

Cultivation of the Orange and Lemon. 127 



would make a perfect bed for all the citrus tribe ; all 

 ingredients, however, should be thoroughly mixed 

 up together. Of course, unless the general soil is 

 naturally rich, or is annually renewed by inundations, 

 as in the case of the Shalla orange groves of the 

 Khasia hills, the trees should be annually manured, 

 when they attain their fruiting age. 



Iron appears to be an important ingredient in the 

 orange soil. It exists in that of the orange groves 

 of Shalla. The red soil of Ceylon is said to be 

 impregnated with iron, and probably the similar red 

 soil of South India, also contains it. I do not know 

 what the composition is of the black soil of the 

 Central Provinces, and other parts ; but probably it 

 contains iron, as the Nagpore oranges do so well in it. 

 I have a notion that iron gives flavor and juiciness to 

 the orange, but to decide this, very careful and pro- 

 longed experiments would be required. However, I 

 may perhaps have discovered a simple mode of detect- 

 ing the presence of iron in the soil, especially when 

 this is not naturally black. I have noticed that in 

 the light coloured soil under - babool trees (Acacia 

 arabica\ after rain, the surface becomes blackened. 

 Tannic acid, with persalts of iron, and gallic acid with 

 proto-salts of iron give a black colour. The babool 

 bark and leaves contain tannin, and the rain falling 

 over a babool tree would naturally wash some tannin 

 on to the ground beneath, tannic acid being soluble 

 in water, in the proportion of ten parts in eight of 

 water. So that it would, I think be possible by the 

 simple means of strewing babool leaves on the ground 

 and watering them, or by irrigating the surface with 

 an infusion of babool bark, to discover the presence 

 of iron in the soil. Anyhow, the probability is that 

 the citrus tree requires it in small quantity, and in 



