water — walled spores in the air) ; (2) by the condensation
of definite masses of protoplasm directly into thick-walled
spores (chlamydospores). Their generation shows all
gradations including the union of (1) ciliated isogametes;
(2) ciliated heterogametes; (3) ciliated sperms, with eggs;
(4) antherid nuclei, with eggs — in all cases producing
zygotes, which usually become thick-walled resting
spores.
266. The dominant idea here is the development of
coenocytes instead of distinct cells, and this has been
consistently adhered to even when the plant body has
shown otherwise a considera])le amount of differentiation.
184
CLADOPHORA AXD VAUCHERIA
1S5
267. They are typically aquatic, green plants (holo-
phytes), but many have become parasites or saprophytes,
and suffered degradation into ''fungi" (hysterophytes).
The number of species now known is about 1260. The
holophytes are readily separated into two classes, the
Lower Tube Algae (Vaucherioideae) and the Higher
Tube Algae (Bryopsidoideae), and from the first have
been derived a considerable number of hysterophytes
which may be separated as a class of Tube Fungi, or
Lower Fungi (Phycomyceteae).
268. Water Flannel (Cladophora) is one of the com-
monest genera of the Lower Tube Algae, occurring in
large tangled masses of stout branched fila-
ments in fresh-water streams, or even in
salt waters. Its coenocytes have thick
w^alls, with two to many nuclei. In their
propagation and generation they so closely
resemble Ulothrix and Microspora that they
were formerly included in the same famil3^
Zoospores with two or four ciUa escape
from the segments and after a free-swimming period
come to rest and grow directly into new plants. Like-
wise biciliated isogametes issue from similar segments,
and fuse into zygotes.
269. The Green Felts (Vaucheria) are good repre-
sentatives of one of the families in which the plant body
is a continuous coenocyte. They are
coarse, green, tubular, branching and
rooted plants which grow in abun-
dance on the moist earth in the vicinity
of springs, and in shallow running
water, forming dense felted masses.
270. They propagate by large compound motile zoo-
spores, formed in the ends of the branches. Each zoo-
FiG. 75.
Cladophora.
Fig. 76. — Vaucheri;
186 PHlTU^r IV. SIPHONOPHYCEAE
spore eventually forms a wall around itself, and then
proceeds to elongate into a new plant-body.
271. Generation takes place in special, usually lateral,
segments. Both antherids and oogones develop as pro-
tuberances upon the stem. The antherid is long and
rather narrow, and soon much curved; its upper portion
becomes cut off by a partition, and in it very small bi-
ciliated sperms are developed in great numbers. The
oogone is short and ovoid in outline, and usually stands
near the antherids. In it a partition forms at its base;
the upper portion becomes an oogone, and its protoplasm
condenses into a rounded body, the egg. At this time
the wall of the oogone opens, and permits the entrance of
the sperms which were set free by the rupture of the
antherid wall.
272. Upon coming into contact with the egg one sperm
fuses with it; the fertilized egg (zj^gote) immediately
begins to secrete a wall of cellulose about itself, and it
thus becomes a resting spore. After a period of rest the
thick wall of the resting spore splits, and through the
opening a tube grows out which eventually assumes the
form and dimensions of the full-grown plant.
Here must be placed half a dozen families of hystero-
phytic plants, the ''Tube Fungi," often known as the
''lower fungi," and to be regarded as degen-
j{i erate descendants of some such holophytic
' form as Vaucheria.
273. The Water-molds {Saprolegniaceae)
are colorless saprophytes or parasites. They
are generally to be found in the water,
Saproiegnia. attached to the bodies of living or dead
fishes, crayfishes, etc., or in decaying animal
or vegetable matter, in or out of the water. The plant-
body is greatly elongated and much branched, and is
WATER MOLDS 187
basally rooted. All its vegetative portion is continuous;
the reproductive portions only are separated from the
rest of the plant-body by partitions.
274. The propagation is very much the same as in
Green Felt. It may be briefly described as follows for
Saprolegnia: The protoplasm in the end of a branch
becomes somewhat condensed, a partition forms, cutting
off this portion from the remainder of the filament, and
the whole of its contents becomes converted by inter-
nal cell division into zoospores provided with two cilia.
These soon escape from a fissure in the wall and are active
for a few minutes, after which they come to rest and their
cilia disappear. In one or two hours they germinate by
sending out a filament, from which a new plant is quickly
produced.
