THE ROOTS OF THE HEVEA 33 



breathing. When the soil is water-logged the roots infallibly 

 suffer. The importance of a thorough system of well-laid-out 

 drains can scarcely be over-rated, especially on flat, low-lying 

 estates. 



While the roots have willing friends in the soil, the beneficial 

 bacteria which supply them with the nitrates and ammonia 

 necessary for food and growth, enemies also lurk there. Deadly 

 fungi lie in wait, ever seeking an opportunity to attack where 

 there are decaying roots of jungle trees to harbour them, 

 or where there is soured soil. The roots of the Hevea, unable 

 to retreat, fall easy victims unless speedy assistance is given. 

 The root idea of every rubber-planter ought to be cultivation. 

 In a well-aerated soil fungi have less opportunity for their 

 malignant action. One would think that it would be evident 

 that when there is close-planting and the roots occupy, nay, 

 crowd, all the available space, there can be no possibility 

 of cultivation. Yet, to this day, well-known planters, and 

 especially Ceylon planters, actually advocate planting 10 feet 

 by 10 feet, attempting to make up for this closeness by culti- 

 vating and heavily manuring the soil. It makes one feel that 

 the conditions cannot be properly understood. 



If one considers a tall Hevea tree 40 or 50 feet in height 

 and under favourable circumstances a Hevea grows to 80 or 

 90 feet high it will be seen what a serious problem the tree 

 has to face to supply not only the cells of the roots and stem 

 with sufficient supplies of moisture, but even the furthest leaves 

 at the tips of its branches. Yet this is necessary. Without 

 supplies of water the leaves cannot manufacture food. The 

 trees have no mechanical pumps at their service wherewith 

 to raise water to such a great height. How, then, do they 

 succeed in supplying their requirements? By two methods, 

 at least working together; by means of root pressure and by 

 means of evaporation. 



The outer cells of the roots and the root-hairs have their 

 walls constructed so as readily to absorb water when enveloped 

 by the moist earth. When the water has entered these 

 cells, it cannot pass outwards again. The cells in question 

 behave as if they have valves which permit the entrance of 

 fluids from without, but which promptly close down on any 

 effort of the water to escape by the apertures where it entered 



