Reproductive Structures of Vascular Plants 773 









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Fig. 15.2— rt, Transverse section of anther of LUium regale; b. somatic divisions in 

 developing archesporinm; r, archesporium, surrounded by differentiating tapetum; 



d, sporocytes in pre-leptotene pfiase. 



The manufacture of lily ovary slides showing the seven-to-eight- 

 nucleate stage is unproductive and expensive. Most of the slides 

 obtained from a ribbon show incomplete embryo sacs. Cutting an 

 ovule longitudinally through the center and having all the nuclei 

 in one section is a matter of chance. Commercial manufacturers have 

 a sales outlet for slides having incomplete sacs and can therefore sell 

 the few choice slides having complete sacs at reasonable cost. For 

 routine teaching, with its attendant breakage of slides, it may be 

 more satisfactory to purchase slides of the seven-to-eight-nucleate 

 stage than to make them. Good fixation has been obtained with fair 

 regularity with Allen-Bouin II and n-butyl alcohol dehydration. 



