RESEARCHES ON THE MUCORINI. 55 



which after the maturation of the sporangium are reduced to 

 the condition of mere mycelial filaments. In fact, they may 

 be found in every part from the cavity of the original spore 

 to the columella of the empty sporangium. But all the 

 genera and all the species of the same genus do not develope 

 them to the same extent. The difference in this respect is 

 especially noticeable in the case of Mucor. 



Chlamydospores are not confined to the Ascomycetes. 

 Woronin has in fact described pedicellate ones in Ascobolus 

 pulcherrimus , and we have also met with them ourselves in 

 Kickxella alahastrina. 



We see therefore that amongst the Mucorini the poly- 

 morphism of the reproductive organs i? very restricted^ since 

 it only ranges between the sporangial form, which may, it is 

 true, be of two kinds, and the chlamydial which also put on 

 somewhat different aspects. What, however, is remarkable 

 is, that the asexual spore is always endogenous; it is always 

 formed within a cell at the expense of the whole or part of 

 the protoplasm, and to permit its escape the containing 

 membrane must be either ruptured or absorbed. 



ChcBtocladium at first sight appears to establish a transition 

 between the sporangial and chlamydial forms of spores, but 

 this is only in appearance, since by its mode of formation, 

 structure, and function, the spore of ChcBtocladium is clearly 

 a sporangiospore and not a chlamydospore. The chlamydial 

 form is still far from completely understood, and its occurrence 

 may, perhaps, not be possible in some genera. 



Sexual reproduction. — After the production of asexual 

 spores the mycelium of the Mucorini produces at particular 

 points, either in the^air {Sporodinia), on the surface of the 

 nutritive medium {Phycomyces), or within it {Mucor Mucedo) 

 zygospores, the result of the mutual interpenetration of two 

 protoplasmic masses of distinct origin. Two perfectly similar 

 hyphae, either straight {Mucor, lihizopus, Chcetocladium) , or 

 arcuate, like the teeth of a vice conie into contact by their 

 swollen extremities. At the same time the protoplasm con- 

 tained in each cell contracts into a S[)here. The double 

 partition between the two protoplasmic spheres is absorbed, 

 and they coalesce into a single mass or zygospore, which 

 increases in size and clothes itself with a tuberculate or 

 echinulate membrane. This is inclosed in addition by the 

 thinner coat of the two original conjugating cells, which 

 becomes coloured (often black), and adapts itself to all the 

 projections of the internal membrane. Generally, the 

 zygospore occupies the whole internal space of the two 

 conjugating cells; in Piptocephalis, however, Brefeld has 



