TAPHRINALES 161 



with exogenous germination, as T. umbelliferarum on Heracleum and 

 Peucedanum and T. Rhaeticum on Crepis, the germ tubes (like the asci of 

 Taphrina) stand beside each other like a hymenium. The endospores 

 develop in a still unknown manner and fill the mature sporangium. In 

 both species, the chlamydospores are capable of immediate germination; 

 in the former, the mycelium winters over in the rhizome (Buren, 1917; 

 Juel, 1921). An explanation of the life cycle of the Protomycetaceae 

 from the point of view of change of nuclear phase is impossible at present, 

 as the nuclear behavior is not clear. From an analogy to the Taphrinaceae 

 and Ustilaginales, one might suppose that the dicaryon results from the 

 copulation of the spores and the mycelium in the host belongs to the 

 dicaryophase. Caryogamy would then occur in the chlamydospores 

 before germination. 



The position of meiosis is still uncertain in this scheme. Biiren (1915) 

 seeks it in the "tetrad-formation!" of the spore mother cells; hence he is 

 forced to consider the spore mother cells as naked asci and the resulting 

 endospore tube as a complex structure, a synascus, which is an entirely 

 isolated structure in the fungi. If one wishes to avoid this explanation, 

 one must assume that the quartering of the spore mother cells does not 

 have the significance of a meiosis and that the spore mother cells, like the 

 protospores of the Mucoraceae and Synchtriaceae, represent only an 

 intermediate stage not connected with change of nuclear phase. Meiosis 

 then, as in the Dipodascaceae and Endomycetaceae, would be sought in 

 connection with the nuclear fusion in the beginning of nuclear divisions 

 (not clearly demonstrated for Protomyces pachydermia and P. macro- 

 sporus but very probable from the observation of Fig. 99, 2 and 3) at the 

 emergence of the endospore. Like the ascus of Dipodascus, the endospore 

 would correspond to an ordinary ascus with still definite sporangial 

 character, but encysted like the zeugites of many parasitic Basidiomy- 

 cetes. Because of these uncertainties, the' systematic position of this 

 family is doubtful. 



Taphrinaceae. — As a representative of this family may be cited 

 Taphrina deformans, which causes serious damage to peach trees in 

 Europe and North America. (Dangeard, 1894; 1896; Eftimiu 1927.) 

 Its hyphae consist of binucleate cells which winter over in the bark, in 

 the pith and in the medullary rays of the year-old twigs. In the spring, 

 they penetrate the leaves emerging from the buds, spread rapidly and 

 stimulate these to the formation of wrinkles by unequal growth. Even- 

 tually they force their way between the epidermal cells of the upper sur- 

 face and form a reticulate tissue between epidermis and cuticle. The 

 individual cells swell during nuclear fusion (Fig. 100, 1), round off, 

 thicken their walls slightly, forming between epidermis and cuticle a 

 compact layer of chlamydospores (Fig. 100, 2) capable of immediate 

 germination. The exospore is ruptured and the endospore with the 



