in Extra- Tropical Countries. 159 



equally hardy, not advancing naturally to extra- tropical latitudes. 

 This reminds us of the great Council-tree, F. altissima, from Java, 

 where it grows in mountains on calcareous ground. F. eugenioides 

 (F. v. M.) from North- and East- Australia, attains a height of 100 

 feet, and produces also columnar air-roots. It is comparatively hardy, 

 reaching extra-tropic latitudes. 



Ficus elastica, Roxburgh.* 



Upper India, to the Chinese boundary, known as far as 28 30' 

 north-latitude. A large tree, yielding its milk-sap copiously for the 

 kind of caoutchouc called Assam-Rubber. Roxburgh ascertained 70 

 years ago, that india-rubber could be dissolved in cajaput-oil (very 

 similar to eucalyptus-oil), and that the sap yielded about one-third of its 

 weight of caoutchouc. This tree is not of quick growth in the change- 

 able and often dry clime of Melbourne; but there is every prospect, 

 that it would advance rather rapidly in any mild humid forest-gullies, 

 and that copious plantations of it there would call forth a new local 

 industry. This tree has grown in Assam to 112 feet with 100 aerial 

 roots in thirty-two years (Markham). In moist Warm climes, accord- 

 ing to observations in Assam by Mr. Gustave Mann, branches lopped 

 oil and planted will speedily establish themselves. Single branches 

 attain a length of 50 feet; the root-crown will attain a diameter of 

 200 feet exceptionally (Haeckel). The import of caoutchouc into the 

 United Kingdom in 1884 amounted to 198,000 cwt., representing a 

 value of 2,266,000, of which F. elastica must have furnished a con- 

 siderable proportion. Markham and Collins pronounce the caoutchouc 

 of F. elastica not quite so valuable as that of the Heveas and Castil- 

 loas of South- America. Heat and atmospheric moisture greatly pro- 

 mote the growth of F. elastica. Like most other Fig-trees, it is easily 

 raised from seed. A tree of F. elastica is tapped in Assam when 

 twenty-five years old. After fifty years the yield is about 40 Ibs. of 

 caoutchouc every third year, and lasts till the tree is over 100 years 

 old. The milky sap flowing from cuts in the stem yields nearly one- 

 third of its weight of caoutchouc; the collected sap is poured into 

 boiling water and stirred till it gets firm; or the sap is poured into 

 large bins partly filled with water; the fluid caoutchouc-mass after a 

 while floats on the surface, when it is taken out and boiled in iron- 

 pans, after the addition of two parts of water, the whole being stirred 

 continuously; after coagulation the caoutchouc is taken out and 

 pressed, and if necessary boiled again, then dried, and finally washed 

 with lime-water. The sap from cuts into the branches is allowed to 

 dry on the trees (J. Collins). Dr. S. Kurz states, that F. laccifera (Rox- 

 burgh) from Silhet is also a caoutchouc-tree, and that both this and 

 F. elastica yield most in a ferruginous clay-soil on a rocky substratum; 

 further, that both can bear dryness, but like shade in youth. Several 

 other species of tropical figs, American as well as Asiatic, are known 

 to produce good caoutchouc, but it is questionable, whether any of 

 them would prosper in extra-tropical latitudes; nevertheless for the 

 conservatories of botanic gardens all such plants should be secured 



