534 3Ir Brool's, The Development of Gnomonia erythrostoma, 



The Development of G~nomonia erythrostoma, the Caiise of Cherry 

 Leaf 8corch Disease. By F. T. Brooks, M.A., Emmanuel College. 



[Received 6 June 1910.] 

 [Abstract.] 



The life-history of this Pyrenomycete may be summarised 

 as follows : Infection of the foliage occurs in the early summer 

 by means of the ascospores. Spermogonia and " coils " ai'e formed 

 in the diseased leaves. It was considered by Frank, who described 

 the outlines of the life-history several years ago, that the spermatia 

 produced in the spermogonia fertilise the " coils " by passing down 

 the trichogynes which arise in association with the latter. The 

 " coils " ultimately develop into perithecia. During the summer 

 the vegetative mycelium passes down the leaf stalk and prevents 

 the formation of the absciss layer. On account of this, the diseased 

 leaves remain hanging on the trees throughout the winter and 

 become the source of reinfection the following season. 



The present investigation concerns an examination of the life- 

 history of this fungus from the cytological standpoint, very little 

 work on the Pyrenomycetes having hitherto been done from this 

 point of view. 



The vegetative mycelium of Gnomonia consists of multinucleate 

 cells. It is intercellular and haustoria are not developed. 



The spermogonia show similarities in structure to those of the 

 Uredineae. The spermatia are long and thread-like and exhibit 

 the cytological characters of male cells. It is considered, however, 

 that they are now functionless, there being no evidence that 

 fertilisation is effected by their agency as Frank supposed was the 

 case. 



The trichogynes occur in tufts of 2 — 5. They do not in- 

 variably arise in association with " coils." It is suggested that 

 the trichogynes though originally receptive organs now perform a 

 different function — serving possibly as a means of aeration. 



The " coils " represent the first stages of perithecial develop- 

 ment. In the centre of each coil one or more slightly differentiated 

 hyphae are found. These are considered to be of the nature of 

 ascogonia. No clear connection can be traced between the 

 trichogynes and these cells. The " coil " undergoes a period of 

 rest before developing further. 



