CELL-CONTENTS AND FORMS OF CELLS. 183 



8. Salmon-pink flowers may be produced by the use of the dye 

 " Brilliant Croceine M. O. O.," which is the sodium salt of ben- 

 zene-azo-benzene-azo-/3-naphthol-disulphonic acid. 



9. Gray flowers may be produced by the use of the dye " Naph- 

 thol Black B.," which is the sodium salt of disulpho-/?-naphtha- 

 lene-azo- a-naphthalene-azo-/2-naphthol-disulphonic acid. 



Calcium oxalate is found in many of the higher plants, and 

 in the algae and fungi as well ; while in the mosses, ferns, grasses, 

 and sedges it is seldom found. It occurs in plants in crystals of 

 either the monoclinic or tetragonal system. The crystals dissolve 

 in any of the mineral acids without effervescence, and their identity 

 is usually confirmed by the use of dilute hydrochloric acid. The 

 crystals of the monoclinic system are rather widely distributed, 

 while those of the tetragonal system are less frequent in their 

 occurrence. 



The crystals belonging to the monoclinic system (Fig. 105) 

 may be subdivided according to their prevalent forms into a num- 

 ber of sub-groups. 



I. SOLITARY CRYSTALS. These are usually in the form of 

 rhombohedra, sometimes in twin crystals of variable size (Fig. 

 108). They are very widely distributed, occurring in a number of 

 modifications in the same plant, and are often very characteristic in 

 the identification of economic products. The 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 affected by the use of hydro- 

 chloric 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 some- 

 what solid, irregularly branching forms (Fig. 109). 



II. COLUMNAR CRYSTALS or " styloids," being elongated prisms 

 of the monoclinic system (Fig. 107, C), and when typical recall 

 the crystals of gypsum. They also occur in twin-forms, some- 

 times replacing raphides, and occasionally show a number of 

 transition forms. 



Solitary crystals in the form of rhombohedra or styloids occur 

 in a number of drugs, as follows: Acer spicatum, calumba, carda- 



