ANTHOPHTTA. 239 



now, such a germinating pollen-cell happens to be favora- 

 bly placed near to an ovule, the pollen-tube may penetrate 

 it and come in contact with the gorm-cell. The nucleus 

 of the tube then unites with that of the germ-cell, and fer- 

 tilization is complete. 



450. The fertilized germ-cell soon begins growing and 

 dividing, producing in a short time a many-celled body — 

 the embryo-plant. The embryo during its growth is nour- 

 ished by the surrounding cells of the prothallium, here 

 called the endosperm. While the embryo has been grow- 

 ing the covering of the ovule (one or two cellular coats) 

 becomes gradually harder and firmer; finally the growth of 

 the embryo stops, and the ovule containing it separates 

 from its supporting leaf as a ripe seed. 



451. After a longer or shorter period of rest the little 

 plant in the seed resumes its growth, the necessary condi- 

 tions being the proper heat and moisture. It is at first 

 quite simple, consisting of a little root and stem and a few 

 small leaves, but with the development of each succeeding 

 leaf it becomes more like the adult plant. 



The flowering plants are separated into two classes, as 

 follows : 



Ovules on an open leaf Class 14, Gtmnospbkm^ 



Ovules enclosed within a closed leaf, 



Class 15, Angiosperm^ 



Class 14. Gymnospebm^:. The Gtmkospbems. 



452. These are plants with solid stems, which bear in 

 most cases small, simple, narrow leaves with parallel veins. 

 Most of them are large trees, and all are terrestrial and 

 chlorophyll-bearing, none being in any wise parasitic. 

 Common examples are the pines, spruces, firs, etc. 



