eB) A ha ek DS GNSS a PRG RAE ap a a 
ee 
1897 ] THE LIFE HISTORY OF SAGITTARIA VARIABILIS 253 
carpels. The glandular secreting cells are epidermal and are 
situated around the lower part (jig. 7), usually extending to the 
adjoining carpels, which often remain sterile and develop no 
embryo. The secreting cells begin to enlarge about the time 
the embryo sac is formed, and after fertilization is accomplished 
they cease their activity and become more or less shrunken and 
disorganized. During their active period the cytoplasm of 
these cells has the characteristic glandular appearance, and the 
nuclei are drawn out into irregular shapes, often having thick 
projections like pseudopodia (jig. 45). 
DEVELOPMENT OF THE MALE GAMETOPHYTE. 
As no suitable material was available the early development 
of the anther was not studied. The pollen mother cells were 
found dividing abundantly. In these numerous figures in the 
mother star stage showed large and well defined centrospheres 
at the poles (fig. 2), and although the exact number of chrom- 
osomes was not determined the reduction was ascertained to 
take place at this division. This fact should be kept in mind in 
connection with any theoretical explanation of the phenom- 
enon of reduction, as it will be seen that the two daughter 
nuclei arising from the reduction nucleus do not belong to the 
first cells of the sexual generation, but to the mother cells of the 
microspores with which the sexual generation properly begins. 
By the time the nucleus of the pollen mother cells is in the 
close mother skein stage, two centrospheres appear at each pole 
of the spindle. By successive divisions the two microspore 
mother cells form the cells of the tetrad. These cells, which 
usually lie in one plane (fig. 4), soon separate, and with little or 
no increase in size develop into the microspores.. The micro- 
Spores possess a very thick wall, from whose outer surface are 
developed prickly projections (fig. 5). 
The microspore soon begins to enlarge and the first division 
of its nucleus takes place, giving rise to the generative and tube 
Nuclei. The two nuclei are at first quite similar, but they soon 
differentiate, the tube nucleus becoming larger, and the ne 
