■Jo THE PLANT WORLD. 



An interesting adaptation is shown by some of the members of 

 the genus Phyllanthus. The genus embraces nearly a score of species 

 in which the leaves are reduced to bracts, and the leaf -functions are 

 carried on by phyllodes, in which the transpiring surface is very lim- 

 ited. In such species movements are not necessary, since the edges 

 of the phyllodes are directed nearly toward the sun, and the danger 

 from the fiercer heats is not encountered. In P. Niruri and other 

 species the leaves are arranged laterally in two ranks on the horizontal 

 branches, in such manner as to resemble the compound leaf of Lathy- 

 rus, the monoecious flowers springing from the axils and depended 

 below giving the appearance of an equally pinnate leaf bearing flow- 

 ers. The oblong-ovate leaves are joined to the secondary branches 

 by pulvinar structures, by the aid of which a closure may be made 

 resembling that of the leaflets of Cassia chcemcecrista. Furthermore, 

 the secondary branch and its leaves behave exactly as a compound 

 leaf, being irritable to light, impact and shock, besides showing both 

 thermotropic and nyctitropic movements. The genus is regarded as 

 one of the oldest of the Euphorbiaceae, and the particular species 

 under consideration must have undergone a long series of migrations 

 and climatic changes. The true leaves were found useless or uneco- 

 nomical in certain cases, and these organs were gradually degraded 

 until they are but minute bracts, while branches were slightly broad- 

 ened to serve the functions of the leaf. P. Niruri is an example of 

 the class retaining the leaves. In order to do this, however, it organ- 

 ized a branch and its leaves as a compound leaf, thus securing the 

 power of regulating the light and heat falling upon the surfaces. 

 Physiologically, the branch and its leaves is a compound leaf. 



The uses of color in plants in the tropics have received much 

 attention in recent years. As a result of some recent researches at 

 Buitenzorg, Stahl concludes that red or violet color in leaves is for the 

 purpose of raising the temperature and increasing transpiration. If 

 this were true it would be expected that leaves in shaded and moist 

 situations would exhibit the most color. Observations by Dr. Ewart 

 in Java and Ceylon, and by the writer in Jamaica and the Rocky 

 Mountains, show that the reverse is true, however. 



Ewart found that the amount of color in the vegetation of the 

 mountain of Gedeh was greatest at the base and decreased toward the 

 summit, where the air was near the saturation point. The writer 

 found that the shoots of young trees in the fierce glare of the sun on 

 the mountain-sides in Jamaica up to 2,000 feet exhibited a marked 

 coloration. Above this the coloration becomes more infrequent, but 

 is shown by a few ferns at 4,000 feet, and is almost wholly absent from 

 the plants of Blue Mountain peak (7,340 feet), which is wrapped in 



