CHAPTER V, COMPARATIVE REVIEW. MUCORINI. 151 



The species of the Mucorini which have zygospores, but no other organs of 

 propagation, have since Ehrenberg's time l received the generic name of Syzygites. 

 Hildebrand 2 has described two such forms, one of which may belong to Chaetocla- 

 dium, the other (Syzygites ampelinus) is of uncertain affinity. 



SECTION XLIII. Typical gonidiophores. It has been already stated that the 

 spore when germinating normally produces gonidiophores as the first result of 

 development in the form of hyphae (simple sporophores) which are characteristic of 

 each species. Every strongly developed mycelium of the species produces similar goni- 

 diophores, which are at least the primary and often the only organs of propagation, if 

 we disregard the deviation from the usual course of development in Sporodinia, which 

 was mentioned above and scarcely requires to be considered. The species that are 

 thoroughly known, those, that is to say, in which zygospores have been observed, 

 have accordingly gonidiophores of a distinct form, which are shown by more than 

 one consideration to be constant and necessary members of the normal development 

 and also to be strictly homologous with one another, and it is these which are here desig- 

 nated typical gonidiophores. There are besides many species in which the zygo- 

 spores and their germination are not known, but which have gonidiophores agreeing 

 so entirely in all essential points with those of typical and thoroughly known species, 

 that they must be regarded as homologous with them and always have been so 

 regarded. These therefore come under the category which we are now considering. 



The gonidia themselves, apart from the doubtful genus Zygochytrium, which may 

 be put aside for the present, are in all cases simple motionless comparatively thin- 

 walled spores, in other respects possessing the usual structure. 



The genera and subdivisions of the group are chiefly distinguished as in the 

 Peronosporeae by the mode of their development, the structure of their sporangia, 

 and the structure and segmentation of their gonidiophores; to these are of course added 

 characters derived from the zygospores, mycelium, &c. The arrangement in the 

 following brief review of this group will be founded on these particulars. I go with 

 Van Tieghem in the definition and naming of the several genera, but merely for the 

 sake of brevity and convenience and without fully approving his minute divisions of 

 the forms ; I differ from him as regards the primary division. Three primary 

 groups may be distinguished according to the manner of forming the gonidia or 

 spores : 



The Mucoreae ; spores formed endogenously in terminal sporangia by division 

 of the protoplasm into several or many portions (see section XVIII). 



The Chaetocladieae ; spores abjointed acrogenously one by one (see section 

 XVI). 



The Piptocephalideae ; spores formed acrogenously and serially by cross- 

 septation (see section XVI). 



i. MUCOREAE. The sporangia (Fig. 71 g, A) are nearly spherical, rarely club- 

 shaped terminal vesicles on the primary stalk or on the branches of the sporangiophore. 

 In Mortierella they are placed with a narrow insertion on the slender extremity of 

 the branch that bears them, and are delimited in the plane of insertion by a horizontal 



1 Verhandl. d. Ges. naturf. Freunde zu Berlin, I, p. 



2 Jahrb. f. wiss. Bot. VI, p. 270. 



