10 FORMATION OF SPORES OF RHIZOPUS AND PHYCOMYCES. 



Strasburger (1880) has given an account of the more general features 

 of the spore formation in 2fue<ir inucedo. He considers that the spo- 

 rogenous protoplasmic mass is cut up Y>\ cell plates analogous to those 

 formed in cell division in the higher plants. This account is, how- 

 ever, very brief and incomplete. 



Shortly afterwards, Biisgen (1882) studied the formation of the 

 spores in Mucor. His conclusion is that the protoplasmic mass is cut 

 up into blocks by cell plates,' and that these blocks are subdivided 

 until the final spores are reached. In this he adds little to Stras- 

 burger's account, 



Leger (1806) published a paper intended to till the gaps in our 

 knowledge of the spore formation in the Mucorinea?. This paper is 

 quite comprehensive, dealing with nearly all the principal genera. 

 Leger studied the spore formation parth' bj' means of sections of 

 material embedded in collodion, but largeh' b}" examining' the sporan- 

 gia in toto or by crushing them under a cover glass. His results 

 agree entirely with those of Van Tieghem. He finds that all the forms 

 investigated agree in having the protoplasm divided at once into gran- 

 ular portions separated b}" nongranular plates. Later, the granular 

 masses are surrounded bv walls and become the spores, while the 

 nongranular plates form the intersporal protoplasm. 



In the case of Rhhojnis nigrleaiu^ Leger finds that when the spores 

 are first formed they arc separated by thin membranes onh'. How 

 these membranes originate he does not make clear. The intersporal 

 substance appears a little later after the spore walls are formed. In 

 this respect RMzojms differs from all the other forms investigated. 



In his description of the formation of the columella, Leger states 

 that the contents of the sporangium are easil}' seen to be differentiated 

 into a lighter and a denser portion. These are then separated by a 

 columella wall, the lighter part being included in the columella and 

 all the denser part remaining outside. Just how the protoplasm is 

 divided and the wall formed he does not tell us. He states that the 

 nuclei in the spores are oval, while those in the columella are spherical. 

 As the spores ripen the cytoplasm disappears from the columella and 

 the nuclei, reduced to nucleoli [sic], remain adhering to the inner sur- 

 face of the columella wall. 



The nucleus is essentially^ the same in all the forms which Leger 

 describes. It consists of a nucleolus surrounded b}' a clear zone which 

 does not stain, and outside of this by a distinct nuclear membrane. 

 The nucleoli are described as so many times larger relatively than I 

 have found them that 1 am entireh^ unable to credit his results. The 

 nuclei, also, as he figures them, are much too large and contain no 

 chromatin. 



Thaxter (1897) has done the most to clear up our knowledge of the 

 spore formation in the Syncephalidw. He states that he was earlier 



