SECTION 16.] 



CELL-CONTKNTS. 



137 



tuber. When the potato sprouts, the starch in the vicinity of developing 

 buds or eyes is changed back, again, first into mucilaginous dextrine, then 

 into sugar, dissolved 

 in the sap, and in this 



form it is made to 

 flow to the grow ing 

 parts, where it is laid 

 down into cellulose 

 or cell-wall. 4C2 *■■> 



421. Besides these cell-contents which arc in obvious and essential rela- 

 tion to nutrition, there are others the use of which is problematical. Of 

 such the commonest arc 



•122. Crystals. These when slender or needle-shaped are called 

 Ruapiiides. They are of inorganic matter, usually of oxalate or phosphate 

 or sulphate of lime. Some, at least of the latter, may be direct crystalliza- 



tions of what is taken in dissolved in the water absorbed, but others must 

 be the result of some elaboration in the plant. Some plants have hardly 

 any ; others abound in them, especially in the foliage and bark. In Locust- 

 bark almost every cell holds a crystal; so that in a square inch not thicker 

 than writing-paper there may be over a million and a half of them. When 



Fig. 462. Some magnified Btarch-grains, in two cells of a potato. 463. Some 

 cells of tin- albumen <>r floury pari of Indian Corn, filled with starch-grains. 



Fig. 464. Four cells from dried Onion-peel, each holding a crystal of different 

 shape, one of them twinned. (65. Some *■<-! 1 s from stalk of Rhubarb-plant, three 

 containing chlorophyll ; two (one torn across) with rhaphidea. 466. Rhaphidea 

 in a .ell, from Ariasema, with small cells surrounding. h'>7. Prismatic; crystals 

 from the hark of Hickory. 168. Glomerate crystal in ■ cell, from Beet-root. 

 (69 \ tew cells oi Locust-bark, a crystal in each. 170. A detached cell, with 

 rhaphidea being forced out, a* happens when put in water. 



