CELL DIVISION BY FURROWING IN MAGNOLIA 383 
as decussate, resulting from the spindles of the second meiotic division 
being at right angles to each other. Type 2 is the result of the spindles 
being parallel and may be called quadrate. Type 3 is the consequence 
of the two spindles being nearly at right angles to each other, and hence 
it is an approach to the first type. Type 4 is a similar approach to 
the second; and Type 5 is the characteristic tetrahedral disposition 
so common in many Dicotyledons. Types 6 and 7 (not represented 
by drawings) indicate mother-cells with four large cells and one small 
cell, and three large cells and one small cell respectively. The figures 
in the perpendicular columns refer to the number of pollen mother 
cells of single stamens, designated respectively as ^, ^, C, and D. 
Table I 
Arrangement of Microspores 
Type 
A 
B 
c 
D 
Total 
Percent 
I 
34 
43 
35 
35 
147 
51-2 
2 
20 
15 
22 
14 
71 
2475 
3 
II 
8 
13 
5 
37 
12.9 
4 
4 
6 
8 
5 
23 
8 
5 
0 
0 
0 
0 
0 
0 
6 
I 
3 
0 
4 
8 
2.8 
7 
0 
I 
0 
0 
I 
.35 
70 
76 
78 
. - . 
63 
287 
100.00 
These figures show that the tetrahedral arrangement of the micro- 
spores is exceedingly rare in Magnoha, if, in fact, it ever occurs at all. 
It also appears that the percentage of the various types of arrange- 
ment is rather markedly constant among various stamens, none of 
those studied departing very far from the mean. Approximately one 
half of the total number of cells in each stamen have the decussate 
arrangement, about one fourth have the quadrate, and deviations from 
these two types make up the remaining one fourth. In the study of 
the fixed material some data have been accumulated as to the relative 
positions of the two spindles during the homoeotypic karyokinesis. 
In 25 of 45 mother cells the spindles were nearly at right angles to each 
other. In the other 20 they were nearly parallel. Inasmuch as the 
latter arrangement is associated with the quadrate disposition of the 
microspores, it is interesting to note that in both cases these are in the 
minority respectively. This agreement between the arrangement of 
the microspores and the corresponding position of the spindles con- 
