THE PLANT. 47 



part of "i^« seed — it exists in minute di'ops, inclosed 

 in six-sided cells, which consist chiefly of gluten ; ^>, 

 the position and comparative quantity of the starch, 

 wliich in the heart of the seed is mixed with only a 

 small proportion of gluten ; c, the germ or chit, which 

 contains much gluten."* 



The location of the earthy parts of plants is of 

 much interest, and show^s the adaptation of each 

 part to its particular use. Take a wheat plant, foi 

 instance — the stalk, the leaf, and the grain, show in 

 their ashes, important difference of composition. 

 The stalk or straw contains three or four times as 

 large a proportion of ash as the grain, and a no less 

 remarkable difference of composition may be noticed 

 :'» the ashes of the two parts. In that of the straw, 

 we find a large proportion of silicic acid and scarcely 

 any phosphoric acid, while in that of the grain there 

 is scarcely a trace of silicic acid, although phosphoric 

 acid constitutes about one hal|^ of the entire weight. 

 The leaves contain a considei'able quantity of lime. 



This niay at first seem an unimportant matter, 

 but on examination we shall see the use of it. The 

 straw is intended to support the grain and leaves, 

 and to convey the sap from the roots to the upper 

 portions of the plant. To perform these offices, 

 strength is required, and this is given by the silicic 

 acid, and the woody fibre which forms so large a 

 proportion of the stalk. The silicic acid is combined 

 with an alkali, and constitutes the glassy coating of 

 the straw. "While the plant is yoimg, this coating is 

 * See Johnston's Elements, page 41. 



