ALGE TT 
but these are more properly aggregates or colonies of 
unicellular units than individual plants. The repro- 
ductive cells of the Protococcacee are always very 
primitive in character, and usually are motile, much 
like their unicellular volvocineous ancestors. The 
third line of development, represented by the Confer- 
vacez, may be assumed to have arisen from the lower 
Volvocinee through the simpler Protococcacex, with 
which they agree closely in their development. The 
origin of the typically multicellular Confervacee from 
the unicellular Protococcacee has been brought about 
by the cohesion of the cells after fission is complete. 
By repeated divisions in a single plane the simpler 
filament of the lower Confervaceze may thus be assumed 
to have arisen. 
The differentiation of the plant body first resulted in 
the establishment of a basal and apical region in the 
unbranched filament, and, later, there arose branched 
forms or a flat thallus. The development of the repro- 
ductive parts parallels very closely that of the Volvo- 
cinew, but the sexual cells in the higher types are borne 
in special organs, antheridia and odgonia. 
The genus Coleochete is the most specialized mem- 
ber of the order, and in the formation of a rudimentary 
spore-fruit (sporophyte) suggests a possible relationship 
with the lowest mosses. 
The three orders—Volvocinez, Protococcacex, and 
Confervaceze —form, then, a continuous series leading 
up to the higher plants, while the other alge are to be 
considered as offshoots of the main stock. Of these, the 
Siphonez have, perhaps, had a multiple origin, the sim- 
plest one being related to the lowest Volvocinee or 
