Monostroma areolatum Setch. & N.L.Gardner

I'iOiiQstroma areolat ..un sp. nov.
S.	& (i. Univ. Calif. Pill. Eot. ?:28l. tO,. 30.;
ill. 3.1. 2. 8 J1 1920.
Thallo d.elioatissi'Tio, luhrico, 20-25 alto, s^ssili,
juveno saccato, mox fisso et lot: os late 0 vat os aut obovatos,
plicatos et crispatos form anti, dilate vlridi; membrane distinct«
minuteque areolata, 9-12/jl crassa; cellulis rotund«? angulatis,
6-7p erassis in seatione transversali subs oh or ids, in areolis
quibus-iue aggregatis.
Frond very delicate, lubricous, ?0-35 v™., high, sessil<=,
saccate v/hen young, soon spli'tting and "orming numerous, long,
?broadly ova‘ '?>, or oho vat e, undulate, plicate and crisped loh es,
pale green; membrane distinctly and finely areolate, 9-12ji thick;
cells v/ith rounded angles, 6-7^1 diarn., sub spherical in cross-
section, grouped within each areole.
Growing on Zostera in tu : »t waters. 3itka, Alaska. .lype no.
3924, Gardner.
This species of Monostr^ma is exceedingly beautiful and is
among the most delicate and. nlaccid of the genus. The frond re-
mains saccate for only a brief period, attaining a height o' only
a millimeter or two. The sack then breaks and the membrane 0Tvr«adS
out at once, early developing small lohes . Finally a ^ew pri-
mary lobes are established and these develop numerous secondary
lobes. The growth on the whole margin greatly exceedsthat of the
interior, and this results in the production of a great number of
folds, making the margin very much crisped. In the thickness of
the frond and shape of the cells K. aredilatum closely approximates
M. zostericola Tilaen. The cells o'-“ the latter are, however, more
angular and more closely placed and the ^Yond is not divided into
areolae. There is a marked difference in the size of these two
species, as well as in their methods of development. V. zosteri-
cola is diminutive, regains saccate for somQ time qrid splits longi-
tudinally, forming several lobes broadening outward. K . areola -
turn very closely resembles the g«nus P^rasiola in the grouping of
the cells as seen in surface view.	NEW YORK BOTANICAL GARDEN
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