i68 
THE PLANT WORLD. 
attracted to the study of plant geography by the works of Hum¬ 
boldt. He spent the summer of 1812 among the mountains of 
Norway and the years 1817-1819 in Italy and Sicily. When he 
came to write up the data collected on these trips and read the 
existing works on plant geography, he realized how little had 
been done toward establishing fundamental laws for the science 
of plant geography, and himself undertook to formulate the laws 
and lay down some rudimentary principles for this new science. 
We owe to Schouw several of the conceptions and much of the 
terminology which have become fixed in the literature of plant 
geography. In addition, he was the first to give definite descrip¬ 
tion of certain societies and to recognize the grouping of plants 
according to the water-content of the soil. The first part of his 
book deals with the effect of external factors upon the distribu¬ 
tion of plants but like the other plant geographers of the time, 
he deals principally with temperature. The edaphic factors are 
fully outlined, but not explicitly treated. The effect of light is 
very briefly treated: he dismisses it by saying “ Without doubt 
it also serves to nourish the plant.” 
Among those who laid scientific foundations for important work 
at the beginning of the nineteenth century, no name is as impor¬ 
tant as that of Augustin Pyrame De Candolle of Geneva. The 
amount and compass of his labors as a systematic and descriptive 
botanist exceed those of any writer before or since his time. In 
addition to various monographs on morphological and physiolog¬ 
ical subjects, he set on foot the great Prodromus Systematis Nat- 
uralis, in which all known plants were to be arranged and de¬ 
scribed at length, a work in which many other botanists partici¬ 
pated, but none to such an extent as De Candolle, who alone com¬ 
pleted over a hundred families. His son, Alphonse, took up the 
work after the father’s death in 1841 and completed it through 
the dicotyledons; the monocotyledons were never worked up. 
Alphonse De Candolle inherited the industry and ability of 
his father and carried out a long series of studies in plant dis¬ 
tribution. He published his most important contribution in 1855 
under the title “ A Systematic Plant Geography.” De Candolle, 
like the other plant geographers of his day, devoted a large part 
