44 LEAVES 



of a dull green colour, paler below. Their surface exhibits under 

 the lens numerous whitish elevated points ; these are caused by 

 cells filled with calcium oxalate, which produce, when the tissue of 

 the leaf dries and shrinks, the appearance described. Neither all 

 specimens of the drug nor both surfaces exhibit this character equally 

 well. 



The leaves should be collected when the plant is in flower, as they 

 are then richest in alkaloid. For the preparation of the extract the 

 larger stalks should be rejected, as it has been shown that the extract 



FIG. 30. Belladonna, showing leaves in unequal pairs. Reduced. 



prepared from them contains less alkaloid than that prepared from 

 the leaves (Ranwez, 1897). For the same reason the dry drug should 

 be as free as possible from stalk. 



Microscopical Characters. The transverse section of the midrib exhibits 

 strands of bast both above and below the wood (bi-collateral bundles), a feature 

 common in Solanacece and in a few other orders, but by no means of frequent 

 occurrence, and hence of use in identifying the leaves. There are no bast- 

 fibres or sclerenchymatous cells. Some of the cells of the mesophyll are filled 

 with numerous, minute crystals of calcium oxalate, best seen when portions 

 of the leaves are warmed with solution of chloral hydrate (5 parts) in water (2 

 parts), or with a mixture of cresol (2 parts) with glycerin (1 part), and examined 

 under the microscope. This is an important character, as it enables these 

 leaves to be distinguished from stramonium, henbane, foxglove, and many 



