West Africa has taken heavy toll not only in money but in life, but the lesson has now been learned, and a system of frequent furloughs combined with a better understanding of the climatic requirements have appreciably lessened the peril.
Their course, owing to the complex orography of the state, is necessarily extremely irregular, and few climatic generalizations can be made.
In one sense, the accumulation of humus and peat is a biological factor, as it is related to the work of organisms in the soil; but the occurrence or otherwise of these organisms in the soil is probably related to definite edaphic and climatic conditions.
They endeavoured to define aspects of vegetation in which the forms exhibited an obvious adaptation to their climatic surroundings.
From the foregoing facts and observations we may conclude, firstly, that some plants and many animals are not constitutionally adapted to the climate of their native country only, but are capable of enduring and flourishing under a more or less extensive range of temperature and other climatic conditions; and, secondly, that most plants and some animals are, more or less closely, adapted to climates similar to those of their native habitats.
This illustrates the extraordinary homogeneity of climatic conditions.
On a smaller scale are the local adaptive radiations which occur through segregation of habit and local isolation in the same general geographic region wherever physiographic and climatic differences are sufficient to produce local differences in food supply or other local factors of change.
Hence, in any cosmopolitan treatment of vegetation, it is necessary to consider the groups of plant communities from the standpoint of the climatic or geographical district in which they occur; and this indeed is consistently done by Schimper.
The rainfall throughout this region is abundant, except in northern Minas Geraes, where the climatic conditions are influenced to some extent by the arid eastern plateau.
Fertilization has been observed at Naples; but it apparently depends on climatic conditions, as at Plymouth the oospheres have been observed to germinate parthenogenetically.