APPEI^DIX. 



MOULD AND YEAST FUNGI. 



We will, in conclusion, briefly consider some micro-organisms 

 nearly related to the bacteria. 



It has already been stated that all plants destitute of chlorophyl 

 are designated as " fungi," while the bacteria, by reason of their 

 mode of reproduction by division, were contrasted as " schizomy- 

 cetes," "yeast" ("sprouting"), and "mould fungi." 



These latter two evidently resemble the bacteria, but differ from 

 them in many important properties. 



The mould fungi belong to the flowerless plants, the cryptogams, 

 and constitute the subdivision of Thallophytes which bear a simple 

 foliage (thallus). This thallus is composed of cells destitute of 

 chlorophyl, having, like the bacteria, a membrane and protoplasmic 

 contents, but no nuclei. They are never reproduced by transverse 

 division (splitting), but are developed, by progressive growth of 

 the ends, into long filaments (hyphse) which frequently become 

 articulated without being disconnected. These hyphae are, besides, 

 characterized by an early ramification uniting the threads into a 

 compact network, the mj^celium. 



At the period of sporulation, some hyphse rise from the mycelium 

 and assume other shapes and conditions of growth as "fruit-hyphae" 

 ("fruit-bearers"). On these the "fruit" (the spores, also called 

 conidia) will arise. This occurs with the single mould fungi in such 

 a peculiar manner that it has been utilized in their classification. 



The number of the various mould fungi is very large and esti- 

 mated by the thousand. We shall consider only such as are par- 

 ticularlj' important to us. 



The generally undivided and unarticulated hj^phge of the muco- 

 rinese rise perpendicularly from the delicate mycelium; a sporan- 

 gium rises on their top, i.e., a globular mass rich in protoplasm, 

 a mother spore-cell, is developed, the contents of which are di- 

 vided into roundish spores by numerous partition walls. The 

 sporangium is capped toward the end by an arched plate, called 

 columella. The sporangium perishes when the spores are ripe and 



