﻿1903] 



MACCHIE OF NEAPOLITAN COAST REGION 



417 



It should be remembered in discussing the conditions of 

 existence of plants during hot and dry periods that they are 

 often exposed to the full heat of the sun, and therefore to a 

 very different temperature from the recorded maximum of a 

 meteorological observatory. Observations on the northwestern 



slope 



M 



Solaro, Capri, at about 350™ above sea level 



gave a temperature in the shade August 20 of 31 .6"' C, at 2 p. m. 

 Burying the bulb of the thermometer a centimeter or two in 

 the soil, in full sunshine, gave a temperature of 50. 5*^, and 

 placing the bulb of the instrument on the surface of the ground 

 and covering it w^ith dry grass, to exclude the direct rays of the 

 sun, gave a reading' of 52.2°. Other days during the same 

 month gave a temperature, as recorded at the neighboring 

 observatory, over three degrees higher than that of August 20. 

 so that the surface temperature, in sunshine, must have been at 

 times as high as 55° C, with a relative humidity as low as 29. 

 This extreme heat is sufficient to demand elaborate protection 

 to prevent excessive transpiration; it approaches the tempera- 

 ture(50° to 60°) of desert soil at midday in summer reported by 

 Volkens.3 Examination near the locality above mentioned 

 showed during early September an entire lack of sensible 

 moisture, /. e., moisture evident to the eye or the touch, to a 

 depth of from i to 2*". 



Some data in regard to temperature and rainfall, as recorded 

 at the Royal Observatory of Capodimonte, Naples, are given in 

 the little table subjoined. It is noticeable that the mean of 



1902 



<^ « 



O 

 41 



n = aj " 



M 



ay 



June 

 July. 



> 



-5 



*- ' 



c 



'x 



>>z 



C3 



n 



'Z *- 



^ 



f-> 



a 3 



^^r 



CTD i 



S 







I 



8. 



35 



2 



3- 



99 





C/l 



> 

 a 





H 





-5 = 2 



x. 



a u 



August 



28 . 73 

 28.66 



II .42 



16.59 



20.50 

 20.29 



.5 - 

 H 



-- - >. 



S-1 



r = = Z ^ 

 S C C O ^ 



= - - S 

 5 fc. 5 u 



"5 " S 



55-3 

 55.0 



53-8 



So. 2 

 8.0 



0.0 



9.0 



21.70 



25.41 



2S.53 

 2S.34 



53-42 



31-64 

 19. 12 



23. 8S 



3 George Volkens, Flora der ^egyptisch-arabischen Wuste 23. Berlin, 18S7. 



