, and it is therefore concluded that the asci, hke those of
the Pezizeae, are heliotropic.

Since, in a fruit-body of a Morchella, the asci in each alveolus point
toward the mouth of the alveolus and since the operculum of each ascus
is situated symmetrically at the end of each ascus, it is clear that, when
spore-discharge takes place, the spores must be shot through the mouths
of the alveoli into the open air.

The folds or walls on a pileus in the Morchellaceae have been compared
with the gills on a pileus in the Agaricaceae. The ascus, as a gun, has
profoundly influenced the structure of discomycetous fruit-bodies ; and
the basidium as a gun has profoundly influenced the structure of hymeno-
mycetous fruit-bodies.

In the Helvellaceae, more particularly in Ptychoverpa bohemica,
evidence indicating that the asci are heliotropic has been obtained.

The asci of the Discomycetes and the basidia of the Hymenomycetes
are structurally and physiologically two very different types of fungus
guns. Whereas the asci are positively heliotropic, the basidia are an-
heHotropic. In the Discomycetes the positive heliotropism of the asci
is advantageous for spore-dispersal, whereas in the Hymenomycetes a
positive heliotropism of the basidia, if it occurred, would be disadvan-
tageous for spore-dispersal.

Chapter III.— Various projectiles of fungi in order of size have been
listed.

A Sphaerobolus gun gives out a distinct sound as it shoots away its
gleba ; and, when a gleba strikes a hard object near its place of discharge,
the impact is audible. Of all fungus guns the Sphaerobolus gun is not
only the largest and most powerful, but also the loudest.

When a Pilobolus gun is discharged, just as in Sphaerobolus, two
sounds can be heard : (1) the sound of the exploding gun, and (2) the
sound of the projectile striking some object.

A hissing sound emitted by the fruit-bodies of certain Discomycetes
when puffing takes place has been noticed, among others, by Desmazieres

468 RESEARCHES ON FUNGI

{Helvella ephippium), de Bary {Peziza acetabulum and Helvetia crispa).
Stone {Helvella elastica), and Johnstone {Otidea leporina).

A simple method for rendering audible the puffing of Discomycetes
has been described. One takes a fruit-body, which is ready to puff, out
of the closed chamber where it has been confined for some hours, and one
immediately places its mouth or upper hymenial side close against an ear.
As soon as the fruit-body puffs (usually in 1-3 seconds), the sound of the
puffing can be easily heard and one can feel one's ear being sprayed by
spores and sap-drops.

By putting fruit-bodies to an ear in the manner just described, the
author has heard the sound of puffing in the following species :

Aleuria repanda, Pustularia catinus,

Aleuria vesiculosa, Pjnronema confiuens,

Ascobolus stercorarius, Rhizina inflata,

Caloscypha fulgens, Sarcoscypha protracta,

Ciliaria scutellata, Sarcosphaera coronaria,

Galactinia badia, Urnula Craterium,

Peziza aurantia, Urnula geaster.
Pseudoplectania nigrella,

The sound produced by most large Discomycetes when puffing
reminds one of hissing, but that produced by Rhizina inflata suggests
effervescence.

The hissing sound produced by the puffing of Pustularia catinus,
Aleuria vesiculosa, Sarcoscypha protracta, etc., is comparatively loud, but
has a duration of only about two or three seconds. On the other hand,
the effervescent sound produced by the puffing of Rhizina inflata is
comparatively feeble, but has a duration of from one to several minutes.
A puffing fruit-body of R. inflata can be passed from one person to another
and thus be heard by several people in succession.

The discharge of conidia by Empusa and Entomophthora and of basi-
diospores by the Uredineae and Hymenomycetes, although inaudible to
the unaided ear, might possibly be heard with the help of a microphone.

The sound emitted by fungus guns has no biological significance.

PART III

Chapter I. — In Collyhia radicata, Tricholoma macrorhizum, Pholiota
radicosa, Coprinus macrorhizus, and certain other Agaricaceae, the stipe
of the fruit-body is prolonged downwards through the substratum for
some distance by means of a so-called rooting base. For " rooting base "
Fayod has substituted the excellent term pseudorhiza which has been
adopted by the author.

GENERAL SUMMARY 469

A pseudorhiza forms a link between a mycelium vegetating in a
buried root or other buried nutrient substance and the aerial part of the
fruit-body which produces and liberates spores.

In most fungi with a pseudorhiza, e.g. Collyhia radicata, the pseudo-
rhiza is annual and unbranched ; whereas in C. fusipes, which is
exceptional, the pseudorhiza is perennial and branched.

Every fruit-body which develops as a pseudorhiza arises in the first
instance as a tiny primordium at the surface of a buried root, etc. This
primordium becomes differentiated into the primordium of the pileus
and the primordium of the stipe. The primordium of the stipe then
becomes differentiated into the primordium of the stipe-shaft and the
primordium of the stipe-base or pseudorhiza. The pseudorhiza of the
very young fruit-body by intercalary growth elongates just beneath the
rudimentary stipe-shaft and pileus and, as it is negatively geotropic, it
pushes the rudimentary stipe-shaft and pileus upwards through the soil,
etc., until these organs reach the surface of the ground. Then the
pseudorhiza ceases to grow in length, the stipe-shaft elongates aerially,
the pileus expands, and the spores are liberated.

The length of a pseudorhiza varies with the depth of the soil overlying
the buried root, etc., in which the mycelium of the fungus has vegetated.

As a rule, a pseudorhiza thickens as it grows upwards so that it is
thickest just beneath the surface of the soil, i.e. in that position where it
is subject to the greatest mechanical strain.

An account of the pseudorhiza of Collyhia radicata, Mycena gnleri-
culata, and Coprinus macrorhizus has been given.

Collyhia radicata, lives upon the buried roots of Beeches, Oaks, Iron-
woods, Horse Chestnuts and, doubtless, other trees. Its pseudorhiza
may attain a length of 16 cm.

The mode of development of the pseudorhiza of Coprinus macrorhizus
in all essentials resembles that of the pseudorhiza of Collyhia radicata.
The fruit-bodies of C. macrorhizus which are to develop a pseudorhiza
arise as primordia upon dense straw-dung situated a little distance below
the general surface of a manure pile, etc. The pseudorhiza by intercalary
growth and response to the stimulus of gravity then pushes the rudiment-
ary stipe-shaft and pileus through the overlying straw, etc., to the surface
of the manure pile, and there the stipe-shaft and pileus complete their
development aerially in the usual way.

In Coprinus macrorhizus, when a young pileus and enclosed aerial
stipe-shaft are injured, the pseudorhiza may branch and give rise to
several new but smaller fruit-bodies.

Chapter II. — The myceUum of Collyhia fusipes vegetates in the wood
of subterranean roots of Beeches and Oaks, and gives rise to fruit-bodies
which are attached to these roots by means of a pseudorhiza.

The pseudorhiza of Collyhia fusipes is perennial and, in the course of
successive years, owing to branching and lateral fusion, may become

470 RESEARCHES ON FUNGI

converted into a large obconic or irregular dark spongy structure. There
is no good reason for regarding such a structure as a sclerotium.

Usually, in the first summer of fruiting of a Collybia fusipes mycelium,
there comes up on a rotten root a soUtary fruit-body which has a simple
pseudorhiza like that of C. radicata. The pileus and aerial stipe-shaft
of this fruit-body then die and decay, but the pseudorhiza buried in the
ground persists and lives on through the winter. In the second summer
the pseudorhiza, at its apex, gives rise to a cluster of new fruit-bodies,
each of which has a pseudorhiza of its own. These new fruit-bodies
eventually die down except for their pseudorhizae which persist. Thus
in the second winter the persistent pseudorhiza is a branched structure.
In the third summer, the pseudorhiza may, as before, give rise to new
fruit-bodies, and so forth, so that, as several years go by, the pseudorhiza
increases in size and becomes more and more branched.

The longest pseudorhiza of Collybia fusipes observed was about
lii inches in length. It was attached to a deeply buried Beech root and
bore a cluster of new fruit-bodies on a tertiary branch. Presumably the
pseudorhiza was three years old and the fruiting season was the fourth
in succession.

In having a pseudorhiza which is persistent and perennial, Collybia
fusipes economises fruit-body material and so, in the end, increases its
output of spores. Thus the persistence of the pseudorhiza of C. fusipes
is a factor of considerable importance to the fungus in its struggle for
existence.

It is a remarkable fact that the fruit-body of Sarcoscypha protracta,
a Discomycete whose mycelium vegetates in buried roots of Poplars,
develops a pseudorhiza which, in its persistence from year to year and
in its branching, exactly resembles the pseudorhiza of Collybia fusipes.
We are here afforded another example of two very diverse plants having
become adapted in the same way to meet the requirements of a similar
set of external conditions.

Chapter III. — Omphalia fiavida, the cause of the American Coffee-
leaf disease, is a luminous and gemmiferous leaf-spot fungus.

In pure cultures on bread and other artificial media, as Ashby first
observed, the mycelium produces in succession : (1) gemmifers, hitherto
misnamed '' stilbum-hodies,'' and (2) perfect agaricaceous sporophores.

Each gemmifer consists of a slender, sohd, tapering pedicel about 2 mm.
long and of a terminal, detachable, multicellular gemma, shaped hke the
knob of a door-handle and about 0-36 mm. in diameter.

The structure of a gemmifer has been redescribed in detail. The
pedicel is sohd, and not hollow as supposed by Puttemans.

Each gemma is an oblate spheroid (a flattened globe) with an apo-
physis of smaller diameter below. Its upper surface is slightly depressed
in the centre. The apophysis encloses and clasps the top of the pedicel
about 0- 1 mm. from the pedicel's extreme end. Peripherally the oblate-

GENERAL SUMMARY 471

sphaeroidal part of the gemma is covered with aerial radiating filaments
which the author has called infection hyphae. It is these hyphae which
enter and infect a new host-leaf when a gemma has fallen upon it.

A sporophore of Omphalia flavida is a much larger structure than a
gemmifer, for it is 0-6-1 -5 cm. in height and its pileus is 1 •5-2-5 mm. in
diameter. It liberates an abundance of spores which readily germinate
in .malt-agar. Freshly-fallen spores were introduced into a wound in a
Bryophyllum leaf, but no infection resulted. From the observations of
others, it appears that the infection of Coffee leaves in Coffee plantations
is due to gemmae and not to basidiospores.

A comparison of the external form and the internal structure of a
gemmifer and of a sporophore of Omphalia flavida justifies the conclusion
that a gemmifer is a highly specialised sporophore in which the pedicel
is homologous with a stipe and the gemma homologous with a pileus.
In a gemmifer the pileus has ceased to develop lamellae and basidia
and has become detachable at maturity and thus converted into an
organ of dissemination.

A pedicel of a gemmifer of Omphalia flavida is at first quite straight
but, as it grows in length, it becomes bent at a little distance above its
base through an angle of 30°-45°. This basal curvature is not due to
gravity. When a number of gemmifers are growing together in a culture,
the pedicels by means of basal curvatures come to diverge from one
another. It thus appears that the pedicels of gemmifers mutually repel
one another.

The abscission of a gemma of Omphalia flavida from the end of its
pedicel in preparation for the detachment of the gemma from the pedicel
by the wind takes place whilst the apophysis of the gemma firmly clasps
the pedicel subterminally, and it is effected by the end of the stipe be-
coming sigmoidally curved and so withdrawing itself from the gemma.
The sigmoid curvature of the end of the pedicel is alv/ays made in a vertical
plane and, as experiments with a Pfeflfer klinostat have shown, is due
to a positive and a negative reaction to the stimulus of gravity.

A ripe gemma of Omphalia flavida which has undergone abscission
from the extreme end of its pedicel and is holding on to the pedicel merely
by means of its clasping apophysis is readily detached from its pedicel
by the wind. When a gemma falls on to a leaf of a host-plant, it usually
settles so that it rests on its sHghtly concave upper surface. Under
moist conditions its jDeripheral infection hyphae then resume their growth
and may penetrate into the leaf's interior tissues.

Detached gemmae of Omphalia flavida retain their vitality for over
24 hours under moist conditions but, when exposed to dry air, they soon
die.

Wounded and unwounded leaves of Bryophyllum calycinum and un-
wounded isolated leaves of Nerium Oleander and of a species of Ficus,
after having been inoculated with gemmae of Omphalia flavida, developed

472 RESEARCHES ON FUNGI

leaf-spots which gave rise in succession to 0. flavida gemmifers and
sporophores. Similarly-treated isolated leaves of Plumbago capensis
developed leaf-spots which produced 0. flavida gemmifers only.

Omphalia flavida is able to form leaf-spots on the leaves of species
belonging to the most diverse families of Flowering Plants and also on
the leaves of various Ferns. A list of the plants which 0. flavida is known
to attack has been given.

The mycelium of Omphalia flavida, when newly obtained from gemmae
developed in the open on Coffee leaves, fruits vigorously. When the
mycelium is grown for several years on artificial media, it gradually
loses its fruiting power, but this can be restored in large measure by
passing the mycelium through living leaves.

The formation of gemmifers on a mycelium of Omphalia flavida is
initiated by the stimulus of light and does not take place in complete
darkness. When an agar-plate in which 0. flavida is developing is ex-
posed to daylight on a laboratory table, the mycelium forms alternate
gemmiferous and non-gemmiferous zones corresponding with the diurnal
hours of daylight and darkness.

The mycehum of Omphalia flavida, both in artificial cultures and in
leaf-spots, is luminous. This discovery has provided a means for diag-
nosing the American Coffee-leaf disease in the dark. At night, in a
Porto Rican Coffee plantation. Professor Albert Miiller was able to see
Coffee leaf-spots very clearly at a distance of 2-3 feet from the leaves
and less clearly, although distinctly, at a distance of 6-10 feet.

Sderotium coffeicola, which causes the Sclerotium disease of the Coffee
plant in Dutch and British Guiana and in Trinidad, resembles Omphalia
flavida in attacking many different kinds of plants, including Coffee and
Ferns, and in producing gemmifers. An account of S. coffeicola, chiefly
based on Stahel's observations, has been given.

A gemmifer of Sclerotium coffeicola consists of a little white knob-Hke
pedicel and of a detachable slender white needle-like gemma 1 •5-4-0 mm.
long and 0-05-0 • 1 mm. thick. The gemmae of S. coffeicola, Uke those of
Oynphalia flavida, are blown about by the wind, settle on host-leaves,
germinate there, and soon produce leaf-spots bearing new gemmifers.

On fallen leaves and on Coffee berries the mycelium of Sclerotium
coffeicola produces sclerotia. On germinating, a sclerotium gives rise to
a feathery mycehum which bears gemmifers. Perfect fruit-bodies of the
fungus, so far as is known, are not produced.

The mycelium of Sclerotium coffeicola is provided with clamp-con-
nexions, and this indicates that the fungus is a Basidiomycete. It is
possible, as Stahel has suggested, that the gemmifers of S. coffeicola,
which are rod-like in form and remind one of the fruit-bodies of certain
Clavariaceae, may be modified fruit-bodies of a Typhula.

GENERAL INDEX

Abnormal discharge, in Pilobolus, 140
Abnormal landing, of Pilobolus pro-
jectile, 150, 158-159
Abnormal pigmentation, in Pilobolus,

54-55, 213
Aborted form, of Omphalia flavida, 404,

412, 416
Abscission, of a gemma, 420-421, 422
,, of Pilobolus sporangium, 73,

76, 135-137
Abscission level, in Pilobolus, 76, 135-

137
Acer Negundo, fruit dispersal, 423
Acetabula vulgaris, hissing of, 329

,, ,, illustration, 327

Acetic acid, and ascus discharge, 33, 291
Adhesion, of Pilobolus projectile, 159-

161
Adjustments, heliotropic, of an apothe-

ciura, 266-267
Aerial stipe, and pseudorhiza, 239
Aerial stipe-shaft, 351, 353, 366
Aesculus Hippocastanum, and CoUyhia

radicala, 348
Agaricaceae, and Discomycetes, 267

„ and Morchellaceae, 315, 319

„ basidia not heliotropic, 324

„ escape of spores, 320

„ geotropic adjustments, 267

„ possible hearing of, 344

„ pseudorhiza in species of,

347
„ rooting bases of stipes in,

347-349
„ unique pseudorhiza in, 393

Agaricus fusipes, a synonym, 375
Agave americana, osmotic pressure, 145
Aiming, of Pilobolus projectile, 41
Air, bombarded by ascospores, 261
„ set in motion by discharged spores,
260-261, 269, 318

Air-currents produced by Morchella,

explanation of, 268-270, 318
Air-space, in Morchella conica, 315, 317
Albertini and Schweinitz, on puffing,

229-230
Albino animals, eyes of, and Pilobolus,

104
Alcohol, and ascus discharge, 33, 231,

232, 291
Alcohol vapour, effect on Pilobolus, 27
Aleuria, and Morchella, 318

,, and sound production, 328-329
„ tactiosensitive, 232
Aleuria Asterigma, and A. vesiculosa, 290
Aleuria repanda, audible puffing, 332-
333
,, „ heard by Durand, 331

,, ,, heliotropism, 266-267

,, „ illustration, 267

Aleuria vesiculosa, and Morchella conica,
315
,, „ and Peziza repanda,

250
„ ,, and Sarcoscypha pro-

tracta, 242, 264
„ and the horse, 302

„ ,, asci in a wrinkled

fruit-body, 295-
296
„ „ ascus curvature, 291,

292, 293, 296
„ „ audible puffing, 332-

334, 340
„ „ bending of asci and

paraphyses, 296-
298
bending of ascus, 255
„ „ causes of puffing, 303

„ „ contraction of ascus,

302
cultures, 287-289

473

474

GENERAL INDEX

Aleuria vesiculosa, description of fruit-
body, 287
„ „ direction of ascus dis-

charge, 295
„ „ discharge of spores,

292-303
„ „ dispersion, 302

„ „ heardby Durand, 331

„ ,, height of spore-dis-

charge, 304
„ ,, heliotropism of asci,

265, 292-297, 300
„ ,, identification of, 286-

290
„ „ illustrations, eight,

288-297, 301
„ ,, paraphyses heliotro-

pic, 273, 297-298
„ „ pigment in cup, 301

„ „ protuberancy of asci,

271
puffing, 228, 230-231,
232, 299
„ „ puffing in laboratory,

302-303
„ „ puffing under natural

conditions, 303-304
„ ,, r a d i a 1 - longitudinal

sections, 292, 293,
294, 296
„ „ results of previous

investigation, 290-
291
„ „ sound of puffing, 303

„ ,, spore colour, 165

„ ,, surface view of hy-

menium, 294
Aleuria vesiculosa var. cerea, 290
Alkalies, and ascus discharge, 291
Allen, F., heard puffing, 341
Allen, R. F., and Jolivette, H. D. M., on
Pilobolus, 34-35, 36, 40-41, 43,
120-121, 127
Aloe americana, osmotic pressure, 144,

