Pogotrichum and Litosiphon. 459 
In the year 1849 the genus Litosiphon was founded by 
Harvey 1 , on the suggestion of D. Moore, to include two plants, 
Asperococcus pusillus , Carm. and Bangia Laminariae , Lyngb. 
Litosiphon pusillus is characterized by Harvey as having e fronds 
tufted, thread-shaped, very long, equal in diameter throughout, 
reticulated, clothed with pellucid hairs ; spores scattered/ 
while L. Laminariae is described as having £ fronds stellately 
tufted, short, cylindrical, blunt, slightly tapering at the base, 
smooth (or hairy toward the apex), transversely banded, the 
bands close together, spores scattered, or several in each 
transverse band.’ 
The two species of Litosiphon show a relationship to one 
another very similar to that of the two species of Pogotrichum 
to one another. L. pusillus grows epiphytically in tufts on 
Scytosiphon lomentarius and on Chorda filum , and, so far as 
is at present known, produces unilocular sporangia only. The 
affinities of Litosiphon and Pogotrichum are so close that it 
was quite natural to suppose P. filiforme might be the un- 
known and missing plurilocular state of L. pusillus. Reinke 
convinced himself that this view was untenable. In discussing 
the affinities of Litosiphon and Pogotrichum , Reinke states 2 
that so close are they that, had he known of the existence of 
‘ P. hibernicumi he would probably not have founded the 
genus Pogotrichum. As, however, the plurilocular state of 
Litosiphon was not known, he thought it best to keep the 
two genera distinct, pending the more complete knowledge. 
I was fortunately able to examine herbarium -material of 
L. Laminariae, in which I saw plurilocular sporangia, like 
those of P. hibernicum in all essentials. Having regard, 
however, to the difficulties of examination, and the nature of 
the material, I preferred to leave the whole question open 
until freshly gathered material could be examined. Hence 
1 W. H. Harvey, Phyc. Brit., Pis. 270 and 245. 
2 J. Reinke, op. cit. S. 63. Murray, in Science Progress (no. 5, 1894), in com- 
menting on my paper and expressing the opinion that I ought to have suppressed 
the genus Pogotrichum , states, inadvertently, that I extracted the information to 
which reference is here made, from Reinke by correspondence. 
I i 2 
