No. 1, JuiiT, 1920] ECOLOGY, PLANT GEOQB 23 



ISO. Buow.v, \V. II. Vegetation of Philippine mountains. The relation between the en- 

 vironment and physical types at different altitudes. Philippine Bureau Sci. Publ. 13: I 134. 

 PI. l-'tl , Jig. I SO, 1919.— The author holds tli.it the different types of vegetation found on 

 tropical mountains arc the result of (he environment and correlates tin' physical types at 

 different elevations with measurements of the environmental factors. The greater part of 

 die publication is taken up wit b .Mount. Maquiling. Bel ween elevations of 100 to 600 meters 

 on this mountain is found a tall, three-story dipterocarp forest, a type of Schimper's tropical 

 rain forest. Here the epiphytes are largely phanerogams and are confined chiefly to the lar- 

 gest branches of the tallest trees. The ground covering consists mainly of trie Beedlio 

 At greater elevations the height of the trees decreases, the number of stories Incomes less, 

 epiphytes more abundant, and the ground covering more mesophytie; at the top there is a 

 mossy forest composed of a single story of dwarfed, peculiarly shaped t rees which are thickly 

 covered with mosses and moss-like plants, and 1 here is a ground covering of mesophyi ic herbs. 

 The measurements of the environmental factors are very detailed and cover a continuous 

 period of two years. The temperature and humidity were measured near the ground in six 

 stations. Temperature was also measured in various situations in trees, by means of maxi- 

 mum and minimum thermometers. Evaporation was measured by Livingston atmometers 

 near the ground, in the top of the canopy of the forests at different elevations, and in the var- 

 ious tree stories. Light was measured in five stations by means of radio-atmometers. — Tem- 

 perature and light intensity decrease with rising elevations and the rates of growth and the 

 heights of the trees at different elevations show a general agreement with the light-temper- 

 ature indices — that is, with the product of light intensity multiplied by temperature indices 

 for growth. Evaporation decreases with the increasing altitude, while the heights of the 

 trees and rates of grow r th also decrease. Near the base of the mountain, however, it would 

 appear that evaporation is high enough to be detrimental to the vegetation. Rainfall is 

 greatest at middle elevations so that it would seem that the development of epiphytes is de- 

 pendent on lower rates of evaporation and greater cloudiness rather than on high rainfall. 

 The moisture content of the soil increases with rising elevations and it is only at the base of 

 the mountain that it ever becomes low enough to be harmful to the vegetation. The in- 

 creased moisture content of the soil and the lower rate of evaporation account for a greater 

 degree of mesophytism in the ground covering at high than at low altitudes. — An account 

 of the vegetation and measurements of environmental factors on Mount Banahao are also 

 included. Here the dwarfing is more gradual than on Mount Maquiling and temperature 

 indices for growth would appear to be sufficient to account for the dwarfing. — From these 

 results it would seem that when dwarfing is gradual, on moist tropical mountains, it may be 

 accounted for by decreases in temperature but that when it is rapid it is due to a combination 

 of low temperature and low light intensity. — Near and at the top of Mount Banahao the rain- 

 fall is heavier than anywhere on Maquiling but cryptogamic epiphytes are not as well devel- 

 oped anywhere on Mount Banahao as at the top of Maquiling. This is due to the fact that 

 on Mount Banahao the humidity is lower and clouds less frequent than on Mount MaquUing, 

 and emphasizes the fact that epiphytes may not be proportional to rainfall. — The writings 

 of many botanists would lead one to believe that they consider tropical vegetation as pecu- 

 liar, and temperate vegetation as more normal. The writer brings forward a number of rea- 

 sons for holding that the reverse is true; that is, that tropical vegetation is a generalized 

 type and temperate zone vegetation a specialized one suited to the alternation of summer 

 and winter seasons. — E. D. Merrill. 



181. Bukns, George P. Weather conditions and plant development. Mem. Brooklyn 

 Bot. Gard. 1: 119-122. June, 191S. — The author maintains that the effect of weather condi- 

 tions presents a problem essentially physiological, and therefore one which is to be investi- 

 gated by accurate experiments under controlled conditions. Mention is made of several 

 methods employed in the past in attacking these problems, and it is shown that conclusions 

 based on general averages are apt to be useless, because such averages conceal the essential 

 facts. The author emphasizes strongly the importance of studying the conditions that obtain 

 during critical periods. — P. D. Strausbaugh. 



