PLATE X. 



Figs. 104-106. Later stages in the development of the spindle showing the gradual 

 drawing together of the outer extremities of the threads to form the 

 upper pole of the spindle. The upper pole of the spindle does not 

 reach the nuclear membrane, but in fig. 105 definite threads extend 

 from the pole to the nuclear membrane. X 744- Fig. 104. Pinus 

 rt'gida, June 13 ; the other figures, Pinus ausiriaca, June 9-10, 189S. 



107. First stage in the development of the sperm-nuclei. X 744- Pinus 

 Strobus. June 9, 1898. 



108. The sperm-nuclei just after the formation of the nuclear membrane 

 showing early stages in the development of the daughter-reticula. 

 The lower nucleus is already slightly larger than the upper one. 

 X 744- Pinus monta7ia uncinata. May 31, 1898. 



109-112. Various stages in the growth of the sperm-nuclei. A cell plate is 

 sometimes apparent as in fig. 1 10, but no dividing wall is ever formed. 

 X 744- Fig. 112. Pinus Strobus, June 10; fig. 109, P. resinosa, June 

 15; fig. no, P. ausiriaca, June 10. Fig. in represents another sec- 

 tion through the upper nucleus of fig. no, and shows how the upper 

 of the sperm-nuclei is frequently indented along its outer surface. 

 1898. 



('74) 



