408 DARLING: MITOSIS IN LIVING CELLS 
as is often the case when fixed and stained. The spindle was 
clearly marked and the spindle fibers distinguishable; anaphase 
and telophase stages could be readily observed; in fact practically 
all of the division figures to be found in fixed and stained material 
were observed in these living cells. The spireme is rather thin in this 
form, so that it could not be detected in the living cell; the nucleo- 
lus with a budlike attachment was plainly seen. The cytoplasm 
in Acer rubrum is not so dense as to obstruct or confuse the view of 
the nucleus as it is in some forms. 
Various stages in the division of the daughter nuclei were as 
clearly seen as were those of the mother cell; these daughter nuclei 
divide very soon after the first division of the mother cell, without 
the formation of the new cell wall. Within twenty-four hours 
after the first cells were seen to have begun division practically 
all of the mother cells in the material had formed the four distinct 
spores, showing that these stages go on rapidly. 
Attempts were made to induce the cells to complete t 
sions by placing them in sugar solutions of various strengths from 
2 per cent to 15 per cent, but in no case did a cell continue to 
divide after being forced out of the anther. : 
Twigs of the silver maple, Acer saccharinum, were brought into 
the laboratory on the same dates as those of the red maple; although 
the cytoplasm is denser and although the division figures were not 
so clearly marked, yet practically all of the stages observed in i 
red maple were seen in the pollen mother cells of this spectes- 
In the Norway maple, Acer platanoides, the division of the pollen 
mother cells takes place much later in the season. On March . 
twigs were brought into the laboratory, and on March 23 te 
mother cells divided. Various division figures were observed ™ 
this species together with a very conspicuous budlike process si 
the large nucleolus. The cytoplasm in this species is more a 
and more granular than that in Acer rubrum, so that the chrom 
somes and spindle fibers were not so clearly seen. 
spore mother cells does not force out of the anther U 
are nearly ready to divide, usually within a day oF ee m the 
in the red maple the tapetal cells become detached sin 
endothecium of the anther at least two weeks before division: ce 
In the European larch, Larix decidua, I have observ 
heir divi- 
