THE 



TROPICAL AGRICULTURIST 



AND 



MAGAZINE OF THE 



CEYLON AGRICULTURAL SOCIETY. 



Vol. XXXIII. COLOMBO, NOVEMBER, 15th, 1909, No. 5. 



Manihot Dichotoma. 



Owing to the interest now beginning 

 to be taken in the new species of rubber, 

 it seems desirable to add a few remarks 

 to those made at the Meeting of the 

 Board of Agriculture on April 7tb of 

 the present year. 



Three acres of the abovenamed species 

 have now been planted out at the 

 Peradeniya Experiment Station. On 

 October 8th the first of these acre plots 

 was exactly two years old from the date 

 of planting. The plot contains 98 trees 

 planted 20'*20' feet apart, and the 

 average circumference at three feet 

 from the ground is just niue inches at 

 the time of writing. This average girth in- 

 cludes that of every tree. Those in the 

 outer rows have made very poor growth, 

 probably owing to the proximity of 

 neighbouring dadaps and other trees ; 

 a few supplies are included ; and several 

 stumps broken off by wind at some 

 distance above the ground, but now 

 beginning to sprout again, were also 

 measured. As a precaution against 

 further damage by wind the majority 

 of the larger trees were pruned three 

 months ago, a good many branches 

 being removed in the process, and it 

 may be supposed that this process has 

 retarded growth to some slight extent, 

 Nevertheless the fourteen largest trees 

 show an average circumference of 14 



inches, and have more than doubled in 

 girth during the past year. 



The second plot at Peradeniya con- 

 sists of trees planted 12' x 12' in November, 

 1908 ; so that these plants are row just a 

 year old. The land upon which these 

 trees are growing was ploughed before 

 planting and has been kept cultivated 

 by means of a disc harrow ever since. 

 The result of this treatment seems to be 

 obvious in the growth of the plants, 

 which average quite 6 inches in girth 

 over the whole area and are already 

 producing seed in considerable quantity. 



The third acre has been planted up 

 during the current year. On half the 

 plot the plants stand 8'x8' (planted 

 from cuttings) and on the other half 

 6'x6' (seedlings) in order to test the 

 effect of close planting. 



A marked characteristic of Manihot 

 dichotoma, which is particularly well 

 seen in the acre of year-old trees, is the 

 extraordinary variability of the species 

 in vegetative characters, This is speci- 

 ally noticeable in the shape of the leaves 

 and fruit capsules. In some cases the 

 leaves might almost be mistaken for 

 those of the ordinary Ceara rubber 

 (Manihot Glaziovii), whilst on other 

 trees the leaf lobes are much longer and 

 narrower and deeply wavy in outline. 

 On some trees, again, the seed capsules 

 are nearly smooth (like those of M. 

 Glaziovii, though larger), whilst on 



