3io BOTANICAL GAZETTE [October 



signs of disintegration. The fourth megaspore is fast disorganizing, 

 being a darkly stained almost structureless mass. The first mega- 

 spore and the nucellar layer over the upper part of the sac show only 

 traces of their former existence. An embryo sac developing from 

 the fourth megaspore is shown in fig. 28. The nucleus is in mitosis 

 for the first division, and the 10 chromosomes can be counted. The 

 three upper megaspores are completely disorganized, and the 

 nucellar cells near the micropyle are paler and with very little con- 

 tents. The vacuole appears early in the two-nucleate sac (fig. 29). 

 It is not common to find the second and the third megaspores per- 

 sisting so long as they have here. The two upper nucellar cells have 

 very little cytoplasm in them and stain much lighter than the others. 



In fig. 30 an entire ovule at a little later stage is shown with less 

 magnification. The nucellar layer has disappeared completely from 

 around the upper part of the sac, leaving it in contact with the inner 

 integument and an open micropyle all the way to the sac. The only 

 part of the nucellus remaining is that below the lower.nucleus of the 

 two-nucleate sac. It is interesting to note that Shreve (20) has 

 shown a similar figure for Sarracenia, all the nucellar tissue except 

 that at the base having been destroyed. The loose, spongy tissue is 

 already appearing in the chalazal end of the ovules. This becomes 

 very conspicuous in older stages. 



Figs. 31 and 32 show the second mitosis in the embryo sac. In 

 one nucleus of each sac it is possible to count the 10 chromosomes. 

 In the first the chromosomes have been formed in both nuclei, in the 

 second only in the lower one; the upper one has the spirem very 

 thick and short and probably shows the early stages of segmentation. 

 In both ovules the nucellar layer has disappeared from the upper 

 half of the sac. The spindles for the second division are at right 

 angles to each other (fig. 33). This sac developed from the second 

 megaspore, and in this case the third one has also begun to develop. 



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