CRYSTALS IN PLANTS. 339 



crystals will be principally prismatic, and are arranged aa 

 if they were beginning to assume a stellate form. Some 

 plants, as mauy of the cactus 

 tribe, are made up almost 

 entirely of raphides. In 

 some instances every cell of 

 the cuticle contains a stel- 

 late mass of crystals ; in 

 others the whole 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, 

 were obliged to be packed 



J„ „„**„— :xi. n xtT Fi?- 184. — Siliceous cuticle from under 



in COtton, With all the Care svrface of leaf of Deuizia 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 Hiccory 



{Gary a alba) may be ob- "W^4j4 "H* "■ k. rr-j, 

 served masses of flattened t^f^* *^H# 

 prisms having both extre- •« &, ^rJwri 



mities pointed. In vertical j3% ^ $L ^Mi i 

 sections from the stem of 7&R "& f ^ 



Elceagnus angustifolia, nu- Mm ^K 4&. ^ 



merous raphides of large size *^M trf, 1 3 



are embedded in the pith. 

 Raphides are also found in 

 the bark of the apple-tree, 

 and in the testa of the seeds % f V, Jk 

 of the elm ; every cell con- ? r w/^ vL, "^J^ 

 tains two or more very -^r J r4^f 7* ^i-is 

 minute crystals. fTjM _ ^fe MV * * 



In figs. 184 and 185 we ^ M * "* W (Tit 

 have other representations rig. ise.-awfceow wrffcfa »/ 6r«i 

 of the crystalline structure iPAanu crutahu). 



z 2 



*B 



