I.IFE OF PLANTS. 



255 



383. 



If we examine still further the changes which take place 

 ill the germen after impregnation, we find this idea of a new 

 life being awakened, confirmed, in the first place, by the 

 swelling which this organ exhibits at the expense of the other 

 parts of fructification, and their coverings. These last decay 

 and fall off. The ovary and the receptacle, and in Hovenia 

 clulcis the fruit-stalk, begin to swell ; and the ovula, which 

 before were only simple vesicles or spherical cells, being now 

 filled with pure water, begin to undergo wonderful changes. 



The skin of the seed begins to thicken by depositions ffom 

 the organising fluid. After some time, which cannot exactly 

 be defined, we are able to distinguish a double covering of 

 the seed ; the exterior, which from analogy is called the 

 Chorion, and the interior, which is denominated the Amnios. 

 The latter, which is for the most part full of a sweet and slimy 

 fiuid (liquor amnii), shews after some time a small point, 

 either swimmimg or fixed to the side of the vessel, which is 

 the first trace of the embryon. It seldom occurs that we 

 find more than one embryon in the same ovulum, although 

 this is observed in the Agrumas and in Fuchsia. It still 

 more seldom happens that no embryon is found in a proper 

 seed, but that it first makes its appearance in the shoot. 



The farther evolution of the seed is different according to 

 the type of its structure ; that is to say, the embryon either 

 does not increase, but remains unevolved, and continues to 

 be like a point, a line, or a fungus. In that case, it does not 

 consume the moisture appropriated to the nourishment of the 

 germ, but this matter becomes thickened by the absorption of 

 of its more volatile parts, and passes at last into the nature of 

 albumen. When this occurs, as in the Grasses and Scitami- 

 neae, we can discover the scutellum or the vitellus appearing 

 as an instrument of evolution. In other instances, the em- 

 bryon becomes thickened at one end, by which also it attaches 

 itself to a substance, which holds the place of the cotyledons,^ 

 and is called the Cotyledonous Body. In some of the Naiadas^ 

 and Zamiae, as well as in the Pine tribe, this body incloses 

 the germ within itself. By the germ it is itself divided, and 



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