6oo 
Brooks.—The Development of 
functioning in a secondary manner as respiratory organs. One naturally 
supposes that as the leaf of the host becomes first yellow, and then brown, the 
assimilatory process dwindles, until no oxygen at all is liberated, while the 
evolution of carbon dioxide continues for a time. Such phenomena may 
very well necessitate the growth of certain hyphae through the stomata to 
the outside atmosphere. Vuillemin ( 31 ) records the interesting fact that in 
the genus Hypostommn , parasitic on the leaves of Conifers, structures con¬ 
sidered by him to be analogous to trichogynes are produced, although no 
spermogonia are present. This also points to the possibility that the 
trichogynes may now perform a function which was not their original one. 
This investigation leads one to look upon the ascocarp of Gnomonia as 
a structure formed in relation to one or more ascogonia in close connexion 
with one another. This association of two or more ascogonia before the 
development of the perithecium is paralleled in the Discomycetes by 
Pyronema confluens ( 23 ) in which several pairs of sexual organs co-operate 
to give rise to a single apothecium. Stahl ( 28 ) states also that in the 
Lichen genus Physma , several archicarps go to produce one apothecium. 
Many other Pyrenomycetes show the presence of definite archicarps before 
the formation of perithecia, but in these the female organs normally arise 
separately one from the other. Fisch ( 15 ) states, however, that in Poly stigma 
rubrum , two ascogonia with their trichogynes may arise in close association. 
The ascogonia of Gnomonia erythrostoma seem to be more closely allied to 
those of Polystigma rubrum than to those of any other Ascomycete as yet 
investigated. Coiled ascogonia have been described also by Kihlmann ( 25 ) 
as occurring in Melanospora parasitica , by Miss Dawson ( 13 ) in Poronia 
punctata , and by Fisch ( 15 ) in Xylaria polymorpha. In Poronia^ however, 
the trichogyne portion is not always present, and in Xylaria it is constantly 
absent. Fisch states, in regard to the latter, that the asci arise independently 
of the ascogonia as they would appear to do also in Gnomonia . He found 
that in Clavicepspurpurea there was no trace of an ascogonium, so that in 
the series mentioned there is an evident reduction in the formation of the 
female organs. When one considers the Lichen genera Collema 2 l\\& Physcia, 
one sees some resemblance between the general form of their ascogonia and 
those of Polystigma and Gnomonia. These four genera are all characterized 
too by the production of spermogonia. The cells of the ascogonia of these 
Lichen genera are uninucleate as described by Baur (a) and Darbishire ( 12 ) 
respectively, a condition in marked contrast to the multinucleate nature of the 
ascogonial cells of Gnomonia. Baur states that in Collema crispum the succes¬ 
sive cells of the trichogyne are clearly connected by strands of protoplasm 
at the time which he considers to be that of fertilization. He infers that the 
pores through which these strands pass enable the spermatial nucleus to pass 
down to one of the ascogonial nuclei below. In Gnomonia no such pheno¬ 
menon has been observed, and the fact that the ascogonia at a later stage 
