MARINE ALG! OF BEAUFORT, N. C. 473 
5. Acrochetium corymbiferum (Thuret) Collins and Hervey, 
Chantransia corymbifera, Thuret, in Le Jolis, 1863, p. 107. 
Chantransia corymbifera, De Toni, 1897, p. 69. 
Acrochatium corymbiferum, Collins and Hervey, 1917, P. 97- 
P. B.-A. Nos. 1040, 1880 (Chantransia corymbifera); not No. 192. 
Plants 2 to 3 mm. tall; basal cell (original spore) 12 to 15 mic. in diameter, sending down into the 
host a branching filament about the size of the erect filament but more irregular and contorted; erect 
filaments arising from the basal cell and the secondary internal filament; cells 8 to 16 mic. in diameter, 
3 to 10 diameters long; branches few below, more abundant above, alternate or somewhat secund, 
virgate, sparingly branched; sporangia sessile or shortly pedicellate near the bases of the branches; cysto- 
carps forming dense, hemispherical clusters of naked spores near the bases of the branches; antheridia 
forming small, dense, short-pedicellate clusters at various pointson the branches; sporangia, cystocarps, 
and antheridia produced on different plants. 
California; Bermuda; England; Atlantic coast of France. 
Very abundant on one plant of Dasya pedicellata growing in harbor, Beaufort, N. C., May, 1907. 
This species has not previously been reported from our coast. While found on only one plant, it 
was probably more abundant, as it was completely hidden by the hairs of its host. No sporangia have 
been observed here. The habit of this species resembles that of A. hoytii (figs. 27 and 28), but it is 
easily distinguished from the latter by its internal basal filaments and its abundant cystocarps. From 
A. affine it is distinguished by its smaller, more superficial basal cell, by its abundant internal horizontal 
filaments, and by its production of sporangia, antheridia, and cystocarps on different plants. 
6. Acrochetium infestans Howe and Hoyt. Pl. CXVIII. 
Acrochetium infestans, Howe and Hoyt, 1916, p. 116, pl. 14. 
Plants consisting of extensive branched basal filaments growing in hydroids and sending out more 
or less numerous external filaments; interior filaments tortuous, intricate, serpentine, or labyrinthine, 
or sometimes straight for considerable distances, mostly 2 to 5.5 mic. in diameter, the branching very 
irregular, lateral, subdichotomous, or very rarely opposite, commonly divaricate from near the middle 
of a cell, the branches often somewhat curved, the interior cells mostly 12 to 60 mic. long, 3 to 18 times 
as long as broad, commonly curved or contorted and of irregular or fluctuating diameter, sometimes 
expanded to form, with cells of adjacent filaments, a subparenchymatous layer composed of irregularly 
shaped cells 9 to 13 mic. wide and 7 to 14.5 mic. long, the terminal cells of branches often enlarged, 
somewhat hooked at the ends, irregularly club-shaped, or somewhat forking, sometimes attaining a 
diameter of 7 to 8 mic.; external filaments up to go mic. tall (or 230 mic., including hairs), the simpler 
ones consisting of a single pedicel cell bearing 1 to 3 sporangia (or, very rarely, the exserted sporangium 
sessile on an internal filament), the larger ones showing 1 to g short, 1 to 3 celled, rarely secund branches, 
the cells 4.5 to 6.5 mic. in diameter, 1 to 2 diameters long; very slender, colorless hairs commonly present 
on the larger external filaments, flexuous and attaining a length of 125 to 170 mic.; sporangia terminal 
or lateral, solitary or in groups of two or three, ovoid or ellipsoid, 6 to 8.5 by 10 to 14 mic.; sexual repro- 
duction unknown. 
Abundant on Clytia minuta (and other hydroids?) growing on Dictyota dichotoma and Sargassum 
jilipendula dredged from coral reef offshore, Beaufort, N. C., August 11, 1914. 
Endemic. 
The hydroids acting as hosts for this alga were usually not obtained in sufficiently good condition 
to warrant determination. Three of the best of these, kindly examined by Prof. C. C. Nutting, were 
identified as (1) Clytia minuta, (2) probably Plumularia sp., (3) Campanularian hydroid. ‘The internal 
filaments grow within the ectosare and are abundant throughout the stalks of the hydroids, occurring 
toaless extent in the rhizomesandhydranths. Various stages, from the ungerminated spore to extensive 
networks of filaments, have been observed. 
7. Acrochetium virgatulum (Harvey) Bornet. Figs. 29 and 30. 
Callithamnion virgatulum, Harvey, in Hooker, 1833, p. 349. 
Callithamnion virgatulum, Harvey, 1853, p. 243. 
Trentepohlia virgatula, Farlow, 1882, p. 109, pl. 10 ,f. 3. 
Cheniransia virgatula, De Toni, 1897, p. 69. 
Acrochetium virgatulum, Bornet, 1904, p. XXII. 
Acrochetium virgatulum, Collins, 1906, p. 193. 
A. A. B. Ex. No. 157 (Chantransia virgatula {. luxurians). 
P. B.-A. Nos. 741 (Chantransia virgatula {. tenuissima). 1594- 
