﻿420 BOTANICAL GAZETTE . [june 



The characteristics which belong to each species are checked 

 in the horizontal line on which the name of the species occurs. 



It is evident at a glance that a majority of these plants have 

 more than one adaptation each to prevent too rapid transpira- 

 tion. Thyrnelaea hirsuta, which is protected in the greatest num- 

 ber of ways, is notable as being equally at home on parched 

 mountain sides and in the somewhat saline, almost waterless, 

 sands of Mediterranean beaches, above the reach of ordinary 

 waves. Six species are set down as deciduous in summer, but 

 they are not all equally so. The most notable of these are Spar- 

 tuitn juiiceufft and Etiphorbia de?idroides. The former generally 

 loses all its leaves early in the dry season and does not usually 

 acquire new ones until the following February, while \.\\e Etiphor- 

 bia, when in fairly good soil, retains all, or nearly all, of its 

 immense number of leaves (much like those of E, Cyparissias L. 

 of the northeastern United States, only on a larger scale). ' But 

 in the scantiest soil, or when found growing in the crevices of 

 sunny cliffs, E, dendroides appears in summer as a rather succu- 

 lent, absolutely leafless, much-branched undershrub of a meter 

 or less in height. The economy in transpiration, due to the leaf- 

 less summer condition of the plant, may be appreciated from the 

 results of a rough experiment. A leafy twig, cut on August 29, 

 Z^"^ long, bore 86 leaves, of an area varying from 9=^*="^ each for 

 the older leaves to about 0.2 5 ^^"^^ each for the youngest ones. 

 The cut end of this twig was sealed with grafting wax, the cut 

 end of a leafless twig was similarly sealed, then both were 

 weighed and left for 48^" freely exposed to the air and sun- 

 shine. On reweighing, the leafless twig was found to have lost 

 5 per cent, of its weight and the leafy one 23 per cent. 



The large number of plants in these macchie which owe their 

 tolerance of extreme drought to a glossy reflecting leaf epider- 

 mis (and usually also to the coriaceous texture of the leaves) is 

 a noteworthy fact. Various species of the same genus are often 

 protected against excessive transpiration in very different degrees. 

 For instance Quercus Ilex, Q. Aegilops, Q. Cerris, and Q. pub esc efts 

 constitute a series of decreasingly xerophytic character. The 

 first has small, extremely coriaceous leaves, with a felt-like 



