198 BIOLOGICAL LECTURES. 



that their use as representative plants and the resulting mis- 

 conceptions among students were abandoned. 



The Fungi most strikingly exemplify the ability manifested 

 by some plants of nearly all the great groups to adapt them- 

 selves to saprophytic or parasitic life with loss of their chloro- 

 phyll and thus of the independent food-making power which 

 characterizes normal plants. 



5. SaccharomyceSt the baker's yeast, presents a fungus of 

 very simple structure, and illustrates in its manner of life the 

 essential features of saprophytism and the phenomena of fer- 

 mentation. It is instructive to compare with the yeast some 

 of the Bacteria which produce the decomposition of organic 

 substances, both from a physiological point of view and as 

 examples of the smallest and most simply organized of known 

 plants. 



6. Rhizopus, which appears abundantly as a black mold on 

 bread, is closely comparable in its sexual reproduction with the 

 conjugate Algae, and presents in simple form one of the char- 

 acteristic organs of non-sexual reproduction among the Fungi, 

 the sporangium. The siphonaceous structure of its filaments 

 recalls that of Vaucheria. If it be preferred to use a form 

 quite closely comparable in its chief features with Vaucheria, 

 one of the aquatic fungi, Saprolegnia or Achlya, may be used. 

 They are readily cultivated on dead flies in water from ditches 

 or pools. 



7. Another familiar acquaintance of long standing among 

 teachers of biology, which apparently owes its continued use 

 to its ubiquitousness, is the blue mold, Penicillium. But the 

 small size of its conidia and the complicated structure of its 

 conidiophores make it inconvenient and less instructive than 

 other forms; besides which, it practically never develops its 

 sexual fructification. Equally unsatisfactory in the former 

 respect, but far better in the latter, is the common mold of 

 fruit preserves, whose greenish conidial stage (Aspergillus) is 

 followed by the yellow sexual fruits (Eurotium). And much 

 better than either of these is the closely related Microsphaera of 

 the lilac or any one of the "powdery mildews." These may be 

 obtained in abundance with a little care, each summer, and are 



