DEPARTMENT OF BOTANICAI, RESEARCH. 63 



Vital Statistics of Desert Plants (by Dr. F. Shreve) : 



Statistical work has been undertaken with the giant cactus (Carnegiea), 

 palo verde (Parkinsonia) , and ocotillo (Fouquieria), with a view to deter- 

 mining the relative numerical proportions of groups of different ages to the 

 total population. Data are being secured which indicate the character and 

 direction of the changes in the population of these species, and through them 

 indicate the secular changes which are going on in the make-up of the vege- 

 tation as a whole. The work indicates a diminution in the succulents and 

 an increase in the sclerophyllous perennials on the clay soil of the Desert 

 Laboratory domain. 



Vegetation in the Santa Catalina Mountains (by Dr. F. Shreve) : 



A study of the climatology and vegetation of the Santa Catalina Moun- 

 tains is being prosecuted in connection with the acclimatization work pre- 

 viously inaugurated by Dr. MacDougal. An aggregate of several weeks 

 of observational work has been done during the summer of 1910, with a 

 view of determining the vertical limits of certain common species in relation 

 to slope-exposure and soil-conditions. The beginnings have been made of 

 an attempt to establish certain native species above their natural limits in 

 order to determine what phase of the climatic complex is most potent in 

 limiting the vertical range. A digest has been made of the climatological 

 records which have been accumulating for four years from the mountain 

 plantations and the intermediate stations. The results have been a deter- 

 mination of the rate of shortening of the growing-season with increase of 

 altitude and the determination of certain principles with regard to the zonal 

 differences in temperature, rainfall, and evaporation conditions. 



Physiology of the Hymenophyllacece (by Dr. F. Shreve) : 



Work on the Hymenophyllacese carried out in Jamaica in 1909 has been 

 completed and the results prepared for publication. This markedly hygro- 

 philous group is shown to have developed several epiphytic species, which are 

 relatively xerophilous, through the ability of their protoplasts to withstand 

 the loss of water from their sap-cavities, in which respect they resemble in 

 some degree the xerophilous ferns of the desert. 



Physiological Plant-geography of the Jamaican Rain-Forests (by Dr. F. 

 Shreve) : 



The observational and experimental work carried on at Cinchona, Jamaica, 

 in the latter part of 1909 is being collated and prepared for publication. 



Vegetation and Climate of the United States (by Dr. F. Shreve) : 



In collaboration with Dr. Livingston, studies are being continued on the 

 distribution of the plant formations of the United States and on the distribu- 

 tion of particular physiological types of plants with respect to the distribution 

 of the climatic factors inducing them. 



