April 1908. J 



301 



Saps and Exudations. 



it is necessary for a young tree to get its 

 head well up above the surrounding 

 vegetation ; they do not therefore grow 

 readily in company. 



Planting at wide intervals of from 20 

 to 30 feet is coming into general use in 

 the case of the more recent Malaya and 

 Ceylon companies. Subsequent thinning 

 can then be dispensed with and the trees 

 can continue to develop unobstructed 

 from 20 or 25 years. There result, 

 under these conditions, trees of rapid 

 growth with a short thick trunk well 

 adapted for tapping, endowed with a 

 high recuperative capacity, and resist- 

 ant to fungus and insect diseases which 

 are further discouraged by the absence 

 of the dead stumps of felled trees. 



On the whole the author sums up in 

 favour of the system of wide planting,— 

 Journal d'Agriculfaire Tropioale, No. 78, 

 December, 1907. 



THE NATIVE RUBBER TREES OP 

 BRITISH GUIANA. 



The trees so far known as capable of 

 producing or likely to produce rubber, 

 growing wild in British Guiana belong 

 to the three genera — Sapium, Hevea and 

 Forsteronia, the first two of which are 

 included in the natural order Euphor- 

 biacese, while Porsteronia belongs to 

 the Apocyna3ese. 



Numerous species of Ficus, known 

 locally as Cumakaballi, occur in the 

 forests, but the latex of none of them 

 has so far been found to yield a sufficient 

 amount of rubber to make the collection 

 of it profitable. 



Mimusops globosa, Gaertin, yields 

 balata, a product which occupies a 

 somewhat intermediate position between 

 india-rubber and gutta-percha both in 

 its composition and in its physical pro- 

 perties, and which fetches a price less 

 than half of that usually obtained for 

 the former. 



SAPIUM. 



The genus Sapium is widely distri- 

 buted throughout the tropics of both the 

 Old and New Worlds. 



The majority of the species are found 

 in South America, including the West 

 Indies, but representatives occur in 

 Tropical Asia, Australia, Malaya, China, 

 Tropical Africa and Madagascar. With 

 the exception of three or four species in 

 South America, I can find no reference to 

 this genus as containing trees capable 

 of yielding India-rubber. 



The members of the genu3 are large 

 shrubs or trees sometimes reaching a 



considerable size, bearing simple, stalked 

 leaves, A very distinctive character of 

 the leaves, which is found in most of the 

 species, is the presence of two small 

 glands visually just below the point 

 where the blade of the leaf joins the 

 stalk. 



The flowers are small and incon- 

 spicuous, and grow in long spikes which 

 bear a few female flowers at the base, 

 while the greater part of the spike is 

 made up of male flowers. Tne male 

 flowers have a membraneous calyx with 

 two or three divisions, which encloses 

 two or three stamens. The female 

 flowers have a similar 3-lobed calyx 

 which surrounds an ovary usually with 

 two or three loculi, each containing 

 one ovule. 



The fruit is a dry capsule measuring 

 not more than half an inch in diameter, 

 showing distinctly usually three divi- 

 sions, which splits open when ripe, dis- 

 closing one seed in each cavity. 



The fresh seeds are surrounded by a 

 thin pulp which is bright red in colour 

 when the seeds are ripe in our native 

 species. This pulp, which in botany is 

 known asthe aril, though quite tasteless, 

 is much sought after by ants, which soon 

 strip it from the seeds when they can 

 get to them. I fancy also that this 

 bright-coloured aril must serve as a 

 source of attraction to birds, because 

 young plants are frequently found 

 springing up in places at long distances 

 from any Sapium trees. The seed-coat 

 beneath the pulp is dark in colour and 

 very hard, so that the seeds if swallowed 

 by a bird could probably pass through 

 its alimentary canal without injury. 



The seeds measure not more than a 

 quarter inch in diameter, and on account 

 of their small size are somewhat difficult 

 to find when they fall on rough ground. 

 In October, 190,3, I was informed that the 

 Indians on the Aruka River, in spite 

 of their keen powers of observation, 

 declared they had not seen the seeds, 

 although they were accustomed to 

 collect the rubber from the trees and 

 also the young plants when they found 

 that there was a ready sale to be 

 obtained for them. 



Observations seem to show that the 

 trees flower from December to February 

 and ripen seeds from March to May. 



All of the specimens of Sapium which 

 were collected and sent to Kew by the 

 late Government Botanist, Mr. G. S. 

 Jenman, have been referred to three 

 species— Sapium Jenmani, Hemsl., S. 

 aucuparium, Jacq., and S, paucinet vum, 

 Hemsl, Some of. the earlier specimen^ 



