PLATE VIII. 



Fig. 83. The pollen-tube which is shown in fig. 70, more highly magnified. 

 X 472. Pinus Sirobus. January 4, 1899. 



84. A pollen-grain and the upper portion of a pollen-tube, showing the 

 stalk- and the generative-cell just before their passage into the pollen- 

 tube. X472. Pinus austriaca. May 3, 1898. 



85, 86. Later stages than the above, showing the passage of the generative- 

 and the stalk-cell into the pollen-tube ; in fig. 86, the two cells are 

 breaking loose from each other. X472. Pinus austriaca. May 10 

 and 17, 1898. 



87. The male gametophyte at the time of the entrance into the tube of the 

 generative- and the stalk-cell ; «./", a bit of the dead nucellar tissue. 

 X472. Pinus St robus. June 9, 189S. 



88. A pollen-grain after the generative and the stalk-cell have passed into 

 the pollen-tube ; taken from the top of the nucellus of the ovule shown 

 in fig. 72. X472. Pinus Strobus. June 9, 1S98. 



89. A few of the cells from that portion of the nucellar cap marked nuc.2 

 in fig. 72. The cells are filled with starch grains. X 472- Pinus 

 Strobus. June 9, 189S. 



90-92. Portions of pollen-tubes showing successive stages in the passage 

 of the stalk-cell over the generative cell, as also the presence of large 

 quantities of starch in the pollen-tube. X472. Pinus resi7iosa. June 2, 

 P. Strobus, May 24 ; P. rigida, June 8, 1898. 



93. The generative cell, bearing on its surface both the tube-nucleus and 

 the stalk-nucleus. In this instance the stalk-cell has passed beyond 

 the tube-nucleus. X 472. Pinus resinosa. June 3, 1898. 



94. The generative cell showing a very early stage in the formation of the 

 spindle. The nucleus is in the extreme uppermost part of the cell. 

 X 744. Pinus rigida. June 8. 



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