STAGES OF GERMINATION. 351 



the liberation of carbonic acid, with a small quantity of acetic acid ; 

 -and as all acids are negative, and like electricities repel each other, it 

 is probable that the seed is at the time in an electro-negative condition. 

 The phenomena of germination are well seen in the malting of barley, 

 which consists in the sprouting of the embryo and the formation of 

 -sugar. The changes produced in the air by germinating seeds have 

 been investigated by Saussure, who showed that in all cases carbonic 

 acid was evolved at the expense of the carbon of the seed. During 

 growth and evolution it would appear that all living beings, whether 

 plants or animals, give out carbonic acid (carbon dioxide), whilst oxy- 

 gen or some oxidising substance is absorbed. Growth and evolution must 

 be considered in a dififerent way from the decomposition of 00^ by 

 leaves, under the influence of light, to provide the starch, gum, sugar, 

 and other materials that are to be organised. 



When aU the requisites for germination are supplied, the seed, by 

 the absorption of moisture, becomes softened and swollen. When 

 albumen or the perisperm is present, it undergoes certain chemical 

 changes by the action of the air and water, so as to be rendered fit 

 for the nutrition of the embryo. These changes consist partly in the 

 conversion of starch into sugar, and are accompanied with the evolu- 

 tion of carbonic acid, and the production of heat. As the fluid 

 matters are absorbed by the cells of the embryo, the latter continues 

 to increase untU it fills the cavity of the seed, and ultimately bursts 

 through the softened integuments. In cases where there is no peri- 

 sperm, the exalbuminous embryo occupies the entire seed, and the 

 process of germination goes on with greater rapidity. The embrjfo 

 speedily swells, ruptures the integument, and is nourished at the 

 expense of the cotyledons, which are often fleshy, containing much 

 starchy matter, as in the Bean and Pea, along with oily matter, as in 

 the Nut and Eape see^l. There are thus two stages of germination — 

 that in which the embryo undergoes certain changes within the seed 

 itself, and that in which it protrudes through the integuments and 

 becomes an independent plant. 



The embryo, nourished at the expense of its perisperm and coty- 

 ledons, continues to grow, and usually protrudes its radicular extremity 

 (fig. 625, 1) in the first instance, which is nearest the surface, and 

 next the micropyle. This, which in the embryo is very short, and 

 confounded with the cauliculus so as to form the first internode, 

 becomes thickened by addition to its extremity (fig. 625, 2J, and the 

 ■division between the ascending and descending axis becomes more 

 marked. The caulicule or axis also elongates, bearing at its summit 

 the plumule, which now appears outside the integuments (fig. 625, 3 51), 

 forming the second internode, either accompanied by the cotyledons, 

 or leaving them still within the seed coats. In the latter case, the 

 •cotyledons are usually fleshy and of a pale colour, and become 