145
Alveolar spaces, diameter, 319
Alveoli of Morchellaceae, 310-319

„ ,, „ asci directed to

moixths, 317—
318
primary and
secondary,
313
,, shape, 313-314

American Coffee-leaf disease, 397-401

American Coffee-leaf disease, control,

401

„ diagnosis

in dark,

439-441

Anacardiaceae, and Omphalia flavida,

432
Anaesthetics, effect on Pilobolus, 27
Analysis of Pilobolus cell-sap, 146-148
Anastomoses, between paraphysal

branches, 300
Anderson, R. S., on Pilaira, 179, 221
Andira inermis, and Omphalia flavida,

432
Anellaria, spore colour, 165
Angiocarpous apothecium, development,

273-277
Angle between two beams of light directed

on Pilobolus, 123, 127
Angle of curvature of asci, 315, 316
Anguillulidae, and Pilobolus, 192
Anheliotropic paraphyses, 273, 278
Anheliotropism, of asci, 324
Animals, and puffing, 308
Animals and plants, sound in relation

with, 344
Annual and perennial fruit-bodies, 394
Annual pseudorhiza, 347-373
Annular furrow, of Coprinus macrorhizus,

365
Antheridium, absence in Ascobolus ster-
corarius, 273
„ absence in Ciliaria scutel-

hitn, 281
Anthina, and Schrotium coffeicola, 454
AntJiopeziza W inter i, a synonym, 236
Anthurium andreanum, osmotic pressure,

145
A nthurium crystalUnum,osmotic pressure,

145
Apandrous Discomycete, 273
Apium graveolens, osmotic pressure, 145
Apocynaceae, and Omphalia flavida, 432
Apophyses, mycelial, in Piloboli, 132,

181-182
Apophysis, of a gemma of Omphalia
flavida, 407, 410, 420-423
,, of a sporangium of Pilobolus

nanus, 200, 211
Apothecium, development, 273-277, 281,

297
Appressoria, of Sclerotium coffeicola,

448-i50
Araceae, and Omphalia flavida, 433
Arachnopeziza aurata, puffing, 228

GENERAL INDEX

475

Archicarp, of Ascobolus stercorarius, 273,
275, 277
„ of Ciliaria scutellata, 280, 281

Argus, and Volvox, 113
Armes, H. P., on Pilobolus cell-sap, 148
Armillaria melka, black pigment in, 166
Asci, and open spaces, 324
„ and width of alveoli in Morchella,

319
„ angle in bending, 306
„ curved, of Helvellaceae, 321-322
„ direction of discharge, 317-318
„ effect of salts on, 291
„ heliotropic, and paraphyses, 296-

300
., heUotropism, 264-324
„ protection of, 300
„ ripe, accumulation of, 321
„ shoot spores toward mouth of

fruit-body, 295
„ sound of individual, 342
„ spatial arrangement, in Sarco-

scypha protracta, 254
„ successive bursting of, 321
,, theory of heUotropism for, 301
,, usually colourless, 301
Asci and basidia, as fungus guns, con-
trasted, 319
Ascoboleae, heUotropism of asci, 264-

265, 270, 271
Ascoboli, and herbivorous animals, 302
Ascobolus, dehiscence of ascus, 73
,, sound of gun, 327-328

„ strains in ascus wall, 231

Ascobolus Crouani, puffing, 228
Ascobolus denudatus, heliotropic asci, 265
Ascobolus fur Juraceus, a sjTionym, 273
Ascobolus immersus, heliotropic asci, 266
,, ,, large spores of, 237

,, „ projectile, 325

„ ,, protuberant asci,

271
„ „ sound probably pro-

duced by, 328
Ascobolus magnificus, apothecial develop-
ment, 297
„ „ heUotropism of

asci, 270-273
„ „ illustrations, 271,

272
„ „ mucilage, 300

„ „ protuberancy of

asci, 271
Ascobolus stercorarius, audible puffing,

332, 336

Ascobolus stercorarius, development of

apothecium,
273-277
„ „ ■ heUotropism of

asci, 276, 277
„ ,, illustrations,274,

276
,, jelly on spores,

302
„ „ mucilage, 300

„ ,, paraphyses, 300

,, violet spores, 301

Ascogenous ceU, 280, 281
Ascogenous hyphae, of Ascobolus ster-
corarius, 274-276
Ascogonium, and archicarp of A. ster-
corarius, 273-277
„ of Ciliaria scutellata, 280,

281
Ascomycetes, ascus discharge, 231
Ascophora Cesatii, and Pilobolus, 196

,, „ patterns on, 185

Ascospores, adhesion of, to one another,
244
and basidiospores, 267
arrangement in a curved

ascus, 302
coloured, 301
discharge of, and recoil of

apothecium, 262
dispersal of, 324
escape from cups, 265
gelatinous meniscus, 302
position in ascus, 244-246
separation on discharge, 290
usually colourless, 301
Ascostoma, of Galactinia badia, 306
Ascostomata, of Discomycetes, 256-257
Ascostome, origin of term, 256
Ascostomes, of Discomycetes, 255-257
Ascus, as a squirt, 247

„ as an explosive mechanism, 243-

250
,, axis of, 255
,, bursting of, 231
,, cause of oblique opening, 255-257
„ contraction of, 246-247, 251,

253, 284-285
,, growth of, in Ciliaria scutellata,

283, 284
„ osmotic pressure, 246
„ position of origin of ascostoma,

256-257
„ shortening of, 246
„ with oblique opening, 246

476

GENERAL INDEX

Ascus-discharge, and a stimulus, 291
Ascus-jet, and hydrostatic pressure, 247
„ observed with a beam of light,

290
„ physics of, 291
Ascus-lid, and puflfing, 231
Ascus-sap, shot away with spores, 260
Ascus-wall, tensions in, 231
Ashby, S. F., on Omphalia jlavida, 397,
404-t06, 411, 433, 436,
437, 438
„ „ on Sclerotium cojfeicola,

443, 444
„ ,, photograph made by, 404

Asymmetry of a spot of light, in man and

PUobolus, 115
Atkins, W. R. G., on osmotic pressure in

leaves, 144, 145
Atkinson, G., photograph made by, 437
Atkinson, G. F., and Collybiafusipes,315
„ „ on Psalliota campestris,

363
Atriplex nuttallii, osmotic pressure, 144
Attachment, of a gemma to a leaf, 425,
429
„ of Pilobolus projectile to

herbage, 10, 148-161
Auriculate apothecia, 310
Autodigestion, in Coprinus macrorhizus,

368
Avena saliva, nature of heliotropism, 107
Axis of an ascus, apparent and real, 255
Azygospores, of Pilobolus nanus, 13, 212
„ of P. oedipv^, 209

Baarn, fungi obtained from, 179
Bachman, E., on carotin absorption

bands, 282
Bainier, G., on Pilobolidae, 9, 198, 221
Baker, H., on Pilobolus, 3, 192, 221
Ballistics, of Pilobolus projectile, 34-36,
63-68
„ of puffing, 261
Banana, and Omphalia Jlavida , 433
Banister, J., discovered Pilobolus, 3,

191-192
Barger, G., capillary-tube method of

measuring osmotic pressure, 31, 140-

142
Bartell and Madison, on electro-osmosis,

31
Basal curvature (of a pedicel), cause,
418-420

„ „ significance, 420, 423

Basal reservoir, origin of, 53-54

Basal swelling (of Pilobolus), 56, 68, 69

,, ,, origin, 10, 53-54

Basal swellings (of Piloboli), 180-183
„ „ intercalary and terminal,

181-183
„ „ solitary and in chains,

181
Basidia, heliotropic, unknown, 324

,, two-spored and four-spored, 355
Basidia and asci, as fungus guns con-
trasted, 319
Basidiomycetes, and Discomycetes, 227-
228
„ and Sclerotium cojfeicola,

453
„ gemmiferous species,

454
Basidiospores, shot away at maturity,

227
Bauch, R., on Mycena galericulata, 355
Beam-of-light, ascus discharge seen by,

290
Beech, and Collyhiafv^ipes, 374, 375, 376,
378-379, 380, 388, 390, 392-393
„ andC.radicato, 348, 350, 351,352
,, decaving leaves, luminosity of,
442, 443
Begonia, and Omphalia jlavida, 432
Begonia discolor, heliotropism, 110
Begoniaceae, and Omphalia jlavida, 432
Berkeley, M. J., on Pilobolus, 194, 221
Bersa, E., on culture of Pilobolus, 13
Bibliography, of Pilobolus, 221-224
Biological significance, of sound from

fungus guns, 344
Bisby, G. R., and CoUybia fusipes, 375
„ ,, and Morchella crassipes,

315
„ ,, and Ptychoverpa bohemica,

324
,, „ on Ciliaria scutellata, 278

,, ,, on CoUybia radicata, 348

,, ,, on Fusarium, discolor sul-

phureum, 437
Blaauw, A. H., on heliotropism, 37, 107,

301
Black pigment, abnormal absence of, in
Pilobolus, 54-55
„ „ ecological significance,

165-166, 167
,. ,, of mycelia of various

fimgi, 166
of Pilobolus, 72, 80,
165-166, 167

GENERAL INDEX

477

Black pigment, of spores of various fungi,

165-166
Black sporangium -wall, characteristic of

PUobolidae, 200
Blackman, V. H., on electro-osmosis, 31
„ ,, on water-excretion,

29-30, 31
Bladder Elf -cup, 287
Bladdery Peziza, 286
Blakeslee, A. F., on sex in PUobolidae, 13
Blast of air, and dispersal of ascospores,
262-263
„ „ „ cause of, 260-262
„ ,, „ detaches a gemma, 423
„ „ ,, effect on gemma on a leaf,

425
„ ,, „ produced by puffing, 257-
260
Blechnum serrulatum, and Sclerotium

disease, 444
Blowing upon Discomycetes, and puffing,

268
Bolton, J., on Pilobolus, 191, 193, 197,

221
Bonorden, H. F., on Pilobolus, 195, 221
Bose, S. R., on luminous leaves in India,

442
Bothe, F., on cause of luminosity in
decaying leaves, 443
,, ,, on luminous Mycenae, 442^43
Boudier, E., illustration of Aleuria vesi-
culosa, 289
„ „ illustration of Pustularia

catinus, 332
„ ,, illustrations of Pilobolus, 4,

23
„ „ on Aleuria Asterigma, 290

„ ,, on Cheilymenia vinacea, 285
„ ,, on compound fruit-bodies,

313
„ ,, on curved asci, 316

,, on drops of Pilobolus, 87
„ on Oalactinia badia, 305
,, on HelveUaceae, 321-322
„ „ on Lachnea scutellata, 278,

279, 280
„ ,, on Melastiza miniata, 285

„ ,, on Morchellaceae, 314

„ ,, on Pilobolus Kleinii, 23

„ „ on Rhytisma, 228

„ ,, on Sarcoscypha, 235-236

„ „ on worms in Pilobolus, 4-5

Boys, C. v., on surface tension, 155, 156
Bread, as a culture medium, 404, 406,
412, 438

»>

Brefeld, O., his nomenclature of Piloboli,
11-12, 197
„ ,, on Ciliaria scutellata, 280

,, „ on drop-excretion in Pilo-

bolus, 28
,, „ on effect of light on Pilo-
bolus, 36-37
„ „ on life-histories of Pilobolus

and Pilaira, 1 1
„ on PiloboUdae, 11-12, 197,
221-222
„ „ on Pilobolus crystals, 89
„ „ on Ptychogaster, 417

,, „ on zygospores of Pilobolus
and Pilaira, 12, 197
Brett, M. A., on puffing of Otidea leporina,

334-335
Briton-Jones, H. R., on Coffee-leaf

disease control, 401
Brown, W. H., on Ciliaria scutellata,

279-281
Brown colour, and spore-discharge in

Morchella and Gyromitra, 321
Brown pigment, and spore-discharge in

Discomycetes, 301
Bruner, L., on electro-osmosis, 31
Bryophyllum, and Omphalia flavida, 432

„ luminous leaf-spots, 439

Bryophyllum calycinum, and Omphalia
flavida, 406, 414, 419, 424, 430-^31,
433-i34, 439
Bryophyllum pinnatum, and Omphalia

flavida, 432
Buder, J., on heliotropism of P^comi/ces
nitens, 107-109
„ „ on heliotropism of Pilobolus,
109
Bulbils, of Pilobolus, 26
Bulgaria, spore colour, 165-166
Bulgaria inquinans, brown spores of, 301
Bulgariae, brown spores of, 301
BuUiard, P., on Collybiafusipes, 375
„ on Pilobolus, 193, 222
„ ,, on puffing, 229

Burnt-out Crater Fungus, 308, 309
Bursting of asci, successive, 235, 321
Butler, E. J., on Sphaerella coffeicola, 401
„ „ vide dedication of this

volume

Calcium oxalate crystals, and unwet-

table cell-

wall, 89,153

„ „ „ illustrations,

88,89

478

GENERAL INDEX

Calcium oxalate crystals, of Pilobolus,

76, 88, 89-
90, 134, 153,
\76
„ „ „ Sderotium

coffeicola,
448, 450
Caloscypha fulgens, audible puffing, 332
Camarophyllus virgineus, 2-spored and

4-spored forms, 355
Canada, luminous leaves in, 442
Capillary-tube method, for determining

osmotic pressures, 31, 140-144
Carotin, and lipochromes, 281

,, function of, in Pilobolus, 71, 99
glowing, 104

in Pilobolus, 18, 50, 51, 71, 98,
99
Carotinoid pigment, in spores of PUo-

bolidae, 180
Carpoboli, and Pilobolus, 194
Caulogaster, and Pilobolus, 195
Cecropia peltata, and Sclerotium disease,

444
Cell-sap of asci, discharge of, 247, 248,

260
Cell-sap (of Pilobolus), analysis of, 24-25,
29, 31, 148
„ and heliotropism, 130
„ attached to discharged sporan-
gium, 147, 149-153, 156-158
„ carries off sporangium, 76, 132,
138
exit from gun, 132-134, 146
„ extraction of, 142-143

jet of, 138
,, osmotic pressure, 140-145
„ uprush during discharge, 139
Cell-wall, local mucUaginisation, and
drop-excretion, 88
„ of an ascus, contraction of,

246-247
,, of paraph yses, mucilaginisa-

tion, 300
„ of Pilobolus sporangium, 72,

165, 167
„ of subsporangial swelling, 135-
137
Cerasus laurocerasus, osmotic pressure,

145
Cesati, V. de, on Pilaira, 195, 222
Chainaerops humilis, osmotic pressure,

145
Chamberlain, on a staining method, 363
CheUocystidia, of Omphalia flavida, 413

Cheilymenia vinacea, ascus curvature,

296
, , , , heliotropism of asci ,

285-286
„ ,, illustration, 286

,, ,, in an ice-house, 282

pigment, 301
Chlamydospores, oi Pilobolus naiiiis, 198,
209
„ of P. oedipus, 209

Chloroform, effect on drop-excretion by

PUobolus, 27
Chloroform vapour, and premature dis-
charge of sporangia, 32-33
Chlorosplenium aeruginosum, puffing,

228
Chlor-zinc iodine, effect on Pilobolus

cell-wall, 135, 136
Chordostylum, and Pilobolus, 194
Chytridiaceae, parasitism, 431—432
Chytridiales, parasitic, 18
Ciboria, puffing, in the open, 304
Cilia of Volvox, and heliotaxis, 112-114
Ciliaria, and Lachnea scutellata, 278
„ and Morchella, 318
,, origin of name, 279
Ciliaria scutellata, and Phillipsia CJiar-
doniana, 255, 256
„ „ and Sarcoscypha pro-

trada, 264
,, ,, ascus curvature, 296

„ „ audible puffing, 332,

336
,, „ bending of an ascus,

255
development, 280-281
,, ,, diagram of develop-

ment, 280
„ „ direction of puffing,

283
„ ,, heliotropism of asci,

265, 282-285
illustrations, 279, 280,
284
,, „ in an ice-house, 282-

283
oU-drops, 282
„ „ paraphyses, 300

„ „ present knowledge of,

278-282
„ „ puffing in the open,

304
red pigment, 281-282,
301
Cinchona, and Omphalia flavida, 433

GENERAL INDEX

479

Clamp-connexions, of Omphalia flavida,
413, 427
„ of Sclerotium coffei-

cola, 445, 453
Clavariaceae, and Sclerotium cqffeicola,
443-454
„ sclerotia of, 453

Cleavage, of protoplasm, 14, 15
Clonostachys araucaria, conidia, 166
Clusius, and CoUybia fusipes, 377-378
Clusters, of CoUybia fusipes, 378-384
Coarse adjustment, in Agaricaceae, 267
„ ,, in Discomycetes,

266-267
Coccomyces, puffing of, 230
Coccomyces trigonus, puffing, 230
Codex of Clusius, and CoUybia fusipes,

377-378
Coemans, E., on effect of light on Pilo-
bolus discharge, 71
„ „ on fate of columella, 80

,, ,, on landing of Pilobolus

projectile, 150
„ ,, on life-history of Pilobolus

oedipus and P. crystal-
linus, 10-11
„ ,, on markings on P. crystal-

linus, 184-185, 186
„ on Pilobolus, 7, 9, 192, 222
,, ,, on P. oedipus, 3

„ „ on Pilobolus species, 195-

196, 197
„ „ on range of Pilobolus gun,

63
,, ,, on spore number in Pilo-

bolus, 74-75
,, on worms and Pilobolus, 4
Coffea, and Omphalia flavida, 433
Coffea liberica, and Sclerotium disease,

444
Coffee, penetration of leaf by a parasite,

427
Coffee-leaf disease, account of, 397-401
,, „ control, 401

„ ,, diagnosis in dark,

439^41
Coffee tree, illustrations, 398^00, 444-

452
Cohn, F., on fate of columella, 80

,, ,, on number of spores in Pilo-
bolus oedipus, 74-75
„ „ on Pilobolus, 8, 195, 222
,, ,, on P. oedipus, 10, 183
Collar, of Pilobolus and its contraction,
132-135