275. The sexual organs also bear a close resemblance
to those of Green Felt. The oogones are spherical, or
nearly so (in most of the species), and contain from one
to many eggs, which are fertilized by means of antherids,
which usually develop as lateral branches just below the
oogones. Fertilization takes place by the direct contact
of the antherid and the passage of its contents into the
oogone by means of a tubular process from the former.
In some species there is no transfer of the contents of
the antherid, and in others again there are no antherids.
These eggs must therefore develop without fertilization,
indicating that sexuality is disappearing in these plants.
Eventually each egg becomes covered with a wall of
cellulose and is thus transformed into a resting spore,
which later germinates by sending out a tube, as in
Green Felt.
276. The Downy Mildews {Peronosporaceae) and
White Rusts (Alhuginaccae) live parasitically in the
tissues of higher plants. They are composed of long
188 PHYLUM IV. SIPHONOPHYCEAE
brant'liino; tubes, whose cavities are continuous through-
out. They usually grow between the cells of their hosts,
and draw nourishment from them ])y means of little
Dranches Hiaustoria), which thrust them-
selves through the walls.
277. The asexual spores (conidia) are
produced upon branches (conidiophores)
which protude through the epidermis of
Fig. 78.— Piasmopara the host. In the Downy Mildews (Per-
onospora, Phytophthora, Piasmopara,
etc. ) these branches find their way through the breath-
ing-pores and bear their spores singly upon lateral branch-
lets; in the White Rusts (Albugo) the conidia-bearing
branches collect under the epidermis and rup-
ture it. Here the conidia are borne in chains
or bead-like rows.
278. In some genera the relationship to the
Water Molds is shown by the fact that these
conidia upon falling into water become true
sporangia, within which few to many zoospores
are produced. These after a free-swimming period be-
come motionless and germinate by means of a tube which
bores its way into the host. In two genera, however
(Bremia and Peronospora), the conidia themselves germ-
inate directly by a tube.
279. The sexual reproduction takes place in the inter-
cellular spaces of the host. Lateral branches of two kinds
appear upon the hyphae; those of one kind (the young
oogones) become greatly thickened and finally assume a
globular shape; the other branches (the young antherids)
become elongated and club-shaped, both becoming sepa-
rated from the main filament by cross partitions. The
antherid comes in contact with the oogone which it
penetrates by a tube, through which fertilization occurs,
BLACK MOLDS LS9
and th('reu])oii the egg socretes a thick doubh' wall, and
becomes a resting spore.
280. The resting spores remain in the tissues of the
host until the latter decay, which is generally in the
spring. Germination then takes place, in some species
by the production of a tube (either germ-tul)e, or co-
nidiophore), in others by the division of the protoplasm
into zoospores whose subsequent development is like
that described above in case of the conidia.
281. The Black Molds (Miicoraceac) are saprophytic
and sometimes parasitic plants; they are composed of
long branching non-septate filaments (hj^phae), which
ahvays form a more or less felted mass, the mycelium.
The protoplasmic contents of the filaments are more or
less granular, but they never develop chlorophyll. The
cell walls are colorless, except in the fruiting filaments,
which are often dark-colored or smoky (fuliginous);
hence the name of Black Molds.
282. The mycelium sometimes develops exclusively in
the interior of the nutrient medium; in
other cases it develops partly in the me-
dium and partly in the air. In some
species the mycelium may attack the fila-
ments of other plants of the same order,
and even exhibit a weak parasitism upon
higher plants.
283. The reproduction of black molds is asexual and
sexual. In the asexual reproduction (propagation) the
mycelium sends up erect filaments, which produce few or
many separable reproductive cells — the spores. The
method of formation of the spores in a common black
mold (Mucor) is as follows: The vertical filaments,
which are filled with protoplasm, become enlarged at the
top, and in each an arched partition forms, constitut-
190 PHYLU.M IV. SIPHONOPHYCEAE
ing the so-called columella. The protoplasm in the
enlarged terminal segment (sporangium) divides into a
large number of minute masses (spores) each of which
surrounds itself with a cell wall.
284. The spores are set free in different ways: in some
cases the wall of the sporangium is entirely absorbed by
the time the spores are mature; in other cases only por-
tions of the wall are absorbed, producing fissures of va-
rious kinds. The spores germinate readily when on or in
a substance capable of nourishing them, by sending out
one or two filaments, which soon branch and give rise to
a mycelium. If kept dry, the spores may retain their
vitality for months.
