CH. xxxviii. STRUCTURAL BOTANY. 4*9 



fertile seed. He pointed out that inside the nucleus of the 

 ovule is a bag or embryo-sac, e, which has been formed out of 

 one of the cells, and that when the pollen-dust d falls on the 

 stigma of the pistil, it sends down a tube which creeps through 

 the micropyle, and laying its extremity upon the embryo-sac 

 causes the young plant to form in it. He also noticed that 

 the root of the plant let is always turned towards the micro- 

 pyle, while the shoot or plumule is turned towards the funicle. 

 It is easy to see this shoot by simply removing the brown 

 seed-skin of an almond, and splitting it in half. The two 

 halves are the two cotyledons or seed-leaves with the little 

 bud or plumule lying concealed between them, the thickened 

 end of it being the rootlet or radicle. 



Robert Brown showed that we may learn a great deal 



FIG. 73. 



1. Nettle-seed cut in half ; a, albumen in which the cotyledon or single seed leaf is 



imbedded. 



2. Almond-seed cut in half. | These two seeds have no albumen, the cotyledon fills 



3. Hemp-seed cut in half. ) the whole of the seed-skin. 



f. Funicle ; h, Hilum, where the seed breaks off from funicle when ripe ; m, 

 M icropyle ; ?, Radicle, or young root ; /, Plumule, or young leafy shoot. 



about the relationship of plants by studying the way in which 

 the embryo is placed. Nos. i, 2, 3, Fig. 73, give three 

 seeds, the nettle-seed, the almond-seed, and the hemp-seed. 

 In the nettle-seed the embryo is upright, and the micropyle 