Colloid, in drops excreted by Pilobolus,

25
Colloidal drops, excretion of, 86, 87, 88
CoUybia, pseudorhiza, 393

sclerotia, 453
CoUybia fusipes, about beeches and oaks,

374
,, and C. longipes, 393
„ „ and C. radicata, 387,

393, 394
,, ,, and Coprinus m.acro-

rhizus, 387, 393
,, „ and death of a beech,

379
„ ,, and Fomes applanatus,

394
„ „ and Sarcoscypha pro-

tracta, 340, 394-396
,, ,, annual appearance, 377

,, „ attached to roots, 379-

381
,, clusters and their

pseudorhizae, 378-

384
„ ,, clusters marked, 385-

386
„ ,, development of pseudo-

rhiza, 386-389
„ ,, distribution, 375

,, ,, evidence that pseudo-

rhiza persists, 385-

386
„ ,, field observations on,

378-384
,, ,, fruit-body described,

374-375
„ ,, function of pseudorhiza,

393-395
„ „ healing of wounds, 390-

392
„ „ historical remarks on,

375-378
„ ,, illustrations, nine, 376-

391
„ ,, imperfect rudiments,

383
,, ,, lateral grafting, 389-

390
,, latex vessels, 392
,, „ mycehum, 392-393

,, ,, parasitism, 392-393

,, ,, pseudorhiza, 239, 240,

344-394
,, ,, pseudorhiza perennial,

347

48o

GENERAL INDEX

Collybia fusipes, pseudorhiza in succes-
sive years, 387-389
„ „ rapid development of

spores, 374
„ „ significance of persist-

ency of pseudorhiza,
393-394
„ „ spongy black body of,

377
„ „ supposed sclerotium of,

375-376, 378, 384-
385
Collybia longipes, and C. fusipes, 393
„ ,, and C. radicata, 352

„ ,, pseudorhiza annual,

347
,, ,, pseudorhiza on oak,

352
Collybia pulla, pseudorhiza annual, 347
Collybia radicata, and C. fusipes, 387,
393, 394
and C. longipes, 352
and Coprinus hmcro-

rhizus, 359
and Polyporus squarno-

sus, 394
and Sarcoscypha pro-

tracta, 239
annual appearance, 352
as a wound-parasite,

352
attachment of pseudo-
rhiza, 349-351
discharge of spores,

350, 351
illustrations, 350
on stumps, 350, 352
origin of pseudorhiza,

348-349
pseudorhiza annual,

347
pseudorhiza described,

348-352
pseudorhizae exhumed,

349-351
spore-discharge period,

351
support given by

pseudorhiza, 351
trees associated with,
348
Colour, of asci and ascospores, 301

„ of spores, 165-166
Colouring matter, function in Discomy-
cetes, 301, 321

Colourless sporangium wall, in Pilobolus

longipes, 54-55
Columbus and his egg, 343
Columella (of Pilobolus), and its dis-
charge, 195
appearence of, 69, 70
contractility, 137
desiccated, 83, 85
development, 61
in projectile, 148-149
isolated, 80, 81
of P. Kleinii, 70, 72, 73, 76
of P. longipes, 75, 80, 81, 85
of P. umbonatus, 176, 177
photographs, 75, 80, 81, 176
shot away with sporangium,
76, 80-81
Columella-wall, adhesion to substratum,

83
Commelina, and Omphalia flavida, 433
Commelina nudiflora, and Sclerotium

disease, 444
Commelinaceae, and Omphalia flavida,

433
Compactness, of fruit-bodies, 319
Compositae, and Omphalia flavida, 403,

432
Compound fruit-body, of Morchellaceae,

313-314
Compound pseudorhiza, development,

386-389
Compressor cell, Pilobolus in, 150-152
Concentric zones of mycelium, 435, 437
Conidia, colour of, and ultraviolet light,

166
Coniferous forests, luminosity in, 442
Conifers, luminous needles, twigs, and

cones, 442
Coniosporium bambusae, and ultraviolet

light, 166
Construction diagrams, for Pilobolus

Kleinii, 91, 92
Contraction, of an exploding ascus, 246-
247, 251 , 253, 284-286, 302
,, of an exploding Pilobolus,

132-140
Cooke, M. C, on Ciliaria scutellata, 278
,, ,, on Collybia longipes, 352

,, ,, on Discomycetes, 236

,, ,, on Pilobolus, 196

„ ,, on Stilbum flavidum, 401,

406
Cookeina, oblique ascostome, 256
Copper sulphate, and ascus discharge,
33, 230, 232

GENERAL INDEX

481

»

Coprini, and herbivorous animals, 302
Coprinus, and audible spore-discharge,
344
,, colour of spores, 165, 166
„ sclerotia, 453
Coprinus cinereus, a synonym, 355
Coprinus comatus, possibility of hearing,

344
Coprinus curtus, and horse-dung fumes, 55

,, ,, drops excreted by, 87

Coprinus ephemerus, colloidal drops, 87
Coprinus fimetarius, a synonym, 355
Coprinus fimetarius var. macrorhizus, 355
Coprinus lagopus, distinguished from C.

macrorhizus, 355-358
Coprinus macrorhizus, and Collybia fusi-

pes, 387, 393
and Collybia ra-
dicata, 359, 368,
370
and Coprinus lag-

opus, 355-358
and Mycena gale-

riculata, 368
branched pseudo-
rhizae, 370-372
characteristics of
fruit-body, 355-
358
cultures of, 357
development in
darkness, 372-
373
development of
fruit-body, 363-
368
distinguished from
C. lagopus, 355-
358
fruit-bodies with-
out a pseudo-
rhiza, 362
hyphae on pseudo-

rhiza, 368
ill us t rati o ns,
eleven, 356-371
mycelium, 368
on horse manure,

357, 359, 369
origin of pseudo-

rhiza, 359-363
primordia listed,

366
pseudorhiza
annual, 347

VOL. VI.

Coprinus macrorhizus, pseudorhiza de-
scribed, 359-373
,, „ substratum, 357

„ „ variations in

length of
pseudorhiza,
362-363
Coprinus stercorarius, sclerotium, 359
Coprinus sterquilinus, and light, 351
„ „ possibility of hear-

ing, 344
,, „ spores, meniscus

on, 302
stipe, 315
Coprophilous fungi, colour of spores,

165
Corda, A. C. J., instituted Pilobolidae,

194-195, 222
Cordyline australis, osmotic pressure, 145
Coremium disease, of Coffee, 445-446
Corner, E. J. H., on Ascobolus sterco-
rarius, 273-277
,, „ on development of

apothecia, 273-277,
297, 298
Correlations, in Sarcoscypha protracta,

253-254
Cortex, of an apothecium, 276, 277, 297,

298, 299
Cows, and Pilobolus, 10-11, 163, 167-168
Cracking, of sporangium wall, 186-187
Crassulaceae, and Omphalia flavida, 432
Crystalloids, of Piloboli, 17-18
Crystals (of calcium oxalate), illustrations,
88, 89
on Pilobolus, 76, 88, 89-90, 134,
153, 176, 180
„ on Sclerotium coffeicola, 448, 450
Cultivation of mycelium, and its sterility,

433-434
Cultures, comparative, of Coprinus

lagopus, and C. macrorhizus, 358
Cup, asci turned toward mouth of, 302,

306-307, 308, 309
Currents of sajj, and ascospores, 291
Currey, F., on Pilobolus, 195, 222

„ „ on Pilobolus discharge, 195
„ „ on worms and Pilobolus, 4
Curvature, basal, of a pedicel, 418-420
„ of apothecium, in Aleuria

repanda, 266-267
„ of asci, in Aleuria vesiculosa,

292, 293, 298, 299
„ of asci, in Oalactinia badia,

306

2i

482

GENERAL INDEX

Curvature, of asci, in Helvellaceae, 321-
333 .
„ of asci, in Morchella crassipes,

315-317
„ of stipe and pedicel, 420-425

„ sigmoid, of a pedicel, 420-425

Curved asci, represented by Boudier,

315-317
Cyclops, and Pilobolus, 113
Cylinder, the hollow, in fungi and

flowering plants, 315
Cystopus candidus, parasitism, 432
Cytology, of Pilobolus, 14-17

Daedalea unicolor, spore-wall and light,

165
Dark thick-walled conidia, and ultra-
violet light, 166
Darkness, and delay in Pilobolus dis-
charge, 137
,, gemmifers not produced in,
434-436
Dasyscypha virginea, puffing, 228
De Bary, A., on Ascobolusfurfuraceus, 273
„ on Pilobolus, 34, 135, 221
„ „ on position of ascospores,

291
„ „ on puffing, 230, 291
„ ,, on sound of puffing, 329
,, ,, on Sphaerobolus, 326

De Maisoiuieuve, D., on worms and

PUobolus, 4
De Vries, H., plasmolytic method of, 140
Dearness, J., and Collybia fusipes, 375

„ „ on C. radicata, 348

Decaying leaves, luminosity of, 442-443
Dehiscence, of Pilobolus sporangium, 72,

73-74
Delacroix, on Omphalia flavida, 406
Depressions, in dried Pilobolus sporangia,

84, 85, 180
Desiccation, effect on a gemma, 427-429,

451
Desmazieres, J. B. H. J., on sound of

puffing, 230, 329
Detachment, of a gemma, 423-425
Deuterophonia tracheiphila, pycnospores

and ultraviolet light, 166
Devil's Cigar, origin of name, 327
Dewevre, A., on Pilobolus, 198-199, 222
Diagnostic value, of sporangial patterns,

187
Diaheliotropic leaves, 110-111

Diaheliotropism, ocellar theory of, 110-

111
Dichroic spores, of Pilobolus, 72, 180
Dickson, J., on Pilobolus, 193, 222
Dickson, L. F., on puffing, 232-234
Dicotyledons, and Omphalia flavida,

432^33
Dillenius, J. J., on Ciliaria scutellata, 278
Dimargaris crystalligena, as a parasite,

18, 19-20
Dimples, in Pilobolus sporangia, 83, 84,

85, 187
Direction, of ascus discharge, 302

,, of light rays, and heliotropic

response, 107-109
Discharge, of ascospores, cause of, 33

of Pilobolus gun, 133-140,
195
,, of Pilobolus sporangia, 10,

33, 56-58, 130-131, 162,
163, 194
Discharged Pilobolus sporangium, dis-
section of, 81-82
Discomycete, apandrous, 273
Discomycetes, and Agaricaceae, 267

,, and Basidiomycetes, 227-

228
„ and Hymenomycetes, 324

„ audible puffing in, 343

„ auriculate, 310

,, colourless asci and spores,

301
„ construction of sessile

apothecium, 298
„ field observations on, 262-

263, 304
„ flat species, 282

„ heliotropism of asci, 255-

257, 264-324
,, inoperculate, 301

„ largest sjiores in, 237

„ list of species in which

puffing has been heard,
332
„ mechanism of heliotrop-

ism in asci, 301
„ method of stud3'ing hy-

menium, 250
„ our knowledge of spore-

discharge incomplete,
262-263
„ paraphj'ses mature before

asci, 297
„ production and liberation

of spores, 225-344

GENERAL INDEX

483

Discomycetes, puffing, 227-263

,, puffing made audible,

321-342
„ radiosensitive, 232, 268-

270
„ significance of puffing,

235, 262
„ simple and compound,

318
small ones puff, 228, 230
„ species puffing in the

open, 304
„ summary, 462^68

„ tactiosensitive, 232, 268

Dispersion, of ascospores, and puffing,
235, 262
„ of gemmae of Oviphalia

flavida, 417, 425
„ of Pilobolus sporangia, 131,

163
,, of Pilobolus spores, 167

Dissepiments (of Morchella), and gills,
319
„ illustration, 317

„ significance, 319

Diurnal periodicity, of Pilobolus, 58-62,

130-131
Division of labour, in sporangiophore of

Pilobolus, 107
Dixon, on osmotic pressure in leaves,

144, 145
Dodge, B. O., on Ascoholus niagnificus,
270, 271
„ ,, photographs by, 8, 37,

271
Dowding, E. S., and Pilobolus longipes,
85
„ „ and P. umbonatus, 181,

182
„ „ on width-ratios in Pilo-

bolus, 183
„ ,, vide Preface

Drawings of Piloboli, remarks on old, 191
Drop-excretion (in Pilobolus), function,
88
„ and sporangium dis-

charge, 88-89
Drops (excreted by Pilobolus), 22-31,
69, 86, 87-89
„ drying of, 86, 87, 88
„ illustrations, 23, 69, 86, 87, 89
Drops of cell-sap, and ascus discharge,
248, 260
„ „ „ shot from Pilobolus
gun, 138

Drying, of discharged Pilobolus sporan-
gium, 82-85

Dung-agar cultures, of Pilobolus longipes,
49-50

Dung-plats, and Pilobolus, 161, 162,
163, 167

Durand, E. J., on audible puffing, 331
,, „ on Peziza vesiculosa, 290

Duration of puffing, 333, 334, 342-343

Dutrochet, H. J., on perception of light
by leaves, 110

Dwarf fruit-bodies, in Coprini, 358

Ear, and puffing, 331-332, 341-342, 343

Ecological theories, of puffing, 235
Economy in structure, in a pseudorhiza,

351
Efficiency, in reproduction, 394
Ehrenberg, on Pilobolus, 194
Elasticity of Pilobolus cell-wall, 134, 146
Electro-osmosis, 31

Elliott, J. S. B., on Aleuria repanda,
266-267
„ ,, on puffing in small

Discomycetes, 228
Elodea canadensis, and Pilobolus cell-sap,

140-141
Empusa, projectile, 325

,, sound production by, 343-344
Empusa muscae, a correction, 344
Endobiella destruens, as a parasite, 19
England, luminous leaves in, 442
Entomophthora, projectile, 325

„ sound production by,

343-344
Enzyme, and abscission in Pilobolus,

13&-137
Epicoccum purpurascens, conidia, 166
Epidermal cells, as ocelli, 110-111
Equisetum telmateia, osmotic pressure,

145
Eriobotrya japonica, and Omphalia

flavida, 403, 433
Ernst, A., and Omphalia flavida, 401, 441
Escape of spores, in Morchella, 318

,, ,, ,, in Morchellaceae, 268-
270
Ether vapour, and premature discharge
of sporangia, 32-33
,, ,, effect on drop-excretion,

27
Eucalyptus globulus, osmotic pressure,

145
Eudorina, eye-spots. 111

484

GENERAL INDEX

Euglena, eye-spot, 111

Evolution, and the pseudorhiza, 240, 396

,, of stilbum-bodies, 416

Excipulum, of an apothecium, 277
Excretion of drops, in Pilo bolus, 22-31,

86, 87-88
Explosion, of PUobolus, 136-13-7, 146, 194
Expulsion, of a jet of Pilobolus cell-sap,

138
External conditions, and breadth of

PUobolus, 33-34
Eye, of albino animals, 104
of Helix pomatia, 99
of man and of Pilobolus, 115
of Mollusca, 99

of Pilobolus, 99, 106, 111, 113
of Volvox, 113
of Volvox globator, 113
Eye-spots of Volvox, and ocellus of
Pilobolus, 111-115

Factors, in working of PUobolus gun,

145-146
Fagus, and Collybia fusipes, 374
Fagus sylvatica, and Collybia radicata,

348
Falck, R., on air-currents produced by
Morchellaceae, 268-270, 318
„ „ on brown pigment of Morchel-
laceae, 321
„ „ on effect of sunlight on

Morchella esculenta, 321
„ „ on escape of ascospores, 268-

270
„ „ ompufdnginAleuria vesiculosa,

303
., „ on puffing in Oalactinia badia,

305
„ „ on radiosensitive and tactio-
sensitive Discomvcetes, 232,
268
„ „ on radiosensitive Morchel-
laceae, 268-270
„ ,, on significance of puffing, 235
„ „ on Temperaturstromungen,

318
,, ,, on time of spore-discharge in
Morchella and Gyromitra,
320
Fat layer, supposed, on Pilobolus cell-
wall, 29, 34
Fawcett, G. L., on Omphalia flavida,
397-400, 417, 432-
433

Fawcett, G. L., photographs made by,

398, 399, 400
Fayod, V., introduced term pseudorhiza,
347, 349
„ „ on pseudorhiza of Collybia

longipes, 352
„ ,, on pseudorhiza of C. radicata,
348-349
Ferns, and Omphalia flavida, 432, 433
,, and Rust fungi, 432
„ and Sclerotium disease, 444, 445
Ferry, R., on Pilobolus, 9
Ficus, and Omphalia flavida, 430-431,
433
,, luminous leaf-spots of, 439
Field observations on Discomycetes,

262-263, 304
Fimbriate cells, of Omphalia flavida,

408-409, 413-414, 415-416
Fine adjustment, in Agaricaceae, 267
„ „ in Discomycetes, 266-

267
Fischer, A., on azygospores of Pilobolus
nanus, 13
„ „ on Sphaerobolus, 326
Fisher, W. R., on puffing, 232-234
Fitting, H., on osmotic pressure, 144
Fitzpatrick, H. M., on Pilaira, 179, 216,

222
Flammula inopus, pseudorhiza, 347
Flat Discomycetes, 282
Flesh, of Morchella conica, 315, 317
Floating, of Pilobolus sporangia, 154-156
Flowering plants, and Pilobolus, 109-

111, 161-168
Focal length, of subsporangial swelling,

101
Fomes applanatus, and Collybia fusipes,
394
blocking layer pig-
ment, 166
Fomes pinicola, parasitism, 432
Fowle, F. E., on reflection of light, 102
France, luminous leaves in, 442
Fraxinus excelsior, osmotic pressure, 145
Fraxinus oxyphylla, osmotic pressure,

145
Fries, E. M., on Galactinia badia, 305
„ on Pilobolus, 194, 222
,, „ synonyms of his Sarco-

scypha protracta, 236
Fringe (of Pilobolus sporangium), and
taxonomy, 180
„ defined, 80 '
„ dissolution of, 84

GENERAL INDEX

485

Fruit-bodies, annual and perennial, 394
„ of Mycenae, luminosity, 443

„ of Pilobolus, periodicity,

130-131
„ of Pilobolus longipes, ab-

normal, 54
Fruit-body, of P. Kleinii, vertical sec-
tion, 69
„ of P. longipes, order of

formation of parts, 54
Fruit-body clusters, of Collybia fusipes,

378-384
Fruit-body primordium, of Pilobolus

longipes, 50-54
Fuckel, L., on largest spores of Pezizae,

237
Fumes from dung, deleterious action of,

55
Function of pseudorhiza, 372, 385, 393-

394
Fungoides, puffing of, 228-229
Fungus guns, basidia and asci compared,
319
„ ,, sound made by, 325-344

Fungus projectiles, in order of size, 325
Fusarium discolor sulphureum, conidial

rings and light, 437
Fusarium murtii, conidia and ultra-
violet light, 166

Galactinia, and Morchella, 318

„ and sound production, 328-

329
„ tactiosensitive, 232

Galactinia badia, and Morchella conica,
315
and Morchellaceae, 314
and Sarcoscypha pro-

tracla, 242, 264
audible puffing, 307-

308, 332, 335
description, 305
direction of ascus dis-
charge, 295
discharge of spores,

