146 



ROLAND THAXTER ON THE 



of germination in this genus of a related type; but as the author describes the swollen 

 extremity of the conidiophore as a basidium, the similarity is not so striking as a com- 

 parison of this with fig. 119, for example, in the present paper, would lead one to infer. 



Cystidia and rhizoids. — Before leaving the conidia and conidiophores, two additional 

 structures must be mentioned, which are of some importance morphologically. These are 

 the so-called cystidia, or paraphyses as they have been called; and a modification of cer- 

 tain hyphae, known as rhizoids, which serve to attach the host to the substratum on 

 which it rests. The cystidia are usually simple hyphae, exceeding the conidiophores in 

 size, and projecting bej^ond them, often to a considerable distance. In some instances 

 they are very large (fig. 306), and readily seen with the naked eye; while in others they 

 do not differ from the conidiophores. They are not, I think, homologues of paraphyses in 

 other fungi, and their office is unknown ; unless, perhaps, they may be considered as rhi- 

 zoids which are functionless from their position ; an explanation which seems to me very 

 probable. A modification of the paraphyses should be mentioned which occurs in E. 

 echinospora, a species in which, contrary to the usual type, the zygospores are very com- 

 monly produced externally. In this case, when the sporophores have emerged from the 

 host, certain of their number may be seen projecting beyond the rest (fig. 297). While 

 the process of spore formation is going on, these hyphae grow rapidly, forming ultimately 

 a delicate network about the mass of mature zygospores. 



The hyphae of attachment, or rhizoids as they may be conveniently termed, consist of 

 hyphae which, growing from the lower and outer portions of the fungus mass, attach 

 themselves to the substratum upon which the host rests and serve to hold it firmly in 

 position. The rhizoids may be simple or variously branched, and their termination may 

 be variously modified into an expanded "sucker" (fig. 249). They do not, I think, enter 

 into soft substances, and their adhesion is apparently due to the presence of a viscous 

 secretion. They are produced with great rapidity, appearing even before the host is dead? 

 and increasing in number with the appearance of the conidiophores. Rhizoids are con- 

 fined to certain species, and generally accompany the digitate type of conidiophores; 

 their presence should not, however, in my opinion, be considered of any importance as a 

 generic distinction. 



It is now necessary to return once more to the condition in which we find the host 

 filled with chlamydospores, or hyphal bodies, in order to examine the phenomena con- 

 nected with the 



Formation of zygospores and azygospores. — As has been previously remarked, the 

 germination of the hyphal bodies or chlamydospores may result in the production of 

 conidia above described; or may lead to the formation of spores called resting spores, of 

 a very different nature, and adapted to withstand successfully conditions that would prove 

 fatal to the conidia in a short time. The passage to this resting condition may be accom- 

 plished by a wholly non-sexual process, in which case the resulting spore has been termed 

 an azygospore, or by sexual union of a type similar to that found in the Mucorini. The 

 spores thus formed are usually of large size, spherical with one exception ; with a highly 

 refractive fatty contents ; surrounded by triple walls, the outer thin and representing the 

 wall of the mother cell, the second much thicker, and the inmost usually as thick as 

 or thicker than the other two combined. 



