68 BOTANICAL GAZETTE [JANUARY 
a more complex garb. BLaauw’s work clearly indicates that the amount 
of effective light and not the direction of the ray is the determining factor in 
phototropism. He believes NoAxk’s” opposing view is due to his overlooking 
the parabolic curve of the tip in the epicotyl of Avena, the shading effect of the 
sporangia of Phycomyces on the perceptive and growth regions of the sporangio- 
phore, and the cylindrical lens effect of the latter organ. On account of its 
lens action the back of the organ in unilateral light is more strongly illuminated 
than the front. The matter is rendered more complex by the focal line lying. 
at different depths with variation in the angle of the incident ray —WILLIAM 
CROCKER. 
The vegetation of Natal.—Perhaps no part of the world is theoretically 
more interesting and practically less known to the phytogeographer than 
South Africa, and it is a satisfaction to record the appearance of two excellent 
papers on the vegetation of Natal by Professor Brews?” of the Natal University 
College. The first paper is of general nature, presenting the ecological factors 
and plant associations of the province as a whole. Although Natal is situated 
considerably to the south of the Tropic of Capricorn, much of the area is 
frostless and has a distinctly tropical vegetation. Especially is this true of the 
coast, where are to be found such tropical types as the mangroves and Pes- 
caprae. Almost all of the coast line is fringed by dunes, reaching a height 
of 50-200 feet, and covered chiefly by xerophytic bush. The vegetation of 
the interior is mostly evergreen dicotylous forest and grassland. The forest 
(generally called bush) resembles ScuimpER’s sclerophyll forests, except that 
they are in regions of summer rather than winter rain. Perhaps the most 
interesting type of bush is the yellow-wood bush, in which Podocarpus domi- 
nates. In the Natal bush epiphytes are relatively scarce, but lianas are very 
abundant. Transitional to the grassland or veld is the thorn veld, essentially 
a savanna, with a dominance of umbrella-shaped Acacia trees. In the veld the 
grasses are changing, largely because of human influences, and it is — 
that the invading grasses are less useful to man than the original gras A 
brief account is given of the marsh or vlei and of secondary ye <e 
is, those due to human influence. 
The second paper is the initial one of a series contemplated by BEWS, 
dealing in detail with the vegetation of small areas in the province of Natal. 
In the veld the dominating natural grass is Anthistiria imberbis; increasing 
areas are being given over to the cultivation. of wattle (Acacia wiollissioa) 
» Bot. Gaz. 58:88-89. 1914. 
 Bews, J. W., The vegetation of Natal. Annals of the Natal Museum 23:253- 
331. pls. 10. 1912. 
a. An ecological survey of the midlands of Natal, with special reference 
to the Pieter district. Annals of the Natal Museum 24:485-545- pls. 7- 
map 1. x 