304-308
heliotropism of asci,

265, 304-308
illustrations, 305-308
oblique puffing, 307,

308
pigment, 301
protuberancy, of asci,
271

Galactinia badia, puffing, 228, 307-308,
332, 335
,, „ puffing in the open,

307-308
„ „ structure of hymenium,

305-307
„ ,, surface view of hy-

menium, 307
,, „ tactiosensitive, 305

Gardenia jasminoides, and Sclerotium

disease, 444
Gases from horse dung, effect on Pilo-
bolus, 49, 55
Gastromycetes, and Pilobolus, 194
Gelatinous collar, of Pilobolus, 14, 16
Gelatinous meniscus, on ascospores, 302
Gelatinous ring (of Pilobolus), 72, 73, 74,
75, 77, 91
„ drying of, 82
„ ,, function, 163

,, ,, in discharged sporan-

gium, 151, 153, 155
,, ,, isolation of, 81-82

,, ,, loss of, 159

,, ,, swelling of, 160, 161

Gelatinous side, of discharged Pilobolus

sporangium, 150, 153
Gemma (of Omphaliaflavidu), abscission,
420^21, 422
adhesion to a leaf, 418, 425, 429
and wind, 423-^25
,, definition of term, 417
,, depression on, 421
,, detachment from pedicel, 423-

425
,, easily detachable, 417
,, effect of desiccation, 427^29
,, germination, 426^29

infection hyphae, 416, 418, 426-
427, 428
,, infection of a leaf, 430
„ mucilaginous exterior, 418
,, no spontaneous fall, 423
,, ripe, easily blown away, 423
„ size and transportation, 417-418
Gemma (of Sclerotium cojfeicola), 446
„ appressoria of, 448-450
„ infection of a leaf by, 448^50
Gemmae (of Omphalia flavida), and
stilbum-he&diS, 397
,, and wind, 420

attached to both sides of a
leaf, 429
„ dissemination, 417, 426
„ germination, 427^29

486

GENERAL INDEX

Gemmae, injured by dry air, 429

,, inoculation experiments with,

429^31
„ luminosity, 439
Gemmae (of Sclerotium coffeicola), 446,
447-451
„ and wind, 420
,, retention of vitality, 451
Gemmifer (of Omphaliu flavida), air-
space in, 408-410
„ apophysis of, 407
„ as an organ, 432
,, never produces spores, 406
„ pedicel and gemma of, 417
„ resemblance to a sporophore,

415-416
„ sigmoidal bending, 407
,, stilbum-ho&y as a, 416-418
„ structure, 406-410
„ summary, 470^72
Gemmifer (of Sclerotium coffeicola),
account, 443-454
„ illustrations, 445-449
„ spore-less, 446
,, structure, 447-448
,, term, 447
,, summary, 472
Gemmifers (of Omphalia flavida), as re-
productive organs, 417-
418
illustrations, 400^08, 419-
428, 435
,, light and formation of, 434-

437
„ mutual repulsion of, 420
„ number on a leaf-spot, 399,
417
General summary, 455^72
Geotropic adjustments, in Agaricaceae,

267
Geotropic stimuli, and sigmoid curvature

of a pedicel, 421
Geotropism, negative, of a pseudorhiza,
354, 393
„ negative, of stipe of

Omphalia flavida, 412
Germany, luminous leaves in, 442
Gill-breadth, in Coprinus lagopus and

C. macrorhizus, 355
Gills, and dissepiments of Morchellaceae,

319

Glass beads, and Pilobolus, 155-156

Glass-ring chamber, illustration, 117

,, ,, use of, 116, 117

Gleba, of Sphaeroholus stellatus, 325

Glow, of red protoplasm, 119
Glycerine, and ascus discharge, 230, 232,

291
Glycogen, in a gemma, 448
Godlewski, on drop-excretion, 27
Gonium, eye-spots of. 111, 112
Grantz, F., on heliotropism of Pilobolus,

37
Grape sugar, and ascus discharge, 230,

232, 291
Grass, and Pilobolus, 10-11, 161-168
Gravity, and basal curvature of a
pedicel, 418^20
„ and sigmoid curvature of a

pedicel, 421
,, effect on pseudorhiza, 370
Green colour, of Pilobolus spores, 72, 180
Greville, R. K., on Pilobolus, 197, 222
Grove, W. B., author's request to, 178,
190
,, early monograph on Pilo-
boUdae, 9, 190, 191, 198
„ hears Pustularia catinus,

331-332
„ on Bref eld's Piloboli, 11-

12
,, on Collybia radicata, 348
„ on diurnal crops of Pilo-
bolus, 11
„ on landing of Pilobolus
projectile, 150, 152-153
„ on Pilobolus spores, 196-

197
„ on Pilobolus worms, 6
,, on range of Pilobolus

Kleinii, 63
„ on sound of Pilobolus

gun, 327
,, on the Pilobolidae, sys-
tematic account, 1 90-
224
,, vide Preface
Growth, intercalary, in a pseudorhiza,
349, 353, 366-367, 393
,, marginal, in an apothecium,

275-277, 297
,, of hyphae in an apothecium,
273-277
Growth-curvature, sigmoidal, 421
Growth-curvatures, of a pedicel, 418-422
Growth-promoting substance, in Pilo-
bolus, 97, 121
Growth -reaction, of Pilobolus stipe, 97
Guava, and Omphalia flavida, 432
Gun, of Pilobolus, 56

GENERAL INDEX

487

Guns, basidia and asci as, 319

„ sound of fungus, 325-344
Giissow, H. T., and Collybia ftcsipes, 375
„ „ and C. radicata, 348

„ „ on puffing in Aleuria

vesiculosa, 303-304
Gymnocarpic apothecium, development

of, 297
Gyromitra, and sunshine, 320-321

„ brown colour and spore-

discharge, 321
„ escape of spores from, 268-

270
,, fruit-body form, 321

„ radiosensitive, 232

„ significance of puffing, 235

,, spore-discharge in the open,

320-321
Gyromitra esculenta, illustrations, 269,

322, 323
„ ,, radiosensitive, 268-

270
Gyromitra gigas, curved asci of, 321-322
Gyromitrae, and the sun, 321
Gyrose depressions, in Pilobolus sporan-
gia, 187

Haberlandt, G., on epidermal cells as
ocelli, 128
„ „ on heliotropism of

leaves, 110-111
Hadwen, G., on horses and Nematode

worms, 6
Hairs, of Cheilymenia vinacea, 285, 286

„ of Ciliaria scutellala, 279
Halo, around discharged Pilobolus

sporangia, 147, 149, 150
Hanna, W. F., and osmotic pressure of

Pilobolus, 143
Haploid and diploid forms of Camaro-

phyUus virgineus, 355
Hara, K., and Collybia fusipes, 375

„ ,, on C. radicata, 348
Hard, M. E., on Aleuria vesiculosa, 286-
287, 333
„ „ on Ciliaria scutellata, 278,

279
Harper, R. A., on Ascobolus furfuraceus,
273
,, ,, on cytology of Pilobolus,

14-17
Harris, J. A., et al., on osmotic pressure,
144

Hastings, S., photographs made bv, 329,

341
Hay, and Pilobolus, 166, 167
Healing of wounds, in a pseudorhiza,

390-392
Heat, and Discomycetes, 268-270

,, and spore-discharge in Morchel-
laceae, 320-321
Heat of sun, and puffing, 235
Hedera Helix, osmotic pressure, 145
Helianthus multiflorus, osmotic pressure,

145
Heliotropic curvature of asci, position

of, 273
Heliotropic equilibrium, in leaves, 110,

128
„ „ in Pilobolus, 97,

119, 129
Heliotropic experiment, on Pilobolus,

115-120
Heliotropic reaction, when absent in

Pilobolus, 131
Heliotropic stimuli, two simultaneous,

in Pilobolus, 122-125
Heliotropism, and carotin, 18

,, cause of, in plants, 107

„ in leaves, 109-111

„ in Pilobolus and leaves,

109-111
,, of apothecia, 266-267

,, of Omplialia flavida, 412

„ of paraphyses, 297-299,

306
,, of Phycomyces nitens, 107-

109
Heliotropism (of asci), 255-257, 264-324
,, concluding remarks, 324

ecology of, 301-302
,, of Aleuria repanda, 266

„ of ^. vesiculosa, 292-303

„ of Ascobolus denudatus,

265
,, of A. magnificus, 270-273

„ of ^. stercorarius, 273-278

,, of Cheili/menia vinacea,

285-286
„ of Ciliaria scutellata, 282-

285
„ of Galactinia badia, 304-

308
of Helvellaceae, 269, 270,
321-324
„ of Melastiza miniata, 285-

286
of Otideae, 309-310

488

GENERAL INDEX

Heliotropism, of Morchellaceae, 269, 270,
310-321
„ of Saccobolus, 265, 266

„ of Urnula Craterium, 308

„ summary, 465—467

,, theory of, 301

Heliotropism (of Pilobolus), 58, 60, 61,
65
„ absent in one develop-

mental stage, 131
„ and subsporangial swel-

ling, 90-109
„ effect of various light rays,

36^0
„ model for illustrating,

128-130
„ reaction period, 115-119

„ significance, 163

„ two-beam problem, 42^5,

120-128
„ window experiment, 62-

63
Helix pomatia, eye of, 99

„ ,, illustration, 99

Helminlhosporium gibber osporum, conidia

and ultraviolet light, 166
Helotium scutula, puffing, 228
Helvella, and sound production, 329
,, fruit-body form, 321

puffing, 229
Helvella crispa, hissing of, 329

,, „ illustration, 328

Helvella elastica, sound of puffing, 329-

330
Helvella ephippium, puffing, 230

„ ,, sound of puffing, 329

Helvella sulcata, curved asci, 323
Helvellaceae, and Morchellaceae, 324
„ and the spring, 320

„ genera of, 321

„ heliotropic asci, 321-324

Herbivorous animals, and Aleuria vesi-
culosa, 302
„ „ and Pilobolus, 3,

10-11, 161-168
Heterothallism, of Pilobolus crystallinus,

13
Hinge of operculum, position of, 251-253
Hiss, produced by puffing, 257, 259, 329
Hone, D. S., on Sarcoscypha protracta,

236
Hooded pileus, in Helvellaceae, 321
Hooks and hook-cells, in an apothecium,

276, 277
Horizontal range, of Piloboli, 67-68

Hornbeam, luminosity of decaying leaves,

442
Horse, and Aleuria vesiculosa, 302
Horse Chestnut, and Collybia radicata,

348, 350, 351, 352
Horse dung, and Nematode worms, 5

„ and Pilobolus, 3, 47-49, 169
,, ,, zygospores of Pilaira on, 12
Horses, and Pilobolus, 163-168

„ Nematode worms of, and Pilo-
bolus, 5
Hosts, of Omphalia flavida, 412, 432-
433
,, of Sclerotium coffeicola, 444—445
Howitt, J. E., on Collybia radicata, 348
Humaria granulata, spore colour and

light, 165
Humariaceae, heliotropic asci, 255
Hutwerfer, name for Pilobolus, 193
Hyaline conidia, and light, 166
Hyalopsora, and Ferns, 432
Hydrochloric acid vapour, effect on Pilo-
bolus, 27
Hydrogera crystallina, and Pilobolus, 193
Hygrophoraceae, 355
Hymenial grooves, heliotropic asci in,

324
Hymenial pits, of Morchella esculenta,

311,312
Hymenial temperature, raised in sun-

"light, 301
Hymenium, development of, in an
apothecium, 274-275
„ of Aleuria vesiculosa, 293.

294
,, of Ascobolus magnificus, 272

,, of ^. stercorarius, 276

,, of Ciliaria scutellata, 284

„ of Discomycetes, closing of

exterior, 300
,, of Discomycetes, colour, 301

„ of Galaclinia badia, 305-307

of Morchellaceae, 310, 319
,, of Omphalia flavida, 412

,, of Sarcoscypha protracta,

250-253
„ subdivided in Morchellaceae,

313
,, submerged in water, 230,

232
Hymenomycetes, and Discomycetes, 324
„ and Morchellaceae,

spore-stream, 321
„ and Sclerotium cof-

feicola, 453

GENERAL INDEX

489

Hymenomycetes, drops excreted by, 87,
88
„ projectiles of, 325

„ sound of basidiospore

discharge, 343-344
,, spore-discharge, 227

Hyphal fusions, in Syncephalis nodosa,

20,21
Hypochnus, sclerotia, 453
Hypothecium, of an apothecium, 276,

277
Hypoxylon, spore colour and light,
165-166

Ice-house, apothecia developed in, 282
Ilex aquifolium, osmotic pressure, 145
Image of an object, produced by Pilo-

bolus, 105
Impact, of a discharged Pilobolus

sporangium, 74
Impact-sound, of fungus projectiles, 326,

327
India, luminous leaves in, 442
Infection hyphae, growth of, 426^27,
428
„ ,, infection of a leaf by,

418, 424, 427
„ ,, of a gemmifer, 416,

418
Inga vera, and Omphalia flavida, 432
Ingold, C. T., on Pilobolus, 45-46, 153
Injurious rays of light, and spores, 165
Inoculation experiments, with Omphalia

flavida, 429-431
Inoperculate Discomycetes, 301
Intercalary basal swellings, in Piloboli,

181-183
Intercalary growth, in a pseudorhiza,

349, 353, 366-367,
393
„ „ in an apothecium,

275
Interlamellar spaces, origin of, in

Coprinus macrorhizus, 364
Iodine, and Aleuria vesiculosa, 287

„ and ascus discharge, 33, 230, 232.

248, 291, 295
,, and Cheilymenia vinacea, 285
,, and Ciliaria scutellata, 280
,, and Melastiza miniata, 285
,, and Pilobolus cell-wall, 87
Ireland, luminous leaves in, 442
Ironwood tree, and Collybia radicata, 348

Irradiation of Morchellaceae by heat,

268-270
Istvanffi, G., and the Codex of Clusius,

377-378

Janczewski, E. v. G., on Ascobolus

stercorarius, 273
Jelly, in Pilobolidae, 200

„ in Pilobolus, 72, 73, 74, 77

„ on spores of Aleuria vesiculosa, 287
Jet, of Pilobolus cell-sap, 138
Johnstone, R. B., on hissing of Otidea

leporina, 330-331

Karsten, p. a., on Sarcoscypha pro-

tracta, 236, 237
KaufEman, C. H., and Collybia fiisipes,
375
„ ,, on C. radicata, 348

Kew Gardens, 307, 374, 376, 378, 385,
390

,, ,, vide Preface

Key, to Pilaira species, 216

,, to Pilobolus species, 201
Klein, J., drawing of Pilobolus, 191
„ on Pilobolus, 9, 196, 222

,, ,, on Pilobolus crystalloids, 17
Klinostat, experiments with gemmifers,

418-420, 422
Knoll, F., on drops excreted by fungi, 25,

87, 88
Kohl, F. G., on Omphalia flavida, 406,

418, 429-430, 433
Krafczyk, H., on sex in Pilobolus

crystallinus, 13, 222
Kunze, G., and Schmidt, J. C, and Pilo-
bolus, 194, 222
Kunze, G., and Schmidt, J. C., on

puffing, 230
Kuyper, J., on Sclerotium coffeicola, 445,

451

Lachneahemispherica, and Morchellaceae,

314
Lachnea scutellata, a svnonym, 278, 279,
284

„ „ heliotropic asci, 266

Lachnea setosa, puffing, 228
Lachnea stercorea, spore colour and light,

165

490

GENERAL INDEX

Lagarde, J., on Ciliaria scutellata, 279
Lamp, heat from, and spore-discharge

in Morchelkt conica, 317
Lamp experiment, with Morchellaceae,

268, 270
Landing (of Pilobolus projectile), 150,
152, 153
„ theoretical explanation, 156-
158
Lange, J. E., on Mycena galericulata,

354
Largest spores in Discomycetes, 237
Latent period, in heliotropism of Pilo-
bolus, 116
Lateral grafting, of pseudorhizae, 389-

390
Latin diagnosis, of Pilobolus umbonatus,

178
Law of inverse squares, and audibility

of puffing, 342
Laying of Pilobolus gun, 163
I^af-mould, and Mycena galericulata,
353
„ luminosity of, 442-443

Leaf -spot, and number of gemmifers,
417, 451
„ development, 450

„ diverging gemmifers on, 420

infection of, 418, 424, 427
Leaf-spots, caused by Omphalia flavida,
399, 400
„ caused by Sclerotium coffei-

cola, 446
emission of light by, 439
Leaves, and Pilobolus, heliotropism of,
109-111
„ heliotropism, 128

luminosity of decaying, 442-443

luminous Mycenae growing on,

443

Leguminosae, and Omphalia flavida, 432

Lens, subsporangial swelling of Pilobolus

as a, 41,90-91,97,99, 111
Lentinus, sclerotia, 453
Lepeschkin, W. W., analysis of Pilobolus

cell-sap, 148
„ ,, experiments with

Pilobolus tubers,
53
„ „ on breadth of sub-

sporangial swell-
ing, 33-34, 183
,, „ on cell-sap concen-

tration in Pilo-
bolus, 33

Lepeschkin, W. W., on drop - excretion

in Pilobolus, 24-
29
,, „ on premature dis-

charge of Pilo-
bolus sporangia,
32-33
Leptopodia, fruit-body form, 321
Leptopodia elastica, oblique operculum,

323
Leveille, J. H., on Collybia fusipes, 375-
377, 378, 385
„ „ on worms and Pilobolus,

4
Level of dehiscence, in Pilobolus, 72,

73-74, 76
licwis, I. M., on puffing in Urnula geaster,

339-340
Lichens, ascus discharge, 231
Light, and abscission in Pilobolus, 71,
137
,, and black pigment, 165-166
,, and dichroic spores, 180
„ and discharge of Pilobolus pro-
jectiles, 34-35
,, and Discomycetes, 264—324
,, and drop-excretion, 27
,, and formation of conidia, 437
,, and formation of gemmifers, 434-

437
„ and formation of Pilobolus fruit-
bodies, 36
„ and heliotropism of asci, 255-257,

