\ January, 1900.] 



it cannot be denied that incisions 

 around the circumference of a tree, of 

 such depth as to penetrate the cambium 

 , layer throughout its entire length, is 

 apt to cause rot, in which certain insects 

 are likely to deposit their ova, the 

 larvaB proving in many instances 

 destructive of, or at least injurious to, 

 the trees, — this being particularly the 

 caso where the "machete" was used 

 as the tapping instrument. But with 

 a modern tool of such design as to 

 prevent too deep an incision being 

 made, it has been found that a cut 

 just impinging upon the cambium layer, 

 and piercing it only at intervals, has 

 not only given the greatest amount of 

 latex, but seems to be necessary to 

 the formation of new bark. Any incision 

 failing to reach and penetrate, at in- 

 tervals, the cambium layer will result 

 in a mere hardening of the surface of 

 the cut without any attendant renewal 

 of the bark. It has been noted by 

 many that the touching or cutting of the 

 cambium layer effects a restoration or 

 new growth of the bark within a period 

 of sixty days, the bark continuing to 

 grew and fill up the entire incision 

 within a year. 



Doubt yet exists as to the best time 

 of the year in which to conduct tapping 

 operations, Mr. James Collins, in his 

 Report on the Caoutchoue of Commerce, 

 published in 1872 under the auspices 

 of the British Government, states that 

 in Nicaragua (where the climatic con- 

 ditions are generally similar to those 

 obtaining on the Isthmus of Tehuantepec) 

 the most favourable time for tapping 

 was during the months of March and 

 April, when the change of foliage was 

 taking place. The following quotation 

 from Mr. O. P. Cook's monograph on 

 Castilloa* also bears upon the point : 

 "The indications are that (internal) 

 pressure attains its greatest intensity 

 in trees which are exposed for a part of 

 the time to a relatively dry atmosphere, 

 and which are accustomed, as it were, 

 to pump water rapidly to supply the 

 leaves. Such trees may, on the contrary, 

 yield no milk at all when the water 

 supply is deficient. It may be expected, 

 therefore, that open culture will require 

 much more careful attention to the 

 time of tapping." The best results, 

 thus far, have been obtained on the 

 Isthmus of Tehuantepec from tappings 

 made during the early months of the 

 dry season (Pebuary and March), before 



*"The Culture of the Central American 

 Rubber Tree." By O. F. Cook, Botanist in 

 charge of Investigations in Tropical Agricul- 

 ture, United States Department of Agriculture. 

 Washington, 1903. 



5 Saps and Exudations 



the weather has become very hot and 

 when the coolest nights and mornings 

 occur. In April and May, when the 

 maximum temperatures of the year 

 are attained, the deciduous character 

 of Castilloa becomes most marked ; and 

 this is the period during which the 

 tree is generally supposed to be in its 

 most quiescent state, and to have the 

 last recuperative power. On the other 

 hand, in the wet season planters are 

 confronted by the physical difficulty 

 of collecting the latex. Some contend 

 that tapping can best be done during 

 the occasional (and very uncertain) 

 rainless spells of the wet season ; and 

 it is upon the latter hypothesis that 

 two tappings per year for Castilloa 

 come within the range of possibility. 

 It has been noticed that the latex is 

 in a much more fluid condition during 

 the early morning hours, turgescence 

 increasing as the diurnal heat reaches 

 its maximum. 



What the financial promoter and the 

 expert prospectus-writer had long since 

 settled to their own entire satisfaction 

 and that of a trusting public, with 

 the same fatuous positiveness as your 

 orthodox theologian dogmatises on the 

 future life— the question of yield—is still 

 to the planter, who should know most 

 about it, largely a sealed book. If he 

 be honest, he will confess that he 

 knows as yet very little about it. What 

 he does know, however, is that a six- 

 year-old tree will not give 1 lb. of 

 rubber. Trees of unknown age, in a 

 state of nature, have yielded as much as 

 i and 5 lb. of rubber at one tapping ; 

 and there are apparently well-authenti- 

 cated records of yields of triple that 

 quantity from very large and presum- 

 ably very old trees. Undue weight 

 seems to have been attached to the 

 generalizations of Herr Th. F. Koschny, 

 of Costa Rica, in this respect. His claim, 

 for instance, of a yield of 3| lb. of rubber 

 from wild trees, 8 or 9 years old must be 

 accepted cum grano salis. There are, as 

 a matter of fact, no recognised means of 

 definitely determining the age of wild 

 rubber trees ; the all-important element 

 in the case in point is, therefore, hardly 

 more than one of conjecture. 



With regard to cultivated trees, whose 

 ages, with very few exceptions, have not 

 yet passed the eighth year, there appears 

 to be a strong disinclination on the part 

 of planters in Mexico to tap their trees 

 to the full extent of their possibilities, 

 owing mainly to a reasonable fear that 

 permanent injury may result through 

 incautious tapping in the light of present 

 knowledge; and since in the case of 

 Castilloa, as with all caoutchouc-produc- 

 ing genera, notable constitutional dif- 



