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 f points to pollen grains 

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



nc — -f^4-~-h- 



FlG. 61. — PiCEA EXCELSA. LOHGITUDIKAL SECTION OE OVULE AT TCME 



or Fertilization, 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 



