4 o2 SCIENCE PROGRESS 



three main primary limbs, and to each of these three secondary 

 branches — nine in all. Wright 1 also favours it, though pointing 

 out that it is unwise to practise it on trees growing in a light 

 soil and exposed situation, for they would in time be liable to be 

 blown over by strong winds, owing to the weight of leaf canopy 

 produced ; they would, in fact, be more top-heavy than unforked 

 trees. 



Petch, 2 mycologist to the Ceylon Government, fears that 

 such treatment will favour the entrance of the fungus Corticium 

 javanicum, a somewhat dreaded bark disease. Ryckmann states 

 that in Java and Sumatra this fungus attacks chiefly the forked 

 trees, either natural or induced. The cleft affords a lodging- 

 place for spores. A split in the wood is liable to occur here 

 through wind or other causes, thus allowing the entrance of the 

 fungus-hypha, and so the commencement of disease. 



Catch Crops. — As a newly planted area of Para rubber will 

 give no return for at least five or six years, and as between 

 the widely planted trees there is much unoccupied ground, 

 some profit may be immediately secured by growing what are 

 called catch crops. Though their cultivation may lead to the 

 payment of small dividends before the rubber comes into 

 bearing, their value is to some extent doubtful, as these inter- 

 planted crops frequently retard the growth of the rubber 

 trees. Cassava (Manihot utilissima) has been largely used, but 

 it is hardly a desirable plant to employ, as botanically it is 

 too nearly related to Hevea. A disease or insect enemy which 

 attacks the one will most likely spread to the other. The 

 subject of catch crops and their desirability is dealt with fully 

 in Wright's book. 3 There is much to be said for and against 

 their cultivation. 



Protective Belts. — A large uninterrupted area occupied by a 

 single species of plant offers a most suitable field for the spread 

 of a fungus or an insect foe. There is nothing to check 

 a disease commencing at one point from spreading rapidly 

 over the whole plantation. Consequently a system of blocks, 

 separated from one another by screens composed of other 



1 H. Wright, Hevea brasiliensis or Para Rubber, 3rd edit. 1908, 48-51. 



2 Petch, Circular and Agric. J ourn., Roy. Bot. Gardens, Ceylon, 1909, No. 21, 

 vol. iv. p. 193. 



3 H. Wright, Hevea brasiliensis or Para Rubber, 3rd edit. 1908, pp. 51-6 (the 

 standard work on rubber cultivation). 



