Marine Plants of Nha Trang — Dawson 
403 
Fig. 18. c, d, Colpomenia sinuosa: a. Habit of a plant of 11330, X 1.5; c, portion of a hemispherical plant of 
11331, X 1; d, habit of a plant of 11350, X 1.5. b, Hydroclathrus clathratus: A small portion of a reticulate plant, 
X 1.5. e, Kosenvmgea nhatrangensis: Transection of a thallus through a sorus of plurilocular sporangia around a group 
of hairs, X 225. 
Hydroclathrus clathratus (Ag.) Howe 1920: 
590. Encoelium clathratum C. Agardh 1822: 
412 (Belle Isle, France) 
Fig. 18^ 
LOCAL DISTRIBUTION: In shallow water, Sta. 
10 (11332); Sta. 4 (11425). 
This species was rare and in young stages 
in January, but by mid-March had become 
fairly common and well developed in the Cau 
Da-Cua Be area. 
Rosenvingea nhatrangensis sp. nov. 
Figs. 18^, 19^ 
Thallo epiphytico, 4-6 cm. alto, ope rhiz- 
oidum multicellularum adnexo, cavo, mem- 
branaceo, molli, breviramato, Ibbato, partibus 
inferioribus ad 2.5-3 cm. diametro, ramis 2-4 
cm. longis, 1.0-1. 5 cm. lads, ramis brevibus 
ultimis lobisque 4-6 mm. lads, terminaliter 
rotundatis; sporangiis plurilocularibus cras- 
siclavatis, 12-16 ix longis, in soris rotundatis 
fixis circiter 250 ju diametro, plerumque an- 
nulum crassum formantibus circum plures 
pilos e depressione exigua in superficie 
orientes. 
Thallus epiphytic, 4-6 cm. high, attached 
by masses of multicellular rhizoids about 10 
fjL in diameter, hollow, soft, thin-walled, short- 
branched and lobed, the lower parts to 2.5-3 
cm. in diameter, the branches 2-4 cm. long, 
1.0-1. 5 cm. wide, the ultimate short branches 
and lobes 4-6 mm, wide, terminally rounded; 
thallus wall 110-150 fx thick, consisting of a 
single surface layer of small, somewhat peri- 
clinally elongated, densely pigmented cells 
mostly 9-11 ^x in length, and a subsurface 
tissue of thin-walled, irregularly rounded, 
colorless cells up to 100 ju in diameter; pluri- 
locular sporangia thick-clavate, 12-16 ix long, 
borne in small, rounded sori about 250 fx in 
diameter usually forming a thick ring around 
a small group of hairs arising from a slight 
depression in the surface. 
TYPE: Holotype is Dawson 11170, Jan. 30, 
1953, in the U. S. National Herbarium. 
