166 



THE INDIA RUBBER WORLD 



[January 1, 1912. 



of the cradle," or destruction of young and growing shrub, as 

 anything that appears like guayule will be cut and shipped to 

 the factories by shrub owners greedy for money. 



Walter E. Parker. 

 General ^Manager, The Mexican Crude Rubber Co. 



A GUAYULE RESUME. 



[In connection with the subject of guayule it seems apropos 

 to reproduce the major part of a paper communicated to the 

 Canadian Section of the Society of Chemical Industry, by 

 Harold von der Linde, vice-president of the Continental Rubber 

 Co. of New York. This is the best non-technical resume of the 

 whole subject of guayule which has yet appeared.] 



D ECENTLY a new source of revenue has been found in Nor- 

 •^ * thern Mexico in the shape of the guayule plant. This plant 

 belongs to the order of Compositae and is a small shrub, weighing 

 about two pounds and standing about two feet high when full 

 grown. It has a dwarfed and gnarled appearance which is very 

 characteristic, and has a sparse olive-green, lanceolate leaf. It bears 

 a small yellow composite flower of an agreeable odor. The 

 guayule shrub contains an extraordinary small amount of mois- 

 ture, and indeed might be mistaken for a piece of dead wood 

 during a large portion of the year were it not for the fact that on 

 cutting into it the bark shows a greenish and somewhat moist 

 section. The w'ood of this shrub is very hard and dense, and 

 has a high specific gravity. Tlie shrub grows on the Northern 

 part of the Central Mexico Plateau in enormous quantities. This 

 district is nearly rainless and is very sparsely populated by a 

 partly Indian, partly Spanish, very poor race. The region is 

 practically grassless and contains no large trees, being a typical 

 desert country. The alkali dirt which is found over most of the 

 plateau is in reality a very rich soil needing only sufficient water 

 to make of the region one of the most fertile in the world. 



Geologically, this region, which has been described with some 

 minuteness by Humboldt, consists of rings of denuded mountains 

 with flat plains at their feet. These flat plains of dry dirt have 

 the appearance of dried-up lakes and this impression is height- 

 ened by the fact that the valleys communicate with one another 

 through gaps or canyons in the mountains, which appear to have 

 been the beds of former rivers. On what might appear to have 

 been the beaches of the ancient lakes — that is to say, on a strip of 

 land running around each ring of mountains somewhat above 

 their bases, the guayule abounds. As a rule the soil selected by 

 the guayule shrub appears to be most unpromising, as the so- 

 called beaches are usually covered with flinty pebbles, many of 

 which have not proceeded very far in the process which usually 

 gives to pebbles a somewhat regular oviform shape. There is a 

 considerable variety of plants growing in the direct neighborhood 

 of these so-called old beaches. In the month of August, 1909, in 

 the course of an hour I picked thirteen varieties of flowers within 

 a very short distance of such a region. The soil under the 

 pebbles in the guayule districts is usually gravelly and less 

 tightly packed than the soil of the plains beneath, which is really 

 largely a dried-out heavy clay. The sub-soil of those beaches on 

 which guayule flourishes is said to be universally composed of 

 white magnesian marl called "Caliche." 



The droughts of this plateau region are sometimes very pro- 

 longed, and in the guayule lands (which range from about 4,000 

 to 8,000 feet above the sea) it is not uncommon to have a whole 

 year practically without rain. On one hacienda in the heart of 

 the rubber district, there was recently a drought, practically 

 complete, of over two years and yet the desert plants managed 

 to cling to life. That this should be possible is accounted for by 

 the fact that each one of the plants has some kind of protective 

 apparatus which either enables it to lie dormant without evapora- 

 tion, or to store up water in a large quantity, or to get more 



than its ordinary share of water. In this way the Maguey, or 

 American Aloe, the Nopal or Prickly Pear, the Yucca or Palma, 

 and many others, store up the water to an enormous extent in 

 the occasional wet seasons ; and as all of these have glazed 

 leaves from which evaporation is extremely slow, they are able 

 to resist prolonged drought. The mesquite bush and some other 

 plants show little but their branches above the ground, the 

 greater part of their trunks being buried, and their roots 

 extending far down into the earth seeking for water. In North- 

 western Mexico it is stated that mesquite rootlets can be seen in 

 copper mine workings at a distance of from 120 to 130 feet 

 below the surface. The fact that the trunks of this tree are so 

 deeply buried and that so many of the rare springs of northern 

 Mexico are situated on the precipitous sides of the denuded 

 mountains, gives rise to the paradoxical saying that in this 

 country one has to climb for water and dig for wood. 



A third class of plants depends for its preservation on the 

 fact that it possesses a waterproof cover — a sort of mackintosh 

 coat — which almost entirely prevents evaporation during the dry 

 seasons. Amongst these are the Gobernadora or greasewood, 

 which secretes an enormous proportion of a very curious and 

 complex resin ; the Candelilla, which is completely covered with 

 a coating of very hard, impervious wax ; and the guayule, which 

 possesses a very thick bark, in the cells of which solid rubber 

 is secreted, forming a more or less complete coating for the 

 plant. In this last case the mackintosh coat is practically the 

 only defence that the plant possesses, as the roots are not long 

 and do not sink deeply. As the guayule shrub does not take up 

 a very large quantity of water even in the wet season it is neces- 

 sary for its cells to become dormant and practically lifeless during 

 the rest of the year. 



Most of our sources of rubber, of which there are probably 

 at least two hundred commercial kinds, consist in the milky 

 juices of a large number of tropical plants. The guayule plant 

 is exceptional in that it yields no milky latex — the rubber existing 

 in the solid state, partially filling the cells of the bark — the cells 

 themselves being lined by a resin which consists probably partly 

 of incipient rubber and partly of degraded oxidized rubber. The 

 plant also contains a considerable amount of two or more essential 

 oils, which give it a very characteristic and not disagreeable odor. 

 Rubber is contained in other parts of the plant besides the bark, 

 but in a smaller quantity, although it is abundant in the roots. 

 It was, of course, not possible to gather the rubber from this 

 kind of plant in the usual way — by tapping, that is — and special 

 methods had to be devised in order to extract it. These methods 

 in the past were both chemical and mechanical, but the mechanical 

 method has now superseded the chemical, which latter is but little 

 used. 



The guayule plant probably lives to the age of forty or fifty 

 years in favorable cases. It is said to be mature in from five 

 to ten years; but very little is certainly known on this subject, 

 and very much of its growth depends upon the rainfall, so that 

 in some districts it is probable that it matures very much earlier 

 than in others. The amount of rubber borne by the plant is 

 generally taken as being about ten per cent. There is a very 

 great variation, however, in the yield of plants gathered in differ- 

 ent districts. Some of the worst grades of guayule shrub will 

 not yield as much as 10 per cent, of rubber, while some of the 

 better grades will yield more. Guayule shrub appears to have the 

 power of hybridizing with other plants. The hybrids, if such 

 they be, have the power of secreting rubber, but it is in very 

 small quantity and usually of poor quality. 



Reproduction occurs in this plant by budding from rootlets 

 and by seed. Of these two methods the seed seems to be the 

 usual vehicle through which new plants appear. Each plant 

 bears an enormous number of seeds, but a large proportion is 

 found to be infertile. 



The history of the guayule industry is very brief. The plant was 

 used for many years in the back country of northern Mexico as 



