BICKNELL: FERNS AND FLOWERING PLANTS OF NANTUCKET 59 
On the coast sands all around the island, sometimes massed in 
great abundance along or among the dunes near the shore. Just 
in flower June 7, 1909. 
SPERGULA ARVENSIS L. 
In cultivated fields and along roadsides ; common and widely 
spread. First flowers June 3, 1909; continuing to bloom through 
September. 
* TISSA CANADENSIS (Pers.) Britton. 
Observed only on Coatue; in full flower and fruit Sept. 7, 
1904. Plants small, often forming compactly much branched tufts 
6-16 cm. in diameter; sepals obtuse or rounded at apex, about 
half the length of the oblong-ovoid obtuse capsule ; seeds I mm. 
in diameter, dark brown, wingless, roughened with minute points. 
Agrees closely with typical examples of Zissa canadensis from 
much further north except that it is not wholly smooth but more 
or less finely glandular-pubescent, at least in its upper parts. I 
met with the same plant, in October, 1909, on Chappaquiddick 
Island, Marthas Vineyard, the most southern point, I think, ex- 
cept Nantucket, from which it has been reported. 
TissA MARINA (L.) Britton. 
Common on salt marshes and brackish shores ; observed in 
flower from early June until late September. 
Plants larger throughout than those of Zissa canadensis and 
more widely branched, sometimes spreading over 4 dm., more 
pubescent and with donger leaves and internodes and larger more 
acute sepals and capsule, the latter little exserted ; seeds smooth, 
only half the size of those of 7. canadensis, 0.5 mm. in diameter, 
and paler in color. No winged seeds were found in any Nantucket 
specimen. 
Tissa RuUBRA (L.) Britton. 
Common in dry sandy places, often in waste ground, Ob- 
served in flower from May until late September. 
NYMPHAEACEAE 
BRASENIA SCHREBERI Gmel. 
In a number of ponds and pools mainly on the eastern side of 
the island. 
