1904] BERGEN--RELATIVE TRA NSPIRATION OF LEA VES 447 
aa) 
bd : Juglans, Populus, Fagus, Cas- 
: Me inter decidu- tanea, Quercus (in part), Ulmus, 
_ Morus, Ficus, Vitis, etc. 
I. Leaves simulta- Calycotome villosa 
| neously deciduous 
y | 2. Summer de- 
ciduous 
Medicago arborescens 
| Euphorbia dendroides 
1. Le e 
of them lasting | Olea europaea 
two years or Pistacia Lentiscus 
more 
I. Leaves not simulta- 
neously deciduous | Rhamnus Alaternus? 
| (evergreen) 2. Leaves lasting | Nerium Oleander? 
| more than one 
rear but less Quercus lexs 
ys Ceratonia Siliquas 
pags: . Arbutus Unedo3 
mis and Nerium Oleander are therefore much less leafy by July 1 
than they were throughout May. 
A large proportion of the time spent was devoted to leaves of the 
so-called Myrtus type; those namely of Olea europaea, Quercus 
Ilex, Rhamnus Alaternus, and Nerium Oleander. 
Four other species, namely, Pistacia Lentiscus, Hedera H elix, 
Smilax aspera, and Viburnum T. imus, were also studied, in order 
to give any conclusions that were reached a more general value, as 
applicable to the sclerophyll trees and shrubs of the region. 
With very species, some comparisons of the relative rate of — 
transpiration for old and new leaves were made as soon as the latter 
had reached their full areal growth. = 
RELATIVE THICKNESS OF OLD AND NEW LEAVES. 
On comparin g the thickness of the old leaves with that of new ones 
of the same Species which had just reached their full area (usually in 
May ) the older ones were commonly found to be somewhat thicker. All 
Of the species in the list above given were examined except Viburnum, 
and : s thickness old leaf _ 
and the average ratio for all seven species was ‘iki 
The steatest disparity was found in Pistacia, which sometimes gave 
* Tatio of 1.48, and the least was in Hedera, which frequently 
ee wed no difference in the respective thicknesses. The greater 
Mckness of the old leaves was not mainly due to growth of the 
* These last fifteen months or but little more. 3 These last eighteen months or more. 
