THE HIGHER FUNGI.
=411. The series of the higher fungi.=—Of these there are two
large series. One of these is represented by the sac fungi, and the
other by the mushrooms, a good example of which is the common mushroom
(Agaricus campestris).
Sac Fungi (Ascomycetes).
=412. The sac fungi= may be represented by the “powdery mildews”;
examples, uncinula, microsphæra, podosphæra, etc. Fig. 225 is from a
photograph of two willow leaves affected by one of these mildews. The
leaves are first partly covered with a whitish growth of mycelium, and
numerous chains of colorless gonidia are borne on short erect threads.
The masses of gonidia give the leaf a powdery appearance. The mycelium
lives on the outer surface of the leaf, but sends short haustoria into
the epidermal cells.
=413. Fruit bodies of the willow mildew.=—On this same mycelium
there appear later numerous black specks scattered over the affected
places of the leaf. These are the fruit bodies (_perithecia_). If
we scrape some of these from the leaf, and mount them in water for
microscopic examination, we shall be able to see their structure.
Examining these first with a low power of the microscope, each one is
seen to be a rounded body, from which radiate numerous filaments, the
_appendages_. Each one of these appendages is coiled at the end into
the form of a little hook. Because of these hooked appendages this
genus is called _uncinula_. This rounded body is the _perithecium_.
[Illustration: Fig. 225. Leaves of willow showing willow mildew. The
black dots are the fruit bodies (perithecia) seated on the white
mycelium.]
=414. Asci and ascospores.=—While we are looking at a few of
these through the microscope with the low power, we should press on the
cover glass with a needle until we see a few of the perithecia rupture.
If this is done carefully we see several small ovate sacs issue, each
containing a number of spores, as shown in fig. 227. Such a sac is an
_ascus_, and the spores are _ascospores_.
[Illustration: Fig. 226. Willow mildew; bit of mycelium with erect
conidiophores, bearing chain of gonidia; gonidium at left germinating.]
[Illustration: Fig. 227. Fruit of willow mildew, showing hooked
appendages. Genus uncinula.]
[Illustration: Fig. 228. Fruit body of another mildew with dichotomous
appendages. Genus microsphæra.
Figs. 227-228.—Perithecia (perithecium) of two powdery mildews,
showing escape of asci containing the spores from the crushed fruit
bodies.]
[Illustration: Fig. 229. Contact of antheridium and carpogonium
(carpogonium the larger cell); beginning of fertilization.]
[Illustration: Fig. 230. Disappearance of contact walls of antheridium
and carpogonium, and fusion of the two nuclei.]
[Illustration: Fig. 231. Fertilized egg surrounded by the enveloping
threads which grow up around it.
Figs. 229-231.—Fertilization in sphærotheca; one of the powdery
mildews. (After Harper.)]
=415. Number of spores in an ascus.=—The ascus is the most
important character showing the general relationship of the members of
the sac fungi. While many of the powdery mildews have a variable number
of spores in an ascus, a large majority of the ascomycetes have just 8
spores in an ascus, while some have 4, others 16, and some an
indefinite number. The asci in a perithecium are more variable. In some
ascomycetes there is no perithecium.
[Illustration: Fig. 231_a_.
Edible Morel. Morchella esculenta. The asci, forming hymenium, cover
the pitted surface.]
=416. The black fungi.=—These are very common on dead logs,
branches, leaves, etc., and may be collected in the woods at almost any
season. The perithecia are often numerous, scattered or densely crowded
as in Rosellinia. Sometimes they are united to form a crust which is
partly formed from sterile elements as in Hypoxylon, or they form black
clavate or branched bodies as in Xylaria. The black knot of the plum
and cherry is also an example.
The lichens are mostly ascomycetes like the black fungi or cup fungi,
while a few are basidiomycetes.
=417. The morels (Morchella).=—There are several species of
morels which are common in early spring on damp ground. Either one of
the species is suitable for use if it is desired to include this in
the study. Fig. 231a illustrates the Morchella esculenta. The stem is
cylindrical and stout. The fruiting portion forms the “head,” and it
is deeply pitted. The entire pitted surface is covered by the asci,
which are cylindrical and eight spored. A thin section may be made of
a portion for study, or a small piece may be crushed under the cover
glass.
=418. The cup fungi.=—These fungi are common on damp ground or
on rotting logs in the summer. They may be preserved in 70 per cent
alcohol for study. Many of them are shaped like broad open cups or
saucers. The inner surface of the cup is the fruiting surface, and is
covered with the cylindrical asci, which stand side by side. A bit of
the cup may be sectioned or crushed under a cover glass for study.
