184 



PLANT-LIFE 



It is worth while to examine the more minute details 

 of the ovule. In Fig. 61 we have a drawing of a 

 longitudinal section of an ovule of Picea at the time 

 of fertilization. The letter p points to pollen grains 

 lodged at the micropyle; note the pollen tubes, t, which 



Fig. 61. — Picea excelsa. Longitudinal Section of Ovule at Time 

 of Fektilization. x 9. 



i, Integument; nc, nucellus; s, part of wing; p, pollen-grains; t, pollen- 

 tubes; c, neck of archegonium; a, venter; o, ovum, n, nucleus of ovum; 

 e, prothallus. 



have penetrated to the neck, c, of the archegonium. 

 At this stage of development the embryo-sac is filled 

 with tissue which is formed prior to fertilization; the 

 tissue is the prothallus, e, corresponding to the same 



