30 
PEDIASTRUM, Meyen. 
P. duplex, Meyen (=P. pertusum, Kirchn.) Prot. Moebius 
gives the following note :—“ Was several times observed in families of 
16 and 32 cells. The lobes of the peripheral cells are finely indented, 
just. as Kirchner figures them in his Microscopic Plant-world of 
Fresh Water” (Plate I., Fig. 22). 
Known to occur in Europe and America, but perhaps generally — 
distributed. 
(Plate VIIL., Fig. 9.) 
SCIADIUM, Braun. 
Plant from a single individual producing a family. Thallus 
(solitary) adnate, micellular; cell elongated, cylindrical, straight, 
attenuated at the base into a slender stem. Gonidia about §, 
t 
sometimes a fourth generation, forming a composite or decomposite 
umbel. Ultimate cells producing free biciliate zoogonidia.—Cookes 
British Freshwater Alge, 89. a 
The cylindrical cell of Sciadium possesses uniformly distributed 
green contents, which are interrupted, in perfectly developed cell, by 
light cross streaks, and are divided into a row of 5-8 about, edi 3 
ich become gonidia. I could not detect nuclei m 2 | 
individual segments of the contents passing into the formation ° : 
gonidia.— Brawn, Rejuvenescence, p. 260.—Cooke l.c. ‘ 
S. arbuscula, Brawn. Cooke’s Freshwater Alge, 39: Leman | 
Cells straight (rarely faleate), obtuse at the apex ; stem about as 3 
as the diameter of the cells. Size: Cells, 0038 mm. (rarely ‘007 mm.) 
diam.—Cooke l.c. : 
Dr. Cooke also gives the following note :—‘* Braun, writing a 
cies—‘It displays an originally obovate tube, generally becom 
elongated into a cylindrical form, obtuse above, and prolonged formle : 
green mucilage, in which a small vesicle may sometimes be distin 
} : wth. = 
i ‘at the 
imperfect birth of the germ cells just described is repeated a ee 
transition to the third and mostly even to the fourth generat 
