Palmella jessenii

NEW YORK
botanical

"garden

PALMELLA JESEHTI, WOOD* - Fresh-water Algae of the United States page
18, February 1872« (Smithsonian contribution to knowledge, 241),

P. thallo indefinite expanso, initio dilute aut laete viride, molle,
pellucidulo; aetate provecta firmo, tuberculoso, saturate olivaceo-
Tiride; eellulis globosis vel ellipticis,- in thalll aetate immaturo,

plerumque singulis aut gemlnis, saepe distantibus,-in aetate provecta
saepe in familias connexis, plertmaue confertis; tegumentis in thalli
aetate immaturo plerumque diffuentibus, aetate provecta plerumque
diffluentibus, aetate provecta plerumque distinctis»

Diam*-Ciell, glob, max, l/350G - •000E81*; cell, oblong, max l/25QOw s

Syn.-P* Jesenii, JQOD, Prodromus, Proc. Am* Philos, Soc., 1869, p. 134

Hab.-In rupibusirroratis, prope Philadelphia,

Thallus indefinitely expandeded, in the beginning soft and pellucid,
afterwards frim, tubercular, deep olive-green; cells globose or el-
liptiptical; in the immature thallus, singel or geminate, frequently
scattered; in the mature thallus often closely conjoined into fam-
ilies, mostly crowded; in the young thallus the teguments of the
cells are mostly dlffuent, afterwards distinct.

BEMABKS.-This little plant was found along the banks of the Schuylkill
Biver, just above Hat Bock tunnel, near Hanayunk, forming in the
early winter a gelatinous mass of two to three lines in thickness,
irregularly and Interruptedly spread over the faee of wet, dripping
rocks. In what appeani to be the younger portions, the jelly was
often quite soft and almost colorless, and had the cells scattered
rather sparsely and distantly through it. The cells were but par-
tially filled with chlorophyl, the caculoe left containing often
numerous granules, and had distinct walls, being, as it were, merely
immersed in the general maternal jelly. In the older fronds the
texture is more firm, the color a deep green, and the bright
green cells are mostly surrounded by a thick, very distinct tegument*
They are also largely arranged in little families of two, four, or
even eight cells, surrounded by a common integument. The oldest
fronds are of a deep olive, almost blackish color, markedly tuber-
culate upon their upper surface and very firm in texture. They
are surrounded by very distinct, firm, dark brown coats (a simple
coat often involving two or more eells), and arranged in groups or
families. As shown by the microscope in the superficial portion
of such fronds, the jelly is of a yellowishrinseous color, and
the cells are themselves of a dark brown tint. The number of cells
in the individual families varies from two to a dozen or more.

Even in these old, firm fronds, the interior portions are frequently
composed of greenish cells, without any distinct teguments or
coat. In such cases the cells are mostly oblong or elliptical,
and very much crowded together. This species appears to come
closest to P. Brebissonii, KTZ,, from which it differs, however,
in its habit of growth and the size of its cells*

Fig, 3 a, pi* 10, represents a fragment of the upper surfaoe of
anv old frond magnified 750 diameters; fig* 3 b, when taken from
the inner jelly of similar fronds*

FRESH WATER ALGA.

NEW YORK BOTANICAL GARDEN

02109828

02109828