462 THE GENUS ISOETES IN NORTH AMERICA. 
spores. Durieu, ]. c. 11, p. 101, distinguished a form with exceptionally large macrospores (0.70 to 0.80 mm. diam.) 
as I. macrospora from a single specimen from the Herb. Acad. N.S. Philad., with the label “ Catskill Mountains” in 
the handwriting of Schweinitz ; but others show sometimes spores of similar dimensions, e. g. specimens from Lake 
Superior; and such have also been found in Europe, though there the spores rarely reach a size of over 0.65 to 
O mm. 
2. I, pyamaa, Engelm. One of the smallest species, with a few (5 to 10) short ($ to 1 inch long), 
stout, rigid, bright green leaves, abruptly tapering to a fine point, with very short, often almost ~ [378 (21)] 
epidermis cells ; orbicular sporangium not spotted, with a narrow velum; macrospores 0.36 to 0.50 
thick, marked with minute, rather regular, — or rarely confluent warts; microspores 0.024 to ae a mm. long, 
almost smooth and brown. — Am. Naturalist, 8, 2 
Found only once, deeply immersed in a ey siphas stream on the eastern slope of the Mono Pass, California, 
7,000 feet alt., H. Bolander.— This curious diminutive species is a close ally to the last by the structure of the leaves 
and the mode of living, but is widely separated from it by the sculpture of the spores ; the shortness of the epidermis 
cells is quite peculiar to it, and so are the close transverse partitions ; the walls of the leaf and the dissepiments are 
thinner than in the last, consisting of only a few layers of cells. The minute tubercles of the macrospores are most 
distinct on the lower surface, but become sometimes confluent on the upper side 
3. I. TuckeRMANI, A. Braun in litt. A small plant with very slender, tapering olive-green leaves (10 to 30 in 
number, mostly 2 to 3 inches long), the outer recurved, walls and partitions rather thick for the diameter of the leaf ; 
5 glcaag mostly oblong, white or rarely brown-spotted, the upper third covered by the velum; macrospores 0.44 to 
6 mm. diam., the upper segments marked with prominent, somewhat parallel and branching ridges, the lower half 
safe microspores smooth or nearly so, 0.026 to 0.032 mm. long. — Engelm. in Gray, Man. 1. c. 676. 
In several ponds and streams near Boston, maturing from August to October; first discovered by E. Tuckerman, 
1848, in the Mystic River very near where it issues from the pond; in the same locality and in Mystic, Spy, and Horn 
Ponds, W. Boott, ‘* always immersed in fresh water, sometimes only a few inches below the surface, often in places 
which are subject to a tide of almost two feet in height, generally gregarious and carpeting the bottom with an olive- 
urf.”. The leaves are usually not longer than two or three inches and, at least the outer ones, recurved ; 
occasionally, in slender specimens, probably from deep water, I have seen them straighter and over 5 inches long. 
The sculpture of the spores is very characteristic; wavy, somewhat branching ridges run from the three upper com- 
missures in right angles; on the lower surface they interlace, covering it with an irregular network. Some specimens 
collected by Mr. Boott at the end of October seem to indicate a second growth, as within the circle of microspore- 
bearing leaves, and after the outer ones with their macrosporangia had fallen, an inner growth bearing macrosporangia 
was noticed. One of his specimens is of particular morphological interest, as it shows four heads or leaf-buds from 
the same healthy and vigorous trunk, three close together on top and a fourth on the side, separated from the others 
by a deep incision in the trunk. This division of the axis did not result from any proliferation of the leaves, but 
most probably from a lesion of the centre of vegetation, and is of very rare occurrence in this genus, where the 
simplicity of the axis is so particularly marked (see above, p. 3 
4. I. EcHINospora, Durieu. One of the smaller species, with 10 to 30 or 40 soft bright green [379 (22) ] 
sometimes reddish leaves, gradually and regularly tapering from a thick base to a very slender elongate 
point absolutely without stomata, 2 to 4 or sometimes 5 inches long; sporangia orbicular to broadly ont unspotted, 
with a narrow velum; macrospores 0.40 to 0.50 mm. thick, densely covered with delicate, erect, gone or slightly 
forked spinules ; microspores 0.030 to 0.034 mm. long, almost smooth. — Bull. Soc. Bot. Fr. 8, 1 
Only in Europe from Northern Italy to Germany, France, and England, extending to cane and Iceland, but 
apparently not in America. 
n this country we have a series of forms which have been distinguished by eminent authority, especially on 
account of the presence of stomata (so various in number and often so difficult to discover) and of a slight difference in 
the form and size of the microscopic spinules which cover the macrospores. I have thought best to unite them spe- 
cifically with the European type, though it seems strange that in the European plant stomata should be absolutely 
absent, and it must remain subject to individual judgment, if not doubt, which view ought to be preferred. Nearest 
to the European true I. echinospora stands the var. Braunii, and the other extreme is var. muricata, — wide-ranging 
forms of a single type. The same difficulties, the same doubts, and the same solution we find in studying some 
foreign forms, and especially those allied to I. velata of the south of Euro 
* * Stomata few. 
I. ECHINOsPoRA, var. BRauntt, Engelm. Rather small, with 13 to 15 green or reddish-green, erect or spreading, 
rather short (3 to 6 inches long), tapering, soft leaves, generally with few stomata towards the tip only; sporan- 
a one to broadly elliptical, spotted, generally $ or even 3 covered by a broad velum ; macrospores 0.40 to 
thick, rarely a little longer, covered with broad, retuse spinules, sometimes somewhat confluent, and 
