EXPLANATION OF THE FIGURES. 489 



FIG. 



9, 10. Pro-embryos during the division into their longitudinal rows of cells ; 



on the 30th June, x 100. 

 11. (The middle figure.) One of the fourth parts of the pro-embryo, at whose 

 lower end the multiplication in the direction of the thickness has begun, 

 X 100. 



Fig. 11 (left-hand figure) to Fig. 14. Plnus Larix. 



11. (Left-hand figure.) End of a pollen-tube drawn out from the corpus- 



culum, which has been just impregnated. 

 11 J . The same object after its apex and the cell hanging to it have been pushed 

 out. 



12. Apex of a pollen-tube, and portion of the cell attached to it, X 400. 



13. 14. Longitudinal section of corpuscula just impregnated, X 150. 



PLATE LX1I. 



Figs. 1 8. Pinus Canadensis. 



1. The upper part of an endosperm shortly before the arrival of the pollen- 



tube at the embryo-sac (on the 7th July of the first year), with two 

 corpuscula laid open by the section, X 200. 



2. Longitudinal section of a corpusculum, into which a pollen-tube has lately 



penetrated (beginning of July), X 200. 



3. Longitudinal section of an endosperm (middle of July). It exhibits two 



corpscula. A pollen-tube has shortly before penetrated to the upper 

 surface of the left hand one. Against the base of this corpusculum the 

 four-celled rudiment of the embryo is compressed, x 200. 



4. A recently impregnated germinal vesicle (middle of July) confined at the 



lower end of the corpusculum, which has been cut through longitudinally, 

 x 400. 

 4*. The same specimen treated with an alkaline ley. 



5. Longitudinal section of a corpusculum containing a rudimentary pro- 



embryo pressed into the base, and another less developed one floating 

 freely, X 100. 



7. A further developed pro-embryo. The walls of the upper cell, which are 



are turned towards the corpusculum, are much thickened by the addition 

 of glassy transparent layers, x 300. 



8. A more developed pro-embryo. In its upper cells are found spherical 



irregular masses, of a glassy substance. The wall of the corpusculum 

 which is detached from the neighbouring cells, and is adherent to the 

 specimen exhibits shallow pits, and flat ridges, seated on the outer 

 side, whose course corresponds with that of the edges of contact of the 

 neighbouring cells (end of July), x 300. 



Figs. 9, 10. Pinus sylvestris. 



9. 10. Young embryos in longitudinal section ; from the 28th June until 7th 



July, x 250. 



