i92°] CURRENT LITERATURE 445 



into one general dictionary, and the omission of the former part dealing with 

 morphology, classification, geographical distribution, economic uses, etc. 



,000 



available at a minimum of trouble. — J. M. C. * 



NOTES FOR STUDENTS 



Tropical rain forests. — Two recent contributions have added considerably 

 to our knowledge of the ecology of tropical rain forests, especially as both 

 present quantitative data concerning habitat and also the vegetation. The 

 first by Brown 6 deals with the vegetation of a portion of the Philippine 

 Islands, and the second by McLean 7 with some of the rain forest near Rio de 

 Janeiro, Brazil, and is the continuation of a report already noticed. 8 This rain 

 forest of Brazil is regarded as the climax type for a large portion of the country. 

 A biological spectrum of the Raunkiaer type would show an enormous pre- 

 ponderance of woody plants arranged in three distinct strata, the ground 

 flora being comparatively open. There is a great diversity of species, with 

 the Leguminosae as the most prominent family, and the Rubiaceae and Pipe- 

 raceae important among the undershrubs. Ferns and lycopods are largely 

 limited to rocky spots. Conspicuous flowers are abundant in the upper canopy 

 and notably lacking below. Buttressed tree trunks are rare, in spite of the 

 frequency of violent winds, but thorny stems are frequent even in large trees. 

 The floristic diversity and the contrasting uniformity of appearance, especially 

 m leaf form, are ascribed to (i) the antiquity of prevailing conditions, and 

 (2) the peculiarity of the environment. The soil is shallow and pervious, 

 with a water-holding capacity of about 40 per cent, and an average water 

 content of 10 per cent. It is deficient in mineral nutrient material and par- 

 ticularly in calcium carbonate. The humus content is about 3 per cent. 

 Mycorhiza are very abundant. A very considerable amount of rain is inter- 

 cepted by foliage and evaporated into the air, thus reducing the rainfall 

 efficiency. Light measurements made with photographic exposure meters 

 show the average ratio of the light outside and that within the deep forest to 

 be 1:0.06; some spectroscopic measurements, however, tend to show that the 

 photosynthetic efficiency of the shade illumination is relatively greater than 

 the actinic. 



The leaves of the forest are in general characterized by their larger size, 

 the small number per plant, and the frequency of nyctitropic movements and 

 of the vertical position. The shade leaves show conspicuous water-storing 

 epidermis, reduced and undifferentiated mesophyll, and occasional epidermal 



W 



Dept. Agric. and Nat. 



Resources, Bur. Sci. Pub. 13:434. pis. 41. figs- 3°- Manila. 1919 



7 McLean. R. C, Studies in the ecology of tropical rain forest; with special 

 reference to the forests of South Brazil. Jour. Ecol. 7:121-172. figs. 10. 1919. 



1 



Box. Gaz. 69:92-94. 1920 



