322 



THE SEED. 



seed-Stalk, or funiculus, or of the placenta itself when there is no 

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

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

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

 as a tough and laferated hody, known hy the name of maee, 

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

 delicate cellular hag, 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 Cakuxcle found at the hilum in 

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

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

 bia), which is a cellular growth from the micropj'le ; but the two are 

 not well discriminated. An analogous cellular growth takes place 

 on the rhaphe of the Bloodroot, of the Prickly Poppy, and of Dicen- 

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



631. The Nucleus, or Keniel of the seed, consists of the AlEu.men, 

 when this substance is present, and the Embryo. 



632. The Albumen, which 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 genni- 

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

 called by Gfertner the alhumeyi of the seed, from 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 well 

 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 is fieshy, as in 



FIG. 603. A seed of the White Water-Lily, with its sac-lilte arillus, magnified. 



