70 SEAWEEDS 
pteris Mertensit and Haplospora globosa have been 
found in British seas at Cumbrae in the Clyde Sea 
area, 
SPLACHNIDIACES. 
General Characters.—The only reproductive organs 
known in this monotypic order are zoospores con- 
tained in sporangia borne within  conceptacles 
resembling in appearance those of the Fucacew, but 
originating in a different manner. The sporangia 
are unilocular and resemble very closely those of the 
Laminariacee. The zoospores presumably germinate 
without conjugation, like the zoospores of other 
unilocular sporangia in the Phwophycew, but no 
observations have as yet been made. The thallus, 
which is of considerable stature, is attached to the 
substratum by a disc, and consists externally of 
parenchymatous cells, and internally of threads 
traversing a ropy mucous mass. It grows by means 
of an apical meristem. Only one species is known, 
viz. Spluchnidium rugosum Grev. 
The Thallus.—Plants of Splachnidium rugosum vary 
from about four inches to a foot in height, and spring 
in five or six separate fronds from a common disc. Each 
frond is of cylindrical form, tapering downwards and 
ending bluntly upwards, while giving off irregularly 
smaller branches of similar form. It is marked by 
numerous pits containing hairs, and at a later stage 
sporangia. The outer wall consists of two layers of 
epidermal cells, small and approximately cubical in 
shape, and three layers of cortical cells, at first poly- 
