THE SEED. 



87 



500. THE FUNICULUS is the stalk of the seed. It is 

 seen at / in the figure, and is always conspicuous in the 

 Bean and Pea. It is through this part that the ovule 

 receives nourishment from the placenta. The scar form- 

 ed by the separation of the seed is called the HILUM ; 

 and this also is conspicuous in the two tribes of plants 

 just referred to, where it is called the eye. 



501. THE ALBUMEN consists of the nutritive tissue 

 which has been elaborated, and becomes persistent in the 

 cells of the ovule. It is composed of a floury, starchy, 

 or farinaceous substance, as in Wheat, Maize, and the 

 other cereal grains ; it is oily in the Sun-flower and 

 Walnut, mucillaginous in the Mallow, and leathery in 

 the Coffee. By this you will perceive that it is not the 

 simple substance which chemists have named Vegetable 

 Albumen. It contains, in fact, nutritious matter of va- 

 rious kinds, for the support of the young plant, which 

 absorbs, or feeds on it during germination, or until it is 

 able to elaborate food for itself. In the cereal grains it 

 constitutes almost the entire seed ; but in the leguminous 

 plants, as the Pea and Bean, it is wholly wanting, its 

 place being supplied by the greatly thickened cotyledons, 

 which are composed of an equally nutritive substance 

 termed legumine (69). The situation of the cotyledon is 

 seen at cc in fig. 19, and you will perceive that it is iden- 

 tical with that of the albumen, as illustrated by the 

 Sedge, fig. 18. 



502. THE EMBRYO being the ultimate end of all 

 vegetation, it must be the important and essential part, 

 for the production, support, and growth of which, all 

 other parts, principles, and powers of the whole plant 

 have been elaborated and exhausted. It contains, in a 

 rudimental state, all the organs proper to its species, and 

 becomes a plant by the development of parts already 

 formed, and not by a new formation. The primordial 

 leaves (118), and the initial stem, are often distinct in 

 the embryo ; and they are conspicuous in the Garden 

 Bean and Pea-nut, as at fig. 11. In the small figure at the 

 right hand is seen the young plantlet, with its delicately 

 folded leaves. The Embryo is usually a straight, club- 

 shaped body, as at fig. 12 ; but it is sometimes variously 

 curved, as at figs. 5 and 8. 



503. THE ARIL is a partial covering investing some 

 *seeds. It is developed either from the funiculus or the 



placenta, and is fleshy or cartillaginous in texture. It 



forms the pulpy envelope of the seed in Mandrake, and 

 in the Roxbury Wax-work it is the scarlet pulp that en- 

 velopes the orange-colored seed. The lacerated covering 

 of the Nutmeg is a fine example of the aril. In many 

 seeds this appendage is a mere scale, and in many more 

 it is wholly wanting. 



GERMINATION. 



504. This term, as you have already learned (122), 

 denotes the first vital action of the seed, by which it is 

 developed into root, stem and leaves, or the organs of a 

 new plant. The circumstances most favorable to germi- 

 nation are, a moderate temperature (in our climate rang- 

 ing from 50 to 60 of Fahr.), air, moisture, and obscu- 

 ration or absence of light. But plants will germinate in 

 much higher and lower degrees than those mentioned. 

 In the Polar regions, certain plants will put forth their 

 hardy germs under arches of ice, which not only shelter 

 them, but admit the sunbeams ; and the Chickweed of 

 our own climate will germinate in a temperature but just 

 above the freezing point ; while tropical plants require 

 more than 100 of heat. 



505. The effect of water is not only to soften the 

 coat of the seed, so as to expand the nucleus, and free it 

 from its integuments by bursting them, but it dissolves 

 the nutritive substances it finds present, and becomes the 

 vehicle of others. It also conveys oxygen, the presence 

 of which is essential. By help of this, the carbonic acid 

 is decomposed, the carbon set free, and the starch, dex- 

 trine, and other nutritive substances, are converted into 

 saccharine matter, by which the embryo is directly nour- 

 ished. Oxygen is also conducted by the air, which is 

 another essential agent ; for no plant can germinate with- 

 out it. The active agents of germination are, then, Heat, 

 Moisture, Oxygen, and Air ; and a negative condition, 

 also necessary, is the absence of light. All these cir- 

 cumstances are often found in a state of nature, where the 

 seeds drop from the parent plant, bury themselves in the 

 soil, and germinate, as in all cases of spontaneous pro- 

 duction. But the ingenuity and intelligence of man 

 secure to cultivated species the most favorable conditions, 

 and thus multiply the chances in then* favor. 



506. When the radicle is protruded from its integu- 

 ments, the lower extremity descends into the soil, the 

 plumule, or opposite extremity, rises into the air, and 

 puts forth leaves* while the radicle itself is stretched, or 



The scar it leaves what called in the Bean ? Of what does Albumen con- 

 sist? Where largely developed ? Howls it in the Sun-flower Butternut 

 Coffee Mallow ? What does it contain? Is it present in the Pea and Bean? 

 By what supplied ? Office of the Albumen ? Is it a simple substance ? To 

 the production of what part have all the parts and powers of the plant contri- 

 buted ? Why ? What does it contain how become a plant its usual shape 



other forms? Describe the Aril. Instances. What is the first vital act in a 

 plant? Most favorable circumstancea What temperature in our climate in 

 the torrid zone frigid ? Mechanical effects of water Chemical effects ? What 

 other agent conducts oxygen ? Active agents required in germination what 

 negative condition ? After protrusion how are the extreme points of tho 

 radicle moved ? 



