240 BOTANICAL GAZETTE [OCTOBER 
surface of the sporange into irregular polygonal areas at the 
time when spore formation is beginning. The lines marking off 
these areas are doubtless the beginnings of the cleavage furrows 
as I have described them for Pilobolus and Sporodinia. Bach- 
mann made no sections, but concludes that the spore formation 
must be a progressive process. 
A sufficient number of forms has been investigated to show 
that progressive cleavage is a widely spread phenomenon among 
the lower plants, occurring in very many cases when multinu- 
cleated masses are to be cut up into smaller cells. That simul- 
taneous cleavage may also occur is quite possible, but the 
evidence for it is not strong except, perhaps, in the case of the 
sporange of the Saprolegniacee. 
I have already shown elsewhere (4) that the progressive 
cleavage of the sporange in spore formation is in principle the 
same process as that which has been described as division by 
constriction in Cladophora and the conidiophores of the mil- 
dews, and it will be of interest: to attempt a comparison of this 
progressive cleavage with cell division as found in the growing 
points of the higher plants, especially from the standpoint of the 
more general theories of cell division. 
Schleiden’s (21) doctrine that the form of a plant is deter 
mined by its cellular composition, including as the two important 
factors the arrangement of the new-formed cells in growing 
regions and the subsequent varying growth and enlargement of 
these cells in their three dimensions, was first opposed y 
Hofmeister. Hofmeister (7 and 8, p. 129) advanced the vee 
that cell-formation is.subordinate to the growth of an enlarging 
organ taken asa whole. He held that the growth of the single 
cells of a vegetative point is controlled and conditioned by some 
formative principle which determines the growth of the comme 
organ, this latter being directed toward simple enlargement OF 
the development of some predetermined form. According 
this view, growth of the vegetative point cannot be interpret 
as determined by the sum of innate growth tendencies of 
individual cells, 
