126 



Elementary Botany 



known as antipodal cells (fig. 243, g\ and their function is 

 unknown. Soon after their formation two nuclei are produced 

 at the other end of the embryo-sac, round which the protoplasm 

 becomes aggregated, forming two embryonic or germinal 

 vesicles or cells (fig. 243, k). These vesicles appear to be 



Fig. 242. — Pollen grains put- 

 ting out their pollen-tube ; 

 A, Dipsacus fullonun ; b, 

 Cucur6ita. 



Fig. 243.— Upper part of the 

 nucleus of the ovule o^ Cro- 

 ats : p, the embryo-'^ac with 

 its nucleus, zk ; k, the em- 

 bryonic vesicles ; g, the 

 antipodal cells. 



Fig. 244.— The process of fertilisation mGladiobis 

 segeinm. I. The two embryonic vesicles at the 

 apex of the embryo-sac ; x^ jc", the filiform ap- 

 paratus ; y' y"i the balls of protoplasm ready lor 

 fertilisation ; se, the wall of the embryo-sac. 

 II. A pollen-tube, iji, which has just fertilised 

 the two embi-yonic vesicles in contact with it ; 

 the cell-walls which surround the balls of proto- 

 plasm are still very thin. III. A somewhatjater 

 sta^e ; the cell walls are thicker ; the fertijised 

 vesicle y' is beginning to develop and to divide 

 into two. 



membraneless before fertilisation, but on the approach of the 

 pollen-tube a cellulose coat is formed round each. The pollen- 

 tube passing into the ovary enters the micropyle of one of the 

 ovules, and, arriving at the apex of the embryo-sac, comes in 

 contact with one of the embryonic vesicles, fertilising it by the 

 passage of the fovilla of the pollen into it by osmosis (figs. 244 



