REPRODUCTION BY SEED 163 



—is formed inside a large ceU— the embryo-sac, which 

 IS developed m the tissues of the ovule. The egg 

 always remains where it is formed, and therefore the 

 male cell must be brought to it. In the higher seed- 

 plants— the Angiosperms (Gr. angios, a vessel ; sperma, 

 seed)— the ovules are enclosed in the ovary, and the 

 pollen-grams can be brought no nearer to the ovules 

 than the stigma. In the lower group of seed-plants— 

 the Gymnosperms 

 (Gr. gymnos, naked), *^' 



pines, firs, cypresses, 

 larches, yews — the 

 ovules are not en- 

 closed, but lie ex- 

 posed to the air. In 

 this case the pollen 

 can be borne direct 

 to the entrance of 

 the ovule. The first 

 step in the produc- 

 tion of seed is the 

 conveyance of the 

 pollen to the stigma 

 of the pistil, or in 

 the case of Gymno- 

 sperms to the ovule 

 itself. This is termed 

 'pollination. When 

 the poUen- grain is 

 deposited upon the 

 stigma it germinates. 

 A long thread-like 

 tube grows out of 

 the grain, penetrates 

 the style, and makes its way towards the ovule. The 

 body of the ovule within which the egg is formed is sur- 

 rounded by one or two coats, but a hole, or pore, is left in 

 the coats — the micropyle (Gr. mihros, small ; pyle, gate) — 

 which affords a passage to the interior. On entering the 

 ovary, the growth of the poUen-tube is directed towards 

 the lips of the micropyle. A liquid secreted at the 

 micropyle attracts ia some way the elongating tube. 

 The tip of the tube enters the ovule, and, reaching 



Fio. 66.— DiAORAM OP Flower at Timb 

 OF Fertilization; (After Prantl and 

 Vines.) 



u, calyx ; h, corolla ; c, stamens ; d, anther ; 

 e, pollen-grains ; /, tube of germinating 

 pollen-giain ; gr, stigma; h, style ; «, ovary; 

 k, micropyle of ovule ; I, egg-cell ; m, em- 

 biyo-sac ; n, integument of ovule ; r, re- 

 ceptacle. 



