XO. ;V_>«)] 



ORGANIC RESPONSE 



25 



slightly less than the amount in the winter. The yearly 

 total is between 35 and 40 inches. The vegetation is 

 characterized by conifers, grasses and a wide variety of 

 herbaceous and shrubby perennials, very few annuals 

 being found here. The mountain streams carry the seeds 

 of the contiguous elevated slopes and valleys in great 

 profusion to the region of the xero-montane plantations 

 and to the lowlands of the character of those around the 

 Desert Laboratory. These three localities form a con- 

 nected series in which the behavior of the tested species 

 may be expected to offer phenomena of wide significance 

 and of direct bearing on many phases of geographical 

 distribution and evolutionary advance. 



The fourth plantation is at Carmel, California, some 

 800 miles distant in a straight line from the first three, 

 within a thousand yards of the Pacific Ocean in a forest 

 of Monterey pine, the soil being granitic sand, with or- 

 ganic material or humus in some places, and a heavy 

 cement in others. The climate is characterized by a win- 

 ter wet season, in which the minima are scarcely below 

 the freezing point and the exposure to such low tempera- 

 tures is for not more than fifteen or twenty hours per 

 year. A period of heavy continued fogs during two 

 months of the midsummer results in minima of 41° F. 

 in July and August, there being almost no precipitation 

 between March and Xovember. The total precipitation is 

 about 18 inches per annum. The place, therefore, has 

 one rainy season, a dry spring and fall, and a cool mid- 

 summer, conditions exceptionally favorable for the sur- 

 vival of species introduced from the localities of the 

 other three plantations of the series. It is obvious that 

 if the data concerning the climatic factors are integrated 

 or summarized and placed in parallel columns a ready 

 means is afforded for detecting the causes which prevent 

 survival or facilitate the development of any form in 

 any locality, and a proper analysis of the same facts 

 may also yield direct suggestions as to the nature of the 

 excitation responsible for any departure on the part of 

 a plant removed from one habitat to another. 



