CHAPTER V. — COMPARATIVE REVIEW. — MUCORINI. 



149 



In the group of Piptocephalideae the archicarps are curved and so disposed 

 that the pair has very nearly the form of an 12 or of an inverted fl. The surface 

 of union lies in the apex of the bow (Figs. 73, 74 Z). In Syncephalis nodosa the 

 archicarps are coiled spirally round one another. Up to the time when the con- 

 jugation of the slender gametes is completed the development is essentially the 

 same as in the first-mentioned cases, but then the product of conjugation swells at 

 the place of coalescence into a spherical vesicle, which bulges on the convex side of 

 the bow of the fl. Protoplasm passes into it in proportion as it increases in size. 

 When it has reached the limit of its growth, it is delimited by a partition-wall from 

 each limb of the bow and becomes a nearly spherical zygospore ; it may at least 

 be so called for the sake of clearness and simplicity, though it is plain that it is not 

 the strict morphological equivalent of the zygospore of the first case, but is a 

 daughter-cell of the zygospore, if the zygospore is the cell which results directly from 

 the conjugation of the pair of gametes. If we adopt the proposed terminology, the 

 spherical zygospore of Syncephalis 

 is placed at the apex of the bow 

 formed by the pair of suspensors, 

 and each suspensor is divided by a 

 transverse wall. 



The behaviour of the zygospores, 

 while they are maturing, is essentially 

 the same in both cases, apart of course 

 from specific differences. The fatty 

 matter in the protoplasm, which con- 

 tinues to be dense and darkly granu- 

 lar, usually collects into several large 

 round drops. A further and exact 



insight intO more delicate pointS Of FIG. 73. Piptocephalis Fresmiana, conjugation and formation of 



zygospores, the development in the order of the numbers. Z a ripe 



StrUCtUI"e in the pi'OtOplaSm is Scarcely zygospore on its suspensors. After Brefeld from Gaebel, Grundzlige. 



Magn. 650 times. 



attainable owing to its opaqueness. 



The wall forms usually wart-like or conical projections on its free outer surface, in 

 Piptocephalis even before the delimitation of the zygospore, only those parts re- 

 maining smooth where it is in contact with the suspensors, and becomes differentiated 

 into a stout episporium the colour of which varies from brown to black, and a thick 

 stratified endosporium formed of more than one layer (Figs. 7a e, 71 C, 73 III, 74 -Z). 

 The latter has either its outer surface quite smooth, as in Chaetocladium, and the 

 projections belong entirely to the episporium ; or it is furnished with stout solid 

 projections which fit into corresponding depressions in the episporium (species of 

 Mucor, Sporodinia). Mortierella is the only exceptional case, in which the episporium 

 is not rough on its outer surface and owing to its close adherence to the investing 

 envelope is but little developed. 



In many species, and in the majority of those which have been named above and 

 represented in Figs. 71-74, the ripe zygospore thus constituted lies naked and without 

 any further covering between the suspensors, which ultimately wither and decay. 

 But in some species an envelope is added to the parts already described in the 

 zygospore. Short branches shoot out in a simple or multiple circlet in the more 



