1908] Cushman,— New England Species of Micrasterias 99 
(1) Polar lobe prominently exserted. 9. M.apiculata. 
2 a " not prominently exserted. 
(a) Cell without spines or spinose projéctions. 
10. M. denticulata. 
(b) [11 with [11 [11 “ 
aa. Polar lobe very narrow, sides parallel for most of their 
length, sinus undulate. 11. М. sol. 
bb. Polar lobe broader, gradually broadening from the base, 
sinus not undulate. 
* A spine on either side of the terminal notch, interlobular 
incisions with a row of denticulations. 12. M. papillifera. 
** No spines close to terminal notch, no surface ornamen- 
tation. 13. M. rotata. 
cc. Polar lobe broad and anvil shaped at apex, angles uncinate. 
8a. М. сопјетіа, var. hamata. 
2. Lateral lobes with fewer divisions, interlobular incisions widely open. 
a. Polar lobe without processes, lateral lobes unequal, upper one with 
three, lower with two lobules. 14. M. Torreyi. 
b. Polar lobe with long processes, lateral lobes typically equal and 
each with two lobules elongated into processes. 15. M. radiata. 
с. Polar lobe without long processes, lateral lobes equal but not 
elongated into processes. 16. Л. crux-melitensis. 
C. Polar lobe with accessory processes one on either side of the lobe asym- 
metrically, not broadened distally as in B. 
I. Lateral lobes each divided, divisions broad and obliquely truncate. 
17. M. americana. 
П. Lateral lobes with only the upper divided or neither, the ends narrowed, 
not obliquely truncate. 19. M. mahabuleshwarensis. 
D. Polar lobe divided laterally. 
I. Semicell three lobed, sides with a conical projection above the basal 
lobes. 20. M. Nordstedtiana. 
II. Semicell five lobed, lobes separated by broadly rounded sinuses. 
21. M. muricata. 
E. Polar lobe with interlocking teeth so that cells are united into filaments, 
lateral lobes with their divisions arranged parallel to those of the oppo- 
site side. 22. M. foliacea. 
1. Micrasrertas OSCITANS Ralfs in Jenner's Flora of Tunbridge 
Wells, 1845, p. 198; Brit. Desm., 1848, p. 76, pl. 10, fig. 2; Wolle, 
Desm. U. S., 1884, p. 116, pl. 33, figs. 3, 4; W. & G. S. West, Brit. 
Desm., 1905, p. 78, pl. 41, figs. 1-4. This species has been reported 
from New England by three observers; Massachusetts (Wolle), 
Lake Quinsigamond, Worcester (Stone), Rhode Island, near Provi- 
dence (Bailey). I have not as yet seen undisputed material from 
New England. Bailey at least had this species for I have found 
excellent drawings of the typical form among his notes. 
2. MiCRASTERIAS LATICEPS Nordst., Desm. Brasil., 1870, p. 220, 
pl. 2, fig. 14; Wolle, Desm. U. S., 1884, p. 115, pl. 37, figs. 4, 5. M. 
incisa, Bail., Micr. obs., 1851, p. 142, pl. 1, fig. 13 (non Bréb.). М. 
disputata Wood, Fr. Alg., 1873, p. 142, pl. 13, fig. 4. Cells of medium 
size, a little broader than long, deeply constricted, semicell three- 
lobed, polar lobe nearly as wide as the cell, lateral interlobular inci- 
