2 



IXTRODUCTOET. 



reproduced by minute dust-like grains called spores, — Flowerless oi 

 Crijptogamous plants. As cryptogamous plants do not often appear as 

 weeds and as their study is rather difficult, they arc left out of con- 

 sideration in the present work. 



5. Flowering plants have two kinds of organs ; those parts which are 

 concerned in sustaining the life and growth of the plant, — Organs of 

 Vegetation ; and those w-hich provide for its perpetuation by means of 

 seed, — Organs of Reproduction. 



6 . The organs of vegetation are three, viz. : Eoot, Stem, and Leaf. 

 These the plant has at a very early stage of its existence. If a young 

 seedling plant, as a Radish, Bean or Pumpkin be taken from the ground 

 as soon as it has " come up,"' it will be found to consist of a short stem 

 with a pair of leaves at the top and a root at the bottom of it. By 

 soaking the seeds until the seed-coat is softened, and then carefully 

 breaking it open, the young plant will be found within, though in a 

 much less developed state. The seed always contains within it the 

 young plant, more or less developed, either lying straight in the seed or 

 variously coiled or folded up ; this is called the Embryo. By the influ- 

 ence of the warmth and moisture of the earth, the embryo bursts the 

 skin of the seed and begins to grow. The sprouting of the embryo is 

 called germination. The parts of the embryo are ; 1st, the little stem, 

 called the Radicle ; and 2d, tlie leaves which in the Radish, Bean, &c., first 

 appear above ground and are usually called Seed-leaves, these are the 

 Cotyledons ; between them there is a little bud (which is not always to 

 be seen in the embryo, but appears soon after it begins to grow), the 

 Plumule. In germination the radicle elongates, the lower end — w^hat- 

 ever the position the seed may be placed in — pushes itself downward 

 into the eartli, and its upper end bearing the seed-leaves is raised to the 

 light and air. That portion of the radicle which goes downward forms 

 the Root or Descending Axis, that w^hich rises above the surface of the 

 earth is the Stem or Ascending Axis. 



In the instances quoted as illustrations (Radish, Bean and Pumpkin), 

 the embryo is large and fills the whole seed ; the seed-leaves, in the Bean 

 especially, are thickened and rounded from being filled with a supply of 

 food w^hich nourishes the young plant until it can form roots and draw 

 sustenance from the soil. In many seeds, as the Pea, Acorn, &c., the 

 cotyledons are very much distended and do not rise to the surface, but 

 only open far enough to allow the plumule to protrude. 



7. In many seeds the embryo, instead of containing the food for its 

 early growth within its cotyledons, has a more or less abundant supply 

 surrounding it, called Albumen. The embryo is placed sometimes in the 

 centre of the albumen — or at one side, or sometimes coiled in a more or 

 less complete ring around it. Seeds which contain albumen are said to 

 be albuminous, those having none, exalbuminous. The albumen may be 

 large in proportion to the embryo, or very sparing ; its texture varies, 

 hcAug farinaceous or mealy (as in Buckwheat), horny or corneous (like 

 that of Coffee), oily (as in the Poppy), or mucilaginous. 



8 In the examples given, the embryo has in each case two cotyledons ; 



