glossy when dry. Colour, when growing, a bright yellowish-green, be- 

 coming more or less olive in the herbarium. The structure within the 

 external membrane is spongy, as in others of the genus, and the contents 

 an unctuous, deep green fluid. 



The species of the genus Caulerpa are pre-eminent among 

 the Green Algae, and the present is one of the most elegant of 

 the Australian kinds. Its Fern-like fronds are produced generally 

 on perpendicular rocks, a few feet below low-water mark, and 

 its surculi spread in wide patches. No other Australian species 

 nearly resembles it, but it is closely related to C. denticidata, 

 Dne., a native of the Red Sea, and somewhat less closely to C. 

 mexicana, Sond., a West Indian species, and to C. asplenioides, 

 Grev., from the East Indies. The specimens distributed by 

 Dr. Wight (n. 151) are referred by Dr. Greville and myself to 

 the true C. sccdpelliformis ; but I have received from Dr. Mon- 

 tagne a specimen from Yemen, identical with Dr. Wight's, under 

 the name " C. denticulata" Dne. It is not, however, denticulate, 

 nor does it agree in other respects with Decaisne's specimens, 

 admirably represented in that author's figure, and I have there- 

 fore transferred it to the present species. 



The frond, after having been dried, is hygrometric, and if 

 moistened slightly on one side, will curl up like the sensitive- 

 fish-toys made out of horn shavings. This property was first 

 pointed out to me by Mr. Henty, of Georgetown, Tasmania, who 

 showed it to me as a sort of " marine Sensitive-plant." His 

 specimens were, I believe, obtained by dredging in deep water. 



Fig. 1. Caulerpa scalpelliformis, — the natural size. 



