XXX. THE SEED OF ANGIOSPERMS. 



nation ends free in a blunt projection. Bounding the scutellum 

 in the upper half of the embryo is the tube-like cotyledonary 

 sheath (c). This sheath surrounds many rudiments of leaves, 

 which decrease in size progressively inwards. The largest of 

 these leaf -rudiments stands outwards in the middle line. Be- 

 tween the youngest (innermost) of the leaf-rudiments lies the 

 growing apex, from this point of view appearing relatively narrow 

 and tapering (pv). Together with the leaf -rudiments this forms 

 the rudimentary bud, the plumule. The plumule and the coty- 

 ledon are borne upon the stem, or hypocotyl (hp). The hypocotyl 

 is prolonged below into the radicle (r), which is directed somewhat 

 obliquely forwards. Even with low magnification this shows the 

 central plerome, closed cone-wise towards the apex, and sur- 

 rounded by the periblem and dermatogen. At the apex the 

 periblem and dermatogen come together into a single layer of 

 cells (compare with this Fig. 87, p. 221). Inside the plerome- 

 cylinder the rudiments of the first vessels can be very easily seen, 

 and traced right up to its apex. The root-cap (cp) lies over the 

 apex of the root as a bright cover. The whole of this -rudimentary 

 root lies in a closed sheath, the coleorhiza (c/), and is sharply 

 limited towards it by a clear line, which indicates the thickened 

 walls of its dermatogen cells. This clear line disappears over the 

 root-apex, between the body of the root and the root-cap. At its 

 base this root-sheath passes over into the tissue of the hypocotyl. 

 At its part which ensheaths the root-apex the coleorhiza is swollen 

 into a clearly distinguishable wart-like projection (compare the 

 figure) ; at its upper edge, where the root-sheath passes over into 

 the hypocotyl, is developed a free outward projection, the epi- 

 blast (I). A string of elongated cells (vs) can be traced from the 

 hypocotyl into the scutellum ; the epidermal cells (ce) on the 

 outer surface of the scutellum are distinguished by their consider- 

 able radial elongation. The scutellum is a sheath-like outgrowth 

 from the base of the cotyledon, and must therefore be looked upon 

 as a part of it. It remains in the seed during germination, and 

 serves as a suctorial organ. The absorption of the food-materials 

 takes place by means of its cylindrical epidermal cells (epithelium), 

 and continues until the whole of the reserve food-materials of the 

 endosperm are exhausted. 



The embryo lies in immediate contact with the spermoderm, 

 while the pericarp is here somewhat thicker, but more loosely 

 constructed. Under the wart-like apex of the coleorhiza, i.e., at 



