26 
PLANT MORPHOLOGY. 
distributed, while those of the tetragonal system are 
less frequent in their occurrence, being found in 
species of Allium , Tradescantia and Begonia, in Pau- 
lownia imperialis and in the Cactacese. The crystals 
belonging to the monoclinic system include a number 
of forms, as follows : (1) Rosette aggregates, or what 
are commonly termed rosette - shaped crystals; (2) 
prisms, pyramids and elongated or irregular hexag- 
onal-shaped crystals; (3) crystal-fibers; (4) raphides; 
(5) cryptocrystalline crystals and (6) membrane crys- 
tals. 
ROSETTE AGGREGATES OF CALCIUM OXALATE. 
The rosette aggregates were first observed by Mal- 
pighi in 1687. They consist of numerous small 
prisms and pyramids, or hemihedral crystals more or 
less regularly arranged around a central axis, and 
have the appearance of a rosette or star. The develop- 
ment of these aggregates may be readily observed in 
the stem of Datura Stramonium. Crystals of this class 
are more widely distributed than any of the others, 
and are found in the following drugs, these being 
grouped according to the size of the crystal. 
VEGETABLE DRUGS CONTAINING ROSETTE AGGREGATES 
OF CALCIUM OXALATE. 
(а) Crystals not more than 7 fi in diameter : Anisum, calendula, 
carum, conium, coriandrum and fceniculum. 
(б) Crystals not more than 15 y in diameter: Caryophyllus and 
humulus. 
(c) Crystals not more than 25 /j- in diameter: Althaea, buchu, 
cannabis indica, cusso, eriodictyon, euonymus, frangula (prisms 
and pynunids also occur), gossypii radicis cortex, pimenta (usually 
smaller). 
( d ) Crystals not more than 35 /* in diameter: Jalapa, pilo- 
carpus, stillingia, viburnum prunifolium and viburnum opulus 
(occasionally). 
( e ) Crystals not more than 100 /( in diameter: Chimaphila (40- 
60y), geranium (45-70.70 and rheum (50-100 / 1 ). 
