10 f Rhodora , [JANUARY 
THE GENUS ELATINE IN EASTERN NORTH AMERICA. 
M. L. FERNALD. 
Ir has become customary to treat all Elatine from the margins of 
ponds and streams in eastern America as Elatine americana (Pursh) 
Arn., — to such an extent that local botanists rarely examine the de- 
tails of the plants. During the past summer, however, while exploring 
the tidal reaches of the lower Kennebec system in Maine, Mr. Bayard 
Long and the writer were much interested in a peculiar prostrate and 
matted Elatine which was found in great abundance in the tidal mud 
of Cathance River at Bowdoinham. The plants of these tidal flats 
differed somewhat in appearance, the smaller plants having the leaves 
cuneate-obovate to oblong and sessile, the larger plants having the 
mostly larger leaves more broadly obovate and petioled. A detailed 
study of this material, as well as all the specimens in the Gray Her- 
barium, the herbarium of the New England Botanical Club, and of 
the Academy of Sciences of Philadelphia (including the herbarium 
of the Philadelphia Botanical Club) shows that we have in the Atlantic 
states and eastern British America three quite distinct species of the 
genus, distinguished not only in the form of the foliage but in the 
floral characters and in the shape, size and markings of the seed. 
The commonest plant is the small species in sandy, gravelly or 
peaty pond-margins with rather small cuneate-obovate to oblong ses- 
sile leaves. In this plant the flowers are dimerous, having two sepals, 
two petals and two stamens. The seed is comparatively thick and 
more or less barrel-shaped, with rounded ends, 0.5-0.7 mm. long and 
220-280 u thick. The seed has distinct longitudinal ribs and between 
them 15-18 obtuse cross-ribs marking off somewhat rectangular reticu- 
lations. This plant, the commonest species in eastern America, was 
well described and illustrated by Nuttall as Crypta minima! from 
“gravelly banks of the Delaware overflowed by the tide.” The plant 
is well illustrated with two sepals, two petals and two stamens, and 
the type material, now preserved in the herbarium of the Academy 
at Philadelphia, has the very characteristic seed of the common plant 
of sandy and gravelly shores. This species, which Nuttall thought 
1Nuttall, Journ. Acad. Sci. Phil. i. 117, t. 6, fig. 1 (1817). 
