50 INTRODUCTION. 



grows, the season of the year, and its dryness or wetness, its natural or cul- 

 tivated state, &c. As a general rule, the time for collecting a vegetable sub- 

 stance depends on the part of it required for use. 



Plants should never be gathered for medicinal purposes whilst very young, 

 as their peculiar principles have not had time to become developed, and hence 

 they are in most cases inert ; thus the young shoots of the Poke, or of the 

 Asclepias, are used as substitutes for Asparagus, and can be eaten with impu- 

 nity, whilst at a later period, they are possessed of acrid and purgative 

 powers. The influence of soil is very remarkable. Most of the Umbelliferae 

 growing in a dry soil are aromatic, whilst those peculiar to wet places, are 

 narcotic and poisonous. The Cruciferse thrive best in damp places, but the 

 Labiatse are principally found in dry situations. The same plant is much in- 

 fluenced by a difference of locality ; thus it is stated, that Cinchona obtained 

 from trees growing in low situations, is always of inferior quality, whilst 

 the bark from the same species, but inhabiting a high and airy spot, is 

 possessed in the fullest degree of those properties for which this article is 

 esteemed. 



Cultivation also exerts the greatest influence on the constitution of vege- 

 tables, and in almost every instance deteriorates their active, but increases 

 their nutritive qualities. Thus, it is found that by cultivation, the dry and 

 tasteless sarcocarp of many of the Pomacese and Drupaceae, becomes pulpy 

 and grateful to the palate, and the unpleasant and narcotic juices of the Celery, 

 become bland, aromatic, and mucilaginous. Hence, as a general rule, plants 

 should be collected where they naturally grow, as their active virtues are 

 there most strongly developed. There is one striking exception to this, in 

 the Labiatae, their aromatic flavour being much enhanced by cultivation. 



Roots. The roots of annual and biennial plants should be collected in 

 the autumn ; the first before the decay of their stem, and the latter on the dis- 

 appearance of the leaves of the first year. Those of perennial vegetables are 

 best collected in the winter, or early in the spring. All intended to be kept, 

 must be carefully washed and dried ; where the root is large and succulent, 

 it must be cut into slices. The aromatic roots should not be scraped, as 

 much of their odorous and active qualities reside in the epidermis. 



Stems. These are either herbaceous or ligneous ; the former are to be 

 gathered after the formation of the leaves, and before the appearance of the 

 flowers. The latter should be procured in the winter, as at this time the 

 wood furnishes a greater quantity of extract. 



Barks. They are to be collected at the season when they can be most 

 easily separated from the wood. They should, in all cases, be procured be- 

 fore the flowers are produced, or after the reproductive process is terminated, 

 as during the time the plant is elaborating the organs necessary to that func- 

 tion, all its powers are directed to that purpose, and other portions of its 

 structure are deprived of their usual proportion of proper juices. Barks 

 should not be taken from very young or very old plants; in the first case 

 they have not attained their full powers, and in the second, they have lost 

 them ; and the quantity of soluble matter in them becomes diminished. The 

 desiccation of stems and barks requires no remark. 



Leaves are to be collected after the flowers are expanded, and before the 

 seeds ripen. An important remark on the collection of the leaves of the 

 biennial narcotic plants has been made by Mr. Houlton. He states that they 

 do not attain to their full powers, until their second year, and that those of 

 the first year's growth are mucilaginous and inert {Jour. Roy. Inst. i. 196). 

 The drying of leaves must be so conducted as to preserve their natural colour, 

 and therefore they should never be exposed to the direct action of the sun. 



