470 BULLETIN OF THE BUREAU OF FISHERIES. 
1. Acrochetium parvulum (Kylin) comb. nov. Fig. 25. 
Chantransia parvula, Kylin, 1906, p. 124, f. 9. 
P. B.-A. No. 1999. (Chaniransia hallandica var. parvula (Kylin) Rosenvinge.) 
Plants 70 to 185 mic. tall, usually 100 to 150 mic.; basal cell 7 to 15 mic. in diameter, usually 7 to 
Io mic., bearing 1 to 6 erect filaments; cells 4 to 10 mic. in diameter, usually 6 to 7 mic., 1 to 3.5 diame- 
ters long, usually 1.5 to 2 diameters; branching frequent, secund or opposite; branches short, tapering, 
nearly every cell bearing a short apical hair which is frequently pushed to one side and may be shed; 
sporangia 6 to 9 by 8 to 14 mic., usually 6 to 8 by 12 to 13 mic., usually sessile, sometimes on a one-celled 
pedicel, frequently opposite; sexual organs borne on the same individuals as the sporangia or lacking. 
Scandinavia. 
Abundant on Polysiphonia harveyi, sea buoy, Beaufort, N. C., July 27, 1909. 
This species may be easily distinguished from the others occurring at Beaufort by its habit and its 
smallsize. Although all the specimens observed were sterile, the characters of the plants agree so closely 
with the published descriptions and figure of Chantransia parvula Kylin that it seems better to refer it 
to this species than to describe it as anew one. In the Beaufort specimens there is usually only one 
erect filament arising from the basal cell, although occasionally as many as four have been observed. 
It has not previously been reported from any region outside of Scandinavia, 
2. Acrochetium dufourii Collins. Fig. 26. 
Chantransia dufourti, Collins, 1911, p. 187. 
Acrochetium dufourii, Collins, P. B.-A. No. 1594. 
P. B.-A. Nos. 1594, 2087. 
Plants 200 to 600 mic. tall, usually 250 to 350 mic.; basal cell (original spore) 5 to 8 mic. in diame- 
ter, bearing 1 to 3 erect filaments; cells 4 to 5 mic. in diameter, 2 to 5 diameters long; branching rather 
sparse, sometimes opposite or alternate, more commonly secund; branches erect, not very closely set, 
not tapering at their apices; sporangia 5 to 6 by 7 to 10 mic., sessile or on 2 one-celled pedicel, on the 
main filament, or on a branch, usually in secund series; sexual organs unknown. 
North Carolina; Bermuda. 
Abundant on Sargassum filipendula, Fort Macon jetty, Beaufort, N. C., usually in company with 
Erythrotrichia carnea and often with Gomiotrichum alsidii, summer and autumn. 
This species most nearly resembles A. hoytii, from which it is distinguished by its smaller size, its 
smaller, superficial basal cell, its less frequent branching with consequent more open habit, and its 
usually less elongated branches not tapering toward the apices. There is usually only one upright 
filament from the basal cell, but sometimes two or three are observed. Two or three plants resembling 
A. dufourii in other respects have been observed on Dictyota dichotoma arising from short, horizontal, 
external filaments with no evident basal cell. If these plants should be referred to this species it would 
show a behavior here similar to that found in A. affine, where, apparently, the basal cell may form 
horizontal filaments and may itself become inconspicuous or disappear. In view of the small number 
of plants observed in this condition, however, the author has been unwilling to change the limits of the 
species to include these. 
This species is not known outside of North America, although, according to Collins (1911), it 
appears to be the plant of the Mediterranean distributed by Dufour as Callithamnion lenormandi in 
Erbario Crittogamico Italiano, No. 953, but not C. lenormandi Subr, in Kuetzing, 1849a, p. 640. 
3. Acrochetium hoytii Collins. Figs. 27 and 28. 
Acrochetium hoytii, Collins, 1908, p. 134. 
Chantransia hoytii, Collins, rg11, p. 186. 
P. B.-A. No. 1540. 
Plants 0.25 to 1.3 mm. tall, usually 0.5 to 0.65 mm.; basal cell (original spore) 12 to 25 mic. in diam- 
eter, spherical or somewhat elongate vertically, then up to 30 mic. long, superficial or slightly embedded 
in the host, bearing 1 to 4 erect filaments, very rarely forming one or more secondary basal cells; cells 
of main filaments 5 to 7 mic. in diameter, usually 2 to 4 diameters long; branching rather frequent 
below, usually rarer above, often secund; ultimate branches usually elongated, often simple or nearly 
so, usually tapering gradually toward the apices; sporangia lateral on the upper part of the filament and 
branches, usually on one-celled pedicels, sometimes sessile, usually secund, oblong, about 5 to 6 by 11 
to 15 mic.; cystocarps very rare, bore on short pedicels near the base of the branches. 
