164 PYRENOMYCETES [CH. 



swollen and apparently mucilaginous; these projecting filaments were re- 

 garded by Frank as trichogynes, but more recently Brooks has found evi- 

 dence that they arise from the outer cells of the perithecium and that, what- 

 ever their origin, they now no longer function as receptive structures. Sper- 

 matia are often found attached to their terminal cells, but, in view of the 

 enormous number of spermatia liberated on the under surface of the leaf, 

 they could hardly fail to be found in relation to any projecting filament. 



In the lower part of the coils certain cells become differentiated by their 

 denser cytoplasm and larger nuclei, and no doubt represent the oogonial 

 regions of the archicarps. No union of nuclei has however been observed 

 in them and it is at least doubtful whether they give rise to the ascogenous 

 hyphae. The latter do not become clearly differentiated till the oogonial 

 cells have disappeared ; asci are formed either from the terminal or sub- 

 terminal cells; in the young ascus two nuclei fuse. 



Throughout the divisions in the ascus and in the division of the spore 

 nucleus Brooks has reported four chromosomes. Those in the first division 

 in the ascus are short and thick, resembling heterotype chromosomes in 

 appearance, and there seems reason to believe that reduction occurs at this 

 stage. 



The life-history of Gnomonia shows many points in common with that 

 of Polystigma\ both are at first leaf parasites, and complete their develop- 

 ment saprophytically on the dead leaf. Both produce spermogonia with 

 filiform spermatia and perithecia developed in relation to coiled archicarps. 



An important point of difference is that in Polystigma a stroma is formed 

 and the fungus hibernates on the fallen leaves below the tree without being 

 injured by their decay; in Gnomonia no stroma is present and the fungus 

 inhibits the formation of the absciss layer so that the withered leaves 

 remain on the branches and provide a matrix in which the perithecia can 

 be formed. 



GNOMONIACEAE: BIBLIOGRAPHY 

 1886 FRANK, B. Ueber Gnomonia erythrostoma, die Ursache einer jetzt herrschenden 



Bhittkrankheit der Siisskirschen im Altenlande, nebst Bemerkungen iiber Infection 



bei blattbewohnenden Ascomyceten der Baume iiberhaupt, etc. Ber. der deutsch. 



Bot. Gesell. iv, p. 200 

 1910 BROOKS, F. T. The Development of Gnomonia erythrostoma, the Cherry- Leaf-Scorch 



Disease. Ann. Bot. xxiv, p. 585. 



Valsaccae 



The perithecia of the Valsaceae are produced frequently in compact 



groups on a black stmma from which their long necks alone project. The 



stroma ,s very variable in form ; it is developed within the substratum and 



: or less d.fferentiated from it, sometimes indicated only by a black 



on the wood or bark of the host and by a black margin, sometimes 



