and the Flagellata . 671 
colourless Flagellate without any green forms being involved 
at all. 
One other interesting organism of this nature ( Sycamina ) 
has been described by Van Tieghem (’80). This seems to be 
a colony of the complexity of Volvox, but, though blackish, 
quite devoid of chlorophyll. Its methods of reproduction 
are unknown, so that it can only be doubtfully suggested that 
it must stand to the Volvocineae in some such relation as 
Polytoma does to the Chlamydomonadeae. 
All these colourless forms were excluded by Wille from his 
Volvocaceae, but further investigation of their characters and 
nutrition necessitates their inclusion in the group. See p. 649 . 
From this outline of the possible Flagellate origins of the 
primitive Chlorophyceae we may pass in the next section to 
consider a special case, in which it has been proposed to create 
an independent phylum of green Algae and to derive it from 
the Chloromonadales. 
Section IV. Heteroko?itae. 
Borzi (’89) proposed to group together into one special 
cohort —Confervales Bz.—certain forms of the Chlorophyceae 
which had been previously distributed among various groups. 
This idea he elaborated in his well-known Studi Algologici (’95), 
and also placed in the group several new genera discovered 
by himself. The characteristics of this cohort are essentially 
cytological. All cells contain discoid yellowish-green chloro- 
plasts which are usually numerous and which lack pyrenoids. 
The stored-up product of assimilation is not starch but some 
fatty substance. The zoospores have also discoid chromato- 
phores, typically two lateral ones, and generally only one cilium. 
The members of this cohort are unicellular, filamentous or 
coenocytic, and so, as with the Chlorophyceae in general, the 
included forms are an ascending series from the structural 
point of view. The lower ranks of this new cohort include 
the Sciadiaceae, which are practically the Characieae of Wille, 
consisting mostly of unicellular forms attached by the base, 
Yy 
