44^ Bulletin 2yC). 



PLACE VARIATION 



As a result of the development of statistical methods and their appli- 

 cation to biological problems, we have recently come to recognize the 

 fact that a living plant is not a stable organism, but is more or less 

 plastic, responding to changes of environment, so that an expression 

 of the condition of the plant at any given time or in a given place may 

 not be true for any other time or locality. This has been demonstrated 

 by the researches of Burkhill (1895), MacLeod (1899), Ludwig (1901), 

 Tower (1902), Shull (1902), Yule (1902), Pearson (1903), Reinohl 

 (1903), and Shull (1904). 



One of the first to emphasize the importance of studies along this 

 line was Davenport (1899), who suggested the term "place mode" 

 to indicate "the condition of a species in a particular locality at a par- 

 ticular time." This idea has been expanded so as to include other 

 constants than the mode, as well as the frequency distribution itself. 

 This broad use of the term has been objected to by Pearson (1902) 

 on the ground that it is not strictly biometric. As a term of more general 

 application which would include all the measurable characteristics of 

 the population Shull (1904) has proposed "place condition." 



Variation from season to season or from year to year in response to 

 fluctuations in environmental conditions has been designated by Tower 

 (1902) as "secular variation." In a subsequent paper (1906), this 

 term has been superseded by "place variation." 



In a study of this phenomenon the following phases may be considered, 

 as outlined by Tower (1906); "(i) place variation, or the variation 

 in any given species in the same locality from generation to generation, 

 or from season to season, or year to year; (2) place condition, as the state 

 prevailing in the population of a given species at a particular locality 

 during one generation; and (3) place constant, determined for the popu- 

 lation of a given species at a given locality for one generation." 



The data on which this discussion is based afford an exceptionally 

 good opportunity for the study of place variation, since complete records 

 have been obtained for four characters in each individual plant for 

 three years, the same individuals being under observation for the entire 

 period. Moreover, the numbers are sufficiently large to represent, to 

 a large degree, the condition of the species. 



A study of the climatic conditions which prevailed during the growing 

 season of each of the three years shows a sufficient degree of dissimi- 

 larity to account for some of the changes observed in the population 

 (Figs. 138 and 139). In 1905, the month of May, when the plants should 

 have been making a vigorous growth, was a period of abnormally low 



