468 THE GENUS ISOETES IN NORTH AMERICA. 
* * Velum complete. 
14. I, Nurratuu, 4. Braun in herb. Similar to the last two species, with an almost globose, slightly grooved 
trunk and 20 to 60 slender bright green leaves, 3 to 9 inches long, with only 3 peripheral bast-bundles ; 
sporangium oblong or oval, entirely covered by the velum ; macrospores very variable in size, between [389 (32) ] 
0.25 and 0.50 mm. thick, densely covered with minute but prominent rounded warts, or, rarely, almost 
smooth ; microspores 0.025 to 0.028 mm. long, papillose, brown. — Engelm. in Am. Nat. 8, p. 215. JZ. opaca, Nutt. 
in Hb. Ac. Phil. 
On damp prairie flats or ge declivities in the valley of the Columbia River, Nuttall ; abundant about 
Silverton in the Willamette valley, Z. Hall, No. 693; at Milwaukee, Oregon, J. Howell (with almost smooth ma- 
crospores) ; Klickitat Co., Washington Ten. on Kamass Prairie and at the base of Mt. Adams, 2,100 feet alt., W. N. 
j eastward on Kamass Prairie of the Coeur d’Aleines in Western Idaho, C. A. Geyer.—The closed velum 
and the much smaller warts of the macrospores distinguish this readily from the two other terrestrial species ; it is the 
only species on which I observe constantly only 3 peripheral bast-bundles, one on each of the three edges, the upper 
middle one being absent. The median dissepiment of the leaves consists of 8 or 9 and the transverse one of 6 to 7 
layers of cells. 
II. TRUNK TRILOBED, bast-bundles and numerous stomata in the quadrangular leaves; velum partial. 
15. I. Cuspana, Engelm. One of the larger species; leaves 30 to 40, 15 inches long, fresh green, with 6 bast- 
; Sporangia oblong, unspotted; velum very narrow ; macrospores 0.30 to 0.40 mm. thick, marked with coarse, 
round, press never confluent tubercles ; microspores 0.024 to 0.027 mm. long, papillose, pale. — Sauvalle, F]. Cub., 
p- 203, nam 
ee oe of rivulets in the pine woods of Eastern Cuba, Chas. Wright, probably floating. — This is the 
only ont species north of the Equator with a trilobed trunk; it compares most closely with the East Indian 
I. Coromandelina according to A. Braun’s observation. The roots form 3 distinct bundles from the 3 grooves ; the 
bast-bundles are found at the four intersections of the dissepiments with the outer walls and at the two upper edges 
of the leaf. 
TABULATED CHARACTERS OF THE NortH AMERICAN ISOETES. 
. |!) Leaves. | 3 a MACROSPORES. | | MICROSPORES. | 
a: 12 3 = 
3 = a ¢ g a]. 2 Native Country 
$ %. S| 3 4 = | 2||Diameter. a ag mt 2 
=) Ss] 9 Cn Milli- St} . illi- urface. 
> & a Si] a a = |a|| metres. metres. 
1. I. lacustris. subm. ; 2- 6 0 |0 (n. |w.}| 0.60~0.80|Cristate, Smooth. Brae New York to Lake 
rior, 
var. paupercula, 2 2 4 0 10 |b. |w.}| 0620.66} “ Nearly do. Rocky Mountains and Cali- 
fornia. 
I Pygmea. memes Bs +1 0 |0 jn. jw. |} 0.36-0.50/Minutely tuberculated. . alifornian Mountains. 
3. I. Tuckermani. bated | 2-3 0 |0 (DB. |sp.}} 0,440.56 a © di reticu Smoothish/ |New England. 
4. I. echinospora, ; 
var, Braunii. eee C 3- 6 ||few. | 0 (b. |sp.|| 0.40~-0.50|Spinulose. Smooth, ||Pennsylvania northward and 
eg | westward and toUtah. | 
var. robusta. weit 5- 8 ||many./ 0 (B. |[sp.|| 0.36-0.55) With longer slende ~ New England. 
ines. 
var, Boottii. ieee © 4-5 |\few. |0 60. |sp.|| 0.40-0.50/ With longer slende Smoothish 
var. muricata. bales 6-12 - 0 ™ w.|| 0.44~0.58 wit bs ar confluen ss 
spi 
5. I. Bolanderi. = 42 2- 44) * |0 (Bb. }w.}} 0.30-0.45/8 ly and minutel Papillose. ifornia,Oregon,and Rocky 
: | tuberew Mountains. 
6. I. saccharate. jamph. | 2 2-3 |\jmany|90 ‘n, |sp.!| 0.40-0.47|Minutely tuberculated = land 
7. I. riparia, 43 8}} * 10 b, |sp.)} 0.44~0.65|Cristate. 8-34 Pennsylvania to NewEngl’d 
8. I. melanospora. + 42 2- 2h) “ 10 ‘c. |w.|| 0.35-0.45|Minutely tuberculated. Smoothish 
9. I. Engelmanni. nota 4° ry oO ee ‘e w.|| 0.40-0.52| Retic 28 rez Delaware to New England 
uri. 
var. gracilis, eae 'e: 912]} “ |4 ‘nm. |w.]| 0.38-0.48 a .024~28 . ennsylvania to New Engl’d 
_ room Lemay 18-25 * 14 bd. jw.]] 0.32-0.48 7 024~27 |Spinulose. 
e 2 10-12 sae 4 mn. |w.}| 0,48-0.56 0.02! ooth. 
10. Ti a “x 2 5- 8 . | 4 0b. |w.}) 0.43-0.48| Coarsely tuberculated. |] ......00. [cece cae 
il. £ flaccida, subm, ?| 2} 15-24 {jmany.}4 « [w.|| 0.30-0.42) Coarsely tuberculated, |} 1... Jesssceceee, Florida. 
| often confluent. 
amph. | 2 5- 6 || * 4 ‘c. |w.|| 0.30-0.38 ao. ac 1 Sa | Reg eSiiiry pt 
var. antes 49 18 * 14 Je |w.}] 0.44-0.55/do. often ee ere 027-30 Papilions, “ : 
12. I. melanopoda. 2) jl -16 |} “ | 4-n. |sp No. 25-0.40 0.023-30|Spin Hinois to Indian Territory. 
var. pallida, ° 2 ah Taeeceey = St | OSA“ | deceit) Salen eeerna manta’ |: Soeiccre © yer tenan exas, 
13.1, Butleri, oe 3-7 * {4 [nn.'sp.t| 0.50-0. 63 peered bene eae lated.) }0. 025-34 rie on Indian Territory. 
var, ue 2) 12 6- 9 bis 4 |nn.\w.}| 0.40-0. ai 0. or nearly smooth | (0.029~31|Spini ennessee 
14. I. Nuttallii. a $-9}} “ 18 |e. le. : 32-0 32 Minutel yt a 025-28 Papillose. Western Idaho to Oregon. 
I. Cubana. 13 15 "16 lm {w. 40|Coarsely tuberculated. | |0 024-27 Juba. 
EXPLANATIONS. — Vecetation — submerged, amphibious, or terrestri: —. Means narrow; n., very narrow; b.,broad ; 06., very 
broad; c., closed. SporRancium —w. mcans white or unspotted; sp., spotted aE ose sclerenchyim-cells. 
