PLATE XXIII. 



Pinus Strobus unless otherwise indicated. 

 Fig. 252a. The lower part of an archegonium after the four nuclei have ar- 

 ranged themselves at the "organic apex" of the oosphere. X62. 



252^. A portion of the above ; the nucleus is in the early prophase of 

 division ; the cytoplasm surrounding the nucleus has became dense 

 and deeply staining. X472. 



253a. The basal portion of an egg ; the four segmentation-nuclei are in the 

 metaphase of the mitosis. X62. June 19, 1899. 



2533. A part of the same showing details. X 472- 



254a. A portion of a lower part of an oosphere after the formation of the 

 eight nuclei of the proembryo. X 62. 



2541^. A part of the above giving details. No cell-walls have as yet been 

 formed, but there is a slight differentiation of the cytoplasm about each 

 nucleus. X472. 



255a. A somewhat later stage than fig. 254a. X 62. 



2553. An enlarged portion of the above, showing cell-walls in the process of 

 formation. X 472. 



256. Vertical section through the base of an archegonium showing that the 

 four nuclei of the upper tier of cells in the proembryo divide before 

 any divisions occur in the four lower cells. X 96- Pinus austriaca. 



257-25S. Figures occurring in the upper part of archegonia during the 

 division of the segmentation-nuclei. These doubtless represent the 

 smaller sperm-nucleus. X472. 



259^-2593. Figures occurring in the upper part of an archegonium at the 

 time of the second division following fertilization ; fig. 259^7 represents 

 the tube-nucleus; the karyokinetic structure in fig. 259^, is the smaller 

 sperm-nucleus, and just above it the stalk-cell is still distinctly visible. 

 X472. 



260. Two macrospore-mother-cells. X S30. Pinus rigida. June 7, 1902. 



261. An axial row showing oblique wall between two of the spores. X 394- 

 Pinus austriaca. June 13, 189S. 



262. a. A section through a prothallium showing unusual origin of 

 archegonia from cells several layers deep in the prothallium. X 75 



( 200 ) 



