OF THE THIRD TANGANYIKA EXPEDITION. 135 
and many diverse forms were observed. Extreme forms scarcely appear to 
belong to the same species, but a careful comparison of all the forms gives 
almost a complete gradation from one extreme to the other. Most of these 
forms have at different times been described under various specific names ; 
but after examining the African plankton-forms it is impossible to recognize 
more than one species, and for the specific name I have retained Meyen's old 
name Pediastrum simplex. This name is a very appropriate one, as there is 
no other species of the genus with a simple radiating process from each 
peripheral cell. 
In any of the forms the cell-wall may be smooth, punctate, or granulate, 
and the processes may be obtuse, truncate, or minutely emarginate. 
In one most interesting form the coenobium was not plane, the cells being 
disposed in the manner of a somewhat simplified Celastrum. Some of these 
cells possessed only one process and others two, and one of them appeared to 
be a resting akinete (РІ. 5. fig. 20). This form was from Victoria Nyanza 
(no. 620): diam. ecnob. 40-46 p; diam. cell 10-17 д. It should be 
compared with Cælastrum cornutum, Lemaire (in Journ. de Bot. févr. 
(1894) pp. 82, 83 cum fig.), and also with Pediastrum Kawraiskyi, Schmidle 
(Algen Hochseen Kaukasus, 1897, p. 5; Lemm. in Ber. Deutsch. Bot. Ges. 
xix. (1901) t. 4. fig. 5). 
Family PROTOCOCCACEZE (or AUTOSPORACEJE). 
Subfam. ÜCgLASTRE.E. 
Genus CCELASTRU M, Nag. 
149. CarAsrRUM MICROPORUM, Nig. er А. Br. Alg. Unicell. (1855) p. 70 ; 
Rabenh. Fl. Europ. Alg. ii. 1868, p. 80. 
Diam. ccenob. 38-90 р; diam. cell. 11:5-27 y. 
Nyasa.—Plankton, Anchorage Bay (13 June, 1904 ; no. 9). 
Victoria Nyanza.—Plankton, near Bukoba (21 Apr. 1905 ; no. 252). 
150. CŒLASTRUM SPHJERIOUM, Ndg. Gatt. еїтг. Alg. (1849) p. 97, t. 5 c. 
fig. 1 a-d. 
Nyasa.—Plankton, Anchorage Вау (13 June, 1904; no. 9). Swampy 
lake margin, Domira Bay (19 June, 1904 ; no. 579). In swamp, Kota Kota 
(20 June, 1904 ; no. 18). 
Victoria Nyanza.— Among Utricularia, near Entebbe (1 Мау, 1905; no. 620). 
151. CŒLASTRUM CAMBRICUM, Arch. т Mier. Journ. (1868) p. 65; Cooke, 
Brit. Freshw. Alg. (1882) p. 46; Lemaire, in Journ. de Bot. no. 4, 
févr. (1894) pp. 79, 80 (cum fig.).—C. cambricum, var. quinqueradiatum, 
Lemaire, 1894. C. pulchrum, Schmidle, in Ber. Deutsch. Bot. Ges. x. (1892) 
р. 206, t. 11. fig. 1; in Ber. d. Nat. Ges. Freiburg, vii. (1893) p. 12, t. 2. 
fig. 10; Bohlin, in Bih. К. Sv. Vet.- Akad. Handl. xxii. (1897) no. 7, p. дб. 
