PREFACE. 



When I went to Java in the Autumn of 1907, having obtained 

 the German so-called Buitenzorg grant, it was, amongst other 

 things, my intention, by studying rubber plants in the tropics, to 

 help to extend our knowledge of the utility and advantages of the 

 various tapping methods that had been described already. This 

 object can be obtained by research in two directions : firstly, on 

 anatomical lines, by studying the process of development 

 of the laticiferous system, the expansion of this system during 

 the diameter growth of the trees, and the renewal of the latex 

 ducts after the infliction of large wounds on the bark, such as 

 those made for the purpose of obtaining rubber ; and secondly, 

 on physiological lines, by ascertaining and investigating 

 all the various influences which tapping has on the vitality of the 

 tree and its component parts, as well as on the renewal of its 

 latex and rubber. Every physiological botanist, who has taken 

 the trouble to wade through the existing voluminous literature 

 on the subject of rubber cultivation, must arrive at the conclusion 

 that all these investigations, especially the physiological ones, 

 are imperative in order, by introducing rational tapping methods, 

 to protect rubber plantations against very unpleasant earlier or 

 later injuries. It is extraordinary, that the opinions on the advan- 

 tages of the various tapping methods so far recommended, are 

 not based on experiments, such as our general physio- 

 botanical knowledge suggests, and which have a definite 

 object in view. It is likewise strange, that there is an utter lack of 

 effort, by minute scientific research, to clear up the points 

 on which the experiences of planters are at variance. 

 Consequently a great uncertainty of opinion still prevails, which 

 can only prejudice the cultivation of rubber. Kecognixrd 

 authorities in the field of rubber investigation have not been able 

 to shut their eyes to this fact. From the literature on the subject 



