1897.] Dr. H. A. Cammins — A Theory of Vegetable Antitoxins. 19 



to be a variety of the same species, produces in Bengal a great quantity 

 of the same resin. 



If plants of warm or tropical regions be placed in our hot-houses, 

 their secretions are either not formed at all or in diminished amount 

 (Bentley, op. cit., p. 824). An almost corresponding difference in disease, 

 poisons may be noted in different countries. We find ague present to a 

 slight extent in England, the poison being of a mild character, while in 

 India and Africa, in many localities, the poison is most intense. 

 Similarly tetanus is said to be very common in Lower Bengal and in 

 the West Indies, especially among horses. Many of these instances may 

 be explained by saying that the heat and moisture facilitate the develop- 

 ment of lower organisms, in the same way as the higher plants grow 

 with a magnificent luxuriance unknown in temperate climates. The 

 poisons of Asiatic cholera and dysentery are very capricious in tlieir 

 choice of habitats. From all these cases we may assume that organic 

 poisons vary greatly in power in the soil with the country in which they 

 occur and this plainly shows the multifarious influences to which the 

 roots of plants must be constantly subjected. We know that certain 

 organisms are harmless or otherwise to animals and the same can be 

 Slid of plants on account of the similarity of their cell-action which has 

 been explained. 



Sec. Y. Contact of peotophytes with roots in the soil — 

 Transpiration. 



Lastly let us consider the probability of contact of these organisms 

 with the roots. We know that a large amount of aqueous vapour is 

 transpired from the leaves : in the case of the oak this amounts to eight 

 and a half times the rainfall over the area covered by the foliage of the 

 tree ; in the Eucalyptus globulus it amounts to eleven times the rainfall. 

 From these facts we clearly see that trees tend to dry the soil, and that 

 the abstraction of water from the area penetrated by the roots, at 

 first tends to dry it ; but there would be a tendency for the water 

 to percolate from the surrounding soil to the immediate vicinity of the 

 roots when extraction was taking place and consequently the former 

 area would be kept constantly moist. Bacteria require a moist or 

 fiuid medium for development and consequently we can imagine that 

 the area af the roots would be infested with them on account of the 

 moisture which exists there, and that they would be likely to cluster 

 round the roots. In many cases this would probably be prevented by 

 the exudation from the roots of toxic substances in order to help the 

 epidermal cells of the root to resist the entrance of these organisms. 



The action of light, heat and electricity are known to have an 



