glO EXPERIMENT STATION EECOP.D. [Vol.36 



about a month of growth these measurements were repeated and. also, the 

 average leaf area and the average dry weight of tops per plant were 

 determined." 



It was found that the conditions at Easton were more favorable for the 

 growth of soy-bean plants than those at Oakland. " The total efficiency of the 

 Easton frostless season for 1914, measured in terms of leaf-product as here 

 used, was about 2.5 times as great as that of the Oakland frostless season."' 

 Stem height, leaf surface, and dry weight furnished the best means of compari- 

 son of the growth rates of the experimental plants. " The rates of growth in 

 stem height were generally more rapid during the first than during the second 

 fortnight of growth from the seed, for both stations. On the other hand, the 

 rates of increase in leaf area (as approximately measured by means of the 

 leaf-product) were generally more rapid during the second fortnight." 



The growth rates generally showed very evident seasonal marches which were 

 most clearly shown by the rate of Increase in stem height and corresponded in 

 general trend to the seasonal marches of the temperature conditions. " The 

 seasonal marches of both the growth rates and the temperature values for Oak- 

 land are quite markedly different from those for Easton. Both ranges are 

 greater for Easton than for Oakland. The highest temperature values and the 

 highest growth rates occurred at Easton. and the growing season was termi- 

 nated by killing frost earlier at Oakland than at Easton. Nevertheless, the 

 last two-week period before autumn frost at Oakland exhibited a higher tem- 

 perature value and higher growth rates than did the last two-week period be- 

 fore frost at Easton. 



" This difference between the magnitudes of the final minimum growth rates 

 observed at the two stations appears to emphasize one of the main differences 

 between a mild, equable, coastal climate and a much more rigorous mountain 

 climate, as these may influence plant growth. In the milder climate of Easton. 

 with its small daily range of temperature, the frostless .season is apt to be pro- 

 longed until the growth of many plants is much reduced or entirely checked by 

 low temperature. In the mountain climate of Oakland, however, with its large 

 daily range of temperature and high nocturnal radiation, very low night tem- 

 peratures and frosts occur earlier in the season, while the day temperatures 

 and the growth rates of many plants are still high. These differences between 

 the two stations, as regards the temperatures and growth rates exhibited at 

 the close of the season (just before autumn frost), are surely intimately asso- 

 ciated with the two types of climate here illustrated, and are of undoubted im- 

 portance in the consideration of plant life in general. 



"Another difference to be noted between the two stations here considered 

 refers to the time of occurrence, within the growing season, of the maxima of 

 temperature and of growth rates. The.se maxima occurred about a month 

 earlier at Oakland than at Easton — a fact that may be of significance in the 

 comparative seasonal climatology ot these stations, at least for the summer of 

 1914. . . . 



"It appears that temperature was clearly the limiting condition (in the usual 

 sense) for growth during the first two weeks, in practically all cases. During 

 the second two weeks of growth, however, with exactly the same environmental 

 conditions, the moisture relation (rainfall-evaporation ratio) appears in oi.any 

 cases to have been the limiting condition for growth, this being e^^pecially 

 true . . . when the temperature was high. It thus appears that if two plants 

 In different stages or phases of their development are exposed to the suuie fluc- 

 tuations in environmental conditions, the limiting condition for one plant during 

 a succeeding period may be of an entirely different nature from that for the 



