292 THE liLACK WATTLl-. INnUSTRV. 



But here again curious phenomena are noticed, for upon an 

 old cattle kraal, or the site of a former Kaffir kraal, both of 

 which sites should be i)articularly rich, it is hardly possible to 

 get a wattle crop raised, and even individual trees which survive 

 are seldom up to the average of similar widely-spaced trees else- 

 where. 



And again, on native lands which have been cultivated in 

 mealies for years without manure a wattle crop germinates 

 freely, but continues a somewhat languid existence as compared 

 with what happens on adjoining land which has not been culti- 

 vated. 



I cannot think that the mealie has removed any necessary 

 manurial ingredient, as the effect is not the same or, at least, not 

 so ])ronounced after good European cultivation, but I do think 

 that the continued bad cultivation of mealies has either en- 

 couraged the abnormal propagation of some bacterium inimical 

 to the wattle, or it has produced conditions unfavourable for 

 the production of the wattle-aiding bacterium. 



If such be the case, that is an instance where the artificial 

 a])plication of Nitragin might be of advantage, but this has still 

 to be proved. 



It is well-known that the open mountain sourveld resulting 

 from the decomposition of dolerite is the soil on which the best 

 growth of wattle is obtained, though it is the worst for most 

 other agricultural crops; also that the wattle bearing quality 

 decreases with an increase of clay, and that, generally speaking, 

 what are known as sweet-velds and thorn-velds are not suitable 

 for wattle. 



The proximity of shale, or its admixture in the soil, is 

 usually injurious, and though wattles do sometimes do well on 

 sandstone or ([uartzite. more selection of site has to be exercised 

 there than elsewhere. 



In Natal the mist-belts and the doleritic soils often go to- 

 gether, and these are imdoubtedly the best localities ; on the 

 other hand, the close-grained thornvelds and absence of mist 

 usually go together, and are the worst wattle sites. 



An article by Mr. C. Williams, Chemist of the Cedara School 

 of Agriculture, a])pearing in the South African Agricultural 

 Jourual, 1914, pp. 79 to 88, gives a series of chemical analvses 

 made at Cedara, the first of which shows the percentage of 

 tannin contents of trees of various ages from one to nine years, 

 which is far from imiform or progressively increasing from 

 youth onward, and i)roves nothing in that respect, but in which 

 the lowest percentage 28.6 per cent, is from trees on thin soil 

 over shale, while the highest normal percentage, 34.5 per cent., 

 is from a dolerite ridge; though two interesting abnormal cases 

 are also given, in which a three-year-old plantation damaged by 

 hail a few months earlier gave 35.3 per cent., though its bark 

 weight was low, while an eight-year-old plantation " below 

 average in growth " gave 34.7 per cent., also on low bark weight. 

 It appears from this and from other experience, that certain 

 classes of injury or retardation of growth tend to increase the 

 percentage of tannin though they reduce the production of bark. 



