322 THE SEED. 



seed-stalk, or funiculus, or of the i:)lacenta itself when there is no 

 manifest seed-stalk. This is called the Aril. It forms the pulpy- 

 envelope of the seed of Podoijhyllum, Euonymus, and Ce- 

 lastrus, or it appears as a mere lateral scale in Turnera, or 

 as a tough and lacerated hody, known by the name of mace, 

 in the Nutmeg. In the White Water-Lily it is a thin and 

 delicate cellular bag, open at the end (Fig. 603). The 

 Aril does not appear in the ovule, but is developed subse- 

 ^"' quent to fertilization, during the growth of the seed. Of 

 the same or similar nature is the Caruxclk found at the hilum in 

 Polygala, forming a loose lateral appendage. Strictly speaking, it 

 is to be distinguished from the Strophiole (like that of Euphor- 

 bia), which is a cellular growth from the micropyle ; but the two are 

 not well discriminated. An analogous cellular growth takes place 

 on the rhaphe of the ]51oodroot, of the Prickly Poppy, and of Dicen- 

 tra, forming a conspicuous crest on the Avhole side of the seed. 



631. The Nucleus, or Kernel of the seed, consists of the Albumen, 

 when this substance is present, and the Embryo. 



632. The Albumen, Avhich has also been termed the Perisperm or 

 the Endosperm, has already been described (125) as the floury part 

 of those seeds in which an amount of nourishment for the germi- 

 nating plantlet is stored up outside of the embryo. This was 

 called by Giertner the albumen of the seed, fi'om some fancied anal- 

 ogy with the white of an egg as to situation or function ; — an un- 

 fortunate term, on account of its liability to be confounded with the 

 quaternary chemical substance of the same name (357), one of the 

 forms of proteine. Being in general use, the term cannot now Avell 

 be discarded. 



633. The Albumen of the seed consists of whatever portion of the 

 tissue of the ovule persists, and becomes loaded with nutritive mat- 

 ter accumulated in its cells, — sometimes in the form of starch- 

 grains principally, as in wheat and the other cereal grains ; some- 

 times as a continuous, often dense, incrusting deposit, as in the cocoa- 

 nut, the date, the coffee-grain, &c. When it consists chiefly of 

 starch-grains, and may readily be broken down into a powder, it is 

 said to he farinaceous, or mealy, as in the cereal grains generally, in 

 buckwheat, «&;c. When a fixed oil is largely mixed with this, it 

 becomes oily, as in the seed of the Poppy, &c. ; when more compact, 

 but still capable of being readily cut with a knife, it iijleshy, as in 



FIG. 603. A seed of the White AVater-Hly, with its sac-like arillus, magnified. 



