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DUNCAN S. JOHNSON 
Fig. 71. The section adjoining that shown in last figure, showing the fourth 
nucleus and megaspore. X 1,250. 
Fig. 72. Similar section of a more elongated embryo sac, with part of one of 
cell walls. X600. 
Fig. 73. Similar section of an embryo sac with 4 megaspore nuclei still con- 
nected by fibres. The central vacuole has increased in size. X 1,250. 
Fig. 74. Similar longitudinal section of ovule with 4 unseparated megaspores. 
X350. 
Fig. 75. Similar section showing first mitosis of the 4 megaspore nuclei. X665. 
Fig. 76. Longitudinal section of an 8-nucleate embryo sac. X665. 
Fig. 77. Longitudmal section of 8-nucleate embryo sac with the nuclei in two 
groups. The nuclei shown in dotted outline are from the adjoining section of the 
same sac. X530. 
Fig. 78. Sagittal section of young fruit and bract showing vascular connection 
with axis. Embryo sac slightly diagrammatic. Xioo. 
Fig. 79. Transverse section of style, near middle of its length. Showing 
small-celled conducting tissue and large tracheae. X125. 
Fig. 80. Longitudinal section of i6-nucleate embryo sac, showing differ- 
entiation of cytoplasm about egg and synergid. The dotted nuclei are from an 
adjoining section. X530. 
Fig. 81. Similar section showing egg and synergid with walls. The nuclei of 
this sac are in 4 groups, showing their derivation from 4 megaspores. X530. 
Fig. 82. Similar section of older sac, with 14 prothallial nuclei grouped near 
center, ready for fusion. Dotted nuclei are from an adjoining section. Cytoplasm 
between vacuoles diagrammatic. X530. 
Fig. 83. Similar section of a sac in which fusion of the 14 constituents of the 
endosperm nucleus has begun, though they are still scattered around the central 
vacuole. The nucleoli of this and following figures are numbered in the order of 
their appearance in focus from one side of the sac to the other. Nucleoli i and 2 are 
in one fusion nucleus and 3 and 4 are in another. X500. 
Fig. 84. Similar section of an embryo sac, showing 13 grouped nuclei of which 
the large one, numbered 11, with a large nucleolus, has been formed by the fusion 
of 2 of the 14 free prothallial nuclei. The cytoplasm is becoming denser about the 
grouped nuclei. The 2 nucleoli in the egg indicate that fertilization has occurred. 
The small nuclei, 5 and 6, were perhaps destined to degenerate. X900. 
Fig. 85. Similar section showing 4 fusion nuclei in an endosperm group (those 
containing nucleoli 1-5). The nucleus at the right is enclosed in a peripheral cell 
against the wall of the sac. (Cytoplasm diagrammatic.) X530. 
Fig. 86. Basal half of similar section, showing more advanced stage of fusion. 
X530. 
Fig. 87. Longitudinal section of sac showing advanced stage of fusion of 
endosperm-forming nuclei, one lobe with 4 nucleoli. This sac is unique among 
those seen in having, in addition to the binucleolate egg nucleus and a synergid 
nucleus, two additional nuclei in the micropylar lobe. They may possibly have 
come from the pollen tube. The number of nuclei in the fusion mass could not be 
counted with certainty. X530. 
