738 A TEXT-BOOK OF BOTANY. 



specific drug can be obtained only by collecting it at different 

 times during the season, assaying it and making preparations 

 from it. Experiments thus far seem to show that belladonna 

 leaves collected in July and August show a higher toxicity than 

 those gathered in September or October. It is quite possible that 

 after the removal of the leaves high in alkaloidal content in July, 

 another crop can be obtained by October. It is important to bear 

 in mind with some drugs that a very slight difference in time of 

 gathering and manner of drying, great variation of the active con- 

 stituents may. be found, as with many' of the Composite flowers. 

 It is only when they are in the bud condition, as in the case of 

 insect flowers, and santonica, that they show the highest amount 

 of active principle. Again, depending on whether an article is 

 gathered to be put upon the market or whether the active prin- 

 ciples are to be isolated, as in the manufacture of the essential 

 oils, different methods are followed, depending upon the nature of 

 the plant and what previous experiments have demonstrated 

 should be followed. For instance, while in the preparation of oil 

 of peppermint the herb is first dried, yet in other cases the col- 

 lected material must be previously macerated in order to obtain 

 the largest yield of oil, as with those plants yielding volatile oils 

 containing either cyano-benzaldehyde or methyl-salicylate. 



Too much attention cannot be given to the entire question 

 of the harvestrng of the crop and proper methods of drying, and, 

 of course, again, depending upon the locality, different methods 

 will be followed. There are some places at certain times where 

 it would be quite possible to dry the drugs out of doors. In other 

 situations it would be necessary to dry them in barns and even 

 in specially constructed drying ovens where artificial heat would 

 be employed. The drying oi leaves, flowers, and seeds is com- 

 paratively simple and can usually be rather quickly performed 

 without any special preparation. In the case of roots and fleshy 

 fruits the drying should be under special protection, and is facili- 

 tated more or less by slicing or comminuting the article. 



In some drugs, in addition to drying, there is a curing process 

 that takes place. By this process of fermentation the active con- 

 stituents are developed. Among the drugs treated in this manner 

 the following may be mentioned : tobacco, vanilla, gentian, 



