1909] OLSSON-SEFFER— VEGETATION ON SEA SHORES 89 



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6 a. m. 8?5 C. 10 A. if. 14 C. 2 p. m. 23?6 C. 



7 A.M. 9.2 II A. M. 17 3 P.M. 27.2 



8A.M. 9.8 I2M. 19.4 4P.M. 27.5 



9 A.M. 11. 4 ip. m. 20.6 5 P.M. 22.4 



6 p. m. 15.9 



un 



About 6o m inland between the pines, and sheltered from winds, the thermometer 

 gave 7?4C. at 6 a. m., 9? 2 C. at 9 A. M., i6?6 C. at noon, 28 C. at 3 p. m., 

 i6?2 C. at 6 p. m. This shows that the temperature was slower to rise in the 

 morning and forenoon, but once high it was also slower to decrease, when the 

 energy of the solar rays w T as diminishing toward evening. 



Observation 576. — Dunes at North Beach, near Perth, Western Australia, 

 September 12, 1902. Maximum in the shade 3i?i C. (8 A. M.-6 P. Iff.). Mini- 

 mum 6?8 C. (6 p. m -8 a. m.). Range 24?3. The instruments, from Negretti 

 & Zambra in London, were elevated 3o cm above ground and shaded by a white 

 canvas tent with open sides. The hourly variation was the following: 



8 a.m. 7? 9 C. 12 m. 23?6C. 4P. m. i9?5C. 



'9A.M.H.2 IP.M. 29.4 5P.M. 16.3 



IOA.M. 15.6 2P.M. 30.7 6P.M. 9.6 



II A. M. 18.6 3 p. M. 20.3 



These data show, as in the previous observation, that the temperature rose 

 steadily until about 2 p. m., although the rise is so much more rapid in these 

 latitudes on account of the greater energy of the sun. In this case, however, 

 over io° in a single hour, and nearly io° more between 4 and 6 p. m. 



Western 



Cooke 



the nights are generally cool the whole year round. 



The influence on vegetation of such a wide range of temperatures 

 m ust necessarily be of considerable importance. Although these air 

 temperatures have been largely affected by radiation, the direct radi- 

 ant heat of the sun is still more important. Actinometric methods 

 °f registering intensity of solar radiation are, as yet, very unsatisfac- 

 tory. Almost the only instrument available for field observations is 

 te so ' call ed black-bulb thermometer in vacuo. The rather casual 

 observations of this kind made bv the writer will be referred to in 



pother pl aC e in connection with 



^ ay suffice > however, to say here that these occasionally taken 

 ^easurements, in spite of their discontinuity, have convinced the 



W. er ^ at the surest and most effective way of attacking the prob- 



getation is to pursue investigations on the 



some 



It 



Des of actinometric records. 



Neither the mean 

 eric temperature is 



