264 DIVISION II,—COURSE OF DEVELOPMENT OF FUNGI. 
small brush-like bodies is a separate plant. The entire lengih in the largest known 
species, Laboulbenia Nebriae, is about ı mm., in most species little or not more 
than o'5 mm. The phenomena observed in them most nearly resemble those known 
in the Ascomycetes, and are named accordingly. The small plant (Fig. 120) is 
attached to the substratum by a filiform or clubshaped stalk, consisting usually of 
two cells one above the other; at the apex of the stalk is a perithecium and a body 
which may be here briefly termed an appendage (a). The perithecium is narrowly 
conical in form or flask-shaped and in some species oblique, and consists when 
mature of a wall formed of a few cells disposed in two layers at the base and one 
layer at the sides with a narrow orifice at the apex; the group of asci which rises 
erect from the base of the perithecium is closely surrounded by its wall. The number 
of the asci and the way in which the spores are formed in them are not exactly 
ascertained. The number of spores in an ascus is said to be 8 and 12; the ripe 
spores are fusiform and colourless, and being divided by a transverse wall into two 
equal cells are therefore compound and bicellular; they escape singly and one after 
another through the orifice of the perithecium, no doubt in consequence of the 
gelatinous deliquescence of the wall of the ascus. The appendage springs from close 
to the base of the perithecium in the form of a segmented hair or filament, varying, 
according to the species, in length and number of cells and presence or absence of 
branches, which in some species are very peculiar in their form and arrangement. 
All the cells in the mature Fungus except the asci, the spores, and the extremities of 
the branches of the appendage, have very thick membranes of a deep and often a dark 
brown colour. : 
The Laboulbenieae have no mycelium; the ripe double spore attaches itself by 
one extremity to the chitinous covering of the insect, and sends into it a small short 
point, which sometimes enlarges into a knob at its extremity and with the surrounding 
chitin soon assumes a brown colour; this point is its only organ of attachment and 
of nutrition. Thus firmly planted it developes at right angles to the substratum and 
reaches its mature state by the necessary successive cell-divisions and differentiations. 
Most of the details of these formations can be seen at once in the accompanying figure 
for the case which it represents, but some important points have still to be cleared up. 
I select the following for special notice, and refer the reader to Peyritsch’s treatises for 
further details. The appendage is developed from the cell of the double spore which 
is the upper one in reference to the point of attachment; it is therefore originally 
terminal and is completed before the perithecium. The stalk and the perithecium 
are formed from the Zower cell of the double spore; the perithecium shoots out laterally 
from beneath the point which is afterwards that of insertion of the appendage, and 
as it increases in breadth it thrusts the appendage to one side. In its earliest stage it is 
unicellular; as it grows it divides by successive transverse divisions into three tiers of one 
cell each, and each tier in acropetal succession then separates by longitudinal division 
into an axile and several parietal cells. But before the longitudinal division begins 
(Laboulbenia vulgaris), or before it has reached the uppermost tier-cell (Stigmatomyces), 
it is observed that this cell puts out a short protuberance at its apex, which is either very 
thin-walled or seems to have no membrane, and disappears again at a later stage of the 
development (Fig. 120 g, 4). Simultaneously with the formation of this protuberance on 
the primordium of the perithecium small thin-walled swellings are seen on the apex or 
