138 Proceedings of the Royal Society of Edinburgh. [Sess. 
Affinities of Peronosporites gracilis. 
The close resemblance to Peronosporites antiquarius is evident at once, 
and has already been pointed out by Seward (10, p. 218). The present 
investigation lends considerable support to the suggestion that both 
organisms should be placed in the same genus : there is a resemblance not 
only in the habitat and vegetative hyphse, but also in the reproductive 
organs. If it were not for the marked difference in the size of the two 
organisms it would be difficult to distinguish between them. The 
similarity between the vesicles shown in Plate, fig. 3, and the so-called 
“ oogonia ” of P. antiquarius is particularly striking. Both organisms 
belong to the Phycomycetes, and among these they are evidently most 
closely allied to the Peronosporacese : these are strong parasites that infest 
the living tissues of land-plants, the whole course of their life-history being 
run inside the tissues of their hosts. There is every probability that the 
members of the genus Peronosporites followed a similar course. The 
absence of transverse septa separating the vesicles from the connecting 
hyphse indicates either the very delicate nature of such septa precluding 
their preservation, or a more primitive form of reproduction. The latter 
is the more probable explanation. 
Synopsis of Characters of Peronosporites gracilis. 
Hoi dzon. — English and French Carboniferous rocks; in England only 
in Lower Coal Measures, so far as ascertained. 
Habit. — Typically in soft parenchymatous cells of stems and roots of 
Lepidodendron and Lyginodendron ; occasionally in tracheidal cells. Intra- 
cellular, endophytic, and very probably parasitic. 
Mycelium. — Hyplise 2 jm to 4/x. Tubular, uniformly thick, and with 
delicate membrane. Branching sparingly and monopodial. No transverse 
septa. Hyphal swellings not uncommon. 
Reproduction. — 1 . Structures shown in Plate, fig. 3, and text-fig. 2 were 
either intercalary sporangia or hyphal swellings with a metabolic function. 
Similar structures were wrongly named “oogonia ” by earlier writers. 
2. Structures shown in Plate, figs. 2 and 4, and in text-fig. 3 are 
comparable with swarm-sporangia of modern Peronosporacese or Sapro- 
legniacese. They differ in the absence of transverse septa, indicating a 
more primitive type of structure. 
Palseomyces bacilloides Ellis. 
Another fungus, markedly different from the one described above, was 
also discovered in specimens from the Lower Coal Measures. This fossil 
