202 HISTOLOGY OF MEDICINAL PLANTS 
section, and the largest diameter is at the centre, from which 
they taper gradually toward either end to a sharp point. 
Raphides occur in bundles, as in false unicorn root (Plate 79, 
Figs. 6, A, B, and C), rarely as solitary crystals. 
In ipecac root the crystals are usually solitary. In sar- 
saparilla root, squill, etc., the raphides occur both in clusters, 
part of bundle, or in bundles, and as solitary crystals. 
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 quan- 
tities 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, spike- 
nard 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 uni- 
form variation. For instance, the largest rosette crystal occur- 
ring in wahoo root bark (Plate 80, Fig. 5) is smaller than the 
largest crystal occurring in rhubarb (Plate 80, Fig. 6), etc. 
The prisms forming the rosette crystals, like all prisms, 
decompose white light, with the result that rosette crystals 
frequently appear variously colored. Rhubarb crystals, for 
