454 SECTIONAL TRANSACTIONS.—K. 
Dr. I. M. Ropertson.—The peat mosses of Scotland (11.15). 
Discussion.—Prof. Dr. L. von Post, Prof. A. G. Tanstey, F.R.S., 
Dr. Frazer, Mr. MITCHELL. 
Dr. F. K. Sparrow.—lInteresting aquatic fungi from Cambridge (12.20). 
During 1932-33 an investigation of the aquatic fungous flora in the 
vicinity of Cambridge was undertaken. Representatives of all the aquatic 
orders of the Phycomycetes were collected and significant data on their 
morphology, biology and taxonomy noted. 
Forty members of the Chytridiales, including three new genera, six new 
species and many forms hitherto unreported from England, were found. 
As representative of the Blastocladiales, six species of Blastocladia, including 
one new to science, were collected, while five members of the Monoble- 
pharidales, one of the Leptomitales, five of the Saprolegniales and a new 
species of Myzocytium, a genus of the Ancylistales, were found. Four 
genera of the Pythiales were collected. The paucity of species of filamentous 
Phycomycetes was not due to the lack of these elements in the flora, but 
rather to the investigator’s greater interest in the rarer and lesser-known 
uniciliate forms. 
AFTERNOON. 
EXHIBITS. 
Wednesday, September 11: 
Mr. T. G. Tutin.—Eel grass (10.0). 
Eel grass, Zostera marina L.., is one of the few marine flowering plants 
found in temperate seas. It has a creeping rhizome, long linear leaves, and 
erect flowering stems, bearing several inflorescences, each enclosed in a 
leaf-like spathe. The flowers are unisexual and devoid of perianth, the 
female consisting of a single ovary, and the male of a single stamen which 
produces thread-like pollen. Zostera occurs on the coasts of Europe and 
North America in considerable abundance, and is of economic importance, 
so that the sudden appearance of disease in the Atlantic, about 1930, was 
speedily noticed. 
A number of different organisms were suggested as the cause of the 
disease, and two at least seem to be serious parasites, but the underlying 
cause is almost certainly the rare occurrence of good crops of seedlings over 
most of the plant’s range. <A fairly high temperature and good illumination 
in the autumn seem to be the necessary conditions for germination, and 
these are seldom forthcoming on the Atlantic coast of Europe. Continued 
vegetative reproduction gives an opportunity for the spread of a normally 
mild parasite, so that a season slightly adverse to the plant may produce 
widespread destruction. 
Dr. E. Asupy and Mr. P. O. Wi1EHE.—Ouantitative studies in the ecology 
of a salt marsh (10.30). 
The distribution of individuals in a pure stand of Salicornia has been 
studied by statistical methods. Toward the sea there are fewer plants per 
unit area than toward the land. This is due to the fact that the seedlings 
require for their establishment a ‘ threshold period ’ free from submergence 
