72 MARGARET C. FERGUSON 



tissue is clearly differentiated about it (fig. 124). The mother- 

 cell in this instance has relatively the same position in the ovule 

 as that shown in fig. 66, plate VI, which was taken from an 

 ovule collected twelve days later. If this cell be the direct de- 

 scendant of a hypodermal cell, it has now become deep-seated 

 by the addition of cells above it ; but there is nothing in the 

 arrangement of the cells of the nucellus either before the 

 appearance of the mother-cell or after it to denote such a course 

 of development. 



The mother-cell is first detected by its larger size and by its 

 failure to stain as deeply as do the other cells of the nucellus. 

 In the first stages of growth the nucleus almost fills the cell 

 (fig. 125), and its weakened capacity for staining is doubtless 

 due to its rapid growth without a proportional increase in the 

 amount of nuclear substance. The nucleus contains in this 

 young stage a delicate reticulum with a varying number 

 of larger and smaller net-knots, and from two to four small 

 nucleoli, not differing materially, except in size and staining 

 power, from the nuclei of the adjacent tissue. This cell in- 

 creases considerably in size before its division so that it becomes 

 very conspicuous in the nucellus, its reticulum taking the chro- 

 matin-stains with greater avidity than at an earlier period. 

 The season of growth for the macrospore-mother-cell may 

 extend over about three weeks. The early stage shown in 

 figs. 124 and 125 represent its size on May 15, 1902, and the 

 spireme stage illustrated in fig. 126 indicates the condition of 

 this cell on June 5 of the same year. 



First Division of the Macrospore-mother-cell. After the 

 mother-cell has attained its full size, the reticulum of the 

 resting nucleus gradually becomes more open, the chromatic 

 granules become more prominent and there arises a beauti- 

 ful, regularly moniliformed, more or less interrupted skein, 

 but a true spireme is not formed until after synapsis (fig. 126). 

 This somewhat branched thread is very delicate, the chro- 

 matic discs are uniform in size and distributed upon the linin 

 with great regularity. It is probable that these apparently 

 homogeneous discs, which have doubtless been derived from 

 the fusion of the smaller chromatic granules, would, under 



