166 



ESSENTIALS OF BOTANY 



ovule m, in Fig. 124, reaches one of tlie cells shown at e, 

 and transfers a sperm nucleus into this egg-cell. The 



latter is thus enabled to 

 divide and finally grow 

 into an embryo. This 

 the cell does by forming 

 cell-walls and then 

 increasing by continued 

 subdivision in much the 

 same way in which the 

 cells at the growing 

 point near the tip of the 

 root subdivide.^ 



194. Nature of the 

 Fertilizing Process. — 

 The necessary feature of 

 the process of fertiliza- 

 tion is the union of the 

 essential contents of two 

 cells to form a new one 

 from which the future 

 plant is to spring. This 

 kind of union is found 

 to occur in many crypto- 

 gams (Chapters XXIII- 

 xxvii), resulting in the 

 production of a spore 

 capable of growing into 

 a complete plant. 



1 See Strasburger, Noll, 

 Schenk and Karsten's Text- 

 Book of Botany, pp. 442-446. 



Fig. 124. Diagrammatic Representation 

 of Fertilization of an Ovule. 



i, inner coating of ovule ; o, outer coating 

 of ovule ; p, pollen tube, proceeding from 

 one of the pollen grains on the stigma ; 

 (,', the place where the two coats of the 

 ovule blend (the kind of ovule here 

 shown is inverted, its opening m being at 

 the bottom, and the stalk/adhering along 

 one side of the ovule) ; a to e, embryo sac, 

 full of protoplasm ; a, so-called antipodal 

 cells of embryo sac ; n, central nucleus of 

 the embryo sac; e, nucleated cells, one 

 of which, the egg-cell, receives the essen- 

 tial contents of the pollen tube ; /, funi- 

 culus or stalk of ovule ; m, opening into 

 the ovule 



