OP THE SEED AND GERMINATION, 



103 



cavity of the epispemi. At other times, the 

 kernel contains, together with the embryo, an- 

 other body, which is named the endosperm; as 

 in ricimis communis, the wheat, &c. 



The structure of these two organs is so differ- 

 ent, that tliey are easily distinguished at first 

 sight. Tlie embrt/o is an organized body, which 

 is destined to become enlarged and developed by 

 germination. The endosperm, on the contrary, 

 is a mass of cellular tissue, sometimes hard and 

 horny, at other times soft and fleshy, which, 

 after germination, shrivels and generally dimin- 

 ishes in size, instead of enlarging. Thus, then 

 germination will remove all doubt as to the na- 

 ture of the two bodies contained within the epi- 

 sperm, when it may not have been satisfactorily 

 determined by analysis and dissection. 



The endosperm is that part of the kernel which 

 forais, around or on the side of the embryo, an 

 accessory body, wliich has no continuity of ves- 

 sels or of tissue with it. It is generally formed 

 of vascular tissue, in the meshes of which is con- 

 tained starch, or a thick mucilage. 



This substance affords nutriment to the young 

 embryo. Before germination, it is entirely in- 

 soluble in water ; but at the first period of vege- 

 table life it changes its nature, becomes soluble, 

 and contributes to the nutrition and develop- 

 ment of the embryo. It is always easy to sep- 

 arate the endosperm from the embryo, as they 

 do not in the least cohere. Its colour is gener- 

 ally white, or whitish, though green in the 

 niisletoe and the substance of which it is formed 

 varies greatly. Thus it is dry and farinace- 

 ous, in many graminece, as wheat, oats, barley. 

 Coriaceous, and, as it were, cartilaginous, in many 

 umbeUiferse. Oleagenous and fleshy, or thick and 

 greasy to the touch, as in ricinus communis, 

 and many other euphorbiaces. Horny, tena- 

 cious, hard, and elastic, asin the coffee and many 

 other rubiacejE, most of the palms, &c. Thin 

 and membraneous ; as in many labiatse, &c. 



The embryo is the already organized body, ex- 

 isting in a perfect seed after fecundation, and 

 which constitutes the compound rudiment of a 

 new plant. When placed in favourable circum- 

 stances, it is converted, by the act of germination, 

 into a plant perfectly similar, in every respect, 

 to that from which it derived its origin. When 

 the embryo exists by itself in the seed, that is, 

 when it is immediately covered by the episperm 

 or proper integument, it is said to be epispermie, 

 as in the kidney-bean. When, on the contrary, 

 it is accompanied by an endosperm, it takes the 

 name of endospernic, as in the graminese, ricinus 

 communis. 



The embryo being a plant already formed, all 

 the parts which it is one day to develope already 

 exist in it, but only in the rudimentary state. 

 It is essentially composed of four parts : 1. The 



radicular body; 2. The cotyledonary body; 3. 

 The gemmule; 4. The caulicle. 



1. The radicular body or radicle, constitutes 

 one of the extremities of the embryo. When 

 gei-mination takes place, it gives rise to the root, 

 or forms it by its development. 



In the embryo in the state of rest, that is, be- 

 fore gei-mination, the radicular extremity is al- 

 ways simple and undivided. When it begins to 

 be developed, it often sends off several small 

 knobs, which constitute so many radicular fila- 

 ments ; as in the graminese. If, in some cases, 

 it is difficult, before gennination, to distinguish 

 the radicle, it becomes easy to do so when the 

 embryo begins to grow. Thus, the radicular 

 body always tends towards the centre of the 

 earth, whatever impediments may be put in its 

 way, and changes into a root, while the other 

 parts of the embryo take an opposite direction. 

 In a certain number of plants, the radicular 

 body itself elongates, and changes into a root, in 

 consequence of the development wliich germina- 

 tion induces in it. This is what is observed in 

 many dicotyledones. 



When the radicle is external and exposed, the 

 plants are named exorhizous. Of this kind are 

 the labiatse, cmcifera;, boragineoe, synanthereae, 

 &c., and the greater number of dicotyledonous 

 plants. 



In other plants, again, the radicle is covered 

 and entirely concealed by a particular envelope 

 which bursts at the period of gennination, to 

 allow it to escape. This body has received tiie 

 name of coleorhisa. In this case the radicle is 

 internal or coleorhizous, and the plants which 

 present this disposition are named endorhizous. 

 To this division belong most of the true mono- 

 cotyledones, such as the palms, the graminesE, 

 IHiaceae, &c. 



Lastly, in some less frequent cases, the radicle 

 is incorporated with the endosperm. Plants in 

 which this organization is observed, are named 

 synorhizous. Of this kind are the pines, firs, and 

 other coniferae, the cycadese, &c. All the known 

 phanerogamous or floweiingplantsbelong to these 

 three great classes. 



The cotyledonary body may be simple and per- 

 fectly undivided. In this case, it is fonmed by 

 a single cotyledon, and the embryo is named mono- 

 cotyledonous ; as in the wheat, the barley, the 

 oat, the lily. At other times, it is formed of 

 two bodies united base to base, which are named 

 and the embryo is then said to be 

 ', as in the bean, ash, elm. All 

 plants whose embryo has a single cotyledon 

 are named monocotyledonous. AU those which 

 have two cotyledons are called dicotyledonous. 



Sometimes there are more than two cotyledons 

 in the same embryo. Thus there are tlu-ee in 

 cupressus pendula; four in pinus inops, and 

 ceratophyllum demersum ; five in pinus laricio: 



