212 



General Biology 



has yet been obtained. Toxins are of great interest and importance as 

 can readily be judged from what has been said. 



Probably, if toxins and enzymes are thought of here in relation to 

 each other, it will lead to a clearer understanding of each. Both can be 

 studied only by the effects they produce, the one injurious, the other 

 beneficial. 



One may also think of several other possibilities on the part of the 

 invading organism. For example, it may live entirely at the expense 

 of its host, in which case it is a parasite; it may live on decayed matter 

 and do littre if any injury, and thus be a saprocyte; or it may actively 

 engage in killing and devouring parasitic invaders and thus be of great 

 value to its host. In the last instance it is known as a phagocyte. 



True yeasts grow by budding (Fig. 87) ; they rarely form mycelia; 

 under unfavorable conditions of growth they may form endospores. 



Oidia grow by budding and as mycelia with spore formation. (Fig. 

 102.) 



Hyphomycetes (Fig. 98) grow as mycelia with spore formation of 

 asexual or sexual origin. 



All authorities seem agreed that there is no sharp line of demarca- 

 tion between the blastomycetes and the hyphomycetes, and most of them 

 place the oidia as a transition form. 



Oidium, showing spores 

 being cut off from the 

 tip of the branch. Such* 

 spores are called coindio- 

 spores. 



Fig. 103. 



Aspergillus Fumigatus. (After Brumpt.) 



Blastomycosis (also called saccharomycosis), is the term applied to 

 the lesions produced by a blastomyces. A variety of organisms have 

 been cultivated from the lesions, and different names have been assigned 

 to them. It is not known if these are distinct entities. 



