50 The Plant World. 



Pseudotsxiga macrocarpa is the characteristic tree of the coastal 

 slope, while the xerophilous Pinus monophylla and Juniperus 

 calif or nica, growing with arborescent yuccas, are the character- 

 istic forms on the desert slope. In other words the two halves 

 of the Upper Sonoran area, considered floristically, have but a 

 trifling percentage of species in common; considered ecologically 

 they have dominant species which are physiologically very 

 unlike. It may well be asked, therefore, wherein the adoption 

 of a ready-made scheme of zones has aided in the exposition of 

 the natural features of the flora in question. — F. S. 



Forests of the Gold Coast. — H. N. Thompson, Conser- 

 vator of Forests for Northern Nigeria, has prepared a report on 

 the forests of the Gold Coast Colony which gives a fund of val- 

 uable facts regarding a region hitherto little known. * The 

 usual moist conditions of a tropical coast are opposed during 

 several of the winter months by a dry northeast wind (the harm- 

 attan) blowing off the Sahara. The coastal belt of evergreen 

 broad-leaved rain-forest is described as being extremely com- 

 plex in composition and as possessing the usual tropical features. 

 It gives way at localities as little as 40 miles from the sea to mon- 

 soon forest, which in turn is rapidly succeeded by savanna forest 

 and bv savanna, as the interior of the colony is reached. The 

 rainfall in the coastal belt is 80 inches, that in the monsoon region 

 about 50 inches, and this amount is still found in the savannas 

 of the hinterland 500 miles from the coast, while the humidity 

 falls from a yearly average of 86 per cent, in the monsoon region 

 to 60 per cent, in the savannas. Trees are "practically absent" 

 in the savannas, and in the savanna forest region there is a 

 mingling of large tropophilous and smaller evergreen sclero- 

 phyllous trees, with a closed carpet of coarse savanna grasses. 

 Clearings in the forested regions become occupied by the savanna 

 grasses to the subsequent exclusion of trees, the reappearance 

 of which is retarded both by the stature and density of the grass 

 formation and bv the annual savanna fires. — F. S. 



A Physical Chemistry Text for Biologists. — The great 

 advances which chemistry has made within the last two decades 



♦Thompson, H. N., Gold Coast, Report on Forests. Colonial Reports — Miscellaneous 

 Cd. 4993. Pp. 238 and map. 1910. (Is. Id). 



