290 Rhodora [DECEMBER 
species known, both epiphytic, occurring in tropical or subtropical 
regions, and both quite distinct from the plant now under considera- 
tion. ‘The nearest described species would seem to be D. compacta 
(Ag.) Born. and Flah., a fresh water plant of Scandinavia of smaller 
dimensions and different habit. It seems safe, therefore, to con- 
sider it as a new species, characterized as follows. 
DICHOTHRIX rupicola n. sp. Marine. Filaments forming a caes- 
pitose stratum, one mm. high, 1 5-22 y diam., erect, penicillate, pseudo- 
branched, ultimate branches flexuous-divaricate, acute. Sheath lam- 
ellate, yellow-brown, near the tip with dilated and lacerate ochreation. 
Trichomes aeruginous green to pale olive, 7-9 p diam., terminating 
in a hair; length of articulations about equal to the diameter. 
Heterocysts basal. Forming a coating on sloping rocks, exposed 
to full force of the waves, Pemaquid Point, Maine, July 18, 1901. 
CODIOLUM PUSILLUM forma Americanum Foslie. The Vaucheria 
pusilla of Lyngbye was placed in the genus Codiolum by Foslie, 
Troms@ Mus. Aarshefter, Vol. X, p. 190, and is distinguished from 
the other species of this genus by the long stipe, slender throughout 
and much narrowed at the base, and by the cylindrical or sub- 
cylindrical “clava,” the latter being from one half to two thirds the 
length of the stipe. In forma Americanum the clava is generally 
longer, sometimes equalling the stipe, otherwise the form is the same 
as the type. 
The specimens collected grew on a rock, near high water mark at 
Marblehead, Mass., covering it with a continuous coating, in the 
manner of C. /ongipes Foslie, but not showing so distinct a mottled 
aspect in drying as the latter. On June 1, 1901, and at a subsequent 
visit June rs, young plants and germinating spores were found in 
abundance among mature plants, and some of the latter were forming 
spores, but none quite perfect were seen. Possibly the emission of 
spores took place at a different time of day from the time of collecting. 
At Pemaquid Point, on the same exposed rocky slope where Dicho- 
thrix rupicola was found, there occurred in pools at about half tide 
level, an abundant growth of what appeared at first to be a Cladophora, 
similar to C. refracta Areschoug, but of denser growth and with slen- 
derer branches. On dissection and microscopic examination it be- 
came evident that the plant was not like any species of Cladophora 
known on this coast, the branching being confined to the extreme 
base of each tuft, the upper part consisting of simple, crisped filaments, 
much like those of AZzoclonzum tortuosum Kuetz. The next suppo- 
