FORMATION OF CELLS, 
II 
bipartition of the nucleus or nuclei of the cell] Generally, the number of daughter-cells 
which arise in this manner is considerable; as an instance may be mentioned the 
formation of spores in Ascomycetes (Peziza^), (Fig. 7). The tubular mother-cells of 
the spores (asci) (a) are at first densely filled with protoplasm, and contain only one 
small nucleus. [This divides into two, and this process is repeated until eight nuclei 
are formed :] the protoplasm becomes frothy, and roundish drops of sap make their 
appearance in it (b, c). The first stage in 
the formation of the spores is the conden- 
sation of the protoplasm in the upper part 
of the ascus, while it remains frothy in the 
lower part (<?,/). In this case eight spores 
are always formed in each ascus within the 
upper dense protoplasm ; /. e. round each of 
the eight nuclei an ellipsoidal protoplasm- 
mass collects (d) ; each consists at first of 
coarse-grained protoplasm surrounded by a 
clear space ; a portion of fine-grained pro- 
toplasm forms the matrix in which the 
spores are imbedded. Afterwards each 
spore becomes more sharply defined ; the 
clear space disappears (e) ; its substance 
becomes more fine-grained and clearer ; 
and in one of its foci is formed a vacuole, 
i.e. a transparent drop of fluid. Finally, 
each spore surrounds itself with a firm 
membrane, the vacuole disappears, and in 
the centre is formed a large strongly re- 
fractive oil-drop, as well as numerous 
smaller ones. 
An example is aflforded by the forma- 
tion of the oospheres of Achlya (Fig. 8) 
of a somewhat diiferent mode of free cell- 
formation. The protoplasm collects at the 
end of a hypha or of a branch of one ; the 
larger end itself swells up into a globular 
form (^, 5), and, after the formation of a 
septum (C), becomes an independent cell 
(the oogonium). [Numerous small nuclei 
are present in the protoplasm (as in C). 
The nuclei multiply by bipartition.] The 
whole protoplasm breaks up into two, 
three, four, or more parts, which very 
quickly round themselves off into a per- 
fectly spherical form ; [in each of these 
several nuclei are uniformly distributed.] 
The parts thus formed {e, e in D) contract 
greatly during their separation, and their 
protoplasm becomes denser by expulsion 
of water; after they have become fertilised by the antheridial tubes («, b in X)), 
they become invested with a cell-wall, [and the nuclei in each coalesce to constitute 
the nucleus of the oospore]. 
Fig. -j.—Peziza cojivexula. A vertical section of the whole 
plant (X about 20); h hymeniuin. i.e. the layer in which the 
spore-sacs (asci) lie ; 5 the tissue of the Fungus enveloping- the 
hymenium at its edge q in a cup-like manner; at the base of 
the tissue 5 are delicate rhizoids, which grow between the 
particles of earth. B a smaller portion of the hymenium (X 550) ; 
sh sub-hymenial layer of densely interwoven cell-filaments 
(hyphre); a-^asci; among them thinner sacs, the paraphyses, 
in which lie red granules. 
^ [Strasburger, Zellbildung und Zelltheilung, 1880 ; Schmitz, Sitzbcr. d. niederrhein. Ges. zu 
Bonn, 1879.] 
