A Vascular Sporangium . 67 
Fig. 4 . —Tracheal group shown in photo. 2 ( x 390). 
t-t tracheal elements. 
5 spores. 
w wall of sporangium. 
g gap in wall. 
Fig. 5.—Tracheal group shown in photo. 3 ( x 390). 
t-t tracheal elements. 
w wall of sporangium. 
F'ig. 6.—Tracheal .element flattened against wall of sporangium (—t l 
at bottom of photo. 1) ( x 530). 
t tracheal element. 
w wall, here one cell thick. 
A REVISION OF THE CLASSIFICATION OF 
THE GREEN ALG^E 
BY 
F. F. Blackman, 
University Lec-turer in Botany, Cambridge. 
AND 
A. G. Tansley, 
Assistant Professor of Botany, University College, London, 
{continued from page 48.) 
5 . Pandorina, Bory, 1824 . 
Ccenobium of 16 (rarely 32 ) pyramidal cells closely 
packed within a spherical investment, the apices of 
the cells nearly reaching the centre of the sphere, the 
broad ends bearing the flagella approaching the surface. 
Gametes 16-32 from a single cell, very variable in size; 
conjugation mainly promiscuous, but the largest (rudi¬ 
mentary female) relatively passive, not conjugating 
inter se. Germination of zygote indirect. 
6 . Eudorina. Ehrenberg, 1832 . 
Ccenobium of 32 (rarely 16 or 8 ) spherical cells rather 
far apart in a single layer within a spherical or oval 
investment. Anisogamy by union of reduced yellow 
pear-shaped swarmers (antherozoids) which are 
produced 64 from a cell, with eggs which scarcely 
differ from vegetative cells. Germination direct. 
7 . Eudorinella. Lemmermann, 1900 . 
Ccenobium of 8 spherical cells, as in Eudorina , but in 
two parallel planes; viewed perpendicularly the four 
cells in each plane form a square and alternate with 
the four cells in the other. Reproduction unknown. 