264-324
„ and heliotropism of Pilobolus,

36-45, 60, 90-131, 163
„ and length of pseudorhiza, 351
,, and Phycomyces nitens, 107-109
„ and Pilobolus spores, 80, 165
„ emission of, by fungi, 437-443
,, injurious action of, on spores,

165-166
„ reflection of, from Pilobolus, 102-

103
„ refraction of, in Pilobolus, 90-96
,, two beams of, action on Pilobolus,

41, 42-45, 120-128
,, ultraviolet, action on spores, 166
„ wave-lengths of, and Pilobolus
heliotropism, 38—40
Light-growth reactions, and heliotropism,

107, 109
Light-perceiving cell-structure, of Pilo-
bolus, 111
Light-perceiving organs, of leaves, 110

GENERAL INDEX

491

Light-screens, and spores, 80, 165-166,

167
Lindau, G., on Ciliaria scutellata, 278
Ling, Yong, on Pilaira, 199, 222-223
Link, H. F., on Pilobolus, 34, 90, 194, 223
Linnaeus, C, on Peziza scutellata, 278
Lipochrome, in various fungi, 281
Liquidum parafifinum, development of

Pilobolus in, 26
„ heliotropism of

Phy c omyces
nitens in, 108-
109
„ „ Pilobolus com-

pressed with,
30-31
Lobing, of a pileus, 321
Long, W. H., on puffing in Urnula
geaster, 338-339
„ „ photographs made bv,

337, 338, 339
Loquat, and Omphalia fiavida, 403, 433
Lowe, C. W., and sound of Pilobohis gun,
327
„ ,, heard puffing, 341

„ ,, on Morchella conica, 314-

315, 316
Luminescence, of Mycenae, 442-443

„ of Omphalia flavida, 397,

437-443
„ of 0. Martensii, 441-4^42

Luminous leaves, cause of emission of
light, 442-443
„ ,, countries found in, 442

Macadam, R. K., on Collybiafiisipes, 375
Macrae, R., and Omphalia flavida, 406
„ ,, drawings assisted with, 272,

408-427
,, „ vide Preface

Magnolia acuminata, osmotic pressure,

145
Malva verticillata, heliotropism, 110
Man, eye of, and Pilobolus, 115
Mango, and Omphalia fl/ivida, 432
Marginal growth, in an apothecium, 298
Marginal hairs, of apothecia, 279, 280,

285, 286
Martens, O., and Omphalia Martensii,

441-442
Martyn, E. B., on Sclerotium disease of

Coffee, 444, 445
Massee, G., on Coprinus m,acrorhi2us, 355
„ „ on Omphalia flavida, 406

Massee, G., on Pilobolus, 199

Mast, S. O., on eyes of Volvox, 112-114

Mat of basal hyphae, in Syncephalis

nodosa, 20, 21
Maublanc, A., and Rangel, E., on
Omphalia flavida, 403-i04, 410-412,
415, 416, 417, 432-433
McAllister, F., on Urnula geaster, 337
McClelland, T. B., on Omphalia flavida,

432
Mcllvaine, C, on Collybia fusipes, 375
Mechanical support, given bv pseudo-

rhiza, 351, 368
„ „ in fungi and flower-

ing plants, 315
Mechanism, of abscission in Pilobolus,
136-137
,, of helio tropic reaction in

Pilobolus, 120
Medulla, in an apothecium, 276, 277
Melastiza Chateri, a synonym, 285
Melastiza miniata, ascus curvature, 296
„ „ heliotropism, of asci,

285-286
,, „ in an ice-house, 282

Melastomaceae, and Omphalia flavida,
403, 433
„ and Sclerotium coffeicola,

444
Meniscus, gelatinous, on ascospores, 302
Mercuric chloride, and ascus discharge,

33, 230, 232, 291
Method for making puffing audible, 321-

343
Micheli, P. A., on Ciliaria scutellata, 278

„ on puffing, 228-229
Michelsen, C, on luminous Coifee leaf-
spots, 440-441
Microascus stysanus, conidia and ultra-
violet light, 166
Microphones and spore-discharge, 344
Microstoma hiemale. a synonym, 236
Milesia, and Ferns, 432
Mitrophora, and Peziza, 314
,, receptacle, 310

Mitrophora hybrida, shape of alveoli,

314
Moca, and Omphalia flavida, 432
Model, of Pilobolus fruit-body, 41-42,

128-130
Molisch, H., on carotin, 281
Mollisia cinerea, puffing, 228
Mollusca, eyes of, 99
Moniliform hyphae, of Pilobolus longipes,
52,53

492

GENERAL INDEX

Monocotyledons, and Omphalia flavida,

433
Monstera deliciosa, heliotropism, 110

„ „ osmotic pressure, 145

Montagne, J. F. C, on Pilobolus, 8, 194,

223
Moraceae, and Omphalia flavida, 433
Morchella, air-currents produced by, 318
„ and Peziza, 314

„ and simpler Discomycetes,

318
„ and sunshine, 320-321

„ browTi colour and spore-

discharge, 321
„ continuous spore-discharge,

320
„ receptacle, 310

,, significance of puffing, 235

„ spore-discharge in the open,

320-321
Morchella angusticeps, illustration, 314
„ ,, shape of alveoli,

314
Morchella conica, and Aleuria vesiculosa,
315
„ ,, and Galactinia badia,

315
and Peziza-cups, 314
and Sarcoscypha pro-

tracta, 264
asci helio tropic, 266
heliotropism of asci,

314-315
illustrations, 316, 317,

318
light physical frame-
work, 315, 317
median-vertical sec-
tion, 315, 317
shape of alveoli, 314
Morchella costata, shape of alveoli, 314
Morchella crassipes, and Peziza-cups, 314
„ „ and Sarcoscypha pro-

tracta, 264
„ ,, Boudier's curved

asci in, 315-317
„ „ heliotropic asci, 315

,, ,, heliotropism of asci,

265
„ „ illustration, 319

„ „ shape of alveoli, 314

„ „ sharply curved asci,

319
Morchella deliciosa, iWustrsiiion, 313

„ „ shape of alveoli, 314

Morchella elata, shape of alveoli, 314
Morchella esculenta, effect of sunlight on,

301
,, ,, experiment with

sunlight, 321
„ „ illustrations, 311,

312
,, ,, radiosensitive, 268-

270
„ ,, shape of alveoli, 314

Mcrrchella rotuvda, shape of alveoli, 314
Morchellaceae, and Agaricaceae, 319
,, and Helve Uaceae, 324

,, and the spring, 320

„ brown pigment, 321

„ compactness, 319

„ discharge of spores, 310-

321
,, heliotropic asci, 255

,, heliotropism of asci, 310-

321
,, radiosensitive, 232, 268-

270
,, receptacle described, 310-

314
,, significance of dissepi-

ments, 319
Morchellae, and the sun, 321

„ escape of spores, 265, 268-

270
Morini, F., definition of trophocyst, 53,
58
„ on Pilobolidae, 190, 199, 223
„ „ on Pilobolus, 9

,, ,, on zygospores of Pilobolus

Borzianus, 13
Morphological character, of asci, 256-

257, 285, 286
Mortierella polycephala, as a parasite, 18,

19-20
Moss, E. H., on Sarcoscypha protr acta, 236
Motor region, of Pilobolus stipe, 92,

93, 97, 98, 100, 118, 119, 121
Mounce, I., heard puffing, 341

„ „ on duration of puffing, 343

Mouth, of alveolus, asci directed toward,
315-318
„ of a cup, asci directed toward,
302, 306-307, 308, 309
Mucilage, and gemmae, 449
,, and paraphyses, 300
„ in Ascobolus stercorarius, 276,

277
„ oi Omphalia. flavida, 409, 4:13,

416, 418, 425

GENERAL INDEX

493

Mucilage cavity, in an apothecium, 274,

275
Mucilaginisation, of cell-wall, 88
Mucilaginous drops, of Pilobolus, 69, 173
Mucor, and Pilaira, 9

„ and Pilobolus, 1-2, 9, 72, 167, 194
,, dehiscence of sporangium, 73
,, parasites of, 19-20
Mucor Mucedo, drop-excretion, 89
Mucor obliquus, and Pilobolus, 8, 193
Mu^crr plasmaticus, crystalloids, 17-18
Mucor roridulus, and Pilobolus, 193
Mucor raridus, and Pilobolus, 192, 193,

197
Mucor urceolatus, and Pilobolus, 193
Mucoraceae, parasitic, 18
Mucorini, and Pilobolidae, 9, 190

„ and Pilobolus, 194

Mucors, and Pilairae, 179

and Piloboli, 49
Mud, and Pilobolus, 1, 3, 56
Miiller, A. S., on luminescence of Om-
phalia flavida, 440
on O. flavida, 432-433,
434
Muller, O. F., on Pilobolus, 3-4, 7, 192,

194, 223
Murrill, W. A., and Collyhia fusipes,

375
Musa sapientum, osmotic pressure, 145
Musaceae, and Omphalia flavida, 433
Mutual repulsion, of gemmifers, 420
Mycelial cords, and pseudorliiza, 347
Mycelial sheets, of Collyhia fusipes, 392
Mycelial strands, of Sclerotium coffdcola,

452
Mycelium, concentric zones, 435, 437
luminescence, 397, 437^43
of Collyhia fusipes, 379, 380-

381, 386, 392-393
of Omphalia flavida, 427, 433-

442
of Pilobolus, 10, 50-52, 172,

181-182
restoration of fertility to, 434
secondary, of an apothecium,
274, 276, 277, 297
„ sterility after prolonged cul-

tivation, 433-434
Mycena, luminous species of, 442-443
Mycena alkalina, non-luminous, 443
Mycena crocata, non-luminous, 443
Mycena dilatata, luminosity of, 443
Mycena epipterygia, luminosity of, 443
Mycena galericulata, a saprophyte, 354

Mycena galericulata, and Coprinus mac-

rorhizus, 368
„ „ hj'phae on pseudo-

rhiza, 354, 368
„ ,, illustration, 353

,, ,, non-luminous, 443

,, „ possible haploid

and diploid forms,
355
„ „ pseudorhiza d e s -

cribed, 352-355
,, „ 2-spored and 4-

spored forms, 355
Mycena galopus, luminosity of, 443
Mycena haematopus, non-luminous, 443
Mycena janthina, non-luminous, 443
Mycena metata, non-luminous, 443
Mycena polygramma, luminosity of, 442
Mycena pura, luminosity of, 443
Mycena sanguinolenta, luminosity of, 443
Mycena siylohates, luminosity of, 443
Mycena tintinnabulum, and M. galeri-
culata, 354
,, „ luminosity of , 442

Mycena vulgaris, non-luminous, 443
Mycena zephira, luminosity of, 443
Mycogone anceps, and Pilobolus, 209

Nageli, on plasmolysis, 140

Narcotics, and discharge of sporangia,

32-33
Natural conditions, and puffing, 303-304
„ „ and spore-discharge

in Morchellaceae,
320-321
Nectria cinnaharina, red pigment, 281
Nematode worms, and Pilobolus, 5-8
Nerium Oleander and Omphalia flavida,
402, 403, 432
„ „ illustrations, 402, 403,

431
„ ,, inoculation of leaves

of, 430-431
„ ,, luminous leaf -spots on,

439
Newton's rings, and asci, 231
Night, and spore-discharge in Morchel-
laceae, 320
Nising, on Pilobolus oedipus, 3
Nitella, experiment on, 28-29
Nitrogen, development of Pilobolus in,

26
Nodular thickenings, of Syncephalis
nodosa, 22

494

GENERAL INDEX

Nolla, J. A. B., and OmpJialia flavida,

434
Non-resultant heliotropic reaction, of

PUobolus, 42-45, 120-128
Nuclei, of Ciliaria scutellata, 281
„ of Pilobolus, 14-17
„ of 2-spored and 4-spored forms
of Mycena galericulata, 355
Number of spores, in Pilobolus Kleinii,
75
„ „ ,, in Pilobolus oedipus,
10,74
Nyctalis, and Omphalia flavida, 417

Oak, and Collybia fusipes, 374, 378, 392-
393
„ and C. longipes, 352
„ and C. radicata, 348, 352
,, luminosity of decaying leaves, 442,
443
Oblique discharge of an ascus, 247-248,

250
Oblique opening of an ascus, 247-248,

251,253
„ „ „ cause of,
255-257
Oblique operculum, of Ciliaria scutellata,

284-285, 286
Ocellar theory of heliotropism, 110-111
Ocelli, of leaves, 128
OceUus, of a leaf, 110-111
„ of Helix pomatia, 99
„ of Pilobolus, 2-3, 47, 106, 110-

111, 166
,, of Pilobolus and eye of man, 115
„ of Pilobolus and eye-spots of
Volvox, 111-115
OceUus function (of PUobolus), 41-42,
90-109
„ „ illustrated by a model,

128-130
„ „ summary, 456-459

Odell, W. S., and Collybia fusipes, 375
„ ,, and Morchella angusticeps,

314
„ ,, and M. deliciosa, 313

„ „ and Otidea onotica, 310

„ „ and Peziza aurantia, 334

„ „ and IJrnula Crateriurn, 309,

335, 336

,, „ on Collybia radicata, 348

O'Donoghue, C. H., and Sarcoscypha pro-

tracta, 237-239
„ „ heard puffing, 341

O'Donoghue, Charles and Dennis, obser-
vations on Sarcoscypha protracta, 237-
239
Oedocephalum fimetarium, a conidial

stage, 290
Oil-drops, and carotin, 18, 71, 281, 282
in Pilobolus, 18, 46, 71
in spores, 245, 249, 251, 280,
305, 306
Oleander, and Omphalia flavida, 402,

403, 406
Olivaceous conidia and ultraviolet light,

166
Omphalia flavida, a leaf -spot fungus,
397^01
account of, 397-443
„ „ and American Coffee-

leaf disease, 397-401
„ ,, and NyctaUs, 417

,, ,, and O. Martensii, 442

„ „ and Ptychogaster, 417

„ ,, and Sclerotium cojfei-

colu, 445, 446, 447,
454
,, „ as a non-specialised

parasite, 431^33
„ ,, attacks many plants,

397
,, „ concentric zones of

mycelium, 435
J, ,, curvatures of pedicel,

418-i25
,, „ desiccation of gemmae,

427-429
,, ,, dissemination, 416

„ ,, fimbriate cells, 408-

409, 413-414, 415-
416
„ gemmifer and gemma,
408, 416-431
,, „ germination of spores,

414, 415
„ „ heliotropism, 412

„ hosts of, 403, 432-433
,, ,, hymenium, 412

,, „ illustrations, twenty-

six, 398-438
„ ,, inoculation experi-

ments with, 42^
431
„ list of hosts, 432-i33
„ ,, luminescence, 397,

437-443
„ „ mucilage in, 409, 413,

416

GENERAL INDEX

495

Omphalia flavicJu, origin of name, 403
,, ,, peculiarities, 397

„ ,, penetration into

leaves, 418
„ „ pure cultures, 404-

406
„ ,, reproduction by

gemmae, 397
„ „ resemblances of gem-

mifer and sporo-
phore, 415-416
„ ,, spores and leaf in-

fection, 414
„ ,, sporophores, 403, 404-

406, 412
„ ,, sterility of mycelium,

433-434
„ „ Siilburn flavidmn as a

stage, 401-406
„ ,, structure of gemmifer,

406-410
„ „ structure of sporo-

phore, 410-414
„ „ summary, 470^72

Omphalia Martensii, luminescence, 441-

442
Open spaces, and asci, 324
Operculum, and heliotropism of asci,
255, 301
,, change in position of, 255

,, oblique position, 284-285,

286
,, of Sarcoscypha protracta,

244-246, 250, 251, 252
,, position of origin, 301

,, symmetrical situation of,

264, 266
Optical sense organ, of Pilobolus, 111
„ ,, ,, of Volvox and Pilo-

bolus, 113
Orange, and Omphalia flavida, 433
Orange pigment, in hymenium of

Discomycetes, 301
Orange-coloured granules, in Pilobolus

Kleinii, 195
Orange-red pigment, in Pilobolus, 18
Orange-red protoplasmic ring, of Pilo-
bolus, shot away, 99
Orhilia xanthostigma, puffing, 228
Orientation, in Volvox, 114
Ortho-heliotropic j^lant organ, and Pilo-
bolus, 1 1 1
Osmotic pressure, in an ascus, 246

„ ,, in flowering plants,

144-145

Osmotic pressure, in Pilobolus, 34, 57,
140-145, 147, 148,
183-184
Ostrya virginiana, and Collybia radicata,

348
Otidea, and sound production, 329
puffing, 229
„ tactiosensitive, 232
Otidea hporina, audible jjuffing, 335
,, ,, heliotropism of asci, 309-

310
hissing of, 330-331
„ ,, illustration, 329

puffing, 310
Otidea onotica, heliotropism of asci, 309-
310
,, ,, illustration, 310

puffing, 310
Oxalic acid, and Sclerotium coffeicola, 450
Oxygen, and Pilobolus development, 26

Palisade liyphae, in young apothecium,

274, 275, 297
Palla, E., on Pilobolus, 9, 190, 199, 223
Panaeolus, spore colour and light, 165
Pandorina, eye-spots. 111
Panus stypticus luminescens, lumines-
cence, 438
Paraffin oil, and Pilobolus, 26, 30, 109
Paraffined glass beads, and Pilobolus,

155-156
Paraffinum liquidum, and Phycomyces

nilms, 108-109
Paraphyses, and asci, 254, 296-300

„ and discharge of asci, 248,

254
and mucilage, 300
anheliotropic, 273, 278, 308
branching of, 300
coloration of, 301
do not anastomose, 300
functions of, 254, 300
heliotropism, 297-299, 306
lateral expansion, 298, 300
mature before asci, 297
origin of, in an apothecium,

274, 275, 297
swelling of, 289
Parasite, non-specialised, 431-433
Parasites, of Pilobolus, 12-13, 18-22
Parasitism, discussion of, 431-432

of Collybia fusipes, 392-393
Parr, R., on heliotropism of Pilobolus,
36, 37^0

496

GENERAL INDEX

Passiflora quadrangular is, osmotic pres-
sure, 145
Pastures, and Pilobolus, 10-11, 160, 161-

168
Patouillard, N., on Mycena galericulata,
354
,, „ on Omphaliaflavida, 406

Patterns, on Pilobolus sporangia, 184-

189
Peck, A. E., photographs made by, 288,

311, 322, 327, 328
Pedicel (of a gemmifer), basal curvature,
418-420
„ defined, 417, 446
,, detachment of a gemma from,

