212 IOWA ACADEMY OF SCIENCES. 



droop probably depends on the way the flower hangs. 

 This trouble begins about the time of formation of macro- 

 spores, and especially about the time of fertilization. In 

 staining no attempt was made to obtain nuclear results in 

 the way of karyokinetic figures, because of the extreme 

 smallness of the cells. Only the most common stains 

 were used, either Delafield's hsematoxylon or a combina- 

 tion stain of eosin and hgematoxylon. In all, about 500 

 flowers were sectioned, but only a few of this number were 

 of any value, because so many were cut obliquely. 



As soon as the leaf which forms the pistil has folded 

 together, there is a proliferation of cells on either side of 

 the suture formed by the fusion of the two edges of the 

 leaf. As a result of the increased number of cells in this 

 region, the nucellus is produced (Fig. 2) and soon becomes a 

 prominent protrusion into the cavity of the pistil. 



In the apical region of the nucellus one of the hypoder- 

 mal cells undergoes marked differentiation. It increases 

 greatly in size, becomes granular, and has a large nucleus. 

 At about the time of the formation of the archisporial 

 cell, the integuments are first making their appearance, 

 the inner one appearing slightly before the outer one 

 (Fig. 3). 



The archisporial cell divides into two, and each of the 

 resulting cells divides again, instead of two or three cells 

 being cut off the tapetal end of the first cell formed, as is 

 frequently the case. The presence of two nuclei in each 

 archisporium (Fig. 5) in the two-celled stage, and the posi- 

 tion of the cells in the four-celled stage (Fig. 6) indicates 

 that each of the first two cells formed divides again. It is 

 the lower cell of the row of four which develops into a 

 macrospore at the expense of the other three (Fig. 7). 

 After the first division of the nucleus of the embryo sac, 

 and about the time or just before the fusion of the two 

 nuclei which form the definetive nucleus, cell walls are 

 formed around the antipodal cells (Fig. 12). The form of 

 the antipodals is generally triangular. Concerning the 

 position of the egg apparatus, it may be at one side of 

 both synergids or below them Figs. 12, 13). The mature 



