THE BEASON WHY. 289 



: He causeth the grass to grow for the cattle, and herb for the service of man : 

 that he may bring forth food out of the earth." PSALM civ. 



the seed, which, moistened and warmed by the soil, yields a kind of 

 glutinous sap, out of which the first members of the plant are 

 formed. And then the tender leaf, looking up tc the sky, and the 

 slender rootlet penetrating the soil, begin to draw their sustenance 

 from the vast stores of nature. 



1151. Of 'what do vegetable structures consist? 



Of membranes, or thin tissues, which, being variously arranged, 

 form cells, tubes, air passages, &c. Of 'fibres, which form a stronger 

 kind of membrane, and which is variously applied to the production 

 of the organs of the plants. And of organs, formed by those 

 elementary substances, by which the plants absorb, secrete, and 

 grow, and fulfil the conditions of their existence. 



1152. Why are seeds generally enveloped in hard cases ? 

 Because the covering of the seed, like the shell of an egg, is 



designed to preserve the germ within from the influence of external 

 agencies, until the time for development has arrived, and the 

 conditions of germination are fulfilled. 



1153. Why does a seed throw out a root, before it forms a 

 leaf? 



Because moisture, which the root absorbs from the earth, is 

 necessary to enable the germ to use the nutrition which the seed 

 itself contains, and ou\, of which the leaf must be eliminated. 

 Moisture forms a kind of gluten, in which the starch of the seed is 

 dissolved, and converted into sugar, the sugar into carbonaceous sap, 

 and the sap into cellular tissue and woody fibre, as the leaves 

 present themselves to the influence of the air and light. 



1154. Why does a plant grow ? 



Because, as soon as membranes and vessels are organised in the 

 young germ, the nutritive fluid, formed by its first organs, begins to 

 move through the fine structures, and from that time the plant 

 commences to incorporate with its own substance the elements 

 with which it is surrounded, that are suitable to its development. 



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