746 
DUNCAN S. JOHNSON 
EXPLANATION OF FIGURES 
53 Longitudinal section of young ovule with two integuments, parietal cell 
already formed. X 350. 
54 Longitudinal section of older ovule, with integuments completed and the 
megaspore mother-cell preparing for its first division. X 350. 
55 Embryo-sac preparing for the second division, each spindle shows about 
eighteen chromosomes. X 600. 
56 Section of a four-nucleate sac, showing a pair of nuclei at each end. X 750. 
57 Section of a four-nucleate sac, showing the nuclei grouped near the middle. 
X 600. 
58 Section of four-nucleate sac with one nucleus at the micropylar end and 
three at the antipodal end. X 600. 
59 Longitudinal section of nearly mature sac, in which the polars have not yet 
moved to the middle. X 600. 
60 Longitudinal section of nearly mature, somewhat abnormal embryo-sac. 
X 600. 
61 Part of longitudinal section of integuments of an ovule with a nearly mature 
embryo-sac. X 350. 
62 Longitudinal section of sac, with fertilized egg, free endosperm nuclei, and 
25 antipodals in the single section. X 170. 
63 Part of a similar section, showing endosperm nuclei, and numerous anti- 
podals in a deep pocket at the base of the sac. X 180. 
