282 



PARTS OF THE EMBRYO PLANT. 



589. The albumen is a store of matter laid up for the nourishment 

 of the embryo. In the Coco-nut and double Coco-nut, it forms the 

 great bulk of the seed, weighing many ounces, while the embryo is 

 minute, weighing a few grains, and lies in a cavity at one extremity. 

 In Coffee, the albumen is the horny portion, the infusion of which is 

 used for a beverage. In Phytelephas it is called vegetable ivory from 

 its hardness, and is used for the same purposes as ivory. In the horny 

 albumen of this Pahn, as well as in that of the Attalea funifera, the 

 Date and the Doom Pahn, the concentric deposition of secondary 

 layers, leaving a small cavity in the centre of the cells, and radiating 

 spaces uncovered with thickening matter, is well seen under the 

 microscope. 



590. The embryo consists of cotyledons or rudimentary leaves, the 

 plumule (plumula, a little feather), or gemmule (gemma, a bud), repre- 

 senting the ascending axis, the radicle (radix, root), or the descending 

 axis, and their point of union the collum, collar or neck ; that part 



of the axis which intervenes between the collar and cotyledons 



being the caulicule (cauliculus, a little stalk), or tigelle (tigellus a 

 little stalk). The embryo varies in its structure in the different 

 498 divisions of the vegetable kingdom. In acrogenous and thallo- 

 genous plants, it continues as a cell or spore, with granular, 

 matter in its ulterior (fig. 498), without any separation of parts or 



the production of cotyledons. 

 donous ( privative xorv^r^av). 



Hence these plants are called acotyle- 

 Endogenous and Exogenous plants, 



Fig. 498. Acotyledonous embryo of Marchantia polymorpha. Such embryos bear the name 

 of spores. 



Fig. 499. Monocotyledonous embryo of Potamogeton perfoliatus nearly mature, r, Kadicle. 

 /, Caulicule or tigellus. c, Cotyledon, g, Gemmule or plumule. 



Fig. 500. Mature dicotyledonous embryo of the common Almond, r, Radicle or young root. 



Fig. 501. The same, with one of the cotyledons removed, r, Radicle, t, Tigelle or caulicule. 

 f, One of the cotyledons left, ic, Cicatrix left at the place where the other cotyledon was at- 

 tached, g, Gemmule composed of several small leaves. 



