Gums, Resins, 



1 



[January, 1910. 



a number of common names, such as 

 palo amarillo, palo Colorado, papelillo, 

 and cucuracho, the first-mentioned name 

 being generally used. Jfc occurs in the 

 dry semi-tropic zone on the slopes of 

 Sierra Madre, at an elevation of 900 to 

 4,800 feet, generally being found above 

 the oak zone, and frequently reaching 

 as high as the pine zone of the moun- 

 tains. It extends southwards from 

 Durango to the southern part of Oaxaca, 

 along the Pacific coast, growing on 

 rather poor, rocky or sandy volcanic soil, 

 and it often forms a part of the xero- 

 phytic plant formations that have 

 established themselves on the dry moun- 

 tain sides. The tree grows to a height 

 of between twenty and thirty-four feet, 

 with a trunk diameter of from seven to 

 twelve inches. In the inner bark of the 

 stem and its branches occur numerous 

 latex-bearing vessels, containing a semi- 

 liquid fluid of milky whiteness, which 

 solidifies on contact with the au\ 

 Chemical examination of this latex 

 shows that it contains from 7*3 to 15*7 

 per cent, of rubber, and from 19 per cent, 

 upwards of resins. The United States 

 Consul at the city of Mexico says that he 

 has personally analysed seventeen latex 

 samples from different parts of the tiees, 

 and from trees growing in different 

 soils. The latex from the lower parts of 

 the trunk contains the higher percent- 

 age of rubber, as is the case with all 

 rubber-producing trees. The branches 

 carry a latex containing mainly resins, 

 the rubber being about 3 to 6 per cent, 

 and occurring in a form which makes it 

 very difficult to be separated from 

 impurities. The coagulation of the 

 latex is not easy, although it can be 

 accomplished. The resulting rubber is 

 of inferior quality and would commer- 

 cially be classed with Guayule rubber, 

 which, it is stated, has commanded a 

 price of about one shilling and three- 

 pence, whereas the price of first-class 

 wild Para rubber was 3s. and 9d. per 

 pound during the last year when rubber 

 prices were low. It may be noted 

 that rubber made according to modern 

 methods from the ordinary Mexican 

 rubber tree-Castilloa elastica—h&s reach- 

 ed the highest standard of Para rubber 

 and has realised the same price. The 

 product of the palo amarillo tree being 

 new, the test of time, which after all is 

 the most important one, has not yet 

 been applied, but taking into consider- 

 ation the low tensile strength, the large 

 percentage of resins, and the rapid 

 deterioration of the latex through 

 enzymes, it is not very likely that palo 

 amarillo rubber will show a better 

 result than the rubber obtained from 

 the guayule shrub. The rubber is easy 



to vulcanise by the ordinary methods. 

 The exploitation of the latex of palo 

 amarillo is beset with considerable diffi- 

 culties. The Consul states that he has 

 tapped these trees in all the different 

 manners generally employed in tapping 

 Hevea, Manihot, Castilloa, Funtumia, 

 Ficus, or Sapium trees, and he has used 

 over twenty of the different tools and im- 

 plements, patented and employed in the 

 rubber fields in Brazil, Central America 

 and Africa, and he says that the proper 

 method of tapping palo amarillo is not 

 easy to determine. It is claimed that 

 the palo amarillo tree is very easily 

 propagated. A young branch cut from a 

 growing tree and planted in the ground 

 will grow. Commercially this does not 

 mean much as the exploitable age of a 

 palo amarillo tree must be at least ten or 

 eleven years. A tree of this age does 

 not give a very large amount of latex. 

 The ordinary Mexican rubber tree, 

 Castilloa elastica, can be exploited when 

 eight years old, and it then gives a 

 larger yield of latex per annum than a 

 ten year old palo amarillo tree. Con- 

 sidering that the latex of the former 

 contains from 25 to 47 per cent, of pure 

 rubber, against about 8 per cent, in the 

 palo amarillo latex, it is difficult to see 

 the advantages of the latter under 

 cultivation. 



THE CULTIVATION AND PREPAR- 

 ATION OP PARA RUBBER * 



(Prom the Gardeners' Chronicle, Vol. 

 XLVI., No. 1192, October, 1909.) 



To Mr. W. H. Johnson belongs the 

 distinction of having, some four years 

 ago, written the first treatise devoted 

 exclusively to Rubber, As might have 

 been expected, when the rapid growth 

 of the rubber industry and the ex- 

 cellence of Mr. Johnson's text-book were 

 considered, the first edition was soon 

 exhausted. 



The present, second, edition has been 

 thoroughly revised and extended to in- 

 clude a wider range of information. 

 The statistics relating to rubber afford 

 the raw material for a striking chapter 

 in the romance of modern industry. 

 Prom 1770, when Priestly recommended 

 its use for erasing lead-pencil marks, till 

 the twenties of last century, when 

 Macintosh began to manufacture water- 

 proofs, the use of rubber was remark- 

 ably limited. The extension of its em- 

 ployment dates from 1836, when Thomas 

 Hancock discovered that crude rubber, 



* The Cultivation and Preparation of Para 

 Rubber, by W. H, Johnson, F.L.S. (London: 

 Crosby, Lockwood & Son. ) 7s. 6d. 



