148 THE ASCOMYCETES 



a few species. Haustoria are lacking. Sadebeck (1893) placed 

 in Magnusiella those species having intracellular hyphae. 



Reproduction. Reproduction among Taphrinaceae is accom- 

 plished bv the formation of a palisade-like layer of asci that arise 

 as terminations of the internal mycelium. Before ascus formation 

 a compact mycelial layer, one cell thick, is formed subcuticularly 

 in most species. In Taphr'wopsis laiirencia the ascus-bearing layer 

 develops within the epidermal cells. All the cells of this layer are 

 binucleate. As they elongate, the nuclei fuse, after which, in 

 most species, a short stalk is cut off at the base of the ascus. In 

 Taphrhm carnea stalk cells are not formed [Juel (1921)], but the 

 cell containing the fused nucleus becomes the ascus. Juel (1921) 

 states that the basal cell nucleus migrates into the cell that is to 

 become the ascus before the cross wall is formed. In T. coryli 

 [Martin (1924)] the fusion nucleus divides reductionally; as a 

 result, the nucleus of the stalk cell and that of the ascus contain 

 n chromosomes. The nucleus in the stalk cell soon degenerates, 

 but that in the ascus divides and redivides to form eight daughter 

 nuclei. Eight ascospores are then formed. In Taphina de- 

 joinmvs the ascospores on discharge germinate by yeast-like bud- 

 ding [Martin (1925), Mix (1924)], but in certain other species, 

 such as T. johansonii, budding takes place while the spores are 

 still confined within the ascus. , 



Circumstantial evidence has long indicated that the ascospores 

 of T. dejoTJiians or the conidia formed by budding lodge be- 

 tween the bud scales and overwinter there. The fact that peach- 

 leaf curl can be very successfully eliminated by the application 

 of a dormant spray [Pierce (1900)] constitutes evidence of how 

 this organism hibernates. In fact, the discovery of lime-sulphur 

 sprays was made as the result of drenching peach trees with lime- 

 sulphur solutions used as sheep dip. The trees adjacent to vats 

 were covered \\ith dip ^\•hile the solution was being changed in 

 the vats. As a consequence trees that were drenched remained 

 leaf -curl free. More direct evidence of hibernation of spores on 

 peach buds was secured by Mix (1924) as the result of bagging 

 and of inoculation experiments. 



In regard to the origin of the binucleate condition of the 

 hyphal cells Martin (1940) states that in T. dejorvians, when the 

 ascospores, buds, or thick-walled spores from culture germinate 



