Special Morphology and Classification. 279 
are also produced ; and one or two per cent. is not yet ac- 
counted for, but may perhaps be assimilated by the Zorada. 
It will grow and multiply actively in a solution in which 
sugar and ammonium nitrate replace the ammonium tartrate; 
and in this case the carbon must be obtained from the sugar. 
Although oxygen is essential to its life, it will live in sac- 
charine solutions which contain no free oxygen, appearing, 
under these circumstances, to get its oxygen also from the 
sugar. It will also flourish in solutions in which the am- 
monium tartrate is replaced by sugar and pepsin, in which 
case the nitrogen of the protein-compounds must be derived 
from the pepsin. 
Penicillium and Mucor may be regarded as types of two 
- different classes of the filamentous Fungi. In the former, 
the whole Fungus, both the concealed part or mycelium, 
and that portion which is exposed to the atmosphere, the 
aérial hyphe, consist of cells which agree in every essential 
- point (except the absence of a nucleus) with the typical cell, 
varying only in size and form. The only reproductive bodies 
are conidia, that is, ordinary cells of a spherical form pro- 
duced at the ends of the aerial hyphze, and detached in suc- 
cession. They are true spores (see p. 178). They have 
the same property as the single Zorwa-cells of retaining 
their vitality for a long period when dried ; and, from their 
extreme lightness, are in this form disseminated with the 
greatest facility through the air. On reaching a nutrient 
substratum they germinate. A bulging makes its appearance 
at one or more points of the cell-wall, and the cell rapidly 
lengthens in one or more directions, and becomes a radiat- | 
ing and branched, but still unicellular, hypha. Subsequently 
the protoplasm divides transversely, septa of cellulose are 
formed, and the hypha becomes multiceliular. It is a uni- 
versal characteristic of all Fungi that the hyphz divide 
transversely only, never longitudinally ; they never anasto- 
mose, though they may become interlaced into a dense weft. 
Some branches of the hyphz extend downwards, forming 
