FORMATION OF SPORES 59 



The mechanics of this method of division are at present 

 unknown. Swingle suggests local contractions of the 

 cytoplasm. Harper uses the term 'cleavage by constric- 

 tion' for this process, and points out that it should be very 

 carefully distinguished from free cell formation, inasmuch 

 as there can be no epiplasm ; hence the process is initiated 

 from the plasma membrane situated either on the periphery 

 of the sporangium, or surrounding the vacuoles, and not 

 from any stimulus of nuclei, or fibrillae, or an aster. 



As previously stated, Brefeld's view as to the homology 

 between sporangia and asci, or the derivation of the latter 

 from the former, is not supported by recent cytological 

 research, inasmuch as it is difficult to conceive such diverse 

 characters manifested by the protoplasm of homologous 

 organs ; there are, however, transitional modes of spore- 

 formation in both groups. 



In the majority of the Mucorineae the sporangia are 

 spherical or hemispherical, but in the section called 

 Syncephalideae the sporangia present a quite different 

 appearance. At the apex of an elongated sporangiophore 

 is a swollen head from which spring numerous closely 

 packed, narrowly cylindrical bodies, each usually contain- 

 ing a single row of superposed spores, the whole resembling 

 an Aspergillus head. The origin of these spores has been 

 variously interpreted. De Bary and Woronin, Brefeld and 

 Fischer consider them as exogenously formed conidia, the 

 latter urging the absence of transitional forms between 

 cylindrical and the typical spherical sporangia as preclud- 

 ing their being sporangia. Leger, however, has shown 

 that these cylindrical bodies are true sporangia, filled with 

 protoplasm containing numerous nuclei, which becomes 

 cut up simultaneously into spores separated by hyaline 



