172 BOTANY AND PHARMACOGNOSY. 



crystals of this group are sometimes mistaken for silica, owing to 

 the fact that in some instances the lumen of the cell is completely 

 filled by the crystal, and the inner wall having the contour of the 

 crystal, it is impossible to determine whether the crystal is af- 

 fected by the use of hydrochloric acid. It should be stated in 

 this connection that silica never occurs as a cell-content in sharp, 

 angular crystals, but either in more or less ellipsoidal or irregular 

 hollow masses, or in somewhat solid, irregularly branching 

 masses. 



Crystal Fibers. — In quite a number of drugs a single mono- 

 clinic prism occurs in each of the parenchyma cells adjoining 

 the sclerenchymatous fibers, and to this single longitudinal row 

 of superimposed cells the name crystal fiber has been applied 

 (Fig. 282, B). 



Raphides are groups of needle-shaped crystals which are 

 found in various plants (Fig. 281, B). These have been mistaken 

 by several observers for calcium phosphate. Calcium phosphate, 

 however, occurs in plants either in solution or in combination 

 with protein substance. The cells containing raphides are long, 

 thin-walled and contain sooner or later a mucilage, which arises 

 from the cell-sap and behaves with reagents much like cherry- 

 gum. The cells are either isolated or occur in groups placed 

 end to end, as in Veratrum viride. 



Cryptocrystalline crystals are exceedingly small (about 0.2 

 to 10 /* in diameter), deltoid or arrow-shaped, and so numerous 

 as to entirely fill the parenchyma cells in which they occur, giving 

 the cells a grayish-black appearance which readily distinguishes 

 them from other plant cells (Fig. 281, D). It has been supposed 

 that they are tetrahedrons, but they are probably hemihedral forms 

 of monoclinic crystals, inasmuch as monoclinic prisms occur in 

 neighboring cells in the same plant or drug, as in stramonium, 

 quassia, etc. 



Membrane Crystals. — There are several forms of crystals 

 which may be included in this group. The so-called Rosanoflf 

 crystals consist of rosette aggregates attached to inward-protrud- 

 ing walls of the plant cell. These, however, do not concern us so 

 much as the large monoclinic crystals which have a membrane 

 surrounding them. The crystal first appears in the cell-sap and 