423-425
,, gravity in relation with, 418-^22
,, sigmoid curvature, 420-425
Pellicle, of Collyhia radkata, 351
Penicillium cruslaceum, conidia and

ultraviolet light, 166
Perception, of direction of light rays by
Pilobolus, 106
„ of images by Pilobolus, 106

Perennial pseudorhiza, of Collybia fusi-

pes, 346, 374-
394
„ „ of Sarcoscypha

protracta, 239-
240, 394-396
Periodicity, in Pilobolus development,

11, 58-62, 130-131
Permeability of protoplasm, 28, 29, 32
Peronospora parasitica, parasitism, 432
Peronosporeae, parasitism, 431—432
Persistency, of a perennial pseudorhiza,
385-386, 393-394
„ of Pilobolus sporangium

wall, 72, 167, 200
Persoon, C. H., on Pilobolus, 4, 6, 8,
193, 197, 223
„ „ on puffing, 229

Petch, T., heard puffing, 332
Petioles, and heliotropism, 110
Petiver, J., on Pilobolus, 3, 192, 193, 233
Peziza, and sound production, 328-329
„ and Sphaerobolus, 326
„ ascus discharge, forces con-
cerned, 33
„ projectile, 325
„ puffing, 229
,, strains in ascus wall, 231
,, tactiosensitive, 232
,, why does it puff ? 235
Peziza acetabulum, hissing of, 329

Peziza Asterigma, and A. vesiculosa,

290
Peziza aurantia, audible puffing, 332,
334
„ ,, illustration, 334

puffing, 228
,, ,, red pigment, 281, 301

Peziza gun, sound of, 328-331
Peziza mirabilis, a synonym, 236
Peziza repanda, a synonym, 33, 250,
289, 290, 333
,, „ of Vol. I is Aleuria

vesiculosa, 33, 250,
289, 290, 333
Peziza vesiculosa, and poisons, 33
Pezizaceae, and Aleuria vesiculosa, 286
„ heliotropic asci, 255

„ protuberancy of asci, 271

,, significance of puffing, 235

Peziza-cups, and alveoli, 314
Pezizae, largest spores in, 237
Pezizeae, and Morchellaceae, 314
Pfeffer, W., on drops excreted by Pilo-
bolus, 22-23, 28, 29
„ „ on plasmolysis, 140

Phacidium, and Coccomyces, 230
Phacidium coronatum, puffing, 230
Phacidium trigonum, puffing, 230
Phanerogams and fungi, mechanics, 315
Phillips, W., on Sarcoscypha protracta,

236
Phillipsia, oblique ascostome, 256
Phillipsia Chardoniana, position of as-

costomes, 255-257
Pholiota radicosa, pseudorhiza annual,

347
Photic equilibrium, in eyes, 115
Photic orientation, of Volvox and

Pilobolus, 113
Photic stimuli. 111

Photically sensitive optical organ, 115
Photochemical change, in Pilobolus, 96,

101
Photochemical equilibrium, 119
Photochemical mechanism, in Pilobolus,

71
Photochemical reactions, of Pilobolus,

106
Photochemically sensitive protoplasm,

99, 104
Photography and puffing, 232-234
Photopositive and photonegative Volvox

colonies, 112
Photosensitive substance, in Volvox eye,
112

GENERAL INDEX

497

Phycomyccs nilens, Budei'.s experiment
with. 1((7-109
„ ., crystalloids, 17

heliotropism, 37, 107-
109
„ illustration, 108
Phycomycetes, crystalloids in, 17-18
Physiological character, of asci, 285, 286
Physioltjgical equilibrium and inequili-

brium in Pilobolus, 9(i
Physomitra, fruit-body form, 321
Pigment, black, in dried drops, 87, 88
,. in paraphyses. 301

in Pilobolus. 18, 54-55
,, of asci and ascospores, 301
Pigment -cup, of Volvox, 112
Pigments, and ascospore-discharge, 301,

321
Pilaira, a valid genus, 179
,, and Mucor, 167

and Pilobolidae, 10
and Pilobolus, 167
„ and rabbits, 179

carotinoid pigment of, 180
connects Mucor and Pilobolus, 9
,, genus defined, 216

named by van Tieghem, 198
Pilaira anomala, and P. Moreaui, 199
from Baarn. 179
history, 195
„ ,. illustration, 217

„ „ name, 10

patterns on, 185
taxonomic description,
217-218
,, zygospores, 12
Pilaira Cesatii, and Pilobolus anomalus,

11
Pilaira dimidiata, described by Grove,
198
„ illustration, 218

„ taxonomic descrip-

tion, 218-219
Pilaira Moreaui, as a new si)ecies. 199
from Baarn, 179
illustration, 220
„ ,. taxonomic description,

220-221
Pilaira niqre-'^rpns, by whom found, 198
„ ,. illustration, 218

taxonomic descrip-
tion. 218
Pilaira Saccardiana, as a new species,

199
illustrati(m, 219

VOL. vr.

Pilaira Saccnrdiana, taxonomic descrip-
tion, 219-220
Pileus, of Morchellaceae, 310

„ rudimentary, pushed up through
soil, 353
Piloboli, and herbivorous animals, 302

,, and Mucors, 49
Pilobolidae, and Mucorini, 190

bibliography. 221-224
BuUer's remarks on, 178—

189
definition of, 200
Grove's early monograph

on, 9-10
Grove's present account of,

178, 190-224
Grove's remarks on, 190-191
historical account, 191-199
in England and Canada, 190
in Saccardo, 190
old key to, 9-10
origin of name, 194
sex in, 12-13
summary, 462

systematic account, 190-224
svstematic arrangement,
^ 199-221
,, zygospores, 197

Pilobolus, a possible enzyme in, 136-137
„ abscission of sporangium, 73,
76, 135, 136
and Chordostylum, 194
and Cyclops, 113
and darkness, 137
and daylight. 131
and herbivorous animals, 3,

10-11, 161-168
and leaves, heliotropism of,

109-111, 128
and leaves, osmotic pressure

of. 140-145
and light, 34-35, 36-41
and Mucor. 1-2. 72, 167, 194
and Mucor obliquus, 8
and Nematode worms, 3-8
and ocellar theory of helio-
tropism, 111
and pastures, 167-168
and Pilaira, 9, 167
and rabbits, 179
and Sphaerobolus, 326
and the human eye, 115
and Volvox, heliotropism,

111-115
and worms, 3-8, 192, 194

2k

498

GENERAL INDEX

Pilobolus, apical view of, 104

„ as a ooprophilous fungus, 161,

167
„ attachment of sporangium,

148-161
„ ballistics of projectile, 34-36

carotin in, 18, 98, 180
,, columella development, 61
„ criteria in distinguishing

species, 180
,, crvstalloids in, 17-18
crystals on, 88, 89-90
,, culture methods, 47-50
,, cytology of, 14-17
„ development and cytology,

14-17
„ development first observed, 10
dichroic spores, 72, 180
discharge of sporangium,
forces concerned, 33
„ diurnal crops of, 11
„ doubtful species, 201
,, early drawings of, 191
,, effect of two beams of light

on, 41, 42^5, 120-128
,, evolution of, 167
„ excretion of drops, 22-31
„ explosion in water, 137
eve of, 99, 106
first record, 3, 191-192
floating sporangia, 154-156
,, genus, 9-10
,, genus defined, 200
,, good species of, 200
„ heliotropic experiment on,

115-120
,, heliotropism, 90-109
„ heliotropism and spore dis-
persion, 163
„ heliotropism and wave-length

of light, 36-40
„ heliotropism in paraffin oil,
109
history of, 1-46, 191-199
,, illustrations, one hundred and

eleven, 2-220
,, impact-sound of projectile, 327
„ key to species, 201

list of species, 200-201
,, lurid red disc of, 104
,, meaning of name, 9

model of, 128-130
„ nuclei of, 14-17
,, number of species, 1, 200-201
on excrement, 1, 2, 3

Pilobolus, on mud, 1 , 3

,, orange-red pigment of, 18
,, osmosis and width of sub-

sporangial swelling, 183-

184
„ osmotic pressure, 34, 37,

140-145. 148, 183-184
parasites of, 12-13, 18-22
„ patterns on sporangia, 184-189
,, periodicity of, 11, 58-62, 130-

131
,, plasmolysis, 140
,, precision of aiming at source

of light, 41
„ red colouring matter, 281

reflection of light by, 102-103
,, refraction of light in, 91-96,

103
,, relations with flowering plants,

161-168
,, relations with herbivorous

animals, 161-168
,, relative diameters of sporangia

and subsporangial swellings,

56, 57
Schuss-bilder, 42, 44
services of herbs and herbi-

vora to, 168
,, solution of two-beam light

problem, 42-45, 120-128
,, somid of gun, 327
,, species observed at Winnipeg,

55-56
,, sporangia, large and small,

189
,, sporangiophore described, 68-

90
,, sporangiophore specialisation,

1-2
,, sporangium, abscission of, 73,

76, 135. 136
„ sporangium described, 72-90
,, spore-wall of, and light, 165
„ summary, 455-462
,, unique in plant world. 111
,, variations in width of sub-
sporangial swelling, 183-

184
„ vitality of spores, 166
,, width-ratio, 183
Pilobolus anomalus, 1 1

„ ,, and Ascophora, 196

and Pilaira, 195, 198
Pilobolus argentinns, taxonomic descrip-
tion, 214

GENERAL INDEX

499

Piloholus Borzianus, as a new species,

199
„ „ taxonomic descrip-

tion, 213-214
zygospores, 13
Pilobolus crystallinus, and P. Kleinii, 13,

191
„ „ si.n^P.microsporus,

12
„ „ and P. Oedipus, 10,

74
„ „ chlamydospores,

198
cytology, 14-17
„ „ effect of light on

development, 36
„ „ experiments on

sex, 13
„ „ germination of

spores, 16, 17
„ „ height of sporan-

gium discharge,
10
history of, 193-196
„ ,, illustrations, 12,

15, 16, 19, 185,
186, 202
jelly of sporan-
gium, 14, 16
„ ,, not observed at

Winnipeg, 56
of Brefeld, 11, 197
„ „ origin of name, 8,

193
„ parasites on, 18, 19

„ patterns on, 184-

187
„ range of gun, 63

,, sporelings, 16, 17

,, spread by cows, 1 1

„ „ taxonomic de-

scription, 201-
203
„ „ zygospores of, 12,

13
Piloholus exiguus, described by Bainier,

198, 221
Pilobolus gun, aiming at a window, 62-
63
„ „ and projectile, general

description, 56
„ „ development, 58-62

„ ,, discharge, 131-140

„ „ factors in effectiveness of,

145-146

VOL. VI.

Pilobolus gun, laying of, and obstacles,
163
„ laymg of, by usmg an
eye, 3, 111
„ „ range, 63-68

,, „ summary, 456-460

Pilobolus heterosporus, and P. Kleinii,

199
,, „ illustration, 208

„ „ taxonomic de-

scription, 207-
208
Pilobolus Kleinii, abnormal discharge,
140
„ ,, abnormal form, 195

„ ,, aiming at a window,

62-63
„ ,, and P. crystallinus, 11

„ „ and P. longipes, 171-

177
„ „ and P. unihonatus,

171-177
„ „ and two beams of

light, 42, 43^5,
120-128
„ „ cracking of sporan-

gium wall, 186-187
„ „ development, 58-59

„ „ dimples in sporangium,

83, 84, 85, 186-189
„ „ discharge of gun, 131-

140
„ „ discharge of projectile,

45-46, 56-58
„ „ distance of discharge,

161
„ „ drops excreted by, 86-

88
„ ,, early drawings of, 191

„ ,, heliotropically curved

stipes, 37
„ ,, heliotropism, 91-109

history, 10, 196-197
„ „ illustrations, thirty-

five, 4, 8, 21, 23, 37,
42, 44, 57, 59, 62-
76, 83, 86, 91-101,
120, 124, 132-139
„ ,, images produced by,

105
,, ,, in culture, 169

,, ,, in pastures, 160

„ „ model of, 129

„ ,, number of spores in a

sporangium, 75
2k2

500

GENERAL INDEX

PUobolus Kleinii

, number of spores pro-

PUobolus longipes, contraction of ceU-

duced on a dung-

wall, 134

plat, 167

crystals, 88, 89-90

>»

J>

observed at Winnipeg,

„ „ dimplesinsporangium,

55

84,85

»»

»9

origin of name, 196

,, „ discharge of projectile,

»f

J»

parasites on, 18, 19

56-58

>»

5»

parasitised by Synce-

„ ,, discovery, 198

phalis nodosa, 20-22

,, ,, distance of discharge,

>>

»»

patterns on, 186-189

161, 162

>»

)>

plasmolysis of young

„ ,, drops excreted by,

and of ripe sporan-

87-88, 173

giophores, 33

,, ,, early drawing of, 191

>>

>>

projectile striking and

„ „ formation of fruit-

adhering, 151

body primordia, 50-

f»

»»

range of gun, 35, 63-68

54

>»

»>

relative breadth of

„ „ germination of spores,

sporangium and

50,51

subsporangiai swell-

,, „ growth of mycelium.

ing, 56, 57

50-52

99

»J

reticulations of gran-

„ „ heliotropic experiment

ules in, 195

with, 115-120

»»

)?

shape of light spot.

„ „ heliotropism, 58, 60,

100-104

61

»>

»»

spore pigment, 180

„ „ illustrations, forty-

»

>>

spores photographed.

four, 2, 21, 48-60,

117

64-89, 105, 106,

99

99

structure of sporangio-

117, 119, 136-189,

phore and sporan-

203

gium, 68-90

„ „ images produced by.

>»

>>

taxonomic description,

105-106

205

„ „ impact of sporangium.

99

?♦

variations in culture.

74

196-197

„ „ in culture, 169

99

5»

vitality of spores, 166

„ „ in pastures, 160, 162

99

)»

width-ratio, 183, 184

„ „ Nematode worms shot

99

>>

zygospores, 12, 13

away by, 7-8

PUobolus

Kleinii forma sphaerosporUy

„ observed at Winni-

11-12,

195, 196, 198, 199

peg, 55

PUobolus lentiger

, and P. oedipus, 196

„ „ osmotic pressure, 140-

PUobolus longipet

% abnormal sporangia.

144

213

„ „ parasitised by Syn-

»»

99

and P. Kleinii, 171-

cephalis nodosa, 18,

177

20-22

»*

99

and P. umbonatus.

„ patterns on sporangia.

171-177

186-189

»»

99

basal swelling, 180-

„ pure cultures, 49-50

183

„ „ range of gun, 35, 63-

ff

99

bombardment by its

68

projectiles, 49

,, „ reddish glow from, 90,

>»

99

cell-sap analysis, 146-

104

148

,, „ relative diameters of

»>

99

cell-wall, 136

sporangium and sub-

Jf

99

colourless sporangial

sporangiai swelling.

waU, 54-55

56,57

GENERAL INDEX

501

Pilobolus longipes, rhythmic develop-
ment, 58-62
„ „ sound of gun, 327

„ „ sporangia discharged

in compressor cell,
150-152
„ „ spore pigment, 180

„ „ spores, 170, 171

„ „ structure of sporangio-

phore and sporan-
gium, 68-90
„ „ taxonomic descrip-

tion, 203
„ „ trophocyst, 180-181

„ ,, vitality of spores, 166

width-ratio, 183, 184
Pilobolus microsporus, and P. crystallinus,

36
„ „ andP. roncZMS, 196,

197-198
„ cytology of, 14-17

of Brefeld, 12
Pilobolus minutus, taxonomic descrip-
tion, 215
Pilobolus Morinii, as a new species, 199
„ „ taxonomic descrip-

tion, 213-214
Pilobolus Mucedo, and P. anomalu^, 197
Pilobolus nanus, azygospores, 13
„ „ basal swelling, 181

„ „ chlamydospores, 198

„ ,, discovery, 198

„ early drawing of, 191
„ illustration, 212
,, sporangial apophysis,
200
„ „ taxonomic description,

211,213
„ „ yellow sporangia, 55

Pilobolus oedipus, abnonnal sporangia,
55, 213
„ „ club-shaped hvphae,

183
„ „ cytology, 14-17

„ „ height of sporangium

discharge, 10
history, 9, 192, 194-
198
„ „ illustration, 209

„ life-history, 10
„ number of spores, 74-

75
„ observed at Winnipeg,
56
of Brefeld, 11-12

ft
it

tt

Pilobolus oedipus, on mud, 3

„ ,, parasites on, 18

„ „ taxonomic description,

208-209
Pilobolus projectile, abnormal landing,

158-159
„ „ after landing, 77-85

„ „ aiming of, 41

„ „ attachment to sub-

stratum, 45-46
,, „ development, 58-62

„ „ discharge of, 45—46,

56-58
„ „ discharge of, illus-

trated, 60
„ dry weight, 36
„ „ force of discharge

of, 36
„ „ illustrations, 48, 60,

77-79, 84-85, 146-
151, 162, 164
landing of, 148-161
„ „ mass of, 36

„ „ rotation of, 46

„ ,, shot into water, 164

„ „ sticks where it

strikes, 58, 153
„ „ velocity after dis-

charge, 35, 66-68
Pilobolus puUus, taxonomic description,

215
Pilobolus roridv^, basal swelling, 181
„ „ Bolton's drawing of,

191
„ „ crystalloids, 77

history, 192-194, 195,
196
„ „ illustrations, 17, 204

„ „ parasites on, 18

„ ,, taxonomic description,

204^205
Pilobolus roseu^, taxonomic description,

214
Pilobolus Schmidtii, taxonomic descrip-
tion, 215-216
Pilobolus sphaerosporus, illustration, 207
„ „ taxonomic de-

scription, 206-
207
Pilobolus umbonutus, a new species, 169-

178, 199
„ „ a,rxd P. Kleinii,ni-

177
„ „ and P. longipes,

171-177

502

GENERAL INDEX

9>

Piloholus umbonatus, basal swelling, 181-

183
„ „ club-shaped hy-

phae, 183
„ discovery of, 169

„ general description,

170-177
„ illustrations, ten,

169-184, 210
„ Latin diagnosis, 178

„ observed at Winni-

peg, 55
„ „ origin of name, 169

„ „ patterns on spor-

angia, 186-187
„ „ spore pigment, 180

„ „ summary, 461

„ „ taxonomic de-

scription, 177-
178, 210-211
„ „ unique among Pilo-

boli, 174
,, „ width-ratio, 183,

184
Pilobolus urceolatus, history, 194
Pine needles, luminous, 442, 443
Pinus Banksiana, and Rhizina inflata,

340
Pinus laricio, osmotic pressure, 145
Piptocephalis arrhiza, as a parasite, 18,

19-20
Piptocephalis microcephala, as a parasite, ,

18, 19-20
Pits, of Morchellaceae, 310
Plants and animals, and sound, 344
Plasmelysis, of Pilobolus, 32, 140
Platycerium alcicorne, osmotic pressure,

