24 CEOTBAL AMEEICAN RUBBER TREE. 



The reduced figure of the fruit given by Cervantes shows the character of the 

 grooved sides and rounded angles of the carpels, but not their indented tips. «■ 



II. The Caucho, or Darien plant. Leaves less thickly tornentose beneath. Fruit- 

 ing receptacles 2 to 3 inches in diameter; crowns of the ripe carpels prominent, 

 pyramidal, acute, acutely 3 to 4-angled. Seed one-third inch in diameter, more or 

 less immersed in the free crown of the carpel. — Darien, on the Chagres and Gatun 

 rivers. 



III. Fruit referred to Ule, from the Belize Estate and Produce Company. Fruit- 

 ing receptacle 1 to 1\ inches in diameter; crowns of the ripe carpels prominent, 

 acute, acutely 3 to 4-angled. Seeds one-fourth inch in diameter, more or less immersed 

 in the free crown of the carpel. — Honduras and Nicaragua. This appears to be a 

 small-seeded variety of the Darien species. 



IV. Fruit of the Tunu or gutta-percha yielding plant, from the Belize Estate and 

 Produce Company. Fruiting receptacles 2 to 2J inches in diameter; crowns of ripe 

 carpels very low, subacute, acutely 3 to 4-angled. Seeds one-third inch in diameter, 

 immersed in the receptacle far below the crowns of the carpels. — Spanish Honduras. 



COSTA RICAN SPECIES OF CASTILLA. 



According to Koschny, four species of Oastilla exist in the forests 

 of Costa Rica, three of which yield rubber, while the gum derived 

 from the milk of the fourth is not elastic, but becomes brittle and 

 resinous. The general shape of the trees and their branches and leaves 

 are said to be the same in all four kinds; the differences enumerated 

 are those of the bark, the colors of which give the names to the three 

 rubber-producing species. 



Costilla alba, hule bianco, or white rubber, has a smooth bark which appears red- 

 dish white from a distance, owing to the presence of a thin white lichen. With age 

 it becomes covered with coarser lichens and mosses and very difficult to distinguish 

 from other forest trees. The bark and bast layer are thicker and softer than those 

 of the other species; it is the most tenacious of life, and yields the most rubber. 

 The milk is a thick fluid, and only about half of it runs down unless it is helped by 

 the fingers; the rest remains in the cuts and dries down in six or eight days unless 

 washed out by the rain while still fresh. Thus the tree does not easily bleed to 

 death. The hule bianco is never found in the denser forests, but is abundant in 

 more open places where the leafy crown can be exposed to the light and at the same 

 time sufficient cover remains for the trunk. It is the only species suited for culti- 

 vation. 



Costilla nigra, hule negro, or black rubber, has bark which ia very rough and dark; 

 also somewhat thinner, tougher, and more fibrous than that of Costilla alba. It gives 

 considerable milk, but thinner and more fluid, and the tree often bleeds to death. 

 On account of this greater susceptibility to injury it is not to be considered for culti- 

 vation. This species appears only in the undisturbed forests and is a true shade 

 species. It is said also to occur with the other species, but is much less abundant, 

 because it has more often died out. 



Costilla rubra, hule Colorado, or red rubber, has a bark so different from the others 

 that it would not be taken for a rubber tree Avere it not for the other characteristics. 

 The bark is distinctly thinner than in other species and the last layer is inconspicuous. 



«The range of the typical Costilla elastica is given as Mexico (south of 21°), Gua- 

 temala, Salvador, Honduras. Nicaragua, and Costa Rica, and the tree described by 

 the Danish botanist Liebman as a distinct species, Castillo costaricana, is held to be 

 the same. 



