770 A TEXT-BOOK OF BOTANY. 



It is apparent that, apart from their solubility, color reactions, 

 behavior towards reagents, etc., the substances with which we 

 are dealing should be prepared in such a manner that isolated 

 crystals are formed and not aggregates or groups. These isolated 

 crystals can then be studied independently. The reason why 



FlG. 423. Hydrastine: large, nearly equidimensional orthorhombic crystals from alcoholic 



solution. 



aggregates are formed is because the crystals are permitted to 

 grow too rapidly on the slide. This is usually the case in the 

 usual method of procedure in securing crystals, i.e., by adding 

 a drop of a solution to the slide, and then allowing it to evaporate 

 spontaneously, under ordinary conditions. If, on the other hand, 

 the rate of evaporation is lessened so that there is a slowing down 

 of the growth of the crystals, individuals may be obtained of 



