PLANT JUICES, THEIR COMMERCIAL VALUES. 20 1 



collector cuts a ring of the bark entirely off, near the ground, placing 

 vessels in a continuous circle around the tree to catch the milk as it 

 flows. Much escapes by falling to the ground between the vessels. 

 This tree has been transplanted and grown successfully in India. 

 Central American rubber is next in value, collected from Castilloa 

 elastica, a large tree growing on the banks of the rivers. This and 

 Ficiis clastica, the potted plant often seen in our houses, with thick, 

 leathery, elliptical leaves, are also cultivated in Mexico, one planta- 

 tion. La Esmeraldo, numbering over 100,000 trees from 10 to 14 years 

 old. They are not tapped until they are 10 years old, when the yield 

 per tree is six ounces of juice, \o% of which is guin. Along the Gulf 

 these trees yield twice as much as when planted on the Pacific coast. 

 The yield should increase from 20 to 25^ every year for 15 to 20 years, 

 when the full-grown tree, 50 to 60 feet high, with a diameter of 4 to 5 

 feet, will yield 20 gallons of milk, or 40 pounds of gum. The tree 

 will last from 60 to 75 years. The fruit is a ficus or fig, contain- 

 ing about 75 small seeds, ripe in January. The plant is propa- 

 gated from seeds and from cuttings. To obtain the milk, V-shaped 

 incisions are made by means of a sharp knife, obliquely inserted. 

 The milk is whipped with a weed called Coyuntla, which makes the 

 milk curdle and separates the crude rubber. Gradual heating, with 

 the juice of several astringent plants mixed with the water, produces 

 the same result. After this the rubber is washed several times, till 

 it becomes white. It is then pressed into moulds, and these are sold 

 in bags weighing 100 pounds each. It is estimated that 525 acres of 

 land, cleared at the cost of $10 an acre (labor being estimated at %\ 

 per day), will net the owner after ten years about $36,000. Each suc- 

 ceeding year the cost of cultivation will be less and the yield greater, 

 so that the net gain will increase at the rate of 20^ per year. After 

 twenty years, when the yield per tree is 4)^ pounds, the income from 

 the plantation will be $258,000. 



African rubber from Mozambique and countries along the coast 

 comes in cakes and balls, called in the trade negro-heads, knuckles, 

 thimbles, tongues, sausages, nuts, etc. It is of two qualities, the 

 finer and purer being pink in color, the poorer black. Asiatic rubber 

 comes from Assam, Borneo, Sumatra, Rangoon, Java and the Malay 

 Archipelago. It is of varying grades, but inferior, all of it, to the 

 American rubbers. 



Two climbers of the Dogbane family, one in Africa, the other in 

 Borneo, yield a fairly good quality of rubber. One of the Asclepida- 

 ceae of India is utilized for its rubber, and there are others. In small 

 quantities this substance occurs in the milky juice of many plants 

 which are of no commercial value. 



