u8 



the roots, and not as a regular storehouse of nutriment from which 

 the plant can at once take up the full of its requirements. I well 

 remember an eminent Chemist remarking to me on the excessively 

 barren character of the soils of the interior in certain parts of the 

 mainland, as shown by analysis, and yet these same lands had 

 grown large tracts of forest and the trees were giants. There can 

 be no doubt whatever that such growth is due, not to the natural 

 or contained fertility of the soil, but to the incidental increment 

 which is continuously being added in the course of seasons by 

 natural accumulations. That leaves and flowers have long been 

 known as fertilizers of no mean kind by practical men goes with- 

 out saying, but the exact manner in which nutriment is taken up 

 and the exact quantity of plant food which is annually derived 

 from this source is yet to be fully determined. In a recent paper 

 on the flowers of the " Bois Immortel" or Erythrina sp. (reprinted 

 in this Number) the large proportion of nitrogen which they con- 

 tain was pointed out and an argument was based upon it for the 

 continued use of this tree for shading cacao plantation. It has 

 been known, however, that the flowers of all kinds of trees contain 

 large amounts of nitrogen, and that it is quite as probable that 

 the flowers of any trees that might be substituted as shade for 

 cacao would contain as much nitrogen as the " Immortel '". 



There can be no doubt whatever that this incidental increment 

 is valuable, as are many others as yet undiscovered or unrecognis- 

 ed, especially so the amounts of nitrogen distributed by the crops 

 of seed from leguminous trees, which fall and rot, for the most 

 part upon the ground. The incidental increment deposited in the 

 form of the excreta of birds, reptiles and insects, and by the death 

 and decay of their bodies is as yet an uncalculated item, and yet it 

 will be found on examination that it is sufficient to account for the 

 supply of certain plant food which would be otherwise absent. 

 The lime and phosphate in the bones of an animal or reptile is 

 comparatively small, but still their bodies give to the soil consti- 

 tuents, which it requires for nourishing certain kinds of plants. It 

 is often argued that as so many thousand bushels or bags of cacao 

 are sent out of Trinidad that the soil must in time become ex- 

 hausted, and the argument follows this line when a supply of 

 nitrogen from the flowers of the " Immortel " is spoken of. We 

 find, however, cacao plantations in full bearing which have been 

 under cultivation 50 or 60 years and producing to-day as much as 

 in the first instance, and without artificial manure. We might be 

 told that the supply of plant food naturally existed in the ground 

 and was made available as required. If we accept this, then it is 

 clear we ought to be able to ascertain exactly by analysis how 

 much food the soil contains and how long the supply will last. 

 But this has as yet never been done, for there has always been the 

 ''incidental increment" which daily and hourly accumulates to 

 upset this addition and subtraction theory, which is so neatly pro- 

 pounded in many cases in the teaching of non-practical men. We 

 are told that so many tons of plant food is removed, but we seldoni 

 get the amount per tree, as the amount would appear too insignia 



