INTRODUCTION. xli 



accompanied man in his migrations to regions 

 most remote from their native soil. The varieties 

 of Apple and Pear which have been produced by 

 cultivation are beyond the power of calculation. 

 These two are most valued for their fruit. Other 

 British trees belonging to the group are the 

 "Whitebeam, Mountain Ash, Service, and Haw- 

 thorn, all more or less valuable for their beauty 

 or the uses to which their timber may be ap- 

 pHed. Malic acid is contained in considerable 

 quantities in apples, and yet more abundantly in 

 the berries of the Mountain Ash. The flow^ers, 

 bark, and root of the last-named tree yield also 

 a large quantity of prussic acid. 



TAMARISCINEiE. 



TAMARISK TRIBE, 



A small order, comprising bushy trees with rod- 

 like branches and a light feathery spray, no part 

 of the leaf being expanded into a plate, but the 

 foliage consisting entirely of scales, which are 

 closely pressed to the stem. Hence the trees of 

 this order are eminently adapted for growing in 

 exposed situations, w^here indeed they are usually 

 found. The majority grow by the sea side, others 

 are found by the banks of rivers and torrents, or 

 in arid districts where the soil is impregnated w^ith 

 salt. In Arabia, one species {Tamarix manmfera) 

 has its branches invested with a sweet mucilaginous 

 substance, which is collected by the monks of 

 Mount Sinai, and sold as a substitute for sugar. 



