160 MEDICAL MYCOLOGY 



by hypertrophy, causing the characteristic curling-. The hyphae force their 

 way between the cells of the upper epidermis and form a reticulate tissue be- 

 tween the epidermis and cuticle (Fig. 29, 2). The individual cells swell dur- 

 ing- nuclear fusion, thicken their walls, and form a compact layer of chlamydo- 

 spores capable of immediate germination. The exospore is ruptured, and the 

 endospore with the protoplasm bulges out as a papilla rupturing the cuticle. 

 When the chlamydospores are entirely empty, the protoplasmic portion is ab- 

 jointed from the empty portion. This apical cell forms the young ascus ; and 

 the empty cell is called the stipe cell. 



The young ascus contains a large diploid nucleus formed by tlie fusion 

 of two hyphal nuclei during the formation of the chlamydospore. This nucleus 

 divides thrice. In the first division meiosis occurs. The protoplasm is in the 

 peripheral layer, which is denser near the nucleus. The developing spores lie 

 embedded in the meager periplasm (Fig. 29, 1). Under suitable conditions of 

 moisture and substrate, they lead a saprophytic existence, developing sprout 

 cells like the yeasts; occasionally sprouting begins within the ascus. In cer- 

 tain species, young, still sporeless asci may develop vegetatively either to 

 hyphae or sprout mycelia. 



The chlamydospores may be interpreted as zeugites, organs in which at 

 the close of the dicaryophase, caryogamy occurs. The position of plasmogamy 

 in the life cycle is still unknown. 



In general the other Taphriuaceae follow the development of Taphrina 

 deformans. In T. epiphylla and in T. Klehahni, Wieben (1927) has reported 

 copulation of blastospores prior to the formation of ineffective germ tubes, which 

 are then binucleate. In T. hullata, on pears and quinces, several dicaryons (in- 

 stead of one) are present in the hyphae but the mycelium becomes binucleate 

 before spore formation. In T. aurea (Fig. 29, 3, 4) on Populus (poplar) and 

 in T. epiphylla on Alnus (alder), there is no formation of a stipe cell. In T. 

 Coryli on Corylus (hazel) the diploid nucleus divides into two daughter nuclei 

 in the chlamydospore. One remains in the basal cell and degenerates, the other 

 migrates into the young ascus and divides there into 8 spore nuclei (Martin 

 1924). 



