462 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
geranium flourishes in the desert air, while another by its side dwin- 
dles and dies, we can only say at present that the latter is not 
“adapted,” or is apparently incapable of “ adjustment ” to the atmos- 
pheric conditions in which it has been placed. We find that plants 
growing in the wash near the Desert Laboratory do not, as a rule, 
succeed in gaining a foothold on the long slope leading to the hill 
near by; they are not adapted to the soil conditions there existing; 
but the creosote bush, which makes its home on these slopes, grows— 
thanks to its capacity of adjustment, even more luxuriantly in the 
wash than on its own domain. Similarly, certain plants of the salt 
spots grow better beyond than within their limits; they have become 
adapted to large percentages of alkali salts, but their capacity of 
adjustment is such that they grow just as well or better along an 
irrigating ditch carrying fresh water. Various other plants in the 
immediate neighborhood have not become adapted to the conditions 
prevailing in the salt spots, nor do they appear capable of adjust- 
ment to them, and accordingly are not found growing in such places. 
We need not multiply citations of these familiar cases. Adapta- 
tion and adjustment have long been words to conjure with, out of 
the desert as well as in it, but we have made so little real scientific 
progress in the definition and determination of the things for which 
they stand that some of our foremost students of ecology seem ready 
to abandon the effort, while others apologize when they use the terms, 
as if they were myths and had better be left alone. But nothing is 
gained, and much may be lost, by this method of procedure. We are 
face to face with a great body of phenomena of the most striking 
character, in connection with which these words are fittingly em- 
ployed. We can not ignore the existence of the facts, and as scien- 
tific men we can not let them alone, while they insistently rise at 
every turn in our pathway and demand investigation. True it is 
that they bring in their train whatever is fundamental in biological 
inquiry—heredity, the direct influence of the environment, and differ- 
ences in the properties of protoplasm in different plants. It is not 
customary, howéver, in laboratories worthy of the name, to shun 
investigations that approach to the deep mysteries of life. There is 
every reason why students of ecological problems should seek, not 
shun, this difficult but hopeful line of study. I say hopeful advisedly, 
for within the past three years there have come under my observation 
various definite cases of adjustment in plants, some of which have 
been accurately measured, correlated with external factors, and ex- 
pressed by curves. Though essentially more difficult, there is no 
reason, as far as now appears, why the different degrees of adaptation 
of two species or varieties to a given external factor may not be simi- 
larly determined and graphically represented, as the expression of a 
definite difference of physiological activity, as shaped by heredity, in 
