308 CARNEGIE INSTITUTION OF WASHINGTON. 



flower shows that the sepals lose their power of movement first, followed by 

 the petals and stamens. In Pachylophus coBspitosus and Aster bigelovi, on the 

 contrary, the movements are induced by temperature changes, cold opening 

 the one and closing the other, while heat has the opposite effect. In both, 

 the effect is readily reversible, in Aster especially it being possible to open and 

 close the flowers repeatedly and at all times of day. The response in the 

 latter bears a definite relation to the age of the head and rays as shown by 

 the number and condition of the disk-flowers that are in bloom. Young 

 heads clo&e or open completely in a few minutes, older ones more slowly, 

 and old ones imperfectly after an hour or more, if at all. 



Experimental Taxonomy, by F. E. Clements, H. M. Hall, and David Mason. 



A series of long-time experiments, designed to test the nature of characters 

 used in the classification and description of plants, was initiated in 1919, 

 and additions have been made in each succeeding year. During 1923 all 

 transplants previously made in this study were carefully curated and their 

 condition recorded. Several hundred new reciprocal and variation trans- 

 plants were made, but especial attention was given to the formation of a 

 series of adaptation gardens where species may be grown under as large a 

 variety of conditions as possible. For example, at 4,500-feet altitude in the 

 Sierra Nevada of California, small tracts were prepared to give the following 

 range of conditions: diy sun, wet sun, diy shade, wet shade, and half shade 

 with the addition of nitrogenous fertilizer. In a series at the Alpine Labor- 

 atory the habitat factors have been measured for a number of years and 

 similar installations will be made from time to time in the other series. Fifty 

 species of plants were selected, mostly herbaceous perennials, and uniform 

 representatives of each were moved into all of the prepared areas. Whenever 

 possible, as in the case of species with root-stocks, the propagules were all 

 taken from a single individual. Since the entire series was repeated in a 

 second set of gardens, the total number of plants moved at this station was 

 500. A similar series of experiments was inaugurated at 9,000-feet altitude 

 in the same range, but here only three sets of conditions were provided. Fifty 

 species were moved in duplicate, making 300 transplants at this station. 



In order to test the effect, upon plant structures, of factors connected with 

 altitude, and in order also to determine the limits of ecesis, some attention 

 has been given to the transfer of sods and rooted plants to different elevations. 

 About 50 alpine and subalpine species of the Sierra Nevada were transferred 

 to a tract at 9,000-feet altitude, many of them as sods with at least one cubic 

 foot of soil; 110 species were similarly transplanted to 4,500-feet altitude; and 

 about 30 species were taken to sea-level. Transplants in the opposite direc- 

 tion, in connection with this experiment, numbered about 75, some of which 

 came from the sagebrush association of eastern California. A considerable 

 number of alpine sods have been moved into the montane zone at the Alpine 

 Laboratory, and 3-5 individuals of characteristic dominants and subdomi- 

 nants of the plains grassland have also been planted in the same climax. The 

 total number of transplants now in position and growing is 2,267, of which 

 607 are in Colorado and 1,660 in Cahfornia. There are 499 species and 

 subdivisions of species represented in the experiments, 237 of these being 

 Rocky Mountain forms and 262 Calif ornian. 



