PLATE VIII. 



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

 X 472. Pinus Strobus. 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. X 47 2 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. X47 2 - 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 ; n.t, a bit of the dead nucellar tissue. 

 X47 2 - Pinus Strobus. June 9, 1898. 



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, 1898. 



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, 1898. 



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. X47 2 - Pinus resinosa. 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 47 2 - 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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