34 
Dixon . — Fertilization of Pinus silvestris. 
EXPLANATION OF THE FIGURES IN PLATES 
III, IV, and V. 
Illustrating Mr. Dixon’s paper on the Fertilization of Pinus silvestris. 
The figures were drawn, by the aid of a camera lucida, from preparations made 
from alcohol-material. 
PLATE III. 
Fig. i. Two pollen-grains on nucellus ; April 24. X750. 
Fig. 2. Body-cell divided into two and broken away from stalk-cell; April 24. 
x 750- 
Fig. 3. Two male cells breaking away from stalk-cell ; April 24. x 750 - 
Fig. 4. Two male cells entering the pollen-tube, followed by the nucleus of the 
stalk-cell ; April 24. x 750. 
Fig. 5. Similar to Fig. 4 ; April 24. x 750. 
Fig. 6. Longitudinal section of the upper portion of the nucellus showing two 
pollen-tubes. The nucleus of the stalk-cell is just passing the two male cells; 
May 5. x 250. 
Fig. 7. Portion of a pollen-tube. Nucleus of the stalk-cell has passed by the 
male cells: May 5. x 750. 
Fig. 8. Branched pollen-tube seen in a longitudinal section of the nucellus; 
May 12. x 250. 
Fig. 9. Longitudinal section of the upper part of the nucellus. The male cells 
preceded by the nucleus of the stalk-cell have come into proximity with the 
nucleus of the pollen-tube at the apex of the tube; May 12. X625. 
Fig. 10. Longitudinal section of the upper part of the nucellus. The annular 
wall of the stalk-cell in the pollen-grain is seen in optical section ; May 19. X625. 
Fig. 11. Pollen-grain emptied of its contents; May 5. x 750. 
PLATE IV. 
Fig. 12. Portion of a pollen-tube, isolated by maceration. The two male cells 
are seen above, and the nuclei of the stalk-cell and of the pollen-tube are lying side 
by side in the apex of the tube ; May 19. x 625. 
Fig. 13. Pollen-tube and upper part of the archegonium shortly after fertilization; 
May 26. x 750. 
Fig. 14. Pollen-tube and upper part of the archegonium. The larger nucleus in 
the cytoplasm of the oosphere is probably the male nucleus surrounded by radial 
striae ; May 26. x 750. 
Fig. 15. Apex of pollen-tube and archegonium. The trail of protoplasm from 
the pollen-tube is seen in the oosphere ; June 6. x 250. 
Fig. 16. Longitudinal section of the archegonium, showing the starch-grains from 
the pollen-tube in the cytoplasm of the oosphere ; May 26. x 250. 
Fig. 17. Longitudinal section of the archegonium after some divisions of the 
oospore; May 26. x 250. 
Fig. 18. Apex of pollen-tube immediately after fertilization ; May 26. X625. 
PLATE V. 
Fig. 19. Formation of the ventral canal-cell ; May 26. X625. 
Fig. 20. Instances of nuclear division from the nucellus. X750. 
Fig. 21. Nuclear division in a young endosperm; April 24. X950. 
Fig. 22. Cells from the wall of the archegonium; May 19. x 750. 
Fig. 23. A dividing nucleus from the upper part of a young endosperm ; April 
24. X950. 
Fig. 24. Nuclear division preparatory to forming the ventral canal-cell; May 26. 
x 750- 
Fig. 25. Ventral canal-cell, x 750. 
Fig. 26. First division of the nucleus of the oospore; May 26. x 750. 
Fig. 27. Nuclear divisions in the base of the archegonium; May 26. X625. 
Fig. 28. Spindles formed in the cytoplasm of the oosphere ; May 26. x 750. 
