Pilinia endophytica Collins

Pilinla Lunatiae Collins, n. sp.
Ehodora 10; 123. pi. 77- £. I'l- J1 •
Ac rob las t e Ite in s ch 1 i. Collins, List, Khodora, Vol. II, p.
43, 190C, as to northHrn Massachusetts localities only; Col-
lins, Holden & Setchell, P.B.-A., ITo . 1.62, 1896. Filament is
basslaribus mox in stratum subparenchymaticum concretis, c*l-
lulis forma ac magnitudine variantibus, rotundatis vel angu-
laribus, ad 15 u diam.; filamentis erectis P-l? u diam., su-
penne incrassatis, T>leriur.que 5-6-cellularibus, rarissime usque
ad 10-cellularibus, dense stipatis, ramifications densa; cellu-
lis ejusclem filamenti variantibus quoad fomam et magnitudinem;
sporangio e cellula terminali forma to, a cellulis ceteris parum
diverse; colore viridi iritenso.
Basal filaments soon "becoming united into a subparenchyma-
tous layer, cells of varying shape and size, roundish or angu-
lar, up to 15 ]i diam.; erect filaments 8-12 u diam., increasing
in size upward, usually 5*6 cells in length, quite rarely up to
10 cells, densely branched and very compact, cells varying in
size and shape in the same filament; terminal cell becoming the
sporangium, differing hut little from any other cell of the fila-
ment; color deep green. On live shells of Lunatia heros Mams,
.Revere Beach, Massachusetts.
This plant is common on the Lunatia shells at Bevere Beach,
so much so that in spring and early summer it is the exception
to find a live shell free from it, and at all times it is to he
found plentiful. It appears to die with the host, for it has
never teen found on dead shells. Its distribution seems to he
very limited, as there is no record of its occurrence except at
this one station, though the Lunatia is found all along the
coast, and the alga has been sought for carefully on the Maine
coast and in southern New England. It always occurs on the spire
of the shell, which in the genus is quite flat; here it forms a
roundish patch, thickest at the centre, the tip of the spire, and
has never been known to cover more than a quarter of the surface
of the shell. The color is a deep rich green, an unusual color
in this genus, where a yellowish color is general. The substance
is dense, and it is only by crushing or dissection that the struc-
ture can be made out. The basal layer is largely continuous, the
filaments showing distinctly only at the edges; the erect filaments
are short, stout, and of cells usually quite irregular in shape;
they increase in size upward, but rather irregularly, th^1 terminal
cell being the largest, with a broad rounded top, but not differing
otherwise from any other cell of the filament; the spores escape
through an opening in the summit, as in other soecies. The general
appearance is ratner that of Gonkrosira than of TM-linla.