404 BOTANY. 



of the suspensor. By the growth and fission of this first 

 cell an elongated tortuous filament the suspensor is at 

 length formed, which develops at its lower extremity a rudi- 

 mentary embryo (eb, Fig. 298, 3). Sometimes each suspen- 

 sor splits into several parallel ones, each of which forms a 

 rudimentary embryo, but in such cases it rarely happens 

 that more than one continues to grow. While the embryo 

 is growing the ovule increases greatly in size, and its coat 

 becomes hardened or otherwise modified. Internally, the 

 endosperm in the embryo sac grows still more rapidly, and 

 finally entirely replaces the other tissues of the ovule. The 

 endosperm-cells at this stage are filled with nutrient materials 

 for the support of the embryo. 



513. The stem of the embryo develops upon the lower 

 end of the suspensor as a very short cylindrical mass ; the 

 end opposite to the suspensor is a growing point (punctum 

 vegetationis), and this produces two or more cotyledons as 

 lateral members ; lastly, upon the end of the axis next to, 

 and under, the suspensor a rudimentary root forms, covered 

 with a few-celled root cap. The fully formed embryo has 

 thus, (1) an axis (called also the hypocotyledonary stem, cau- 

 licle, and erroneously the radicle) ; (2) the cotyledons ; (3) a 

 growing point above the whorl of cotyledons (called also the 

 plumule) ; (4) a rudimentary root, which is the true radicle, 

 and to which alone the term should be applied. 



514. When the ovule and its contained embryo reach the 

 stage last described above they constitute the Seed. The 

 growth of the embryo is suspended, and the tissues which 

 maintained organic connection between the ovule and the 

 parent plant are absorbed, thus setting the seed free. Under 

 proper conditions the suspension of the growth of the em- 

 bryo may be prolonged for some years without the loss of 

 its power of resuming it again ; this latter, or the germina- 

 tion of the seed, takes place whenever the necessary amounts 

 of heat and moisture are present. The first stage in germina- 

 tion is the swelling of the endosperm, which ruptures the 

 hardened integument (testa) ; this is followed by the rapid 

 elongation of the axis (caulicle) of the embryo, by which (In- 

 growing root is pushed out (Fig. 300, II.} ; the latter forms 