145
Pleodorina, eye-spots of, 111
Pleotrachelus fulgens, and Pilobolus zy-
gospores, 12
„ „ as a parasite, 18-19

Pleurocystidia, and Omphalia fiavida,

412
Pleurotus citrinatus, pseudorhiza annual,

347
Pleurotus Ruthae, pseudorhiza annual,

347
Plukenet, L., illustration of Pilobolus,
192
„ on Pilobolus, 3, 191-192,
223
Plumbaginaceae, and Omphalia flavida,

433
Plumbago, and Omphalia flavida, 423

Plumbago, luminous leaf-spots, 439
Plumbago capensis, inoculation experi-
ments upon, 431
Poisonous substances, and ascus dis-
charge, 33, 230-
232, 291
„ „ effect on Pilo-

bolus, 27
Polypodium iriodes, osmotic pressure, 145
Polyporaceae, basidia not heliotropic,
324
„ escape of spores, 320

Polyporus, sclerotia, 453
Polyporus squamosus, and Collybia radi-

cata, 394
„ „ blocking layer, 166

,, „ parasitism of, 432

Poly stigma rubrum, red pigment, 281
Poplar root, and Sarcoscypha protracta,

396
Populus alba, osmotic pressure, 145
Porto Rico, Coffee-disease in, 398—401
Postage stamp, and Pilobolus spor-
angium, 161
Potassium nitrate, and ascus discharge,

230, 232, 291
Premature discharge, of Pilobolus spor-
angia, 32-33, 88
Pressure, applied to Pilobolus, 30-31
Primary alveolus, of Morchellaceae, 313
Primitive eyes, of Volvox, 112
Primordia, of Pilobolus fruit-bodies, 26,
50-54
„ various, of Coprimis macro-

rhizus, 366
Primordial utricle, of Pilobolus, 140
Primordium (in Coprinus niacrorhizus),
of carpophore, 363
of gills, 364
of pileus, 366
of pileus-flesh, 365
of stipe, 365
of stipe-base, 366
of stipe-shaft, 366
of whole fruit-body, 366
Pringsheim, E. G., and Czurda, V. (on

Pilobolus), ballistics, 35-36
Pringsheim, E. G., and Czurda, V.,helio-

tropism, 36, 42-43
Pringsheim, E. G., and Czurda, V., range

of gun, 63
Pringsheim, E. G., and Czurda, V.,

velocity of projectile, 68
Problem of reaction of Pilobolus to two
beams of light, 120-128

GENERAL INDEX

503

Protection of Pilobolus spores, 165-166,

167
Protoplasm, and discharge of sporangia,
33
„ cleavage of, 14, 15, 16, 17

„ flow of, in Pilobolus, 50

„ of asci, stimulation of, 231,

232, 291
„ of Pilobolus sporangiophore,

70-72, 91, 92
„ permeability and excretion

of drops, 28
red, 18, 53, 54
Protoplasmic bridle, in ap. ascus, 291,

293, 302
Protoplasmic septum (of Pilobolus), 69-

71, 91-93, 98,
101, 103, 115,
119, 123, 125-
128
„ „ expulsion of, 137,

139
Protospores, of Pilobolus crystallinus,

16
Protozoa, eye-spots. 111
Protuberancy of asci, 245, 246, 271-273
Psalliota campestris, early developmental

stages, 363, 364
,, „ geotropic adjust-

ments, 267
„ „ packing of gills, 319

Psathyrella disseminata, colloidal drops,

87
Pseudoplectania nigrella, audible puffing,

332
Pseudorhiza, account of, 347-396
,, and a sclerotium, 373

,, and a true root, 349

and darkness, 372-373
,, and evolution, 240, 396

„ and gravity, 370

„ and light, 351

„ and mycelial cords, 347

„ and pseudosclerotia, 347

„ and sclerotia, 347

„ and secondary fruit-bodies,

372
„ and spores, 394

„ annual and perennial, 347,

393, 394
„ as an organ, 352, 372, 393-

394
„ attached to a root, 349-351

„ branched and unbranched,

347

Pseudorhiza, branching of, in Collybia

fusipes, 386-389
branching of, in Coprinus

rnacrorhizus, 371
branching of, in SarcoscypJm

protrada, 239-240, 395-

396
conduction of food-
materials, 393
crookedness, 354
development, 348-349, 353,

362-368, 386-389
erroneous description of,

373
evidence of persistence,

385-386
excavation of, 349, 361
function of, 368, 370, 372,

385, 393-394
fusoid part of mechanical

importance, 351
geotropism, 393
healing of wounds in, 390-

392
hollow, 353

increases in thickness up-
wards, 354
intercalary growth, 366-

367, 393
length of, and soil depth,

351, 353
mechanical support given

by, 393
negatively geotropic, 354
obstacles encountered by,

370
of Collybia fusipes, 374-394
of C. radicata, 247-252
of Coprinus rnacrorhizus,

355-373
of Mycena galericulata, 352-

355
of Sarcoscypha protracta,

239-240, 394-396
origin of name, 347, 349
perennial, account of, 374-

396
secondary, 395
solid, 351, 367
solid or hollow, 370
summary, 468-470
supposed downward

growth, 359
tapering extremity, func-
tion of, 351

504

GENERAL INDEX

Pseudorhiza, tortuous course of, 370
„ upward growth of, 393

„ variable length, 349-351,

370
Pseudorhizae, lateral grafting, 389-390
Pseudorhizal mass, of Collyhia fusipes,

389-390
Pseudorhizal strand, of C. fusipes, 381,

382, 384
Pseudosclerotia, and the pseudorhiza,

347
Pteridophyta, and Omphalia flavida, 433
Ptychogaster, and O. flavida, 417
Ptychoverpa, fruit- body form, 321
Ptychoverpa bohemica, curved asci, 322-

323
„ ,, heliotropic asci,

323-324
„ „ large spores of, 237

Puffing, a mechanical phenomenon, QSl
and a blast of air, 257-260
and animals, 308
and darkness, 342
and heat, 232

and law of inverse squares, 342
and poisonous substances, 230-

232
and salts, 230

and sornid production, 329-343
and the ear, 331-332, 341-342,

343
and touching, 232, 304, 305, 308,

309
and wind, 308, 332
as a ballistic phenomenon, 261
caused by a stimulus, 231-232
comparative sounds, 342
definition of, 227-228
direction of, 240-243, 283, 307
duration in minutes, 342-343
duration in seconds, 333, 334
effect on air, 260-262
energy of sound waves of, 342
explanation of cause of, 231-232
hiss produced by, 257, 259
historical remarks on, 228-232
illustrated by photographv, 232-

234
in Aleuria vesiculosa, 333-334
in A. vesiculosa under natural

conditions, 303-304
in Ascobolus stercorarius, 336
in Ciliaria scutellata, 283, 336
in Discomycetes, 227-263, 327-
343

PuflBng, in Galactinia badia, 305, 335
in Morchellaceae, 321
in Otideae, 310, 330-331, 335
in Peziza aurantia, 334
in Pustularia catinus, 331-332
in Pyronema confluens, 336
in Rhizina influta, 340-343
in Sarcoscypha protracta, 227-

263
in the field, 238-239
in Urnula Craterium, 335-336
in U. geaster, 336-340
method of making audible, 331-

343
significance, 235, 262
sound of, 230, 238, 328-343
successive, 299, 303, 331, 340-

341
summary, 462-465
under natural conditions, 303-
304, 343
Pulvinus of leaves, and heliotropism, 110
Purton, T., on Pilobolus, 194, 197, 223
Pustularia, and sound production, 328-
329
„ projectile, 325

„ tactiosensitive, 232

Pustularia catinus, audible puffing, 331-
332, 333, 340
,, ,, illustration, 332

Puttemans, M. A., on Omphalia flavida,
432
„ „ on Stilbella flavida,

406, 407
Pycnopodium, and Pilobolus, 195
Pycnopodium lentigerum, and Pilobolus,

195
Pycnospores, and ultraviolet light, 166
Pjrrenomycetes, ascus discharge, 231
Pyronema confluens, apothecial develop-
ment, 297
,, ,, audible puffing, 332,

336

QuELET, on Ciliaria, 279
Quercus, and CoUybia fusipes, 374
Qu£rcus Robur, and C. radicata, 348

Rabbits, and Pilaira, 179

„ and Pilobolus, 179
Rabinovitz-Sereni, on resistance of
spores to ultraviolet light, 166

GENERAL INDEX

505

Radiosensitive Discomycetes, 232, 268-

270, 321
Rain, and Pilobolus, 3, 161, 163, 167

„ and stilbum-heads, 401
Rain-water, and Collybia radicata, 351
Ramsbottom, J., and Collybia fusipes, 378
Range, of Pilobolus gun, 63-68
Ray, J., first record of Pilobolus, 3, 191,
192, 223
„ „ on Ciliaria sctdellata, 278
Rays of fringe, in Piloboli, 176
Rea, C, on Mycena galericulata, 355
Receptacle, of Morchellaceae, 310, 311,

317
Recoil of apothecium, during puffing,

261-262
Red colour, of Ciliaria scutellata, 278
,, „ of Sarcoscypha, 235, 237

Red colouring matter, in various fungi,

281
Red disc, of Pilobolus, 104
Red eye-spots, of Protozoa, 111
Red particles, in paraphyses, 251
Red pigment, in eyes of Pilobolus and
Volvox, 113, 115
„ ,, of Pilobolus, function, 71,

99, 115, 137
Red protoplasm, of Pilobolus, 71, 91, 92,

104, 119, 130-131, 137
Reflection of light, from Pilobolus, 102-

103
Refraction of light, in Pilobolus, 91-96,

103
Refractive index, of paraffin oil, 109
Refractive indices, for Pilobolus, 93-96
Regel, K., on heliotropism of Pilobolus,

36,37
Rehm, H., on Ciliaria scutellata, 278
,, ,, on Galadinia badia, 305
,, ,, on Peziza vesiculosa, 290
„ „ on Sarcoscypha protracta, 236,
237
Relhan, R., on Pilobolus, 194, 223
Retina, in Pilobolus eye, 98-99
Rhizina, and sound production, 329
Khizina iyiflata, and distance from ear,
341-342
audible puffing, 332,

340-343
illustration, 341
long duration of pufifing,

342-343
mucilage, 300
nature of sound pro-
duced by, 343

Rhizina inflata, puffing in the dark, 342
„ ,, puffing in the open, 304,

343
Rhizomorpha subterranea, black pigment,

166
Rhizomorphs, of Sclerotium coffeicola,

452
Rhythmic development, of Pilobolus

longipes, 58-62
Rhytisma acerinum, puffing, 228, 230
Rhytisma salicinum, puffing, 229-230
Ribs, of alveoli of Morchellaceae, 312-

313, 317
Ricken, A., on Mycena galericulata, 354
Ridges, in alveoli of Morchellaceae, 317,

319
Riss-stelle, of Pilobolus, 71, 135
Ritter, H., drawings of Pilobolus urn-
bonatus, 210
,, ,, finds a new Pilobolus, 169
Roberts, H. F., heard puffing, 341
Root, and pseudorhiza, contrasted, 349
Rooting base, of Agaricaceae, 347, 357
,, of Hymenomycetes, 239
Root-parasite, Collybia Jusipes as a, 379,

393
Roots, and Collybia fusipes, 392

,, pseudorhiza attached to, 349-
351, 379-380, 386, 388
Root-tip, and pseudorhiza, 353
Rosaceae, and Omphalia flavida , 433
Rosellinia, spore-colour and light, 165-

166
Rotati6n, of Pilobolus projectile, 152,

153, 156
Roundworms, and Pilobolus, 5
Roze, E., et Cornu, M., on Pilobolus, 198,

223
Rubiaceae, and Omphalia flavida, 433
Rutaceae, and 0. fiavida, 433

Saccardo, p. a., on Pilobolidae, 9, 190,
223
,, „ on Sarcoscypha pro-

tracta, 236
Saccharum officinale, osmotic pressure,

145
Saccobolus, heliotropism of asci, 265,
266
„ illustration, 266

Sachs, J., on Ascobolus furfuraceus, 273
Sahara, osmotic pressure in the, 144
Salts, and puffing, 230-231, 232

5o6

GENERAL INDEX

Saprolegnia, dehiscence of sporangium,

73
Sarcoscypha, description, 235
Sarcoscypha coccinea, heard by Durand,

331

„ „ illustration, 330

„ „ occurrence, 236

,, ,, red pigment, 301

Sarcoscypha protrada, a specialised Dis-

comycete, 264

„ „ anastomosis in

paraphyses, 300

„ „ and CoUybia fusi-

pes, 240, 294-
296

„ „ and Morchella,

318

„ „ andMorchellaceae,

269-270

„ „ angle of aperture,

242

„ „ ascus as an ex-

plosive mechan-
ism, 243-250

„ ,, audible puffing,

332

„ „ bending of ascus,

255

„ „ blast of air pro-

duced bv, 257-
260

„ „ campanulate apo-

thecium, 240-
243

„ „ contraction of

ascus, 246-247,
251

„ „ correlations and

efficiency, 253-
25i

„ „ direction of puff-

ing,240-243,246

„ „ discovery at Win-

nipeg, 237

„ „ distribution, 236-

237

„ „ illustrations,

eleven, 238-
258, 395

„ „ large spores of,

237

„ „ paper on, 266

„ „ paraphyses, 244,

251, 252, 253-
254

Sarcoscypha protracta, pigment, 301

„ „ presumed helio-

tropism of asci,
255
„ „ pseudorhiza, 239-

240, 394-396
puffing, 227-263
,, „ puffing in the

field, 238-239
„ „ radial-longitu-

dinal sections,
249, 250-253
recoil of, 261-262
,, ,, spore dispersal,

262-263
,, „ spore position,

244-246, 252
„ „ summary, 463-

465
„ „ surface views of

hymenium,250-
253
„ „ synonyms, 236

„ „ test-tube experi-

ment with, 257-
260
Sarcosphaera coronaria, audible puffing,

332
Scales, hairy, of Coprinus macrorhizus,

363-364
Scarlet pigment, in hymenium, 301
Schizophylluin commune, spore-walls and

light, 165
Schmidt, A., on Pilobolus, 223
Scientific Club of Winnipeg, puffing

heard by, 341
Sclerotia, and pseudorhiza, 347

„ of Sclerotinia sclerotiorum, 233

„ of Sclerotium cojfeicola, 445,

446, 451-453
„ retention of vitality, 452
Sclerotinia baccata, a synonym, 236
Sclerotinia libertiana, puffing, 232-234
Sclerotinia sclerotiorum, illustrations, 233,

234
puffing, 232-234
„ „ recoil of apothe-

cium, 262
Sclerotinia tuberosa, heard by Durand,

331
Sclerotium, and the pseudorhiza, 373
„ definition of, 373

„ of Coprinus stercorariiis, 359

„ supposed, in CoUybia fusipes,

375-376, 378, 384-385

GENERAL INDEX

507

Sclerotium, supposed, in Sclerotinia

baccata, 236
Sclerotium coffeicola, a basidiomycete,

445, 453
„ „ and Clavariaceae,

454
„ „ and Omphalia fla-

vida, 445, 446,
447, 454
„ „ and Typhula, 453

„ „ entry into leaves,

448^51
„ ,, gemmifers of, 443-

454
„ ,, illustrations, eight,

444-453
„ ,, name, 443

„ „ not luminous, 441

„ „ sclerotia, 451^53

„ ,, summary, 472

Sclerotium disease, of Coffee, 444 446
Scolecite, of Ascobolus stercorarius, 273,

276, 277
Scopoli, J. A., on Pilobolus, 8, 192-193,

223
Scotland, luminous leaves in, 442
Scott, K., heard puffing, 341
Seaver, F. J., on Melastiza Chateri, 285
„ „ on obUque ascostomata,

255-257, 285
„ „ on Ptychoverpa bohemica,

324
Secondary alveoli, of Morchellaceae, 313,

314
Secondary mycelium, of an apothecium,

276, 277, 297
Selaginella mertensii, osmotic pressure,

145
Senn, G., on refraction of light in

Vaucheria, 93
Septum of protoplasm (in Pilobolus), 91,

92, 93, 98-99,
115, 119
„ „ „ expulsion of, 137,

139
Sessile apothecium, construction of, 298
Setae, of Cheilymenia vinacea, 285, 286

„ of Ciliaria scutellata, 280, 281
SejTnour, A. B., on Syncephalis nodosa,

20
Sex, in the Pilobolidae, 12-13
Shadow (in Pilobolus), of sporangium, 166

„ of subsporangial swelling, 100
Shadow photograph, and Omphalia
flavida, 438

Sheep dimg, and Pilobolus, 13, 170
Shirai, M., on CoUybia fu-sipes, 375

„ „ on C. radicata, 348
Sigmoid curvature (of a pedicel), 420-
425
„ „ in a vertical plane,

422
„ „ when absent, 422

,, ,, significance, 423^25

Silver nitrate, and ascus discharge, 230,

232, 291
Simple method for making puffing

audible, 321-343
Skewer observations, on Collybia fusipes,

385-386
Smooth rim, of oi)en Pilobolus sporangio-

phore, 146
Snail, eye of, 99

Sodium carbonate, effect on asci, 291
Sodium chloride, and ascus discharge,

230, 232, 291
Sodium hydroxide, effect on asci, 291
Soil depth, and pseudorhiza length, 351,

353
Sordaria, spore-colour and light, 165
Sorokin, X., on Pilobolus, 36
Sound, and plants and animals, 344

of fungus guns, 325-344, 467^68
„ of Pilobolus projectiles hitting

glass, 49
„ of puffing, 230, 238, 257, 328-343,

467-468
,, of Sphaerobolus gun, 327
Sowerby, J., on Pilobolus, 193, 223
Spatial arrangements, for basidia and

asci, 319
Spegazzini, C, on Ompjhalia flavida, 408

„ on Pilobolus, 199, 223
Sphaerella mffeicola, on Coffee leaves,

401
Sphaerobolus, and Peziza, 326

and Pilobolus, 194, 326
„ has loudest fungus gun,

326
„ impact sound of projectile,

326
„ sound of gun, 326

Sphaerobolus iowensis, range of projectile,

326
Sphaerobolus stelkUv^, projectile and its

range, 32.5-326
Sphaerobolus stellatus var. giganteus,

326
Spinellus fusiger, crystalloids, 17-18
Spiral rolling, of Pilobolus cell-wall, 137

5o8

GENERAL INDEX

Sporangia (of Pilobolus), height of dis-
charge, 10, 6a-67
crystals on, 88, 89-90
dispersion, 131

dried discharged, in fields, 160
float in water, 153-156
on grass-blades, 164
orange-yellow, 54-55
patterns on, 184-189
premature discharge, 32-33
worms shot away with, 6-8
yeUow, 212-213
Sporangiophore (of Pilobolus), and caro-
tin, 18
„ contraction of, 132-140

