274 



Methods in Plant Histology 



between pollination and fertilization is known (about 72 hours in 

 lAliurn), pieces of the stigma and style showing pollen tubes can be 

 selected with some certainty. . 



Oogenesis. As in spermatogenesis, the early stages will be found 

 in preparations of floral development. The preparations of Capsella 



FIG. 98. Lilium philadelphicum: photomicrograph of second mitosis in megaspore 

 mother cell chromo-acetic acid; safranin, gentian-violet, orange. Cramer contrast 

 plate; 4mm. objective; ocular X4; Abbe condenser camera bellows, 1 meter; yellowish- 

 green filter and also a strong filter such as is used in outdoor work; camera bellows, 

 1 meter; exposure, 7 minutes. X626. 



will show the origin and development of the nucellus (megaspo- 

 rangium) and also the megaspore mother cell. The division of the 

 megaspore mother cell to form four megaspores takes place shortly 

 before the bud begins to unfold. A massive megasporangium with 



