RICHARDS. — DEVELOPMENT OF ^CIDIA. 263 



The basidia are comparatively short, aud.the layer below them, 

 which may be called the sub-hymenial layer, is much more closely 

 compacted than in any of the forms jareviously described in this paper. 

 It is also noticeable that the base of the hymenium, which iu other 

 cases, at least in the younger stages, is often somewhat rounded, is 

 here practically flat, since the basidia almost all terminate on the same 

 level. The primordium progresses iu its development witliout much 

 variation from the general rule, except that the amount of pseudo- 

 parenchymatic tissue is relatively smaller, and the surrounding weft 

 of hyphre relatively larger than iu the three cecidia already described. 

 It was evident from the appearance of the young hymenium, iu which 

 the basidia develop much more nearly simultaneously than in the 

 cases already noted, that there was some variation in the development 

 of this form from the types previously examined. 



Below the young basidia in the sub-hymenial layer there could be 

 distinguished fertile hyphse, from which the basidia are budded out, 

 and sterile hyphas that wound in among them (Fig. 12). The former 

 could be separated from the latter on account of their power of stain- 

 ing deeply. This layer of sporogenous hyphjE which underlies the 

 pseudo-parenchyma gives rise to the basidia more nearly at the same 

 time than they arise, for instance, in ^cidium Caladii, although even 

 here it is apparent that the younger basidia are the ones nearer the 

 periphery of the hymenium. The fertile hyphaj arise from the 

 branching of hyphag tliat make their way up from below, and appar- 

 ently the sporogenous layer may arise from more than one of such 

 hyphfe. This course of development much more nearly corresponds 

 to that given by Neumann * than any of the others do, but is not 

 exactly as he describes it in the aecidia he investigated. 



It was in this species especially that hyphfe were seen protruding 

 through the stoma, but examination failed to show any connection 

 of such hyphae with the primordia, and it was probably due more to 

 the very great crowding of the mycelium in the leaf than to any 

 other cause. The subsequent development of the spores and perid- 

 ium failed to reveal any noteworthy peculiarities. This tecidium is 

 especially interesting as showing a variation from others in the matter 

 of its development, but a discussion of this point will be reserved 

 until a few words have been said about some other fecidia which 

 afforded interesting facts, especially regarding the formation of the 

 peridium. 



* Loc. cit.. 



