﻿4i8 BOTANICAL GAZETTE [june 



maxima of daily temperatures Is a little higher, the mean daily 

 humidity a trifle lower, and the rainfall notably more than at 

 Capri. On the mainland in general the temperatures would run 

 somewhat higher and the humidity lower than at Capodimonte. 

 The total rainfall for the year at Capodimonte (average of 35 

 years) is 865.5"^"*. In an average winter there are only two days 

 in which the temperature falls below 0° C. 



The plants w^hich constitute the macchie of the territory under 

 discussion show their xerophytic character more by their mech- 

 anisms for the prevention of transpiration than by their provi- 

 sions for absorbing water or for storing it in large quantities. 

 The most notable succulent plants found in the Neapolitan 

 region are two introduced species, Agave americaiui L., and 

 Opuntia Ficus-indica Mill., neither of which occurs as a member of 

 the plant societies here treated. The root systems of most of the 

 plants which constitute macchie are extensive and in the case of 

 many of the species examined by the writer contained more tissue 

 than the stems. The most nofably developed roots examined 

 were those of Daphne Gnidinm. This occurs as an undershrub, 

 with slender clustered stems, usually less than a meter in height. 

 In one specimen examined the average height of the stems was 

 70^"^ and the total length of the tap root and its immediate 

 branches was 490''"', with a diameter at the crown of 7*'°'.' The 

 leafy stems together weighed 190^"", while the root system (not 

 quite all secured) weighed 3,030^^. The roots evidently con- 

 tained much water, and this accounts for the fact that the Daphne, 

 after four months of rainless, hot weather, showed perhaps less 

 signs of distress than any other member of the plant society to 

 which it belonged except Thymelaea. 



It has seemed to the writer best worth while to devote his 

 attention mainly to the discussion of the various hindrances to 

 transpiration which present themselves in the most evidently well- 

 equipped of the xerophytic shrubs and undershrubs already 

 enumerated. These adaptations may perhaps best be exhibited 

 in some such table as the following: 



