6 BOTANICAL FEATURES OF NORTH AMERICAN DESERTS. 
the Salton Basin, and the study of the conditions in the two localities 
contemporaneously may confidently be expected to yield results of great 
value. 
An examination of the effect of the advancing shore-line upon desert 
vegetation was made in May, 1906, and a more serious expedition was 
made to both basins in February, 1907, in which areas were selected and 
surveyed for detailed investigation as to the conditions of soil moisture, 
salt content, and physical factors of the soil, together with the move- 
ments and development of plant societies. 
Another general problem requiring the focused effort of the Labora- 
tory is comprised in the influence of altitude and climatic factors upon 
vegetation with respect to the direct reactions by which individual adap- 
tation is accomplished and to possible alterations in the transmission of 
hereditary qualities. 
As a result of various horticultural and agricultural activities and of the 
constant interchange of living material which has taken place among 
botanical gardens and other collections of living plants, assembled for ob- 
servational purposes, a large number of species have been transferred 
from one country to another, and some observations as to alterations 
in habit and form resulting from such removals are recorded. A few 
experimental tests have been made in the cultivation of species through a 
range of altitude and some of the morphological changes induced have 
been described. Itis known that the color, time of bloom, habit, struc- 
ture of the root and shoot, general aspect of plants, and economic value 
may be greatly altered by cultures at various altitudes, but no systematic 
tests have been made to determine to what factors in the climate these 
differences are due. ‘The solutions of the problems involved would settle 
some of the most important problems in general physiology and would 
also go far in enabling us to account for the structure and form of the 
species of which the vegetation of the earth is composed. 
It is by means of experimental observations of this kind that it also 
may be hoped to obtain evidence as to the inheritance of somatic varia- 
tions, a question which has been a much vexed one for many years. No 
adequate tests have yet been made to ascertain whether ornot the marked 
changes induced in plants by cultivations at altitudes higher or lower 
than the normal are fully transmissible to succeeding generations grown 
under other conditions. 
The practical problems of acclimatization offer some highly peculiar 
conditions. Thus,two separated localities may offer meteorological con- 
ditions apparently similar,so far as ordinary methods of weather records 
show, yet the exchange of plants between the two places will be attended 
with but indifferent success, even when differences in composition of the 
soil are accounted for. It seems unnecessary to point out that when the 
factors in climate have been accurately analyzed as to their effect upon 
