NEW OR CRITICAL BRITISH ALG2E. 
19 
call the British plant P. filiforme , Pice., f gracilis. The new genus 
may be described as follows : Fronds unbranched, tufted, fila- 
mentous, growth intercalary.. Vegetative cells formed of many, 
more rarely of a single row of cells. Plurilocular sporangia 
formed from isolated or from several contiguous cells of the vegeta- 
tive filaments, intercalary ; in individuals composed of a single 
row of cells formed by division of one of the cells in the continuity 
of the frond into a number of smaller ones. P. filiforme f. 
gracilis filaments, 4-8 m.m. in length, usually composed of a single 
row of cells, 15-20 p broad, 15-30 p long, arising from a basal 
disc composed of one layer of cells. 
P. Hibemicum. Johns. Irish Naturalist, Part I., p. 4. 
Coast of Clare, Iieland. Dr. T. Johnson, Weymouth, E. B. 
In his account of the preceding species Keinke mentions that 
Dr. Johnson had found, on the coast of Ireland, another species of 
the genus * Pogotrichum which was distinguished by the fronds 
penetrating the host plant instead of arising from a basal 
disc. Dr. Johnson, in the first part of the “ Irish Naturalist,” 
states that he intends to publish a figure and description of the 
plant under the name Pogotrichum Hibemicum. I have found the 
plant at Weymouth, where it appears to be not uncommon in the 
spring of the year, fringing the tips of Laminaria saccharina in 
shallow sandy pools near low water mark. Had it not been that 
the filaments, which grew in patches of considerable length, did 
not arise from a basal disc, but penetrated the substance of the host 
plant, although very slightly, I should unhesitatingly have referred 
my specimens to Pogotrichum filiforme. 
Streblonema sphaericum, Thur. in Le Jolis Alg. Mar. Cherb. p. 73. 
In the fronds of Mesoglcea vermicularis. Fairlie, E. M. Holmes, 
Cumbras, E. B., not uncommon. 
Fronds from 10-15 pc thick, irregularly branched, here and there 
angularly bent, joints about as long as broad ; unilocular 
sporangia, spliserical or oval, 35-40 p in diameter, sessile or shortly 
stalked ; plurilocular sporangia ovate, acute, often containing only 
one row of zoospores. 
Ectocarpus minimus, Nagel. 
Dover, Nageli, Berwick, E. B. 
A minute species growing on the fronds of Himanthalia lorea 
and various Fuci. To the naked eye nothing is visible but a minute 
velvety coating of a yellowish-brown colour, forming patches on 
the frond of the host plant. The fronds are erect and very 
slightly branched, the sporangia ovate-acute, terminal, stalked. 
The whole plant bears a very close likeness to E. terminalis , from 
which it is distinguished by its fronds penetrating the substance of 
the host plant, while in E. terminalis the secondary filaments arise 
from a layer of more or less closely united creeping primary fila- 
ments. 
