162 



COMPARATIVE MORPHOLOGY OF FUNGI 



protoplasm bulges out as a papilla, rupturing the cuticle. When the 

 chlamydospores become entirely empty, the protoplasmic portion is 

 abjointed from the vacuolate portion (Fig. 101, 1). This apical cell 

 forms the young ascus; the vacuolate chlamydospore is called the stipe 

 cell (in systematic literature). 



The young ascus (Fig. 102, 5) contains a large diploid nucleus formed 

 by the fusion of two hyphal nuclei during the formation of the chlamydo- 

 spore. This nucleus divides thrice. In the first division, the spindle is 

 generally transverse and here meiosis occurs. The protoplasm is in a 

 peripheral wall layer, which is denser near the nucleus (Fig. 102, 8). 

 The developing spores lie imbedded in a meager periplasm. In water, 

 or sugar solutions, they develop sprout mycelia like yeasts; occasionally 

 sprouting begins in the ascus, which then becomes filled by a dense sprout 

 mycelium (Fig. 101, 4). In certain forms, young, still sporeless asci 

 may develop vegetatively either to hyphae or sprout mycelia (Fig. 101, 2). 

 These sprout mycelia are apparently biological substitutes for conidia 

 since they fulfil the functions of propagation. 



1 



Fig. 100. — Taphrina deformans. 1. Subcuticular, binucleate ascogenous hyphae before 

 caryogamy. 2. Young chlamydospores. (After Dangeard, 1894.) 



Thus the chlamydospores may be interpreted as zeugites, organs in 

 which at the close of the dicaryophase, caryogamy occurs. In this sense 

 they would be considered homologous to the probasidia and sclerobasidia 

 of the Auriculariales, to the teliospores of the Uredinales and the smut 

 spores of the Ustilaginales, and thus the conceptions to be discussed 

 under the Basidiomycetes, concerning the differentiation of zeugite and 

 the sporophores and the encysting of zeugites, would also be important 

 for the Ascomycetes. Although the validity of this interpretation is not 

 yet certain, with these reservations it may be useful. The position of 

 plasmogamy in this life cycle is unknown. In analogy to the Protomy- 

 cetaceae and Ustilaginales one would expect it in the sprout mycelium 

 although copulation has not yet been observed there. 



The other Taphrinaceae follow, as far as known, the development of 

 Taphrina deformans. In Taphrina bullata on pears and quinces, however, 

 several dicaryons instead of one are present in the hyphae, but the myce- 

 lium becomes binucleate before spore formation. 



