IN EXTRA-TROPICAL COUNTRIES. 7 



but its yield is less, as the tree is smaller and the bark thinner. 

 It is of rapid growth, content with almost any soil, but is gen- 

 erally found in poor sandy ground near the sea-coast, and thus 

 also important for binding rolling sand. Experiments instituted 

 by me have proved the artificially dried bark to contain from 

 30 to 45 per cent, tanning principle, full-grown sound trees 

 supplying the best quality. The aqueous infusion of the bark 

 can be reduced by boiling to a dry extract, which in medicinal 

 and other respects is equal to the best Indian catechu, as 

 derived from Acacia catechu and A. suma. It yields about 30 

 per cent., about half of which or more is mimosa-tannic acid. 

 This catechu is also of great use for preserving against decay 

 articles subject to exposure in water, such as ropes, nets, fishing- 

 lines, &c. While, according to Mr. Simmons, the import of 

 the bark of oaks, hemlock-spruce, into England becomes every 

 year less, and while the import of sumach and gambir does 

 not increase, the annual demand for tanning substance has 

 since the last twenty years been doubled. A. pycnantha is 

 also important for its copious yield of gum, which is in some 

 localities advantageously collected for home consumption and 

 also for export. By improved methods the fragrant oil of the 

 flowers would doubtless be fixed, though its absolute isolation 

 might be difficult and unremunerative. 



Acacia retinodes, Schlechtendal. 



South-East Australia. Ascertained already in 1846 by Dr. 

 Hermann Behr to yield a good tanner's bark and much gum. 

 This Acacia is ever-flowering, and in this respect quite excep- 

 tional. It likes river banks, but never grows beyond the height 

 of a small tree. 



Acacia saligna, Wendland.* 



South-West Australia, where it is the principal tree chosen for 

 tanner's bark. It is a wide-spreading small tree, fit for avenues. 

 The bark contains nearly 30 per cent, of mimosa-tannin, and 

 is extensively used by tanners in West Australia. The tree 

 has proved in Algeria to resist the sirocco better than most 

 species (Dr. Bonand). A. cyanophylla (Lindley) is a closely 

 allied species, serving the same purposes. 



Acacia Seyal, Delile. 



In the Libyan and Nubian deserts. This thorny tree exudes 

 a brownish kind of gum-arabic. It is adapted for the most 

 arid desert country. In any oasis it forms a large and shady 

 tree. Native name " Soffar." 