285. Sexual reproduction (generation) may take place
after the production of asexual spores, but it appears to
be of rare occurrence in our commonest species. Two
filaments in the air or within the nutritive medium, in
contact send out small branches (here regarded as re-
duced sexual organs, the one an antherid, and the other
an oogone) ; these elongate and become club-shaped, and
at the same time become more closely united to each
other at their larger extremities; a little later a transverse
partition forms in each at a little distance from their
place of union; the wall separating the new terminal seg-
ments is now absorbed, and their protoplasmic contents
unite into one common mass (the zygote) ; the last stage
of the process is the secretion of a thick wall around the
new mass, thus forming a zygospore, i.e. a resting spore,
which eventually germinates and sooner or later gives
rise to a new plant.
286. In some Black Molds both gametes are formed
upon different branches of the same mycelium (homo-
thallic forms, monoecious). In many, however, the
plants are of two kinds (dioecious), and sexual reproduc-
INSECT FUNGI 191
tion occurs only when hyphae of the two kinds come into
contact (heterothaUic forms).
287. The Insect-fungi {Entomophthoraccne) are well
represented by the Fly-fungus {EntoniophtJiora muscae)j
which in the autumn is destructive to house-flies. It
consists of small tubular coenocytes which grow in the
moist tissues of the fly, and at last pierce the
skin, producing minute terminal spores, which
give the fly a powdery appearance. These
spores (called, also, conidia) may be seen as a
whitish halo surrounding the spot to which the
fly (now dead) has attached itself. Round
and thick-walled resting spores (formed by
the union of gametes similar to those of Black
Molds) have been observed in some species, and may be
studied in the Grasshopper Fungus {Entomophthora
grylli), which destroys great numbers of grasshoppers
every autumn.
The Sexual Organs of the Water Molds, Downy Mil-
dews, Black Molds, and Insect Fungi show a progressive
degeneration from the typical structure occurring in the
Green Felts. In the Water Molds there is a suppression
of the sperms, the antherid protoplasm being transferred
directly to the egg. This is continued with little change
throughout the Downy ]\Iildews and White Rusts, which
being non-aquatic could scarcely make use of motile
sperms. The sexual organs of the Black Molds are
apparently of the same general type as those of Water
Molds and Downy Mildews, each being an end cell cut
off from a reproductive filament, but in Black Molds
these filaments show little differentiation. They unite
prematurely, before the oogone has developed an eg^,
and before the other filament has developed its anthei-
idial protoplasm. They are physically under-developed
192 PHYLUM IV. SIPHONOPHYCEAE
sexual organs, and are to be regarded as mere vestiges of
the fully developed antherids and oogones of the Green
Felts. They are sexual organs on the road to extinction.
In the Insect Fungi the sexual organs are still more de-
generated and vestigial in structure.
288. The commonest example of the Higher Tube
Algae is the little Bladder Alga (Botrydium), found on
»^ moist ground. It is a globular coenocyte
a millimeter or two in diameter, with a
branching root below. When in good
vegetative condition it is bright green, but
later it may be dull red. It is known to
Fig 82— P^opagatc by uniciliated zoospores, and
Botrydiuni^ind thick wallcd chlamydosporcs. Its genera-
tion was long supposed to be by the union
of biciliated isogametes, but these are now thought to
belong to Protosiphon, a similar plant ^vith an unb^anched
root.
289. In the shallow waters of the ocean there are
larger Bladder Algae (Valonia) that when young are
single globose or club-shaped coenocytes, firmly rooted
below. They may reach several centimeters in height,
and ultimately become more or less divided
into segments. Their propagation and
generation appear to be much like that
of the little Bladder Algae.
290. The Sea Ferns (Bryopsis) are erect,
slender, cylindrical, single coenocytes, rooted
below, and pinnately branched above, and fig. 83.— Bry-
look like little trees, or fern-leaves. They Slaru."^ '^'^"
generate by biciliated heterogametes. They
occur along the shores of the warmer oceans.
291. The pretty Sea Umbrellas (Acetabularia) are
also erect, slender, cylindrical, single coenocytes, rooted
STONEWORTS
193
below; but here the branches are in one terminal whorl
and are united into an umbrella-like structure. They
generate by biciliated isogametes. They occur in shal-
low tropical or sub-tropical marine w^aters.
