Dictyerpa jamaicensis Collins

HEW YORK

BOTANICAL

garden

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Phycotheca Bereali-Amaricaaa. Collins, Eoldsn, and Setebell.

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780. Dictyerpa Jamaicensis coiiins. :

8* N. L. OfliTTON, 1 Sii
Washed ashore in tangled masses, Hope Bay and Manchioneal,

Jamaica, July, 1900.

MRS. C. E. PEASE & MISS E. BUTLER.

The description of this plant will be published in a forthcoming
paper on the algae of Jamaica.

NEW YORK BOTANICAL GARDEN

00887770

F. S. C.

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Di.c tyqrna Jamaicensis n. g. & sp.

Proc. Am. Acad. Arts, k S(£^). ^6:251. 1901.

^rond filiform, 1-3 mm. diam. up to 2 dm. long; consisting
of two layers of cells, and inn^r layer of large, colorless, cy-
lindrical cells, at)out thrne diameters long, symmetrically,arran-
ed; an external monostroma tic layer of "brown rectangular cells
from one to three diameters long, in distinct longitudinal series.
Branching di- or trichotomous, with occasional irregularly placed
lateral "branches, mostly at wide angles, each 'branch ending in a
large, depressed-hemispherical cell, by whose division the growth
of the branch proceeds. TuCTts of very fine, rust-colored or color-
less confervoid rhizoidal filaments at irregular intervals on th«
frond. vructification? Washed ashore, Manchioneal, July, 1900.

P. B.-A., Ho. ?80.

Though evidently "belonging to th*> Dictvotaceae, this plant
differs from any genus of the family yet described, in having the
frond terete throughout. Many Dictvotaceae have prostate root-
ing filaments from which the erect fronds arise, 'but in all species
found in Jamaica this prostrate growth is quite insignificant in
comparison with the plant in question. It was found washed ashore
in two places, in considerable quantity, and in no case shows any
indication of fructification, or of producing er^ct flattened fronds.
It may seem hazardous to give it a generic name, but as it is a
plant of quite distinct habit, and cannot be now identified with
any named form, it seems to require at least a provisional name.

As washed up on the beach, it appeared like rolled and twist-
ed strings. The dried plant is quite black in color, and under a
hand lens shows closely set constrictions, probably due to the
large interior cells being of uniform length, and terminating at
the same level, as in the frond of Polvsiphonia. These constric-
tions are lost when the frond is remoistened.

00887770