28 ENGELMANN—THE GENUS ISOETES IN N. AMERICA.'' [386 
a tributary of Coosa river, Floyd Co., in slow-flowing water about a foot 
deep, A. W. Chapman. 
The trunk of this species is larger than I have seen it in any other, and 
more variable in form; sometimes it is quite flat and over one inch wide, 
especially in var. valida , or it is thick; and I have seen it even twice as 
high as it was wide, 4^ lines wide in the largest transverse diameter and 7 
lines high; this, however, is a very unusual form. The plant is submerged 
in spring with the leaves partly floating; later, when the water recedes, 
the older leaves are spread out on the mud, but the later growth becomes 
erect; var. gracilis is often more or less submerged, and its weakly devel- 
opement is probably owing to this circumstance, while var. valida is the 
stoutest form we have, and one of the stoutest in the whole genus, perhaps 
only I. Malinveriana of the rice fields of Lombardy surpassing it. Avery 
small form, only 5 inches high, has been collected in a springy place on a 
rocky hillside near Wilmington, Del., by A. Commons, otherwise not dis¬ 
tinct. The Georgia variety, characterized by its larger spores, ought to be 
fui ther studied. In my Missouri specimens I find, among many of the ordi- 
nary type with white sporangium, a few where this organ is uniformly 
brown, not spotted. The dissepiments of the leaves consist, the median 
of 3 to 4 and the transverse one of 2 to 3 layers of cells. The well marked 
reticulation of the macrospores is formed of very thin fragile laminae, not 
of thick ridges as in some other species. 
10. I. HoweLlii, Engelm. n. sp. Middle sized, leaves (10 to 25) bright 
green (5 to 8 inches long) with thick dissepiments; sporangium oval (i£ 
to 2\ lines long), unspotted, £ to £ covered by the velum; subulate ligula 
as long as sporangium; macrospores 0.43 to 0.48 mm. in diam., rough, 
with prominent rounded single or sometimes confluent tubercles. 
On border of ponds at the Dalles of the Columbia, Oregon, J. & T. J. 
Howell , 1880, not quite mature in June. — I insert this species which has 
just been communicated to me through the kindness of Mr. G. E. Daven¬ 
port, while the manuscript is in the hands of the printer; this must excuse 
some discrepancies in the foregoing pages, where no reference could be 
made to it. The new species is distinguished from the similar I. Bolan- 
den by the longer leaves, larger more prominently marked macrospores, 
and especially by the distinct peripheral bast-bundles, which place it near 
the foregoing one, by the thick dissepiment consisting of 4 to 6 layers of. 
cells, and by the unusually narrow and long ligula; the tubercles of the 
spores are quite prominent, as high as they are wide, rounded at top; 
microspores light brown, smooth. — Among the specimens of this species, 
and probably collected with it, I find a single one similar in the structure of 
the leaf, but without a trace of a velum, the sporangium being entirely 
naked and only attached by the median line to the leaf base; it is unfortu¬ 
nately immature, and can only be indicated as a probably new species, 
/. nuda. This would not be the first instance of two species growing 
together in the same pond or lake; in Mystic Pond we find I. Tuckermani 
2 3 4 5 6 7 8 9 10 MissoOr 
Botanical 
copyright reserved garden 