292. In the Stoneworts (Charales) we find the highest
development of the coenocytic structure. The plants
are erect, slender, cylindrical rows of coenocytes, rooted
below, and bearing many whorls of free branches. The
stems are often corticated with a parallel layer of smaller
coenocytes. They occur in the fresh or brackish waters
of ponds and lakes.
293. The generation of Stoneworts is heterogamous,
that is by the union of bicihated sperms, with non-ciliated
eggs. The sperms are pro-
duced in compound antherids
which are globular many-
celled bodies, in the interior
of which certain multicellular
filaments (the antherids) pro-
duce the sperms singly in the
cells. Each sperm is a spiral
thread of protoplasm, provided with two long cilia at
one end, by means of which it swims rapidly through
the water.
294. The oogone is a single cell, which soon becomes
covered (corticated) by the growth from below of a layer
of five spirally wound coenocytes, which are prolonged
into a 5- or 10-cclled crown. This covering, which here
develops before fertilization, is analogous to the protec-
tive covering which in Coleochaete, forms after fertiliza-
tion has taken place. In the oogone is the egg, which is
non-ciliated, and very much larger than the sperms.
295. The sperms enter the opening at the apex of the
oogone and one of them entering the egg fertilizes it.
13
Fig. 84.— Chara.
194 PHYLUM IV. SIPHONOPHYCEAE
The oogone and its covering now become thicker-walled
and constitute a spore-fruit. The latter soon drops off
and falls to the bottom of the water, where it remains at
rest for a time and later germinates by sending out a
jointed filament, which eventually gives rise to a branch-
ing plant like the original.
296. About IGO species of Stoneworts are known, all
included in the single order Charales. The two f amiUes,
NiteUaceae and Characeae are separated by the structure
of the crown, which is 10-celled in the former, and 5-
celled in the latter. The principal genus of the first
family is Nitella, and of the second Chara; each contains
in this country a dozen or more widely distributed
species.
297. Summary. The attempt has been made in the
foregoing pages to treat the coenocytic plants in accord-
ance with the theory that they have been derived from
the many-celled filamentous algae of the Ulothrix type
in the Phylum Chlorophyceae, where the segments of the
filaments are true cells, each having a single nucleus.
And it is regarded as probable that the coenocytic struc-
ture was gradually attained by the formation of fewer
and fewer partitions in the succession of filamentous
plants.
298. Accordingly the Cladophoraceae are given place
at the beginning of the phylum, and they are regarded
as having given rise to two general lines of development,
one of which is characterized by the retention of a dis-
tinctly filamentous structure, while in the other the
coenocyte undergoes great differentiation into ''root,''
"stem" and "leaves." If we designate these Hues by
their highest holophytic representatives, we may call
them (1) the Vaucheria line, and (2) the Chara line.
299. In passing from Cladophoraceae to Vaucheriaceae
EVOLUTION OF SIPHONOPHYCEAE 195
the plant body has become almost completely non-septate
and the sexual reproduction has become heterogamic.
This plant body and heterogamic generation have been
bequeathed to the hysterophj^tes of this line (Class
Phycomyceteae) , and both suffer marked degeneration
in passing from family to family.
300. So also we may trace an evolutionary line from Cla-
dophoraceae to Valoniaceae (and Botrydiaceae), Bryop-
sidaceae, Dasycladaceae, and the Charales, in all of which
the erect, rooted and regularly branched plant body
becomes more and more marked. Here there is again a
passage from isogamy to heterogamy.
Laboratory Studies. Note: In addition to those mentioned
below many marine forms, as Codium, Penicillus, Halimeda,
Udotea, etc., occur in warm seas, and may be studied with
profit, (a) Collect a quantity of Water-flannel (Cladophora)
and put it into a large dish of water, leaving it over night.
Next morning the side of the dish which is nearest to the hght
will show a green band at the water's edge, due to the mjTiads
of zoospores which escaped during the night. Mount a drop
of water and search for zoospores. Occasionally the escape of
zoospores may be seen by mounting a number of filaments and
searching carefully.
(b) Collect a quantity of terrestrial Green Felt (Vaucheria)
and preserve it in a dish of water. After a few hours a large
number of zoospores may be observed collected at the edge of
the water nearest to the light.
(c) Examine carefully mounted specimens of the bright green
filaments, and look for the thickened branches which produce
the zoospores.
(d) Select some of the oldest, j'cllowish filaments. Mount
and examine with a low power for the sexual organs. In col-
lecting specimens for the study of the sexual organs it is usually
necessary to take those masses which arc yellowish and appear
to be dying or dead.
