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CANE SUGAR.Among other plants grown in tropical countries as green manure areSesbania aegyptiea, Crotallaria pincea and C. laburnifolia, Phaseolus semierectus,Arachis hypogaea (the earth nut), Soja hispida (the soy bean), Dolichos lablab(the bonavist bean), Phaseolus mungo (woolly pyrol), Indigo tinctoria (the indigoof commerce), and, in Hawaii, a variety of lupine.The percentage of nitrogen in some of these plants is given below : 18 —Sesbania aegypticaCrotallaria labumifoliaPhaseolus semierectusArachis hypogaea PlantArachis hypogaea Fruit .3 er cent.Water.82-3079-8081-0080-00"Per cent.Nitrogen.•68•70•52•582-76Rotations.—Different crops have a predilection for different forms ofmineral matter, and thus remove from the soil very different amounts of thedifferent constituents of plant food, so much so that the ash of a crop may consistin general of one predominant constituent; by growing continually one.and the same crop on the same piece of land there is then a tendency toexhaust one particular constituent. If, however, different crops be grown inrotation, an element of plant food which was removed in large quantities inone year- is not absorbed to such an extent by the succeeding crop, and by thetime the crop first in rotation is planted a second time a sufficiency of theparticular material exhausted by this crop will have become available, due tothe natural process of disintegration which soils are continually undergoing.As an example of such a rotation, the Norfolk system may be quoted; this iswheat, roots, barley, clover; the roots are consumers of potash, the wheattakes up phosphates, the barley absorbs silica, and the clover feeds largely onlime and magnesia.It is especially to be noted in this rotation that the wheat follows theleguminous crop of clover; wheat is a crop that responds to a supply of nitrogenin this case in part provided by the root residues of the clover; the cane, too,demands, as is shown in the manuiial trials quoted above, for its successfulgrowth a supply of readily available nitrogen, and in certain districts aleguminous crop precedes the cane crop.Cane growing districts may be divided into those where the cane formsthe sole output of the soil, and those where it is alternated with other crops.Into the first category fall the districts of Cuba, the Hawaiian Islands, BritishG-uiana, Trinidad, Eiji. In Java, Egypt and British India, a completerotation is practised, and in Louisiana and Mauritius the cane fields arerotated with leguminous crops which are ploughed in.In Egypt, on the lands controlled by the Daiia Sanieh, cane was grownfor two years, preceded by a year's fallow; following on the cane crop corn andclover were grown; the cane itself was not manured, with the object of