CRYSTALS IN PLANTS. 



°°>9 



oo\ 



crystals will be principally prismatic, and are arranged aa 

 if they were beginning to assume a stellate form. Some 

 plants, as many of the cactus 



tribe, are made up almost > — ' V-0 < I N V / 

 entirely of raphides. In ' 

 some instances every cell of 

 the cuticle contains a stel- 

 late mass of crystals ; in 

 others the wiiole interior is 

 full of them, rendering the 

 plant so exceedingly brittle, 

 that the least touch will 

 occasion a fracture; so much 

 so, that some specimens of 

 Cactus senilis, said to be a 

 thousand years old, which 

 were sent a few years since 

 to Kew from South America, \ Tv \ r\ 

 were obliged to be packed 



• ,, ..l 11 xl 5 Fig- 1S4 — Siliceous cuticle from under 



in COttOn, Wltn all the Care surface of leaf of Deutzia scabra. 



of the most delicate jewel- 

 lery, to preserve them during transport. 



Raphides, of peculiar figure, are common in the bark of 

 many trees. In the Hiccorv 



(Carya alba) may be ob- 



IB 



M "W* 



served masses of flattened ^||^^ #^CW 



prisms having both extre 

 mities pointed. In vertical 

 sections from the stem of 





fT 



J* 





Elceagnus angustifolia, nu- kM A" ^- \ > 



merous raphides of large size ^M ^ j^ O 



are embedded in the pith. #Lfc ^ *^ £]^ 

 Raphides are also found in ^fTT vt, -^V'TH 



the bark of the apple-tree, Hq "^ P *, H 

 and in the testa of the seeds ^ f l fl 3V ^ H » 



of the elm ; every cell con 

 tains two or more very 

 minute crystals. 



In figs. 184 and 185 we 

 have other representations 

 of the crystalline structure 



*rO 



n 



Fi£. 185. — Siliceous cuticle of Gran 

 (Phar us cristatus) 



z 2 



