CALCIUM OXALATE, 133 
The proof that the plant formations in question are really 
calcium oxalate is readily afforded. The crystals are not solu- 
ble in acetic or oxalic acids, but soluble, and without efferves- 
ence, in hydrochloric acid; this solution gives, upon the addition 
of potassium acetate, an abundant precipitate of indistinctly 
crystallized calcium oxalate. ; 
After short contact with concentrated sulphuric acid, the 
oxalate crystals are converted into long, lance-shaped crystals of 
gypsum, 
The oxalate crystals are presumably formed in the plant by 
the gradual confluence of dilute solutions of oxalates with calcium 
salts. In many cases this occurs with the co-operation of or- 
ganized structures. The rosettes often inclose an uncrystellized 
nucleus, and the needle-like tufts of oxalate are fixed, for in- 
Fig, 62.—Rosettes of calcium oxalate from Rhubarb (see Figs. 142, 146) and Radix 
Saponaric. ; 
stance in Sarsaparilla and many other cases, in a mucilaginous 
(plasmatic) integument; if the oxalate be dissolved in hydrochloric 
acid (spec. gray. 1.1), the integument remains behind, and may 
easily be made recognizable by staining, for example, by means 
of carmine or aniline-red. This covering of protoplasm may 
be detected also with greater distinctnessin Bulbus Scille. Ifa 
fine section of this is moistened with alcohol, a contraction of 
the mucilaginous contents of the cell ensues, in the middle of 
which darker granules will appear, which are seen to be crystal- 
line in polarized light. Water dissolves the mucilage and leaves 
the crystals behind, which, without doubt, are to be regarded as 
the first rudiments of the oxalate prisms often so handsomely 
developed in the Sgwill. The latter are surrounded by a sac, 
and frequently become enlarged to such a degree as to extend 
