ACROCHAETIUM 87 
of it for a very minute examination, but its general microscopic 
appearance, taken in connection with Montagne’s description and 
figures, leaves us in no real doubt that it is specifically identical 
with the plant now described and figured from the same locality 
and in part on the same host. The only essential fault in Mon- 
tagne’s description would appear to be in an exaggerated idea as 
to the length of the plant as expressed in “Fila 2 lineas ad semi- 
роШсет longa.” Montagne’s specimens, so far as preserved, аге, 
like Coker’s, scarcely more than І mm. long. However, in Mon- 
tagne’s first description the only reference to size is “ microscop- 
ique.” Montagne seems to have recognized the true affinities of 
the plant by associating with it in his herbarium a specimen of 
Callithamnion Savianum Menegh. on leaves of Zostera from Genoa, 
sent to him by Meneghini. 
Among the more recently and more critically described species, 
the nearest relative of Acrochaetium clandestinum is probably 
Chantransia attenuata Rosenv. (Kgl. Danske Vidensk. Selsk. 
Skrift. VII. 7: 106. f. 35. 1909), found growing on Desmarestia 
aculeata in one of the sounds of Denmark, but according to Rosen- 
vinge’s description and figures of this species, the Peruvian plant 
is taller, somewhat coarser, and more copiously branched, its 
branches are longer, its main filaments diminish in size towards 
the base rather than towards the apex, its cells are longer, its 
sporangia are smaller instead of larger than the supporting 
sterile cells, and the plant is apparently destitute of hairs. 
Of the Barbados Acrochaetium flexuosum Vickers (Ann. Sci. 
Nat. Bot. IX. 1: 60. 1905) as distributed by Miss Vickers 
(Alg. Barbad. 98), we have seen only imperfect specimens, but 
have better ones of what we suppose to be the same species on the 
same host (Chaetomorpha media—‘‘C. antennina ”) from Porto Rico. 
In these the cells are much shorter than in the Peruvian plant, being 
rarely 3 times as long as broad (often 6 times in the Peruvian) 
and the chromatophore is usually more or less H-shaped in optical 
section with a large bulge from one side towards the center of the 
cell—quite different from the vires cmd of A. а 
The West Indian plant forms larger more densely te masses 
and usually has numerous decumbent filaments колен inter- 
mediate in character between those of the disc and those that 
