FERTILIZATION AND DEVELOPMENT OF SEED 2OI 



bent ov 



stands 

 angles. 



less blended, the coats of the ovule can be seen in a lengthwise 

 section as two distinct layers of tissue, but there is a circular 

 opening at the apex of the ovule, so that there is a communication 

 from the outside. This 

 opening is the micropyle. 

 The stalk of the ovule 

 attaches it to the wall of 

 the ovary. In a straight 

 ovule the ovule stands 

 out straight in line with 

 its stalk. In a right- 

 angled ovule the stalk is 

 bent over at the upper 

 that the ovule 

 about at right 

 angles. In the inverted 

 ovule the upper end of the 

 stalk is bent so strongly 

 that the ovule is inverted 

 and the stalk is then 

 joined with the side of 

 the ovule. This part of 

 the stalk is called the 

 raphe (see fig. 152 for 

 details). 



317. The embryo sac 

 and egg. At the close 

 of the development of the 

 ovule a sac is formed 



Within it, known aS the down through the style, and along the wall of the 



ovary to the micropylar end of the embryo sac. 



embryo sac. This em- 

 bryo sac contains several nuclei, usually eight, lying in the 

 protoplasm. One of these eight nuclei in the embryo sac, with 

 the protoplasm around it, is the egg cell. 



318 Fertilization. When the pollen tube grows into the 

 ovule at the micropyle it enters the embryo sac, into which it 



Fig. 153- 



Diagrammatic section of ovary and ovule at time 

 of fertilization in angiosperm. f, funicle of ovule; n, 

 nuccllus; m, micropyle; b, antipodal cells of embryo 

 sac; e, cndospcrn nucleus; k, egg cell (two synergids 

 at the side); ai, outer integument of ovule; ii, inner 

 integument. The track of the pollen tube is shown 



