364 



METHODS IN PLANT HISTOLOGY 



In very young stages, before the appearance of the integument, the 

 ovary may be removed from the flower and placed directly in the fixing 

 agent, but at fertilization and later stages, strips should be cut off from 

 the sides of the ovary in order to secure more rapid fixing and more 



Fig. 131. — Lilium philadelphicum: photomicrograph of second mitosis in megaspore mother- 

 cell. Chromo-acetic acid; safranin, gentian violet, orange. Cramer contrast plate; 4-mm. objective; 

 ocular X4; Abbe condenser; camera bellows, 1 m. ; yellowish-green filter and also a strong filter such 

 as is used in outdoor work; exposure, 7 minutes. Negative by Miss Ethel Thomas. X626. 



perfect infiltration with paraffin. The dotted lines in Figure 132 C 

 show about how much should be cut off. This is a much better plan 

 than to secure rapid fixing and infiltration by cutting the ovary into 

 short pieces, because the ovules will be in about the same stage of de- 

 velopment throughout the ovary, and when one finds desirable stages 

 like those from which these photomicrographs were taken, it is gratify- 

 ing to have these pieces as long as possible. 



