GUM EESEARCH 71 



Series B. Eight trees, tapped as above, but, in addition, an auger hole made into the 



denuded wood. 



In most cases no gum was found exuding from between the bark and the 



wood, and in no case was any trace of gum found exuding from the hole in the 



wood itself. 

 Series C. Six trees treated by boring holes with an auger, through the bark and into 



the wood. 



In the case only of one tree was gum found exuding, and from one only of the 



several auger holes in it. 

 Series D. Five trees treated by removing a wedge-shajjed piece of the bark and liber, 



and bruising the adjoining bark Isy blows of the blunt end of a small axe. 



Three of these trees yielded no gum at the point of tajoping. The remaining 



two yielded a fair amount, but very dark in colour, especially where it exuded from 



the cracks in the bruised bark. 



No further reliable observations were made on the above experimental tappings. It 

 was intended when they were instituted that observations be made periodically — once 

 every two or three weeks — in order to watch the course of the exudations. It appears, 

 however, that the forest officer in charge of the district did not visit them until three 

 months after the date mentioned above, when he reported the practical absence of gum 

 from any of the trees except those which had been chemically treated. We were 

 therefore left somewhat in the dark in this connection ; but, in view of the fact that 

 the apparently sound trees, both of White Talk and of Bed Talk, did not yield gum 

 when tapped in the ordinary way, there seems to be strong evidence that, at least in 

 the immediate district in which these experiments were performed, the conditions were 

 not naturally favourable for gum production. Taken altogether the results appear to 

 justify the following conclusions : — 



(a) In the district in question sound white talh and red talh trees — i.e. trees 

 which have not been injured by fire or which have not suffered marked mechanical 

 injury — are not susceptible to the action of the gum-producing microbe, and will not, 

 therefore, yield gum on simple tapping in October and November. It appears evident Conclusions 

 that at this time the ground is still sufficiently moist, from the lately fallen rains, to 

 keep the trees in a resistant condition. 



Such trees would probably yield gum if tapped at the end of February or, better, 

 in March, when the weather is hot again and the soil contains less moisture. On the 

 other hand, the soil itself appears to be of rather good texture and fairly rich, which, 

 again, is unfavourable for gum production under ordinary conditions. 



(6) Trees w'hich have been injured by fire are more susceptible and yield gum 

 fairly readily ; but such gum is very frequently coloured to an objectionable degree. 

 Even in the case of these fire-injured trees, it would seem preferable to perform the 

 tapping as late as possible after the rains, so that the exudation may not be checked 

 by the colder weather of December, January and February. 



(c) Tapping by cuts with a sharp instrument, such as a spoke-shave, will probably 

 be least effective, since such cuts appear to heal too quickly. This metliod, has, however, 

 not yet been tested on trees known to be in a low state of vitality, and therefore most 

 suitable for gum production. 



id) Bruising of the bark around a cut allows freer outlet to the gum and increases 

 its production ; but the resulting gum, especially if it exudes through cracks in the 

 bruised bark, is coloured to an objectionable degree. 