Mushrooms (Basidiomycetes).
=419. The large group of fungi= to which the mushroom belongs is
called the basidiomycetes because in all of them a structure resembling
a club, or basidium, is present, and bears a limited number of spores,
usually four, though in some genera the number is variable. Some place
the rusts (Uredineæ) in the same series (basidium series), because of
the short promycelium and four sporidia developed from each cell of the
teleutospore.
=420. The gill-bearing fungi (Agaricaceæ).=—A good example for
this study is the common mushroom (Agaricus campestris).
This occurs from July to November in lawns and grassy fields. The
plant is somewhat umbrella-shaped, as shown in fig. 232, and possesses
a cylindrical stem attached to the under side of the convex cap or
pileus. On the under side of the pileus are thin radiating plates,
shaped somewhat like a knife blade. These are the gills, or lamellæ,
and toward the stem they are rounded on the lower angle and are not
attached to the stem. The longer ones extend from near the stem to the
margin of the pileus, and the V-shaped spaces between them are occupied
by successively shorter ones. Around the stem a little below the gills
is a collar, termed the ring or annulus.
[Illustration: Fig. 232. Agaricus campestris. View of under side
showing stem, annulus, gills, and margin of pileus.]
[Illustration: Fig. 233.
Agaricus campestris. Longitudinal section through stem and pileus.
_a_, pileus; _b_, portion of veil on margin of pileus; _c_, gill; _d_,
fragment of annulus; _e_, stipe.]
[Illustration: Fig. 234.
Portion of section of lamella of Agaricus campestris. _tr_, trama;
_sh_, subhymenium; _b_, basidium; _st_, sterigma (_pl._ sterigmata);
_g_, basidiospore.]
[Illustration: Fig. 235. Portion of hymenium of Coprinus micaceus,
showing large cystidium in the hymenium.]
=421. Fruiting surface of the mushroom.=—The surface of these
gills is the fruiting surface of the mushroom, and bears the gonidia
of the mushroom, which are dark purplish brown when mature, and thus
the gills when old are dark in color. If we make a thin section across
a few of the gills, we see that each side of the gill is covered with
closely crowded club-shaped bodies, each one of which is a _basidium_.
In fig. 234 a few of these are enlarged, so that the structure of
the gill can be seen. Each basidium of the common mushroom has two
spinous processes at the free end. Each one is a _sterig′ma_ (plural
_sterig′mata_), and bears a gonidium. In a majority of the members of
the mushroom family each basidium bears four spores. When mature these
spores easily fall away, and a mass of them gives a purplish-black
color to objects on which they fall, so that a print of the under
surface of the cap showing the arrangement of the gills can be obtained
by cutting off the stem, and placing the pileus on white paper for a
time.
[Illustration: Fig. 236. Agaricus campestris. Soil washed from “spawn”
and “buttons,” showing the minute young “buttons” attached to the
strands of mycelium.]
=422. How the mushroom is formed.=—The mycelium of the mushroom
lives in the ground, and grows here for several months or even years,
and at the proper seasons develops the mature mushroom plant. The
mycelium lives on decaying organic matter, and a large number of the
threads grow closely together forming strands, or cords, of mycelium,
which are quite prominent if they are uncovered by removing the soil,
as shown in fig. 236.
[Illustration: Fig. 237. Agaricus campestris; sections of “buttons” of
different sizes, showing formation of gills and veil covering them.]
=423.= From these strands the buttons arise by numerous threads
growing side by side in a vertical direction, each thread growing
independently at the end, but all lying very closely side by side. When
the buttons are quite small the gills begin to form on the under margin
of the knob. They are formed by certain of the threads growing downward
in radiating ridges, just as many of these ridges being started as
there are to be gills formed. At the same time, threads of the stem
grow upward to meet those at the margin of the button in such a manner
that they cover up the forming gills, and thus enclose the gills in a
minute cavity. Sections of buttons at different ages will show this, as
is seen in fig. 237. This curtain of mycelium which is thus stretched
across the gill cavity is the veil. As the cap expands more and more
this is stretched into a thin and delicate texture as shown in fig.
238. Finally, as shown in fig. 239, this veil is ruptured by the
expansion of the pileus, and it either clings to the stem as a collar,
or a portion of it remains clinging to the margin of the cap. When the
buttons are very young the gills are white, but they soon become pink
in color, and very soon after the veil breaks the spores mature, and
then the gills are dark brown.
[Illustration: Fig. 238. Agaricus campestris; nearly mature plants,
showing veil still stretched across the gill cavity.]
