Miscellaneous, 



168 



[August, 1911. 



Samples of these black soils have been 

 analysed and compared with samples 

 of the red soils where pineapples make a 

 thrifty growth. The following results 

 were found : — 



1. The black soils contain less acidity 

 than the red soils. 



2. Only one important difference 

 has been found in the chemical composi- 

 tion of these soils, viz., in regard to the 

 manganese content. The black soils 

 contain many times as much manganese 

 as the red soils. The black colour of those 

 areas may in part be attributed to the 

 presence of higher oxides or manganese, 

 the presence of which is evidenced by 

 the hydrochloric acid test. 



3. The black and red spots are not 

 separated by sharp lines of division, but 

 rather gradually merge cne into the 

 other. There is, therefore, an interme- 

 diate area surrounding the yellow spots 

 on which the pines show the yellowing 

 to a lesser degree. With the view of 

 determining whether the manganese 

 likewise decreases in passing from the 

 black soil to the red, several series of 

 samples from different places were 

 drawn at regular distances apart in pass- 

 ing from the black to the red soil. Ana- 

 lysis of these samples has revealed the 

 fact that there is a close correlation 

 between the degree of yellowing of the 

 pines and the percentage of manganese 

 in the soil. It has been shown further 

 by the use of the guiacum and aloin 

 tests that the plants grown on black soils 

 are more vigorous oxidizing agents than 

 the plants grown on the red soils. 

 Bertand found that the ash of oxidizing 

 enzymes contains considerable amounts 

 of manganese, and that the addition of 

 soluble manganese salts to the oxidase 

 greatly accelerated their oxygen carry- 

 ing power. All the results obtained 

 above seem, therefore, to point out that 

 the etiolated appearance of the pines 

 grown on black soils is brought about by 

 the increased activity of the oxidase due 

 to tbe presence of large amounts of 

 manganese. Actual oxidation of the 

 chlorophyll seems to take place. An 

 examination under the high power 

 microscope of the cross section of the 

 yellow leaves shows that for the most 

 part the chlorophyll bodies have been 

 destroyed. 



Use of Carbon Bisulphid fob 

 Killing Weeds. 

 (Press Bulletin No. 20.) 



This chemical has been used with 

 success for killing Crotalaria incana, 

 lantana, guava, prickly-pear (Opuntia 

 sp.) and Stachytarpheta dichotoma. 



The carbon bisulphid is poured on the 

 stem at a point about six inches above 

 the surface of the ground, On small 

 stemmed plants like Crotalaria about a 

 tea-spoonful of commercial bisulphid 

 was poured, the amount being increased 

 for larger plants, up to two table-spoon- 

 fuls for guava bushes, eight or ten 

 centimeters in diameter. On most plants 

 carbon bisulphid shows no effect until 

 after the lapse of a considerable period 

 on large guavas, sometimes two or three 

 months. On others the effect is seen in 

 from one to thirty days. When the 

 trees killed by carbon bisulphid were 

 dug out and examined their roots were 

 found to be dead to the tip and their 

 whole tissue discolored. Apparently, 

 carbon bisulphid causes the death of 

 plants by its freezing effect and also 

 by a poisonous action as evidenced by 

 the complete destruction of the roots to 

 their tips, in some instances more than 

 two meters from the point where the 

 carbon bisulphid was applied. 



In working with this chemical, it is 

 always necessary for the workmen to 

 keep to the windward in order to avoid 

 the fumes, which, if inhaled continuous- 

 ly, may produce serious effects. It must 

 be also remembered that the material is 

 highly inflammable and should be pro- 

 tected from accidental flames. In some 

 localities the difficulty of transporting 

 containers may render the method en- 

 tirely impracticable. On the other hand, 

 the use of carbon bisulphid in the 

 destruction of weeds has the advantage 

 that young sprouts do not come up from 

 the roots. The necessity of grubbing 

 out all the roots is thus obviated. Under 

 such circumstances it would merely be 

 necessary to allow the weeds to stand 

 until they are dead, after which the 

 trunk and large roots would be removed, 

 as is necessary in any case ,in clearing 

 the land. 



For obvious reasons, carbon bisulphid 

 will never become the usual means of 

 getting rid of weeds. But on a small 

 scale, and specially in dealing with 

 weeds which can grow from fragments 

 left in the ground, it has a use in supple- 

 menting other methods. Regarding 

 its effect upon the soil, the balance 

 of the scanty evidence indicates that 

 it is favourable ; and this is explained 

 by the recent observation at Rotham- 

 sted that it will completely destroy all 

 protozoa in the soil, but not quite 

 all the bacteria on which the protozoa 

 feed. The nitrogen-fixing bacteria, 

 freed of their enemies, multiply rapidly, 

 and soon causb a great increase in the 

 amount of available nitrogen. 



