128 LIST OF SEEDS, BULBS, TUBERS, EPC: 
IsorTes :—Aquatic or growing in mud; stems corm- 
like; leaves elongated and rush-like, sporangia very 
large, ennwrapped by the dilated bases of the leaves. 
T. lacustris:—Mountain lakes, Pennsylvania, New 
York and New England, Lake Superior and northward. 
I. echinospora, variety Braunii:—Ponds and lakes, 
New England, New York, Pennsylvania and north- 
ward. 
I. riparia:—Margin of pools, Connecticut and north- 
ward, gravelly banks of Delaware. 
I. Engelmanni:—Shallow ponds, Massachusetts, 
Connecticut, Pennsylvania and Middle States. 
I. Melanopoda:—Shallow ponds, Central and North- 
ern Illinois and westward. 
Order SALVINIACE. 
AZOLLA—Small moss-like plants ; the stems pinnately 
branched, covered with two-lobed imbricated leaves, 
and emitting rootlets on the under side. Conceptacles 
in pairs beneath the stem; the smaller ones acorn- 
shaped, containing at the base a single macrospore with 
a few corpuscles of unknown character above it; the 
larger ones globose, and having a basal placenta which 
bears many pedicellate microsporangia which contain 
masses of microspores. 
A. Caroliniana:—Floating on quiet waters, from 
Lake Ontario westward and southward, appearing like 
a reddish hepatic moss. 
Order ELATINACE/ (Waterwort Family) :—Lit- 
tle marsh annuals, with membranaceous stipules be- 
tween the opposite dotless leaves ; minute axillary flow- 
ers like those of the chickweeds, but the pod two to 
five celled and the seeds as in St. Johnswort. 
Elatine Americana:—Margin of ponds, etc., New 
Hampshire to Illinois, Virginia and southward. 
