THE PROBLEM OF SEX IN PLANTS 
345 
some of the lowest forms, cell-division always results in 
reproduction, in the higher forms it only paves the way 
FIG. 251.- Spirogyra sp. A, terminal portion of vegetative filament; 
B, stages of scalariform conjugation; C, preparation for lateral conjuga- 
tion; D, zygospores formed by lateral conjugation. 
to increasing the size of the given individual, that is, to 
growth. In other words, between cell-division and re- 
