210 HISTOLOGY OF MEDICINAL PLANTS 



tamarac (Plate 85), quassia, uva-ursi, quebracho, and in wild 

 cherry (Plate 86). 



The crystals of morea nutgalls (Plate 82, Fig. 3) are octo- 

 hedrons, and they resemble the crystals of calcium oxalate found 

 in urinary sediments. 



While studying the prisms, focus first on the upper surface 

 and then down to the under surface in order to observe the 

 forms accurately. 



There are several plants in which more than one form of 

 crystal occur. Rosette crystals and prisms are associated, for 

 instance, in cascara sagrada, frangula, condurango, dogwood, 

 and pleurisy root (Plate 87, Figs, i, 2, 3, 4, and 5). 



An important factor to be kept in mind in studying crystals 

 is the number — whether abundant, as in rhubarb, or sparingly 

 present, as in mandrake, etc. Variation in the number of 

 crystals is not uncommon, even in different parts of the same 

 plants. In wahoo stem bark, for instance, there are several 

 times as many rosette crystals as there are in the root bark. 



Crystals of calcium oxalate are freely soluble in dilute 

 hydrochloric acid without effervescence; but they are insoluble 

 in acetic acid and in sodium and potassium hydroxide solutions. 

 With sulphuric acid they form crystals of calcium sulphate. 



CYSTOLITHS 



Cystoliths consist of calcium carbonate deposited over and 

 around a framework of cellulose. 



FORMS OF CYSTOLITHS 



The forms of cystoliths differ greatly in the different plants 

 in which they occur. 



In the rubber-plant leaf, the cystolith resembles a bunch of 

 grapes and is stalked; in ruellia root (Plate 87, Fig. i) the cysto- 

 Hths vary from nearly circular to narrowly cylindrical, and no 

 stalk is present; also the cystolith nearly fills the cell in which 

 it occurs. In the hair of cannabis indica (Plate 88, Fig. 3), the 

 cystolith varies in form according to the size and shape of the 

 hair, but in all the hairs the cystolith appears to be attached to 

 the upper curved part of the inner wall of the hair. 