„ division of labour in, 107

,, structure, 68-90

Sporangiophores, of Mucor and Pilobolus,

1-2
Sporangium (of Pilobolus), after being
shot away, 148-149
„ attachment of, 10, 45^6,

148-161
„ contraction on drying, 83

„ dissection of, 81-82

drops on, 86, 87-88
„ drying up of, 82-85

„ removal with a needle,

75-76
„ structure, 56, 68-90

„ submerged, 154

Sporangium wall, of Mucor and Pilobolus

compared, 167
Sporangium wall (of Pilobolus), breaking
up, 74, 77, 78
characteristics, 72
colourless, 54-55
crystals on, 88, 89-90
function, 165-166
lower band of, 72, 76
supposed breaking

down, 46
„ unwettable, 153, 155-

156, 163-165
Spore-cloud, of Sarcoscypha protrada,
240,241,257
„ of Sclerotinia sclerotiorum,

photographed, 232
Spore-discharge, and external conditions,
235
„ and heliotropism of

asci, 264-324
„ and movement of air,

260-262
„ effect on air, 269

Spore-discharge, in Morchella, and tem-
perature, 320-321
„ in Morchella esculenta,

exposed to sun, 301
„ in radiosensitive Dis-

comycetes, 321
Spore-dispersal, in Discomycetes and
Hymenomycetes, 324
in Pilobolus, 10-11, 74,
167
Spore-size, and wind, 320
Spore-stream, in Morchellaceae, 321
SpoTeVmg,s,oi Pilobolus cry sf/iUinus, 16, 17
Spores, and the perennial pseudorhiza,
394
and wind, 320
large, of Ptychoverpa bohemica,

324
largest in Discomycetes, 237
movement in an ascus, 283, 284
not produced by a gemmifer,

406, 410
of Discomycetes and Agaricaceae,

320
of Morchellaceae, escape of,

268-270
position in an ascus, 291
shape of, in Coprinus lagopus
and G. macrorhizus, 356
Spores (of Pilobolus), and impact of
sporangium, 74, 77, 78, 79-80
„ carotinoid pigment in, 180
,, development, 15-17, 61
„ dichroism, 72

,, germination, 10, 17, 50-51, 181
„ nuclei of, 16-17
,, number, 74-75, 167
„ protection of, in discharged spor-
angia, 150
„ vitality of, 165-166
Spores durables, of van Tieghem, 13
Sporobolomycetes, spore-discharge, 227
Sporodinia grandis, crystalloids, 17-18
,, ,, drop-excretion, 89

Sporophore-rudiments, metamorphosis

of, 454
Sporophores (of Omphalia flavida), in
nature, 417
,, structure, 410-414

Spot of light, as a photochemical stimu-
lus, 121
„ „ „ in eye of man and of

Pilobolus, 115
„ „ „ in Pilobolus, 92, 93, 95-98,
100-101, 104-106

GENERAL INDEX

509

Spot of light, in Pilobolus, movement of,
116,118-119,121-128
„ „ „ in Pilobolus, shape of,

100-104
pring, appearance of Morchellaceae and
Helvellaceae in, 320
Squirt, ascus as a, 247
Squirting, of an ascus, 291
'Squirting apparatus, of Pilobolus, 2, 41
Squirting function, of subsporangial

swelling, 90
Squirting mechanism, of Pilobolus gim,

131-132
Stahel, G., on Sclerotium cojfeicola, 443-

454
Stakman, E. C, on recoil in Sclerotinia

sclerotiorum, 262
Sterile ribs, of Morchellaceae, 313, 317
Sterility, of mycelium of Omphalia

flavida, 433-434
Stem, K., on electro-osmosis, 31
Stilbellu flavida, 406
Stilbum, and a stilbum-hody, 416

„ a,nd Stilbum flavidum, 403
Stilbum flavidum, as a stage in Omphalia
flavida, 401-406
„ „ as aborted O. flavida,

404, 412
., „ origin of name, 401

Stilbum-hodiea (of Om,phalia flavida),
401, 402, 405, 406
„ evolution of, 416

„ origin of, 415-416

Stilbum-hody (of Omphalia flavida), an
effective organ, 416
„ as a gemmifer, 416-418

,, misnamed, 416

„ never produces spores,

406, 410
„ structure, 406-410

Stilbum-he&d (of Omphalia flavida), 397,
401, 404, 405, 406, 407
„ and infection of Coffee

leaves, 401
detachable, 401,406
Stimulus, and ascus discharge, 231, 232,
291
„ heliotropic, in Pilobolus, 96-
97, 100, 122-123, 125
Stipe, of Helvellaceae, 321

of Morchella conica, 315, 317
of Morchellaceae, 310
of Pilobolus, 53, 56, 69, 90-109,
130-131
Stipe-bases, of CoUybia fusipts, 381, 385

Stipe-shaft, elongation of, 367-368
Stipes, function, 320
„ hollow, 315
„ of Agaricaceae, rooting bases,

347
„ of Agaricaceae and Morchellae,

315
„ of Copriniis lagopus and C.
macrorhizus, 357
Stipitate apothecia, recoil of, 262
Stomatic clefts, and Sclerotium, cojfeicola,

450
Stone, R. E., on CoUybia fusipes, 375
„ ,, on puffing of Helvetia

elastica, 329-330
Strains, in an ascus wall, 231
Streaming of protoplasm, in Pilobolus,

51,53
Stroking away a Pilobolus sporangium,

75-76
Strongylus larvae, and Pilobolus, 5
,, ,, illustrations, 6, 7

Strongylus vulgaris, and Pilobolus, 5
SubpUear spaces, 320
Subsporangial swelling (of Pilobolus), 56,

69,75
abnormal dis-
charge of, 140
and discharge of

gun, 131-140
as a lens, 5, 111
breadth and ex-
ternal condi-
tions, 33-34
contraction, 132-

140
development, 58-

61
drying of drops

on, 86, 87
images produced

by, 105
intercalation of,

166
ocellus fimction

of, 90-109
pyriform or ellip-
soidal, 173
rolling-up of frag-
ments, 137
shadow of, 100
shape of different

species, 180
summary, 456-
459

510

GENERAL INDEX

Subsporangial swelling, two functions of,

90
„ „ variations in

width, 183-184
,, „ worms on, 6

Substratum, of Coprinus lagopus and

C. macrorhizus, 357
Suction pressure, in Pilo bolus, 30-31
Sugar, in Pilobolus, 148
Sugar solutions, and Pilobolus sporangio-

phore, 33
Sulphuretted hydrogen vapour, effect on

Pilobolus, 27
Sulphuric acid, action on dried Pilobolus
sporangia, 84
„ „ and ascus discharge, 33,

230, 232
Sumatra, luminous fungi in, 442
Sun, and Gyromitra, 321
„ and Morchellae, 321
„ and radiosensitive Discomycetes,

321
,, and Verpae, 321
Sunlight, and apothecial pigments, 301
and puffing, 303-304
„ and spore-discharge in Mor-
chella escuhnta, 301, 321
Sunshine, and Pilobolus spores, 165

„ and spore-discharge in Mor-

chella and Gyromitra, 320-
321
Sun's rays, injury of spores by, 165
Support, mechanical, in fungi and

flowering plants, 315
Surface tension, and Pilobolus, 153-156
Sympodial growth, in an apothecium,

275-277, 297
Sympodium, of persistent stipe-bases,

381
Syncephalis, and Pilobolus zygospores, 12
Syncephalis nodosa, a parasite on Pilo-

boli, 18, 19-20, 49
„ ,, description of, 20-22

„ „ illustration, 21

Syncephalis reflexa, a parasite on Pilo-

boli, 18, 19-20
Syncephalis sp., as a parasite, 18, 19

,, ,, illustration, 19

Syringa vulgaris, osmotic pressure, 145

Tabernaemontana, and Omphalia

fiavida, 432
Tactiosensitive Discomycetes, 232, 268,

303

Taxonomic description, of Pilobolus

umbonatu^, 177-178
Taxonomy of Pilobolidae, additional

criteria, 180
Temperature, and puffing, 235

„ and puffing of Sarcoscypha

protrada, 240-241
„ and spore-discharge in

Morchellaceae, 320-321
„ rise of, in Morchella escu-

hnta, 321
Temperaturstromungen, Falck's view on,

268, 318
Tensions, in ascus wall, 231, 232
Terminal basal swellings, in Pilobolus,

181-183
Test-tube experiment, on Pilobolus,

154
„ ,, on puffing in <Sar-

coscypha pro-
tracta, 257-261
Thames mud, and Pilobolus, 3, 192
Thaxter, R., on Pilobolus umbonatus,
170, 178
,, ,, on zygospores of P.
Kleinii, 13
Thornbury, H. H., photograph made by,

438
Thunderstorms, and Pilobolus, 161
Tilletia, sound of spore-discharge, 227
Time of appearance, of Morchellaceae,

320
Tode, H. J., on Pilobolus, 4, 6, 8, 193,

223
Torsion, in heliotropic reactions, 110
Touch, and puffing, 304, 305, 308, 309
Trail, J. H. W., on Sarcoscypha protracta,

236
Transverse ridges, in alveoli, 317, 319
Trehalose, and Pilobolus, 148
Tricholoma macrorhizum, pseudorhiza,

347
Trophocyst, of Piloboli, 180-183

,, of Pilobolus longipes, 51,

52, 53, 60, 61
,, of P. umbonatus, 172

,, origin of name, 53, 58

Tuber, of Pilobolus longipes, 50, 51, 52,

53, 60, 61
Tuck, in sporangium wall of Pilobolus,

79, 84
Tulasne, L.-R. and C, on Ascobolus ster-

corarius, 273
„ on puffing, 229,
230

GENERAL INDEX

511

Turgor, in Pilobolus, 26, 27, 30, 32, 33,

57
Turgor pressure, and drop-excretion, 88
of Pilobolus, 147, 148
„ „ of Pilobolus cell-sap,

140-145
Two beams of light, and Pilobolus
heliotropism, 41, 42^5, 120-128,
458, 459
Two-spored basidia, of Mycena galericu-

lata, 355
Types of fungus guns, 325
Typhula, and Sclerotium coffeicola, 453-
454
„ sclerotia, 453
Typhula gyrans, a parasite, 454
Typhula variabilis, a parasite, 454
Typhula varians, a parasite, 454

Ulmus campestris, osmotic pressure, 145
Ulmus crassifolia, Urnula geaster on

roots of, 337, 338, 339
Ultraviolet light, effect on conidia, 166
Umbo, of Pilobolus umbonatus, 169, 176-

177
Unequal illumination, and heliotropic

response, 107-109
United States of America, luminous

leaves in, 442
Universal veil, of Coprinus macrorhizus ,

363, 364
Untouched apothecia, puffing of, 303-

304
Unwettability, of collar of Pilobolus,
134-135
„ of sporangium wall of

Pilobolus, 46, 72, 89,
153-156, 158, 165
Uredineae, and sound of spore-discharge,
343-344
„ basidiospores as projectiles,

325
„ parasitism, 431-432

„ red pigment, 281, 282

„ spore-discharge, 227

Uredinopsis, and Ferns, 432, 433
Umula, and sound production, 329
Urnula Craterium, audible puffing, 332,
335-336
,f „ heliotropism of asci,

309, 335
>. „ illustrations, 309, 335,

336

Urnula Craterium, paraphyses anhelio-
tropic, 308
„ „ puffing, 308

,, ,, puffing in the open,

304
Urnula geaster, audible puffing, 332, 336-
340
„ „ illustrations, 337, 338,

339
Ursprung, A., and Blum, G., capillary-
tube method, 31
Ursprung, A., and Blum, G., experiment

on Pilobolus, 30-31
Ustilagineae, parasitism, 431-432
Utah desert, osmotic pressure in the, 144

Vacuole, of Pilobolus fruit-body, 69, 70
Vahl, M., on PUobolus, 193, 223
Vaillant, S., on Ciliaria scutellata, 278
Van der Wey, H. G., on heliotropism in

Pilobolus, 36, 43^5, 121, 128
Vanterpool, T. C, and Galactinia badia,
307
,, ,, and Omphalia flavida,

405-406, 430^31,
432-433
,, ,, on 0. flavida, 439

Van Tieghem, P., drawings of Piloboli,
191
„ „ on azygospores of Pilo-

bolus nanus, 13
,, ,, on crystalloids of Phy-

comycetes, 17-18
„ „ on crystals on Pilo-

bolus, 89
,, ,, on dehiscence in Pilo-

bolus, 73
,, „ on parasites of Pilo-

bolus, 18-20
,, „ on patterns on Pilo-

bolus crystallinus,
185-186
„ „ on Pilaira, 9, 198

„ „ on Pilobolidae, 223

,, „ on Pilobolus, 9

„ ,, on Pilobolus longipes,

180
,, ,, on P. nanus, 55

,, „ on P. oedipus, 55

„ ,, on Pilobolus species,

196, 197-198
„ ,, on Synceplialis nodosa,

20

512

GENERAL INDEX

Van Tieghem, P., on zygospores of

Pilaira anomala, 12, 198
Variations, in Pilo bolus patterns, 187-
189
„ in width-ratios of Piloboli,

183-184
Vaucheria, refractive index for, 93
Verpa, and Ptychoverpa bohemica, 323-
324
„ fruit-body form, 321
„ radiosensitive, 232
„ significance of puffing, 235
„ sun's effect on, 321
Verpa bohemica, a synonym, 323
Vertical range, of Pilobolus gun, 63-67
Virginia, Pilobolus discovered in, 3,

191
Vitis sicyoides, and Sclerotium disease,

444
Vitis Veitchii, osmotic pressure, 145
Vochting, H., on perception of light by

leaves, 110
Volvocaceae, eye-spots of. 111
Volvox, a heliotropic reaction by, 114
„ and Argus, 113
„ and Pilobolus, 111-115
,, illustrations, 112, 114
„ mechanism of heliotropic re-
actions, 112-115
,, structure cf eye, 112
Volvox globator, eyes of, 113
Von Marilaun, K., on Anthopeziza

Winteri, 236
Von Waldheim, A. F., on Pilobolus, 36
Vuillemin, P., on Aleuria Asterigma, 290

Wakefield, E. M., and Oalactinia badia,

307
„ ,, and Pustularia cati-

nus, 332
„ „ on Collybia fusipes,

385-386, 387, 392
Walker, L. B., on Sphaerobolus pro-
jectiles, 326
Wall (of Pilobolus sporangiophore), 70
,, elasticity of, 87
,, fragments of, 137
,, mucilaginisation of, and drop ex-
cretion, 88
Wall (of Pilobolus sporangium), char-
acteristics, 72
,, dehiscence of, 72, 73-74
„ fragments of, 74, 77, 78, 80

Wall-tuck, in Pilobolus, 84, 85
Warming, effect of, on Morchellaceae,

268-270
Warmth, and Gyromitra, 320-321
and Morchella, 320-321
Water, adhesion to discharged Pilobolus
sporangium, 153
„ and formation of a subsporangial

swelling, 34
„ and sporangium wall, 89-90
„ bursting of Pilobolus under, 137
„ excretion of, by Pilobolus, 22-31
,, withdrawal of, from asci, 291
Water-excretion energy, measurement

of, 26
Watery drops, excreted by Pilobolus, 86,

87-88
Waxy Peziza, 303
Weber, and Pilobolus, 193
Weir, J. R., on Coprinus macrorhizus,

359, 363, 371, 372, 373
Weis, A., on drop-excretion, 28-29, 30
Welsford, E. J., on Ascobolus furfuraceus,

273
Westerdijk, J., on a culture method for

Basidiomycetes, 404
Width-ratio, of Piloboli, 175, 180, 183

„ of Piloboli, definition of,

183
Wiesner, J., on heliotropism, 37
Wiggers, F. H., on Pilobolus, 193, 224
Wilson, W. P., on excretion of drops by

Pilobolus, 22, 27-28
Wind, and gemmae, 420, 423-425, 448
„ and Pilobolus sporangia, 160, 161,

163
„ and puffing, 235, 308
„ and spore-dispersal after puffing,

262
„ and spore-size, 320
,, and stilbum-he&ds, 401
Window experiment, on Pilobolus, 62-63
Wistaria sinensis, osmotic pressure, 145
Withering, W., on Pilobolus, 193, 224
Wood, luminous Mycenae growing on,

442^43
Worms, and Pilobolus, 3-8, 192, 194
Woronin, M., on archicarp of Ciliaria

scutellata, 281
Wounds, and infection by Omphalia
flavida, 402
„ and inoculation of leaves, 430-
431, 433-434
healing of, 390-39^
Wrinkles, in sporangia, 180

GENERAL INDEX

513

Xylaria, spore-colour and light, 165-

166
Xyloma salicinum, pufiing, 229

Yautia, and Omphalia flavida, 433
Yellow pigment, in apothecial hymenium,
301

Zebrina pendula, and Omphalia flavida,

433
Zelhier, J., on lipochromes and carotin,

281, 282
Ziegenspeck, H., on puffing, 231-232
Zobel, and Pilobolus, 195
Zones of mycelium, in Omphalia flavida,

435
Zoophyte, Pilobolus as a, 3^
Zopf, W., imperfect drawing of Pilo-
bolus, 191

„ „ on carotin in Pilobolus, 18,
71,99

„ ,, on heliotropism of asci, 265,
270

Zopf, W., on lipochromes, 281, 282
„ ,, on parasites of Pilobolus, 18,

19
„ ,, on patterns on Pilobolus crys-

tallinus, 186
,, ,, on Pilobolus, 224
,, ,, on Pilobolus crystals, 89
„ ,, on Sphaerobolus, 326
„ „ on zygospores of Pilobolus
crystallinus and P. Kleinii,
12, 13
Zygospore formation, and parasites,

12-13
Zygospores, of Pilaira anomala, 12, 13,
198
,, of Pilobolus Borzianus, 13,

199
,, of P. crystallinus, 12, 13, 202

„ of P. crystallinus, conditions

of formation, 13
M of P. crystallinus, illus-

tration, 12
of P. Kleinii, 12, 13, 205-
206