198 
ECONOMIC BOTANY 
of facts with but few general principles, but with the great 
attention now being given to it in all parts of the world 
this will probably soon be altered. We shall deal here 
mainly with the various classes of vegetable products, their 
sources, and methods of collection and preparation. For 
this purpose it is most convenient for the present to use 
an artificial grouping, chiefly according to the nature and 
uses of the products, employing eight chief heads, the last 
of which is a miscellaneous assemblage. For individual 
products reference should be made to the general index. 
I. Gums, Resins, Caoutchoucs, Guttaperchas, 
6cc. These products arise from the drying or coagulation 
of saps or other excretions, or are obtained from them by 
distillation or otherwise. 
Gums result from the disintegration of the internal 
tissues, and exude from stems or elsewhere ; they are 
common in plants of dry countries, such as N. Africa or 
Australia. They are collected from natural or artificial 
wounds, and usually brought to market in the form assumed 
by the exudations. They swell or dissolve in water, but 
are insoluble in alcohol or ether. Chemically, gums may 
be roughly divided into three classes, according to whether 
they consist mainly of arabin, bassorin, or cerasin. Arabin 
is fully soluble in water, and forms the best mucilage ; good 
gum-arabics (Acacia spp.) are almost entirely composed of 
it. Bassorin, of which gum-tragacanth (Astragalus spp.) 
almost entirely consists, is only slightly soluble. Cerasin, 
which is largely found in cherry gum (Prunus), is insoluble, 
merely swelling up in water. Gums are used for adhesive 
purposes, and in calico-printing, sizing, colour-making, 
confectionery, and pharmacy. Innumerable plants yield 
gums, but few are of commercial importance except those 
mentioned. 
Resins are the products of secretion or disintegration 
of the cells or tissues ; they are usually formed in special 
cavities or passages (p. 115). They are commercially 
collected on a large scale from wounds made in the bark, 
and are brought to market in the forms assumed by the 
exudation or in artificial masses. They are insoluble in 
water, but dissolve in alcohol, ether, or carbon disulphide, 
and burn with a sooty flame. They may be roughly 
