In most drugs the crystals are entire; but in squills, where the raphides are very large, they are broken. In phytolacca (Plate 79, Fig. 1) and in hydrangea the raphides are usually broken, owing to the fact that these drugs contain large quantities of fibres which break them up into fragments when the drug is milled.
There is the greatest possible variation in the size of raphides in the same and in different drugs, but the larger forms are constant in the same species.
Raphides are deposited in parenchyma cells and in special raphides sacs. These crystals are always surrounded with mucilage.
ROSETTE CRYSTALS
Rosette crystals are compound crystals composed of an aggregation of small crystals arranged in a radiating manner around a central core. This core appears nearly black, and the whole mass is nearly spherical. The free ends of the crystals are sharp-pointed or blunt.
Characteristic rosette crystals occur in frangula bark, spikenard root, wahoo stem, root bark, rhubarb, etc. (Plate 80, Figs. 1, 2, 3, 4, 5, and 6).
These crystals are very variable in size. This variation is illustrated by the crystals of Plate 80.
Usually there is a variation in size of the crystals occurring in a given plant, but for each plant there is a more or less uniform variation. For instance, the largest rosette crystal occurring in wahoo root bark (Plate 80, Fig. 5) is smaller than the largest crystal occurring in rhubarb (Plate 80, Fig. 6), etc.
PLATE 79
Raphides