118 
individuals shew spermatia. In the winter cystocarpic 
individuals are in the majority. The plants usually 
disappear from the flora by the end of May. This lack of 
conformity to the usually accepted canons of behaviour 
for Rhodophyceae may possibly be correlated with the 
fact that Polysiphonia Brodizi is a winter annual in the 
littoral zone whatever it may do in deeper waters, and 
makes its first appearance in the pools in October and 
disappears from the littoral flora by the end of May. The 
same data have been observed for the periodicity of 
occurrence and reproduction of Rhodomela subfusca. The 
plant appears in pools of the littoral zone as sporelings 
in November. By January, these plants have reached a 
stature of two or threeinches and occasional plants bearing 
Spermatia have been recorded for this period. Plants 
bearing tetraspores are found in March in abundance but 
from February onwards cystocarpic individuals appear in 
increasing proportions until May when the plants retreat 
from the littoral zone. Here again the rhythm is not 
very clearly defined and is associated with a winter annual 
habit. 
20. Melobesia minutula, Foslie. 
This minute calcareous alga has been found associated 
as an epiphyte with the fronds of Halopteris filicina. It 
may possibly be of common occurrence since it is present 
on Halopteris plants collected at different times from three 
different localities—Port St. Mary (March), Plymouth 
(May), and Anglesey (August). The specimens have been 
examined by Professor Rosenvinge and identified as 
Melobesia minutula Foslie. Under a list of synonyms, 
Professor Rosenvinge has included the name of Lithocystis 
Allmanni, a genus described by Harvey, “‘ Phyc. Brit.” 
Vol. II, Plate 166. The Port Erin specimens are, however, 
distinct from Lithocystis in that they shew minute cortical 
cells covering the pericentral walls of the thallus cells. 
