194 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



5. The possible reduction of shade trees in certain centres, on account 

 of their tendency to encourage pests and disease, and to retard the growth 

 and output of the estate. 



6. The increase of the area of mixed plantations — mixed, not inter- 

 mixed — the hardier trees, such as rubber and others, to be planted as 

 belts around or through the main crop. This will not only remove the 

 risk of relying entirely on one crop, but restrict the area of pests and 

 disease, and, when such appear, enable the planter to treat them at once 

 before the mischief spreads further. 



Other improvements no doubt will come in the train of these, 

 especially as regards the sweating of cacao, of which we still have but an 

 indifferent knowledge. Whilst on this point I should like to call attention 

 to " Bulletin " No. 10 of the Surinam Agricultural Department, wherein 

 Dr. Sack, as a result of his investigations into the causes and effects of 

 sweating cacao, makes the following assertion : "The sweating of cacao is 

 primarily a biological and not a chemical process." This was proved by 

 the fact that samples treated, one with formaldehyde and the other with 

 chloroform preparations, both destructive to life, but not influencing 

 chemical activities, did not ferment, while the temperature remained 

 at 28° C. The temperature of the other samples not so treated, but 

 fermented in the usual way, rose from 28° C. (82° F.) to 40° C. (104° F.), 

 but when treated with chloroform fermentation ceased. Another experi- 

 ment showed that sugar in the pulp is essential to fermentation and 

 the incident rise of temperature. This was proved by the fact that 

 beans washed before being put to sweat did not ferment until syrup was 

 added. The vitality of the seed is destroyed during fermentation. The 

 seeds die at 44° C. (111° F.), whilst in sweating in the ordinary way the 

 heat will go up to 112 3 or 113° F. It is also claimed that the 

 change of colour is due to an enzyme. If steeped in boiling water 

 no change takes place until unsteeped kernels are added. This, of 

 course, is nothing new ; Dr. Axel Preyer, in 1901, wrote on the matter in 

 " Tropenptfanzer," and showed that the fermentation of cacao was brought 

 about by living organisms just as is the fermentation of tobacco, &c. 

 Preyer succeeded in breeding pure cultures of these organisms. 



As regards manuring, this matter and the extermination of pests can 

 be said to go hand in hand, for the cacao tree is such a faithful servant 

 that it will wear itself out in fulfilling its duty, and it is not its fault if, 

 as it gets weaker and worn out, it cannot throw off the enemies that 

 attack it. It is for its owner to see that it receives its proper nourish- 

 ment, and is not left to starve while he spends the money on himself 

 that the trees so willingly bring to him. As we now stand we have in 

 many of the older centres to cure the diseases, but to cure is by no 

 means sufficient, the planter must take precautions that the disease does 

 not return. This can only be avoided by building up the strength of 

 the tree as you would that of a human being, and so help it to withstand 

 the returu of the old complaint. Recent experiments in the West Indies 

 and elsewhere have proved the great benefits to be derived from mulching. 

 Even when this treatment consisted only in burying leaves and green 

 matter, the trees paid well for the labour involved. Moreover, the results 

 have proved phenomenal when the material collected for the purpose of 



