THE GENUS ISOETES IN NORTH AMERICA. 467 
oblong (2 to 4 or even 5 lines long), spotted, with narrow velum, ligula triangular-subulate ; macrospores [887 (30)] 
among the smallest in the genus, 0.25 to 0.40 mm. in diam., with depressed tubercles often confluent into 
worm-like wrinkles, or almost smooth ; microspores also smaller than usual, 0.023 to 0,028 or rarely 0.030 mm. 
long, spinulose.— Durieu in Bullet. 1. ¢.; Gray, Man. 1. ¢, 
ar, PALLIDA. A larger plant, leaf-bases pale, velum usually much broader, covering } or } of the sporangium ; 
macrospores only 0.30 to 0.35 mim. thick. 
An exclusively western species, in low prairies and fields overflowed with at least one inch of water in spring, or 
in shallow ponds which dry up in summer, in stiff clayey soil, in company with the ordinary vegetation of such locali- 
ties, e.g. Nasturtium sessiliflorum, Hypericum mutilum, Elatine, Penthorum, Ludwigia, Ammannia, Alisma, Juncus, ete., 
from Northern and Central Illinois, Ringwood, G. Vasey; Athens, Menard Co., E. Hall; to Clinton, Iowa, G. Vasey, 
the Indian Territory, in low places in the saline flats near Limestone Gap, G. D. Butler, and to the wet pine woods in 
Hempstead Co. and about Houston, Texas, where the variety occurs, E. Hall. Maturing in June or beginning of July. 
— Mr. Hall was accidentally led to the discovery of this plant on his farm in 1853 by finding its trunks and spores in 
turning up the soil for brick-making ; he has since made many interesting observations about it; he does not find it 
every year: thus in 1877 there was none at all in localities where before and since it abounded, though the season was 
wet ; another time he found it copiously only in plough furrows in a meadow, and not elsewhere ; in wet seasons, 
when the water is deeper than usual about the plants, the leaves become longer, more flaccid, and even decumbent, and 
the spores mature later or not at all. In ordinary seasons the leaves disappear entirely in July, and nothing but the 
trunks remain, and about them the numerous spores, both of which are eagerly sought after by mice and other animals. 
The spores germinate whenever sufficient rain falls in the later summer months, and perfect meadows of young plant- 
lets can be observed in wet autumns. Sometimes the plants are seen as fresh in September as in May, and already 4 
to 6 inches high, and in 1865 they were so much favored by the season that a second crop was gathered in November 
with perfectly mature spores ; but it is scarcely probable that these could have been seedlings of the preceding summer, 
though Mr. Hall is inclined to think so. 
The polygamous character of this species has been alluded to on page 369. I will here only add, that a number 
of moneecious specimens show a preponderance of one or the other sex, aud that in a few I have found leaves, which 
bear male or female sporangia, irregularly mixed. 
The dissepiments of the leaves consist of 6 to 9 layers of cells, the lower median being the thickest. Besides the 
normally 4 peripheral bast-bundles we find here often several smaller accessory ones, which increase the 
rigidity of the leaves. In no species have I seen the macrospores so variable in size in the same sporangium; [388 (31)] 
large and small ones are indiscriminately mixed ; and they are also remarkably variable in their sculp- 
ture, showing distinct or confluent vermiculate tubercles, or a nearly smooth surface ; the dividing ridges or commis- 
sures are very prominent and smooth. The leaf-bases of the typical form of this species are black and shining, and 
justify the name given by that zealous botanist Jacques Gay, who in his seventy-fifth year was still anxious and able to 
climb the high mountains in the centre of France, to study in their lakes the two European species which had just then 
become prominent through the labors of his friend Durieu de Maisonneuve, and who left us such a vivid description 
of his hardships, excitements, and pleasures on that trip (Bull. S. B. F. vols. 8 & 9) ; death prevented him from pub- 
lishing it, but his name remains connected with it. Now and then a paler specimen is seen, and the Texan form is 
always pale, and distinguished also by its broader velum. 
13. I. Bortert, Zngelm. Dicecious, smaller than the last, with a subglobose trunk and thinner and more rigid 
bright green leaves, 8 to 12 in number and 3 to 7 inches long ; sporangium usually oblong, spotted, without any or 
with a very narrow velum ; ligula subulate from a triangular base ; macrospores larger than in last, 0.50 to 0.63 mm. 
in diameter, similarly marked with knobs or warts, distinct or sometimes confluent ; microspores 0.028 to 0.034 mm. 
long, dark brown, papillose. — Bot. Gazette, 1878, p. 1. : : 
Var. immacuLata. Larger, leaves sometimes ‘as many as 60, 6 to 9 inches long ; sporangium without spots ; 
macrospores rather smaller, 0.40 to 0.56 mm. in diam. ; microspores 0.029 to 0.031 mm. long, spinulose. : 
In the saline flats (called alkali flats, but impregnated with sulphates) of the Indian Territory, near Limestone 
Gap, between Arkansas and Red rivers, associated with the few coarse plants which can live in those localities over- 
flowed in winter and spring, and baked hard in summer and autumn, such as Iva angustifolia, Ambrosia pstlostachya, 
Arenaria Pitcheri, and with Isoétes melanopoda, but in rather drier localities than this ; maturing in May and June, 
G. D. Butler. The variety near Nashville, Tenn., in cedar barrens, in damp places on the limestone flats, with Leaven- 
worthia, Talinum, Sedum pulchellum, Schenolirion, several Junci, etc., A. Gattinger. — This species, also peculiar to 
the Mississippi Valley, is quite unique in this genus by its dioicity, though its nearest ally, the last-mentioned one, 
approaches it. this it is readily distinguished by the absence of the velum, by the deep brown color of the 
microspores and the larger size of the macrospores ; in these last I notice the peculiarity that the ridges themselves 
which separate the faces of the spores are also more or less tuberculated, while in other species they are quite smooth. 
