382] TRANS. ST. LOUIS ACAD. SCIENCE. 25 
B. Amphibious, partially emerged, submergedonly in the earlier period of their 
growth or temporarily; stomata always present. 
* Without peripheral bast-bundles; intermediate between the Sub¬ 
merged and the truly amphibious species, 
f Velum partial. 
6. I. saccharata, Engelm. A small plant, usually with a flat, de¬ 
pressed trunk; leaves subulate, olive-green, spreading, 10 to 20 in number, 
.2 to 3 inches long; sporangium oblong, spotted* with a narrow velum; 
ligula triangular; macrospores 0.40 to 0.47 mm. thick, covered with very 
minute distinct or sometimes a little confluent warts; microspores papil¬ 
lose, 0.024 to 0.028 mm. long.—Gray Man. 1 . c. 
On the banks of the Wicomico, below Salisbury, and of the Nanticoke 
rivers which empty into the Chesapeake Bay, eastern shore of Maryland, 
^above salt water, scattered on a thin stratum of mud covering a bed of 
gravel, overflowed by the tides, in company with Sagittaria fusilla , Eri- 
ocaulon, Tillaca simplex , Micranthemum Nuttallii , etc., W. M. Candy. 
The trunk is in this species unusually flat, about half as thick as it is wide 
in the direction of the groove; about one inch of the base of the leaves is 
pale, and covered with mud agitated by the tides, the upper part is olive- 
green and when out of water apt to be borne down by mud; stomata 
abundant ; macrospores as if sprinkled over with minute white grains of 
sugar, whence the name. 
7. I. riparia, Engelm. A larger plant with slender but rather rigid 
deep green leaves (about 15 to 30 in number), 4 to 8 inches long, rarely 
longer; stomata numerous, dissepiments thick, consisting of about 4 layers 
of cells; sporangia mostly oblong, distinctly spotted by groups of brown 
sclerenchym cells, £ or rarely £ of it covered by the velum ; macrospores 
among the largest, o 45 to 0.65 mm. in diam., marked with jagged crests 
isolated, or anastomosizing, especially on the lower surface, which thus 
becomes somewhat reticulated; microspores more or less tuberculated, 
•0.028 to 0.032 mm. long.—Flora, Regensb. Mar. 31, 1846; Am. Jour. Arts 
& Sci. 3, p. 52, 1847 : Gray Man. 1 . c. 
On the banks of the lower Delaware river between the limits of the tides 
in mud covering gravel, from Burlington, T. A. Conrad, to Wilmington, 
W. M. Canby, and especially about Philadelphia, where Nuttall first dis¬ 
covered and W. S. Zantzinger , E. Durand and the later botanists have 
abundantly collected it, associated with Elatine , Limosella,'Micranthe- 
mum , Sagittaria pnsilla, etc.; also in millponds and still parts of streams 
in New England, Uxbridge, J. W. Robbins , BrattleborOugh, C. C. Frost , 
and northward, maturing in August and September. — Near I. lacustris , 
with leaves as dark green and almost as rigid, and with spores approach¬ 
ing it in size and sculptu§e, but readily distinguished by its stomata and 
>by the spots on the sporangium; from /. echinospora var. Braunii , with 
which smaller forms it may possibly be confounded; it can always be 
known by the darker, stiffer leaves and especially by the character of the 
spores. Some of the Uxbridge specimens, entirely submerged 2 to 4 feet 
0 1 2 3 4 5 6 7 8 9 10 m.ssoOr 
Botanical 
cm copyright reserved garde 
