SEEDS AND FRUITS. T33 



Comparison of cross and longitudinal sections shows that we have 

 here a straight embryo lying in the centre of the seed, with its 

 radicle pointing towards the caruncle, and a pair of flat, beauti- 

 fully veined seed-leaves closely pressed together. There is no 

 evident plumule. Surrounding the embryo is a cheesy substance, 

 the albumen, which fills up the space between it and the seed- 

 coat. With care, it can be scraped away, leaving the embryo 

 entire. The seeds of violet can be understood after examina- 

 tion of the preceding, but the embryo is much smaller in propor- 

 tion (cf. fig. 53), while in buttercup (fig. 30) and larkspur most 

 of the seed is occupied by albumen. In all these 

 cases the nutritive matters are formed in the 

 embryo sac, which increases in size and fills up 

 the whole of the space within the seed-coat. Such 

 albumen is called endosperm. In a few cases, 

 however, the embryo sac, with its contained endo- 

 sperm, is comparatively small. Most of the albu- 

 men is in this case perisperm, and belongs to the 

 nucellus. 



Examine now a grain of maize (Indian-corn). Fm 53- Zsection 

 This is really a fruit, as it includes the wall of of Albuminous 

 the ovary, here dry and closely adherent to the emb'ryo^su? 

 seed. A little pointed projection on the broad end rounded by en- 

 of the grain is the remains of the style. The yellow 

 part of the grain is endosperm, but on one side, near the pointed 

 base, is a whitish patch. This is the embryo, situated, as in all 

 grasses, outside the endosperm. It can be detached from a soaked 

 grain ; and careful scrutiny will show that radicle and plumule 

 are wrapped up in a single seed-leaf or cotyledon, part of which is 

 closely applied to the endosperm, and receives the special name 

 of scutellum. By cutting through a grain longitudinally, taking 

 care to halve the embryo, the relation of parts will readily be 

 understood, and a loose, white region of the endosperm will be 

 seen (fig. 54). Grains of wheat, barley, and oat may usefully be 

 compared with maize. All of them possess a single seed-leaf, 

 which is a leading character of monocotyledons. A date-stone 

 is a monocotyledonous seed of different type. Here the endo- 

 sperm is horny, and composed of thickened cellulose cell-walls. 

 On one side of the stone is a groove ; in the centre of the opposite 

 side the micropyle will be found as a small depression. By cut- 

 ting the seed transversely across through this, a small embryo will 

 be found, its radicle directed towards the micropyle. The cotyle- 

 don is sheath-like, and encloses a microscopic plumule. 



A huge seed belonging to the same class of plants is the cocoa- 

 nut. The hard shell does not belong to the seed, the coat of 



