ENGELMANN THE GENUS ISOETES IN N. AMERICA. 383 



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. Ckickering, and in Canada West, 

 Crow river, Hastings Co., J. Macoun (here in running water with ^ra- 

 senia and Potamogetoti), 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. 



t t 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 2i inches long), dis- 

 tichous, slender, tapering, light green, spreading; sporangium orbicular 

 or almost obcordate, 4 to i 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 Amphiantkus pusillus, discovered by W. M. Canby, 

 observed since by .^. G^aj 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 arrangementof 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 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 sporangia, 2 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 



