Special Morphology and G lassification. 263, 
particular stages in the development of higher Fungi, or are 
independent forms of life arising from specific germs of their 
own ; the beer-yeast, for example, being a low type of the 
Ascomycetes. (For further particulars see p. 277). 
The cell-wall of Fungi consists of cellulose, which how- 
ever 1s only very rarely coloured blue by iodine and sul- 
phuric acid, and is therefore considered a special modifica- 
tion, under the name Fungus-cellulose. Very often the 
outer layers of the cell-wall swell up and pass over into a 
gelatinous or mucilaginous condition. 
The cells of Fungi contain neither nucleus, starch- 
grains, nor chlorophyll ; but their characteristic contents 
are a fatty oil. Calcium oxalate is very commonly found 
on the surface of the cells, very rarely in their interior. 
The thallus of Fungi consists of two principal parts, the 
mycelium and the receptacle. ‘The former is developed at 
once on germination, and either consists of simple filaments, 
or forms loose flocculent masses, branching bundles, pelli- 
cular expansions (as Penicillium when growing on fluids), or 
finally, compact tuberous masses, the ‘ sclerotia,’ as in ergot. 
Its term of life is longer or shorter, often several years, and 
it produces the receptacles only once or repeatedly (z.e. may 
be either monocarpic or polycarpic). 
The receptacle or stroma is, as a rule, the most con- 
spicuous part of the Fungus, and is popularly regarded as 
the whole, as in the mushrooms. Fertile hyphe, consisting of 
only a single filament, usually erect, are distinguished from 
true receptacles of a compound structure. , 
In the fertile hyphz the terminal cells of the principal 
filament and its ramifications become the mother-cells of 
the reproductive cells or spores, their growth as a rule then 
ceasing. <A fresh growth of the lower portion, however, 
frequently begins after the ripening of the first spores, which 
soon again terminates with a new formation of reproductive 
organs, the process being sometimes again repeated after a 
time. ; | 
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