18] LIFE HISTORY OF THE PONTEDERIACEA: 325 
mer of which has the characteristic reticulate thickenings of 
- mendothecium. 
The mother cells are very large in comparison with the sur- 
-unding cells. About the time they break apart and become 
tunded, there is a very considerable increase in size, The 
thromatin assumes a beaded structure and the nucleus enters 
itt the synapsis stage, which has been frequently described in 
nother cells, The chromosomes, when first distinguishable, are 
: thick and irregular, and lie scattered about in the nuclear space. 
i When arranged in the equatorial plate they have become more 
regular in outline and can be counted readily. The number is 
| maven ( fig. 32), and the same number appears in the second 
- division ( fig. 35). This is the reduction number. Although I 
eve not been able to count with certainty the chromosomes in 
~ the ordinary vegetative nuclei, I have ascertained the number 
; tobe not far from thirty. 
: : Successive stages in the two divisions which end in the forma- 
- Tonof the microspores are shown in figs. 3 1-364. The divisions, 
8 common in monocotyledons, are successive, each daughter 
‘ forming a wall about itself before the second division. 50 
%S observed, the nuclei resulting from the first division do 
i. fier into aresting condition. Very frequently they, have 
2 nucleoli, and in such cases there are numerous bodies in the 
: {9 which stain like nucleoli (fig.34)- These bodies 
—. be sSe a the cytoplasm even when a distinct nucle: 
Sate within the nuclear membrane. . 
se ual arrangement of the tetrads is shown in fig. 36 (cf. 
eof such a grouping as 36a is quite common. : 
 Microspores continue to enlarge they assume an ellip- 
shape. The generative and tube nuclei, very unequal in 
