35 
This form has not been noticed among plants of I. echinospora 
from western sections. - It apparently has the same range as I. 
Tuckermani 
Round Pond, Woburn, (type locality), and in a brook in Tofit 
swamp, Lexington, Mass., W. Boot. Also in Chebacco Pond, Es- 
sex, Mass., and at East Kingston, N. H. 
/ V 
236. 1. echinospora muricata Engelm. Leaves a bright 
green, 6-16 inches long, with few stomata ; macrospores 400-580 // 
with shorter, thicker and more confluent spinules ; otherwise like 
var. Braunii. 
Woburn creek, (type locality), and Abajona river near Boston, 
Mass., W. Boot. Mouth of Pompa*nusuc river, Norwich, Vt. ; Po- 
wow river, East Kingston, N. H. ; margin of the St. Johns at Mad- 
awaska, Me., M. L. Fernald. 
When the leaves of this variety are very long the upper part 
assumes a spiral form, leaves of 12 or 15 inches having the upper 
half twisted into several convolutions, the plants in this case be- 
ing entirely submerged. 
/ 
230. I. Iacustris L. Leaves 10-30, dark green, somewhat 
rigid, pointed but scarcely tapering, 3-6 inches long, without sto- 
mata or peripheral bast-bundles ; sporangia unspotted ; velum 
about one-third indusiate ; spores of both kinds large ; macrospores 
500-800 fj, in diameter, spherical, marked all over with short, thin 
flexuous ridges ; immature spores often appearing granulated ; mi- 
crospores 35-45 fi long, smooth, light gray commissural ridges 
cristate. 
Usually gregarious in gravelly soil on the bottom of lakes un- 
der 1-5 feet of water. In New England this species has been rarely 
collected : Fresh Pond near Cambridge, Mass., W. Boot. Uxbridge, 
Mass., J. W. Robbins. Echo Lake, N. H., Prof. Tuckerman. Brat- 
tleboro, Vt., Frost. 
Plants collected on the tidal tract of the Merrimac river, six 
or eight miles from its mouth and near low water mark, are simL 
