PHANEBOGAMIA. 



231 



end of which an emhryo soon begins to form by the fission 

 of cells in three planes (Figs. 131, B, and 132, Zto IV). ■ 

 488. At first the embryo is a minute rounded cell-mass 

 attached to the end of the row of cells, and in some plants 

 it passes but little beyond this stage until after the ripen- 

 ing of the seed. In most cases, however, the cell-mass con- 

 tinues its growth until it has formed a little stem bearing 



Fig 133 —Magnified sections of seeds, showing embryos and endosperms. A, 

 Oat- B Sedge; C, Coffee; D, Marsh-marigold; E, Bitter-sweet; F. Cfoosefoot; 

 O Nettle; S, Oak; I, Sweet Pea; J, a Mustard. In ^ to X), small or minute 

 embryo in large endosperm; E to G, larger embryo and smaller endosperm; 

 H to J, large embryo and no endosperm. 



rudimentary leaves above and a root below. There are to 

 be found all degrees of simplicity in the embryos of An- 

 giosperms, from the rounded cell-mass (thallus) to the well- 

 formed plantlet provided with distinct root, stem, and 

 leaves. 



489. While these changes are going on, cells arise in the 

 basal part of the embryo-sac and increase rapidly, generally 

 filling up a considerable part of its cavity. These cells 



