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64
THE MARINE ALGÆ OF NEW ENGLAND.
at the apex, formed from the superficial cells; fronds covered with clusters of hairs;
paraphyses wanting.
A small genus, containing probably not more than half a dozen good species, which are widely diffused.
In the Nereis Am. Bor. the genus is placed by Harvey in the Dictyotaceæ. That order is now restricted to
a group, not represented, as far as is known, on the coast of New England, in which there are quiescent
spores, tetraspores, and antheridia, but no zoospores, and Punctaria is evidently related to the
Phæosporeæ, judging by its sporangia. Litosiphon pusillus, a small parasite on various algæ, is closely
related to Punctaria, but differs in having a filamentous frond and more simple sporangia. It probably
occurs on our coast, bulb has not yet been observed.
P. LATIFOLIA, Grev.; Phyc. Brit., Pl. 8; Études Phycol., p. 13, Pl. 5.
Fronds pale olive-green, gregarious, shortly stipitate, lanceolate or obovate, four to
twelve inches long, one to five inches broad, substance tender.
Var. ZOSTERÆ, Le Jol. (P. tenuissima, Phyc. Brit., Pl. 248.)
Fronds thin, pale, lanceolate at both extremities, narrow, margin undulated.
On different algæ at and below low-water mark. Spring and summer. Europe.
P. PLANTAGINEA, (Roth) Grev.; Phyc. Brit., Pl. 128. Pl. IV., Fig. 5.
Fronds deep brown, gregarious, broadly lanceolate, attenuated at base, one to three
inches broad, three inches to a foot long, substance somewhat coriaceous.
Orient, L. I.; Point Judith, R. I., Olney; Wood’s Holl, Gloucester, Mass.; Europe.
Summer.
It is not altogether easy to distinguish our two species in some cases, although as a rule they are
sufficiently distinct. P. latifolia is much the more delicate of the two, and has a greenish tinge. When in
fruit it is punctate, the dots being the sori. Both forms of sporangia are often found simultaneously on
the same frond. In P. plantaginea the frond is decidedly brown and rather coriaceous, and the punctate
spots are caused by the dense clusters of hairs which are often found to correspond on both sides of the
frond. Both species are common in spring and summer, and although often washed ashore in
considerable quantities on exposed beaches, they prefer quiet bays.
FAMILY DESMARESTIEÆ.
Fronds branching, cylindrical or compressed, with an axis of filaments composed of
elongated cells and a cortex composed of spheroidal cells; unilocular sporangia
formed by the direct transformation of the cortical cells; plurilocular sporangia
unknown.
DESMARESTIA, Lamx.
(In honor of A. G. Desmarest, a French naturalist.)
Fronds olive-brown, solid, cylindrical or compressed, much branched, attached by a
disk, cortical layer composed of small polygonal cells,