(e) Kill a few flies in strong alcohol and place them in a dish
containing algae freshly gathered from some ditch or pool.
After a day or two the flics will usually be found to be covered
196 PH\XUM IV. SIPHOXOPHYCEAE
with whitish masses of radiating hj'-phae of Saprolegnia or
related genera. Remove some of these hyphae and examine
for zoospore formation. Somewhat later oogones and antherids
may often be found. A water mold {Saprolegnia ferax)
frequently occurs upon the bodies of young fishes, especially in
fish-hatcheries where it is occasionally very destructive.
(/) In the Spring the leaves and stems of shepherds'-purse
and peppergrass may often be found covered underneath with
a white mold-like growth {Peronospora parasitica). Carefully
scrape off a little of this growth and mount first in alcohol,
afterward adding a little potassium hydrate. The irregularly
branching filaments will be seen to bear here and there white,
broadly ellipsoidal conidia. Similar studies may be made of
the Grape-mildew {Plasmopara viticola) on grape-leaves in
autumn, and the Lettuce-mildew {Bremia lactucae) on cultivated
and wild lettuce from spring to autumn.
(g) Make very thin cross-sections of a leaf affected with a
Downy Mildew, when the latter has passed the period of its
greatest vegetative activity. Mount in alcohol (to drive out
air-bubbles), then add potassium hj'drate, and look for the
resting-spores, which in some species are of a dark brown color.
(h) White Rusts occur on man}?- plants: one {Albugo Candida)
on shepherd's-purse, peppergrass, radish, etc.; another {A.
hliti) on Amaranthus; and another (.4. portulacae) on purslane.
For conidia make very thin cross-sections of leaves, through a
white-rust spot, and mount as above. The resting spores
(which are dark brown) are easily obtained in the leaves of
Amaranthus and purslane and in the distorted stem of the
radish.
{i) In the study of Black Molds it is mostly necessary to
make use of alcohol for freeing the specimens of air; afterward
they usually require to be treated with a dilute alkah (as a
weak solution of ammonia or potassium hydrate), which
causes the filaments to swell up to their original proportions.
{j) Cut a lemon in two, and, squeezing out most of the juice,
expose the two halves to the air af an ordinary laboratory or
living-room for a few days, when various molds will begin to
develop. Under favorable circumstances Black Mold (Mucor)
will predominate. It can be told by its dark color and the
minute round black sporangia on the ends of the erect filaments.
LABORATORY STUDIES 197
Mount a few filaments (as directed in i above) and examine
filaments, sporangia, and spores.
{k) Moisten a piece of bread and then sow here and there on
its surface a few spores of Black Mold; cover with a tumbler or
bell glass. In a few hours a new crop of Black Mold will Ijogin
developing. The nutritive mycelium may be studied by
teasing out small bits of the newly infected bread.
(0 Place several clean glass slides in contact with a culture of
black mold, as described in (^•). By removing these at different
times the various stages of growth of the mold may be easily
studied.
{m) Collect a number of large fleshy fungi (Boletus, Lactaria,
Agaricus, etc.) and place under bell jars for a couple of days.
Usually a cream-colored mold {Sporodinia grandis) will begin
to develop upon some of these. Transfer it to pieces of bread
as in (A-) and study in a similar way. After a few days the
zygospore formation will be observed, as this species is homo-
thallic.
{n) In the latter part of summer and in the autumn examine
the dead flies which adhere to windowpanes, door-casings, and
especially to wires and strings hanging from the ceiling. ' The
whitish powder around the fly will indicate the presence of the
Fly-fungus {Entomophthora muscae). Mount some of this
white powder in water and examine under a high power. Tear
out small bits of the distended abdomen of the fly, and examine
for internal portions of the parasite.
(o) In the autumn look for dead grasshoppers attached to the
tops of weeds and grasses. Examine their interior tissues for
thick- walled resting spores of Entomophthora grylli.
(p) In damp weather in the summer look for Botrydium on
the hard, smooth ground of unused paths. It often appears
on compact soil in greenhouses in the winter.
iq) Specimens of Valonia, Bryopsis, Caulcrpa and Acetabu-
laria may be obtained of dealers in laboratory material for
study and examination.
(r) Search the sandy margins of ponds, lakes, and slow streams
for Stoneworts (Charales). They are generally found in water
from a few centimeters to one or two meters in depth. Pre-
serve such specimens temporarily in water which is frequently
changed, but for future use preserve in alcohol. Study as