160 MUCOR 



Let us consider precisely what this process implies. Before 

 it takes place the protoplasm is continuous throughout the 

 whole organism, which is therefore comparable to the un- 

 divided plant cell shown in Fig. n, A. As in that case, the 

 protoplasm divides into two and a new layer of cellulose is 

 formed between the daughter-cells. Only whereas in the 

 ordinary vegetable cell the products of division are of equal 

 size (Fig. n, E), in Mucor they are very unequal, one being 

 the comparatively small sporangium, the other the rest of 

 the hypha. 



Thus a Mucor-plant with a single aerial hypha becomes, 

 by the formation of a sporangium, bicellular : if, as is ordi- 

 narily the case, it bears numerous aerial hyphae, each with 

 its sporangium, it is multicellular. 



Under unfavourable conditions of nutrition, septa fre- 

 quently appear at more or less irregular intervals in the 

 mycelial hyphse : the organism is then very obviously multi- 

 cellular, being formed of numerous cylindrical cells arranged 

 end to end. 



The sporangium continues to grow, and as it does so the 

 septum becomes more and more convex upwards, finally 

 taking the form of a short, club-shaped projection, the colu- 

 mella, extending into the interior of the sporangium (c 2 ). At 

 the same time the protoplasm of the sporangium undergoes 

 multiple fission, becoming divided into numerous ovoid 

 masses, each of which surrounds itself with a cellulose coat 

 and becomes a spore (p 1 , D 2 , sp). A certain amount of the 

 protoplasm remains unused in the formation of spores, and 

 is converted into a gelatinous material (g), which swells up 

 in water. 



The original cell-wall of the sporangium is left as an 

 exceedingly delicate, brittle shell around the spores : minute 

 needle-like crystals of calcium oxalate are deposited in it. 



