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CHAPTER V.—COMPARATIVE REVIEW.—ASCOMYCETES.—PENICILLIUM. 205 
in every direction, and at the same time numerous branches begin to be formed on 
the neighbouring mycelial hyphae which grow rapidly round the others, and inclose 
them in a compact envelope composed of from 8-16 layers of cells which leave no 
interstices. The elements of this enveloping weft thrust themselves everywhere in 
between the ascogenous hyphal branches; in their early states they are much 
narrower than these and therefore easily distinguished from them in section. The 
spherical sporocarp which in this state is about 0.05-0.09 mm. in size now 
increases to an average size of o.5 mm. and more, and this increase is chiefly due to 
the enlargement of the cells of the envelope. The great mass of the inner substance 
is the part most strongly affected, and its cells become irregularly polyhedral and 
colourless, and are provided with much thickened pitted cellulose-membrane and 
hyaline cell-contents which turn dark yellow with iodine. The membranes of the cells 
of two or three peripheral layers become yellowish brown in colour and form a thick 
persistent outer wall, while a few layers on the outside do not share in the thickening: 
and are cast off when the sporocarp is ripe. With the commencement of these 
changes the ascogenous hyphae elongate and force themselves in between the growing 
tissue of the envelope in irregular courses in every direction. In doing this they do 
not appear to form many new branches or to increase much in breadth, and the latter 
is the case also with the cell-layers of the envelope which are in contact with them. 
In sections through an older sporocarp we therefore find in the interior in the large- 
celled tissue of the envelope ascogenous hyphae cut through in various directions, 
transverse, oblique or longitudinal, accompanied by small-celléd tissue. The cell-walls 
of these ‘ascogenous hyphae also become thickened, and when this thickening has 
reached a certain point in them and in the envelope, there is a pause in the develop- 
ment, a resting condition. This lasts 7-8 weeks, if the sporocarp is placed as 
soon as it is ripe in moist surroundings which are favourable to further development ; 
but the resting state cannot last much longer, according to Brefeld’s observations, 
if the surroundings are dry, for dry sporocarps 3-4 months old proved incapable _ 
of further development. If the sporocarps are placed within the time stated on 
a moist substratum in a suitable temperature, they recommence their development; 
the ascogenous hyphae begin to branch copiously, the branches grow at the expense 
of the colourless tissue of the envelope which is by degrees entirely dissolved, and 
again branch, and at length a large number of small eight-spored asci connected 
together in rows and resembling those of Eurotium are formed on branches of 
the last order. There only remains at last of the whole sporocarp the pores and 
the brownish yellow outer wall, which forms a loose envelope round them. Of 
the details of these changes which may be obtained from Brefeld, it will be sufficient 
to mention here, that the branches formed on the ascogenous hyphae are of two kinds; 
comparatively slender ones which penetrate between the cells of the tissue of the 
envelope, ramify copiously in it and are evidently used to effect the dissolution of that 
tissue and to take up the products of the dissolution, but do not form asci; and 
secondly, thicker much curved forms with short branches of their own, from the 
ramifications of which the asci are ultimately produced. These facts recall the. 
two forms of hyphae in the ripening sporocarp of Elaphomyces (see page 193). 
The entering of the sporocarp on a resting period and the change from this to the 
formation of asci at the expense of the tissue of the envelope has its analogue in the 
