2 6 ENGELMANN—THE GENUS ISOETES IN N. AMERICA. [38$ 
deep in water, have slenderer and longer (even 12 inches) leaves. The 
trunk, mostly thick, I have once found 3-lobed. Germinating spores and 
young plantlets were found in June by Mr. Durand indicating germination 
in spring and early summer; 
Farther northward, in Maine, J. W. Chickering , and in Canada West, 
Crow riyer, Hastings Co., J_. Macoun (here, in running water with Bra- 
senia and Potamogeton ), a form occurs with very few stomata on leaves- 
and apparently two weak bast-bundles, an upper and a lower one, very- 
pale spots on the sporangia and smoothish microspores, which might be 
designated as var. Canadensis , but too little is known about it as yet to- 
form a definite opinion. 
f f Velum complete. 
8. I. melanospora, Engelm. One of the smallest species, with a flat, 
only slightly bilobed trunk; leaves few (5 to 10, 2 to ik inches long), dis¬ 
tichous, slender, tapering, light green, spreading; sporangium orbicular 
or almost obcordate, £ to 1 line long, entirely covered by the velum, 
unspotted; ligula short-triangular, obtuse, or about semi-orbicular; ma¬ 
crospores 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, smoothish or slightly papillose.—Transact. St. Louis Acad. Sci. 3, 
p. 395> note. 
Stone Mountain near Atlanta, 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 dews, and completely dried 
up and baked for weeks or months under the action of the glaring south¬ 
ern sun on the bare rock, when only the little shrivelled trunks with their 
black withered matted roots remain, to revive under a fresh supply of' 
autumnal rains;, with Amphianthus pusillus, discovered by W.M. Canby , 
observed 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 moist¬ 
ened, and, vegetating in the room through winter, fully developed in early 
summer, 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 velpm and its dark spores; it seemed to thrive best when only 
the base of the leaves was covered with water. The trunk is unusually 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 
dissepiments consisting of only two layers of cells. The sporahgia, £ 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. 
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Botanical 
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