1907] Cushman,— New England Species of Pleurotaenium 103 
P. TRUNCATUM (Bréb.) Niig., Gatt. Einz. Alg., 1849, p. 104. Closte- 
rium truncatum Bréb. in Chev., Micr., 1839, p. 272. Docidiwm trun- 
catum Bréb. in Ralfs, Brit. Desm., 1848, p. 156, Pl. XXVI, fig. 2; 
Wolle, Desm. U. S., 1884, p. 48, Pl. IX, figs. 6 & 7. Cells large, 6-9 
times as long as wide, decidedly attenuated towards the apex, 11-15 
apical tubercles, their bases depressed below the actual end of the semi- 
cell; cell wall coarsely punctate. Length 450-520 ji; breadth 53-80 x; 
apex 37-45 u.— Me.: Orono (Harvey, W. West). Mass.: Pondville! 
Carver’s Pond, Bridgewater! This does not appear to be common 
in New England, as it has appeared in but two of the many lots of 
material examined. It seems to be common in the British Isles, 
however, and has a wide distribution elsewhere. 
P. EHRENBERGII (Bréb.) DeBary, Conj., 1858, p. 75. Docidium 
Ehrenbergii Bréb. in Dict. Univ. Hist. Nat., 1844, Vol. V, p. 93. 
Cells of medium size, 15-18 times as long as wide, somewhat atten- 
uated towards the apices, a basal inflation and one or two additional 
ones above it; apices with 7-9 tubercles, cell wall punctate. Length 
350-496 u; breadth 21-32 s; apex 12.5-19 j.— Mass.: Tewksbury 
(Lagerheim)! Randolph! Halifax! Lake Watuppa, Fall River! Nan- 
tucket! Although this is the most frequent species of the genus in 
the British Isles according to the Wests, in New England there are 
other species that occur more frequently. 
P. EHRENBERGII var. ELONGATUM West, Jour. Linn. Soc. Bot., 
Vol. XXIX, 1892, p. 119. Cells narrow and much elongated, about 
25 times longer than the diameter. Length 573-660 4; breadth 
25-30 u; apex 19-22 4.— N. H.: Pudding Pond, North Conway! 
Mass.: Halifax! 
P. EHRENBERGIT var. UNDULATUM Schaarschm., Magyar Tudom. 
Akad. Math. s. Termeszettud. Kozlemenyek., Vol. XVIII, 1882, 
p. 278, PI. I, fig. 21. Cells larger than in the typical form and with the 
sides undulate throughout their length. Length 496 w; breadth 25 x; 
apex 15 j.— N. H.: Pudding Pond, North Conway! 
P. TnRABECULA (Ehrenb.) Nüg., Gatt. Einz. Alg., 1849, p. 104, 
Pl. VI, fig. A. Closterium Trabecula Ehrenb., Beitr. zur Kentniss 
der Organis. der Infus., 1830, p. 62. Docidium Trabecula Wolle, 
Desm. U. S., 1884, p. 48, Pl. IX, figs. 2-4, Pl. XII, figs. 1-7. Cells 
large, 9-19 times as long as wide, sides of semicells nearly straight, 
apices rounded truncate, usually without tubercles. Length 320- 
620 u; breadth at base 25—44 p; apex 23-27 p.=— Me.: Orono (Har- 
