May 1908.] 



419 



Saps and Exudations* 



e.g., the Lauclolphias which ave also 

 climbing shrubs, and Funtumia dlastica, 

 the silk-rubber tree of West Africa, 



Mr. Jenman describes the Macwarrie- 

 balli in a later part of his report as 

 possessing a soft bark about f inch or 

 more thick, somewhat scaly on the 

 outside, especially in the upper part 

 of the stem. The milk issues equally 

 from its whole thickness, except from 

 the exterior surface layers. 



" The wood is very soft and contains 

 a good deal of water which dilutes and 

 drips with the milk from the lower end 

 of the stem, when that is cut in two, but 

 very little runs from the upper end," 



" The lower part of the stems always 

 or nearly always, I found spirally curv- 

 ed, though slightly, for they are nearly 

 straight, like the untwisted parts 

 of a rope under tension, which just 

 shows a trace of spiral undulations. 

 This character I found by examining 

 very young plants was acquired in the 

 infancy of the plants, by twining on 

 some small sapling, by which alone they 

 seem to ascend to the branches of the 

 larger trees, which eventually alone 

 support them. These young trees, which 

 thus serve the convenience of the vine 

 andeuable it to reach the light aloft that 

 is necessary to its well-being and matu- 

 rity, are probably strangled in the course 

 of its development. In the upper parts 

 and in parts lying on the ground which 

 have dropped from their supporting 

 branches, this spiral form is often quite 

 absent, and they are perfectly straight; 

 often, however, the upper part is as 

 spiral in form as the lower, and as often, 

 too, parts are twisted together, the 

 separate stems "laid" like the strands 

 of a rope." 



The Macwarrieballi is generally dis- 

 persed over the whole of the great forest 

 region of Guiana. 



In his work on " Les Plantes a Caout- 

 chouc et leur Culture," Professor Dr. 

 O. Warburg mentions another species 

 of Forsteronia, F floribunda, G. F. W, 

 Meyer, which is a native of the forests 

 of Jamaica and the latex of which 

 furnishes an excellent rubber, but it has 

 only been so far imported into Europe 

 as small samples. 



Method of Tapping.— The method of 

 tapping employed by Mr. Jenman to 

 obtain the latex after cutting down the 

 stem, was that of making a simple cir- 

 cular cut by drawing a knife round the 

 stem to the depth of the bark, making 

 the cuts at distances of about 8 inches 

 apart- 



Mr, Jenman afterwards suggests an 

 alternative method which he believes 

 would give the best results, viz., making 

 53 



use of ladders to tap the stem, as it 

 hangs straight down against the trunk 

 of the tree supporting it. A vertical 

 slit is to be made up the stem from the 

 bottom to the top, placing a vessel at 

 the bottom to catch the milk aj it begins 

 to run. Leading into this vertical slit, 

 short oblique slits are cut alternately 

 on each side, 6 to 9 inches apart, embrac- 

 ing only half of the circumference of the 

 stem. The same process might be re- 

 peated on the opposite side of the stem. 



Yield op Latex.— I have previously 

 quoted Mr. Jenman's remarks about 

 the rapid flow of the latex from the 

 creeper when first cut, but owing to 

 the comparative smallness of the 

 seem the flow soon falls off, though it 

 continues to drop for about ten minutes. 

 Mr. Jenman writes:— "Yet considering 

 the small diameter of the stems, the 

 milk seems extraordinarily abundant 

 and of wonderful richness in caoutchouc. 

 In somi cases as it rushed out it formed 

 threads and hung in running fibres from 

 the branch to the cup. On several 

 occasions I noticed that, instead of milk, 

 pure liquid caoutchouc seemed to run. 

 No doubt the dryness of the weather at 

 the time, less water being consequently 

 present in the bark, had much to do 

 with this result and with the impression 

 produced on my mind of the richness of 

 the milk in pure rubber." 



"In straining it afterwards in a per- 

 forated tin to separate bits of bark that 

 had dropped in, the milk formed a 

 covering of caoutchouc over the bottom 

 of the vessel in the very brief time that 

 it was running through, only a few 

 seconds. 



From the stem, tapping it as high as 

 the first branches of the tree that had 

 supported it, 30 to 40 feet, we obtained a 

 quart bottle of milk and quite as much 

 more was wasted by our hasty work, in 

 diipping on the ground after the cups 

 were removed from the old to new cuts 

 and by coagulatiou in the fissures, 

 besides all that was left in the bark." 



Mr. Jenman found that on tapping 

 again the plant bled the previous day, 

 the milk again ran freely but not so 

 freely as when first bled. Judging from 

 what he observed on subsequent visits, 

 he considers that on the first tapping, 

 unless it be done very thoroughly, only 

 about a fifth or a sixth of the milk is 

 procured. 



The time taken to coagulate a quart 

 bottle of the latex into rubber, so as not 

 to be stickly when handled, in a tin pan 

 about 10 inches in diameter, shaded from 

 the sun, was six days. The rubber was 

 then washed in the usual dark-coloured 

 creek water which Mr. Jenman saya 



