PAPERS OX BOTANY 151 



hvphal threads is variable and examples may be fomid 

 of different modes. 



In one developmental series, representative of the sym- 

 phogenoiis method, formation of the pycnidial primor- 

 dium begins by the lateral budding of one or more cells 

 of a hyphal thread (Fig. 28), cells of various shapes and 

 sizes being cut off. A second hypha, lying beside the first, 

 buds, and the branches resulting from these two parent 

 hyphae unite. In other cases, this second hypha is in- 

 cluded in the formation, by the uniting of a branch of 

 the first hypha with a cell of the second (Fig. 27). Occa- 

 sionally, additional main mycelial threads may become 

 involved. 



From this stage on, regardless of how initiated, the 

 process is one of rapid branching, with many connecting 

 links fo lined between the hyphal threads (Fig. 29). 

 Much looping and interlacing of main and branching 

 hyphae ensues, which results in a dense mass of mycelial 

 cells. The outer portion or covering then becomes mem- 

 braneous and darkens in color. Further internal de- 

 velopment and cell differentiation of the mass, results in 

 a pycnidium (Fig. 30). 



Conidia. Conidia were rarely found, as scores of 

 seemingly mature pycnidia were examined without evi- 

 dence of fructification. The method of procedure was 

 as follows : Bits of apple skin on which it was thought 

 good material might be present were placed in concen- 

 trated potassium hydroxide over night. The next morn- 

 ing the skin was washed and the pycnidia removed to a 

 glass slide, in a small amount of water. A cover glass 

 was placed on the material, and individual pycnidia ob- 

 served under the low power, were forced open by care- 

 ful pressure with the scalpel. Where conidia were ob- 

 served extruding through the characteristic slit, they 

 were stained with iodine. 



The conidia (Figs. 23, 31), are almost hyaline, one- 

 celled, and while varying in shape, are somewhat ob- 

 long, straight or slightly curved, muticate, measuring 

 10-20 X 4-7/i. The conidia appear to be sessile, or borne 



