242 BOTANY. 



produced. Each ovule has one coat which grows up from 

 below, almost covering it; but as the ovules grow they 

 bend down, so that the opening through the coat comes to 

 be below (Fig. 143, A and B). 



456. In the axis of the ovule near its apex a cell becomes 

 differentiated from the rest as the archespore ; this grows 

 larger, divides several times, and one of the deeper-lying 

 daughter-cells growing rapidly becomes a macrospore 

 (embryo-sac). The macrospore now forms many nuclei, ^ 

 which eventually become as many cells, filling it up with 



a solid tissue (the sexual plant, or prothallium), and in 

 this are developed one, two, or more rudimentary arche- 

 gones, each with its germ-cell. Thus we see that the 

 dqvelopment which takes place here inside of the ovule 

 (which corresponds to the spore-case) is similar to that 

 which in the Lycopods takes place only after the macro- 

 spore has separated itself from the parent-plant. 



457. Fertilization takes place as follows: The scales of 

 the cone open slightly, permitting the pollen, which has 

 been carried in the wind, to roll down to their bases where 

 the ovules are. Here the pollen-cells germinate, and their 

 tubes enter the opening in the ovule-coat and push through 

 the tissues to the archegones, where the pollen-protoplasm 

 is fused with that of the germ-cell (Fig. 144). 



458. As a result of the fertilization there is first a 

 growth of a row of cells (called the suspensor, erroneously), 

 upon the end of which the embryo begins to form. The 

 root-end of the embryo is always in contact with the sus- 

 pensor, so that, taking the whole embryo at maturity, the 

 supensor is at one end and the little leaves at the other. 

 Moreover, the root-end of the embryo is always directed 

 toward the opening in the ovule- or seed-coats. The em- 



