CALGIUM OXALATE. 131 
Forms of peculiar appearance, produced by hemitropy, and 
recognizable by their inwardly inclined angles (Fig. 59), occur 
in the bark of Guaiacum officinale and Quillaia Saponaria.* 
Much less widely extended, at least within the sphere of drugs, 
are well-devoloped forms of the quadratic system (Fig. 60), such 
as are found forinstance in oak-galls (Fig. 61). Oxalate crys- 
tals of this system also occur in many leaf-stalks, and are par- 
ticularly handsome in the Cactex, in species of Begonia and in 
Paulownia imperialis Siebold, furthermore in Urceolaria seru- 
posa Ach. and other lichens. 
ve 
Fie, 59.—Twin crystals of calcium oxalate from Cortex Guaiaci or Cortex Quillaiw 
Saponarie; a, lying on the lateral surface; c, somewhat turned; b, more strongly mag- 
nified and turned to the extent of 90° (Dippel). 
In Rhiz. Rhei, Rad. Saponaria, Rad. Althee, in Cortex 
Granati Radicis, in figs, cloves, and in a very large number of 
other parts of plants belonging to our department (Fol. Eu- 
calypti, Figs. 127, 128), the oxalate crystals are most densely 
crowded together in the form of clusters (Fig. 62); each of which 
generally occupies a single cell. In these cases only the points of 
' Further details are given by Holzner, ‘‘ Krystalle in den Pflanzen- 
zellen,” Flora, 1867, 499. Sachs, ‘ Lehrbuch der Botanik” (IV.), 66. 
Compare also Figs. 102 and 159, 
