ORGANS OF REPRODrCTION. 



335 



it is more or less separated into distinct compartments by the 

 folding inwards of the endopleura as already described (see p. 

 331) ; in such cases, thealbiimen is said to be ruminated, as in 

 the Nutmeg, Betel-nut {fig. 743, 2^), and Papaw. 



b. The Embryo is the rudimentary plant, and is present in all 

 true seeds. The presence of a true embryo is the essential 

 characteristic of the seed of flowering plants ; for a spore, as the 

 reproductive body of a flowerless plant is called, has no true 

 embryo, the rudimentary plant being only developed from it after 

 its separation from the parent (see p. 358). The embryo being 

 the rudimentary plant it is necessarily the most important part 

 of the seed, and it contains within it, in an undeveloped state, 

 all the essential parts of which a plant is ultimately composed. 

 Thus we distinguish, as already noticed (see p. 10), three parts 

 in the embryo ; namely, a radicle, ])hnmde or gemmnle, and one 

 or more cotyledons. These parts may be readily recognised in 

 many seeds ; thus in the embryo of the Lime {fig. 744), the 

 lower portion, r, is the radicle or portion from which the root is 



Fig. 743. 



Fig. 744. 



Fig. 743. Vertical section of 

 the fruit of Areca Catechol. 

 c. Remains of perianth. 

 /.Pericarp, j). Ruminated 



albumen, e. Embryo. 



Fig. 744. Embryo of the 

 Lime-tree (Tilia eurapcea) . 

 c, c. Cotyledons, with five 

 lobes arranged in a pal- 

 mate manner, r. Radicle. 



developed ; the two expanded lobed bodies above, c, c, are the 

 cotyledons, and between these, the plumule or rudimentary 

 terminal bud is placed. In the Pea, again {fig. 14), the two fleshy 

 lobes, c, c, are the cotyledons, between which there is situated a 

 little bud-like process, the upper part of which is the plumule, n, 

 and the lower part, r, the radicle. These parts are still better 

 observed when the embryo has begun to develop in the process of 

 germination ; thus in fig. 15, which represents the French Bean 

 in that condition, r is the radicle from which the roots are being 

 given off, the cotyledons are marked c, c, and the plumule is seen 

 coming off from between the cotyledons, and forming a direct 

 continuation of the axis from which the root is developed below. 

 By some botanists, the point of union of the base of the plumule 

 with the radicle and cotyledons, is called the caidicide or tigelle ; 

 this is generally a mere point, but at other times it forms a short 

 stalk {figs, 14, 15, and 728, t). Plants which thus possess two 



