Division of the Generative Nucleus in Pines . 223 
mitosis. The protoplasmic condensation is seen from below looking toward the 
nucleus. X3&50. Pinus austriaca, June 4. 
Fig. 37. The sperm-nuclei just after their formation, x 850. Pinus montana , 
var. uncinata , May 31. 
PLATE XIV. 
Figs. 38-43. Various stages in the formation of the daughter-nuclei, x 850. 
Figs. 38 and 43, P. Strobus , June 9 and 10 ; Fig. 39, P. resinosa, June 15 ; Figs. 40 
and 42, P. austriaca , June 10. Fig. 41 represents another section through the upper 
nucleus of Fig. 40, and shows how the upper of the sperm-nuclei is frequently 
indented along its outer surface. 
Fig. 44. This pollen-tube, having approached an egg that had already been 
fertilized, has turned aside and is passing up over the endosperm so that the normal 
position of the cells appears exactly reversed ; n. a., neck-cells of the archegonium. 
x 330. Pinus Strobus , June 20. 
Fig. 45. The generative cell and another nucleus, not the stalk-nucleus, just 
passing into the pollen-tube. x 540. Pinus Strobus , May 20. 
Figs. 46 and 46 b. Cross-sections through the two sperm-nuclei after they have 
attained full size and have about reached, in their downward passage, the middle 
of the nucellar cap. x 850. Pinus Strobus , June 15. 
Fig. 47. The sperm-cells after all traces of the spindle have disappeared, but 
before the two nuclei have come together, x 540. Pinus Strobus , June 13. 
Fig. 48. The same after both nuclei have come to lie in the upper part of their 
cytoplasm, x 540. Pinus Strobus , June 10. 
Fig. 49. Lower portion of a pollen-tube which has penetrated about two-thirds 
the length of the nucellar cap. x 540. Pinus Strobus , June 14. 
Fig. 50. Lower portion of a pollen-tube which is just pushing between the neck- 
cells of the archegonium. P, pit in apex of tube, x 540. Pinus Strobus , 
June 20. 
Fig. 51. A pollen-grain showing an increase in the normal number of nuclei, 
x 540. Pinus austriaca , May 17. 
Cornell University, 
July 1, 1900. 
