August, 1909.] 



109 



Saps and Exudations. 



market, and the outcome is awaited 

 with interest. Rubber produced in this 

 way should run lower in resin than that 

 obtained directly by the other processes. 

 The great bulk of the Guayule rubber 

 now coming into the market is obtained 

 by the third, the mechanical process. In 

 this the shrub is crushed and then 

 ground with water in pebble-mills. The 

 rubber in the plant theu becomes appa- 

 rent as small particles ^ inch in diameter 

 and from T V to | inch long. The details 

 of the succeeding operations to separate 

 the rubber from the woody matter are 

 for the most part kept secret and doubt- 

 less vary in different factories, but it 

 may be said in a general way that the 

 procedure is based on the fact that when 

 soaked with water the woody fibre 

 becomes water-lodged and sinks, while 

 the rubber being lighter than water 

 floats on the surface of the tanks and is 

 skimmed off. It is then washed, sheeted 

 on steel rolls, and either shipped moist 

 or first dried by hanging the sheets in 

 any airy room or by heating gently in a 

 vacuum. If the mechanical process is 



properly conducted, a practically com- 

 plete extraction of the rubber from the 

 shrub is secured. 



Guayule rubber obtained by the 

 mechanical process is black on the 

 surface when it reaches the market, but 

 olive to light brown within. The dry 

 crude rubber contains about 20 per 

 cent, resin. Some factories also produce 

 a brand from which the resin has been 

 in great part extracted, but the demand 

 for this seems comparatively small. 

 Guayule rubber softens more quickly on 

 the rolls than most other rubbers, and 

 therefore requires to be handled some- 

 what differently, but once this is under- 

 stood, the working of Guayule rubber of 

 good quality presents no difficulty. It 

 can be substituted for many of the 

 African rubbers, is used to advantage 

 in boots and shoes and many other lines 

 of manufacturing, and seems to be grow- 

 ing in favour. The Guayule rubber 

 recently reported as received at the 

 port of New York was— September 

 850,000 lbs,, October929,5001bs., November 

 1,444,000 lbs. 



DYES AND TANS. 



BLACK WATTLE. (ACACIA 

 DECURRENS). 



By D. B. Hutchins. 



(From the Agricultural Journal of 

 British East Africa, I., Pt, L, April, 1909.) 



The well-known Wattle that has been 

 so largely planted in Natal (under the 

 name of A. Mollisima) is Acacia de- 

 currens variety mollis. The averae-e pro- 

 duction cf bark, mine-poles and firewood 

 is estimated as being worth £100,000 a year 

 for Natal, £75,000 for bark and £25,000 

 for poles used locally or sent to the 

 mines. It grows best in Natal at ele- 

 vations between Maritsburg and Colenso, 

 particularly along the so-called "mist 

 belts." The coastwise limit of good 

 growth is at Inchanga 2,000 feet ele- 

 vation, 40 inches rainfall, and about 30 

 miles from the sea. The mean temper- 

 ature at Inchanga would be about 63° 

 or 64^ which is the mean temperature 

 of Nairobi. There are several varieties 

 of Black Wattle, viz., mollis normalis, 

 pauciglandulosa, leichardtii. The three 

 last occur in Queensland. Two at least 

 of these are growing in Natal. A. de- 

 currens var. mollis is the commonest in 

 Australia, and that which is almost ex- 

 clusively planted in Natal, Cape Colony 

 and the Transvaal. Normalis is the local 



Sydney variety, and leichardtii and 

 pauciglandulosa local varieties found 

 north of this as far as the tropics. As 

 an ornamental tree the normalis variety 

 is the prettiest with its delicate foliage, 

 like that of Asparagus creeper in our 

 ferneries. At Tokai near Cape Town 

 this variety has been grown sufficiently 

 abundantly to yield a fair supply of seed. 

 I have seen occasional specimens of it in 

 Natal. It is well worth growing as an 

 ornamental tree. The Black Wattle is 

 one of the "Golden Wattles" of Aus- 

 tralia, and all its varieties most beauti- 

 ful when in flower in Spring. 



Those who wish to consult an Aus- 

 tralian work on the subject of Wattle 

 growing cannot do better than read 

 " Wattles and Wattle Barks, being hints 

 on the conservation and cultivation of 

 Wattles, together with particulars of 

 their value" by J. H. Maiden, Govern- 

 ment Botanist, N. S. Wales, (Technical 

 Educational Series, No- 6, Sydney.) 



Those who are interested in Black 

 Wattle cultivation in Natal should read 

 an excellent paper by Mr. T. R. Sim, 

 Conservator of Forests, printed in a re- 

 cent number of the Natal Agricultural 

 Journal. 



The data given below are extracted 

 from Mr. Sim's paper and my own 

 otes during a visit to Natal, 