[Illustration: Fig. 239. Agaricus campestris; under view of two plants
just after rupture of veil, fragments of the latter clinging both to
margin of pileus and to stem.]
[Illustration: Fig. 240. Agaricus campestris; plant in natural position
just after rupture of veil, showing tendency to double annulus on the
stem. Portions of the veil also dripping from margin of pileus.]
[Illustration: Fig. 241. Agaricus campestris; spore print.]
[Illustration: Fig. 242. “Fairy ring” formed by Agaricus arvensis
(photograph by B. M. Duggar). The mycelium spreads centrifugally each
year, consuming the available food, and thus the plants appear in a
ring.]
[Illustration: Fig. 243. Amanita phalloides; white form, showing
pileus, stipe, annulus, and volva.]
=424. Beware of the poisonous mushroom.=—The number of species
of mushrooms, or toadstools as they are often called, is very great.
Besides the common mushroom (Agaricus campestris) there are a large
number of other edible species. But one should be very familiar with
any species which is gathered for food, unless collected by one who
certainly knows what the plant is, since carelessness in this respect
sometimes results fatally from eating poisonous ones.
[Illustration: Fig. 244. Amanita phalloides; plant turned to one side,
after having been placed in a horizontal position, by the directive
force of gravity.]
=425.= A plant very similar in structure to the Agaricus
campestris is the Lepiota naucina, but the spores are white, and thus
the gills are white, except that in age they become a dirty pink. This
plant occurs in grassy fields and lawns often along with the common
mushroom. Great care should be exercised in collecting and noting the
characters of these plants, for a very deadly poisonous species, the
deadly amanita (Amanita phalloides) is perfectly white, has white
spores, a ring, and grows usually in wooded places, but also sometimes
occurs in the margins of lawns. In this plant the base of the stem is
seated in a cup-shaped structure, the _volva_, shown in fig. 243. One
should dig up the stem carefully so as not to tear off this volva if
it is present, for with the absence of this structure the plant might
easily be mistaken for the lepiota, and serious consequences would
result.
[Illustration: Fig. 245. Edible Boletus. Boletus edulis. Fruiting
surface honey-combed on under side of cap.]
=426. Tube-bearing fungi (Polyporaceæ).=—In the tube-bearing
fungi, the fruiting surface, instead of lying over the surface of
gills, lines the surface of tubes or pores on the under side of the
cap. The fruit-bearing portion therefore is “honey-combed.” The sulphur
polyporus (Polyporus sulphureus) illustrates one form. The tube-bearing
fungi are sometimes called “bracket” fungi, or “shelf” fungi, because
the pileus is attached to the tree or stump like a shelf or bracket.
One very common form in the woods is the plant so much sought by
“artists,” and often called Polyporus applanatus. It is hard and woody,
reddish brown, brown or grayish on the upper side, according to age,
and is marked by prominent and large concentric ridges. (This form is
probably P. leucophæus.) The under side is white and honey-combed by
numerous very minute pores. This plant is perennial, that is, it lives
from year to year. Each year a new layer is added to the under side,
and several new rings usually to the margin. If a plant two or three
years old is cut in two, there will be seen several distinct tube
layers or strata, each one representing a year’s growth.
In some of these bracket fungi, each ring on the upper surface marks a
year’s growth as in the pine polyporus (P. pinicola). In the birch
polyporus (P. fomentarius) the tubes are quite large. It also occurs on
other trees. The beech polyporus (P. igniarius, also on other trees)
often becomes very old. I have seen one specimen over eighty years old.
Not all the tube-bearing fungi are bracket form. Some have a stem and
cap (see fig. 245). Some are spread on the surface of logs.
[Illustration: Fig. 246. Coral fungus. Hydnum coralloides, spines
hanging down from branches.]
=427. Hedgehog fungi (Hydnaceæ).=—These plants are bracket in
form or have a stem and cap, or are spread on the surface of wood; but
the finest specimens resemble coral masses of fungus tissue (example,
Hydnum, fig. 246). In most of them there are slender processes
resembling teeth, spines or awls, which depend from the under surface
(fig. 247). The fruiting surface covers these spines.
=428. Coral fungi or fairy clubs (Clavariaceæ).=—These plants
stand upright from the wood, leaves, or soil, on which they grow
(example, Clavaria). The “coral” ones are branched, while the “fairy
clubs” are simple. The fruiting surface covers the entire exposed
surface of the plants (fig. 248).
[Illustration: Fig. 247. Hydnum repandum, spines hanging down from
under side of cap.]
[Illustration: Fig. 248. Clavaria botrytes.]