76 



BEPORT OF CHEMICAL LABOEATOBY 



Production 

 from large trees 

 unaffected by 

 early rains 



Temperature 

 records 



vary enormously in this f^arden also, not only in their total yield of gum, but also in the 

 relative amounts produced at the beginning and towards the latter half of the season. 

 For these differences, as in the case of the younger trees, there was no apparent cause, 

 trees which gave only a small amount of gum being in many cases as large and, so far 

 as one could see, as healthy as others from which a very much larger amount was obtained. 



It will be seen that the rain at the beginning of April was followed by no increase 

 in the amount of gum exuded by these large trees. Probably the rain was not sufficient 

 to cause any increased flow of sap, and no new leaves appeared in consequence of it. 

 It might be of interest to tap a few trees about the middle of the rainy season, when 

 they are in full leaf, with a view to seeing if any gum was exuded before the wounds 

 had time to heal up. 



Dr. Beam has pointed out in the Third Eeport of these Laboratories that it is usually 

 considered inadvisable to tap trees on a cold day, and has given the results of some 

 exi^eriments confirming this. It does not seem to be the case, however, that the 

 exudation of gum has a tendency to increase as the season advances and the days 

 become warmer. 



Near the end of December Mr. Bisset was kind enough to send me a maximum and 

 minimum thermometer, readings of which I took every day, and it may be of interest 

 to state briefly the variations in temperature for the four succeeding months. A convenient 

 method of doing this, without tabulating the whole figures, will be by giving the absolute 

 and also the average maximum and minimum temperatures during each interval between 

 the collections of gum. This is sufficient to give a fair idea of the weather for each 

 period, as apart from differences of temperature, the conditions remained the same the 

 whole time with the exception of about ten days at the beginning of April when the 

 weather was rather cloudy. 



TEMPERATURE AT TAIARA, .JANUARY T(.) APRIL, 1909 



There was thus a gradual but regular increase in the temperature during these four 

 months, but in si:)ite of this the amount of gum produced declined nearly as steadily. The 

 explanation of this lies probably in the fact that there was a continuous decrease in the 

 amount of sap available for the production of gum. 



Dr. Beam has mentioned the fact that the natives are first of all agriculturists, and 

 therefore do not trouble to tap their gum trees until they have secured their crops. If these 

 trees described above be taken as a fair average, however, it would probably pay the owners 

 of gum gardens to take the trouble of tapping them as soon as possible after the rains, 



