66 VAN TIEGHEM AND LE MONNIER. 



axis of growth of the conjugating cell, from which it is pro- 

 duced. The two oospheres have their axes parallel and 

 consequently when fused produce a zygospore whose axis 

 preserves the same direction. In this change of direction in 

 the axis of the new individual we find an additional analogy 

 with the sexual process in Alg£e. 



Usually, the amount of nutriment stored up in the zygo- 

 spores is exhausted by the formation of the terminal sporan- 

 gium, and this is the only case described by Brefeld ; but in 

 the germinations which we have watched ourselves we have 

 often seen the formation of a partition at about one third of 

 the length of the principal filament from its base, and below 

 this partition a strong branch given oif, which is also termi- 

 nated by a large sporangium. In one instance this branch 

 also exhibited near its base a partition beneath which a 

 small branch was given oif, terminated by a small sporangium 

 with very few spores and a minute columella. 



Contrary to the opinion of Berkeley and De Bary, we regard 

 this plant as belonging to a distinct genus. Its partly aerial 

 mycelium, the mode of origin of the fructiferous hyphae in 

 groups Avith tufts of rootlets, the remarkable colouration of the 

 protoplasm of the spores and of the wall of the fructiferous 

 hypha, and above all the curious vice-like arrangement of its 

 reproductive apparatus and the dichotomous processes with 

 which it surrounds the zygospore, are characters which are 

 not met with in any species of Mucor. A similar sexual 

 apparatus only occurs in Piptocephalis which is remotely 

 allied to Mucor ; and the dichotomous processes have not at 

 present been detected in any others of the group. From all 

 these points of view this plant merits a generic rank. 



Brefeld has proceeded hastily in following De Bary and 

 Woronin and in reducing all the types of Mucorini to the 

 two genera Mucor and Piloholus. It is true that Chcetocla- 

 dium and Piptocephalis , which he holds to be distinct, are, 

 according to him, not Mucorini at all. But in this we 

 ourselves believe that he is mistaken. 



Thamnidium. 



Link described in 1816 under the name of Tliamnidium 

 elegans a Mucorinious fungus of which the principal 

 fructiferous hypha terminated in a large sporangium, with 

 a columella similar to that of Mucor, and which produced 

 laterally numerous repeatedly dichotomous branches, of 

 which the final ramifications, according to him, bore spores.' 

 1 Link, ' Observ. in Ord. Nat. Plant. Dissert.,' i. 



