THE GENUS ISOETES IN NORTH AMERICA. 465 
tt Velum complete. 
8. I. metanospora, Engelm. One of the smallest species, with a flat, only slightly bilobed trunk ; leaves few 
(5 to 10, 2 to 24 inches long), distichous, slender, tapering, light green, spreading; sporangium orbicular or almost obcor- 
date, $ to 1 line long, entirely covered by the velum, unspotted ; ligula short-triangular, obtuse, or about semi-orbicular; 
macrospores 0,35 to 0.45 mm. in diameter, roughened with distinct or rarely somewhat confluent warts, dark colored; 
microspores 0.028 to 0.031 mm. long, amoothiah or slightly papillose. — Transact. St, Louis Acad. Sci. 3, p. 395 note.* 
ne Mountain, near Atlante, Georgia, covering the bottom of shallow excavations on the naked granite surface, 
a few inches deep and a few feet in diameter, holding about one inch of light, black soil, and at best a couple of inches 
of water supplied only by rains and epi and completely dried up and baked for weeks or months under the action 
of the state southern sun on the bare rock, when only the little shrivelled trunks with their black withered matted 
roots remain, to revive under a bak supply of autumnal rains (with Amphianthus pusillus), discovered by W. M. 
Canby, Susie since by A. Gray and myself; maturing in May and June. A cake of them taken home with me 
began to sprout soon after being moistened, and, vegetating in the room through winter, fully developed in early sum- 
mer, and afforded a fine opportunity for studying this curious little species, interesting on account of its native locality, 
its endurance of drought, its mode of growth, and the phyllotactic arrangement of its leaves, its entire velum and its 
dark spores ; it seemed to thrive best when only the base of the leaves was covered with water. The trunk is unusu- 
ally flat and only slightly grooved underneath and on one side, only about $ to 1 line thick and 2 to 4 lines in the 
longer and not much more than half as much in the shorter diameter ; distichous leaves soft and slender, their dissepi- 
ments consisting of only two layers of cells. The sporangia, } to ? line wide, readily separate from the leaf-bases, so 
that they are sometimes found adhering to the trunk after the leaf itself has already fallen away. The 
macrospores, only 8 to 20 in each sporangium, are black when moist and dark gray when dry; in some I (384 (27)] 
find the warts much smaller than in others, but never wanting ; microspores also quite dark bro 
* * With peripheral bast-bundles. 
+ Velum partial. 
9. I. Enaetmannt, A. Braun. Our largest species, with numerous (25 to 100) long (9 to 20 inches or more) 
light green leaves, with abundant stomata ; nea seseape oblong to linear-oblong, unspotted ; velum narrow ; 
ligula elongated from a triangular base ; macrospores 0.40 to 0.52 mm, thick, delicately ee bes papi ; micro- 
spores 0.024 to 0.028 mm. long: generally smooth. — Ss ora, 1 c.; Am. Jour., l. c.; Gray, 
. GRACILIS, Engelm. Often submerged, with fewer bi to 12) leaves, 9 to 12 ‘lite Sint the bast-bundles 
sill quite small, or only two of them. — Gray, Man. 1 
Var. vatipa, Engelm. The stoutest of all our species; on to 100 or even 200, 18 to 25 inches long, keeled 
on the upper side; sporangium often linear-oblong (4 to 9 lines ak 4 or often $ or even } covered by the broad 
velum; macrospores rather smaller, 0.32 to 0.48 mm. thick; microspores 0.024 to 0.027 mm. long, spinulose. — Gray, 
an, 
Var. Groraiana. Similar to the type; leaves few (in the only specimens seen 15, 10 to 12 inches long), rather 
slender ; oval sporangium with narrow velum; macrospores larger, 0.48 to 0.56 mm. thick ; microspores 0.028 to 0.031 
mm. long, smooth. ; : 
ponds and ditches, immersed in mud, rarely found in slow-running streams, in company with the ordinary 
vegetation of such localities, Bidens, Polygonum, Lycopus, Carices, Leersia, etc.; mature in summer; probably through- 
out the Middle States, but thus far only found —from Massachusetts: Arlington Brook, Alewife Brook, West Cam- 
bridge Brook, Woburn, WV. Boott. Rhode Island: Newport, W. @. Farlow. Connecticut : Meriden, F. W. Hali — 
to New York: Peekskill, a H. il New Jersey: E. Durand, 0. F. Austin, and others. Pennsylvania: Bethle- 
hem, C. J. Moser, E. Durand, F. Wolle ; Delaware Water-Gap, S. W. ns so J. G. Hunt; Philadelphia, £. 
Durand, C. E. Smith, and sahara Delaware: W. M. Canby, A. Commons. Virginia: Salt Pond Mountain, with 
Parnassia asarifolia, W. M. Canby. uri: St. Louis, N. Riehl, and 6. Engelmann, 1842, in a single locality, 
where it was soon afterwards destroyed rag cultivation: not found otherwise west of the Alleghany Mountains. Var. 
gracilis seems to be a northern form: Brattleborough, in Clark’s Pond, 0. €. Frost ; Colebrook’s, in a shallow stream 
with asters bottom, J. W. Robbins; New Haven, in fresh water on a tidal shore, D. 0. Eaton ; Newport, oe = 
Thurber ; Passaic River, near low-water mark, J. Ennis. Var. valida was discovered in Penney Irena Warri 
Mark, Sictcairneme Co., and Smithville, Lancaster Co., T. €. Porter; and in Delaware, Wilmington 
M. Canby. Var. Georgiana comes from a mountain stream, Georgia, the Horseleg Creek, a satiety a [385 (28)] 
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, ye more variable in form; sometimes it is 
quite flat and over one inch wide, especially in var. valida, or it is thick ; I have seen it even twice as high as it 
was wide, 44 lines wide in the largest transverse diameter, and 7 lines high: this, however, is a very unusual form. 
* The original description is reproduced above, pp. 401, 402. — Eps. 
59 
