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. 



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



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



culum, which has been just impregnated. 

 11 s . 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. 



Eigs. 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. 



Eigs. 9, 10. Pinus sylvestris. 



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



July, x 250. 



