(197 ) 
Dr. D. T. MacDougal, first assistant and director of the 
laboratories, is carrying forward the study of the relations of 
soil-temperature to vegetation upon which subject he has 
published ConTRipuTion 44. An investigation of corre- 
lations in leaves has been completed and published as Con- 
TRIBUTION 43. His studies on the life-history of polymorphic 
aquatics, begun early in 1902, have been continued. In addi- 
tion to results concerned with the influence of various external 
conditions upon structure and form, they may also be expected 
to furnish evidence upon the inheritance or non-inheritance 
of acquired characters. 
Since May, 1902, Dr. MacDougal has been coéperating 
with Professor Hugo de Vries, Director of the Botanical 
Garden at Amsterdam, Holland, in testing certain features 
of the mutation theory of the origin of species recently pro- 
posed by him. One series of cultures of the parent species 
of the evening primrose, and mutant forms derived from 
it has been finished; a second series has been begun. 
An investigation of the influence of carbon monoxide, illu- 
minating, and other gases upon plants has been undertaken 
in codéperation with Professor H. M. Richards, and some 
important results have already been obtained. 
As a member of the Advisory Board of the Desert Botani- 
cal Laboratory of the Carnegie Institution, a tour was made 
in company with Frederick V. Coville, of the deserts in New 
Mexico, Chihuahua, Arizona, and California in February, 
1903. A site for the laboratory was selected at Tucson, 
Arizona, and a building has been erected, which is now 
equipped and is open with its facilities for investigators. The 
results of the special studies of desert conditions have been 
brought out as Publication 6 of the Carnegie Institution 
under the title of ‘« Desert Botanical Laboratory of the Car- 
negie Institution.” Additional results have been published 
in the Plant World for November, 1903, and reprinted in 
the Garden publications as ConrrizuTiIon 46. During the 
trip made in selecting a location for the Desert Laboratory, a 
number of living and preserved specimens of plants were 
secured by means of funds of the Garden. 
