490 EXPLANATION OF THE FIGURES. 



Fig. 11. Pinus balsamea. 



FIG. 



11. Longitudinal section of the embryo-sac of P. balsamea, filled by a few large 

 cells ; at the beginning of May of the first year. 



PLATE LXI1I. 

 Tigs. 1 1-2. Taxus baccata. 



1. Longitudinal section of an ovule at the end of March. The shaded part 



shows the position of the cells destined to become embryo-sacs, x 30. 



2. The cells of this part, x 300. The contents of the rudiments of the 



embryo-sacs are contracted by tincture of iodine. 



3. Apex of the ovule in the middle of April, in longitudinal section. The 



course of the pollen-tube, which at this time is very delicate, is exposed, 

 x 150. 



4. The embryo-sac and neighbouring cells from an ovule cut longitudinally ; 



end of April, x 300. 



5 7. Further developed embryo-sacs ; detached (6th May), x 300. 



8. Embryo-sac and one of its neighbouring cells ; detached (17th May), 



X 500. 



9. Embryo-sac ; detached, x 300. 



10. Longitudinal section of the nucleus of an ovule, through which two pollen- 



tubes have penetrated to the embryo-sac (22nd May), x 200. 



11. Lower end of a pollen-tube with a portion of the endosperm cut through 



longitudinally ; both detached. Impregnation has not yet occurred ; the 

 rosette is still uninjured, x 350. 



12. Young rudiment of a pro-embryo with a portion of the membrane of the 



corpusculum detached, x 350. 



Fig. 13. Taxus Canadensis. 



13. Apex of the endosperm with the end of the pollen-tube and an impregnated 



corpusculum with the rudiment of a pro-embryo in longitudinal section ; 

 on the 10th June, x 300. 



PLATE LXIV. 



Fig. 1. Taxus Canadensis. 



1. Longitudinal section of the upper end of an endosperm witli the pollen- 

 tube; on June 5th. Two corpuscula are laid open by the section; 

 the right hand one is impregnated ; the impregnated germinal vesicle 

 occupies the lower third part of it, x 300. 



Fig. 2. Taxus baccata. 



2 Lower ends of two pollen-tubes with portions of the endosperm, which has 

 been cut through longitudinally, soon after impregnation. The pollen- 

 tubes are drawn away for a short distance from the endosperm ; the left 

 hand one has in consequence been torn at the outermost apex, x 300. 



