VEGETABLE CYTOLOGY 
55 
the crystals already formed will increase in size. To get satisfactory 
results the saturated solution must be of the same temperature as 
the mount. 
12. Calcium Oxalate. — This substance occurs in many plants 
always in the form of crystals. It is apparently formed by the reac- 
tion of salts of calcium, which have found their way into the cell 
sap from the soil, with oxalic acid which is manufactured by the 
plant. Calcium oxalate crystals dissolve readily in mineral acids 
without effervescence. They are insoluble in acetic acid or water. 
These crystals are classified according to form and belong either to 
the monoclinic or tetragonal system. 
Crystals belonging to the Monoclinic System and Examples of Drugs 
Containing them: 
1. Solitary — Hyoscyamus, Acer Spicalum, Viburnum Prunifolium. 
2. Rosette Aggregates — Althaea, Gossypii Cortex, Stramonium, 
Granatum, Rheum, Foeniculum. 
3. Columnar (Styloids) — Quillaja. 
4. Raphides — Convallaria, Sarsaparilla, Veratrum, Scilla, 
Phytolacca. 
5. Micro-crystals (Crystal sand) — Belladonnae Radix, Cinchona, 
Stramonium. 
6. Crystal Fibers — Cascara Sagrada, Prunus Virginiana, 
Glycyrrhiza. 
7. Membrane Crystals — Aurantii Dulcis Cortex, Limonis Cortex, 
Condurango. 
Solitary crystals, usually in the form of rhombohedra, occasionally 
in twin crystals, occur as sharp angular bodies each one often com- 
pletely filling up the lumen of a cell. 
Rosette aggregates consist of numerous small prisms or pyramids, 
or hemihedral crystals arranged around a central axis, appearing 
like a rosette or star. 
Columnar crystals or styloids are elongated prisms. 
Raphides are groups of acicular or needle-shaped crystals which 
occur in long thin-walled cells containing mucilage. They are 
more frequently found in Monocotyledons than in any other plant 
group. Micro-crystals (sphenoidal micro-crystals or crystal sand) 
are minute arrow-shaped or deltoid forms completely filling the 
