46 
HISTOLOGY OF VEGETABLES. 
sue, in contact with the medullary rays. Other forms 
of crystals, as the rhombohe- 
dron, and a small stellate form, 
shown in Fig. 27, D, are also 
found in the bark of the lime. 
In a vertical section of the stem 
of Eleeagnus, represented in 
Fig. 30, numerous prismatic 
raphides of large size are visi- 
Prismatic raphides in cells of ble in the pith. Raphides are 
the pith of Elceagnus angusti- 
also found in the bark of the Ap- 
ple-tree , as shown in Fig. 31, 
and in the testa of the seeds of 
the Elm , as shown in Fig. 32 ; 
each cell contains two or more 
Raphides in the bark of the very minute crystals. 
Apple-tree. ' 
It is not at present known 
FI Gr 3 ^ • • 
what office raphides perform in 
the economy of the plant. Some 
have gone so far as to state that 
they are deposits to be applied 
towards the mineral part, or 
skeleton of the plant, but the 
fact of their being insoluble in 
Raphides in the testa of a seed vegetable acids Would pi OVe this 
of the Elm. view of their use to he erro- 
neous. The more rational supposition is, that they 
are accidental deposits, formed by the action of vege- 
table acids upon lime or other bases, derived by the 
