284 
The leaf of C. aléa, though similar in many respects, does not 
show the same adaptation to extremes of climate. It is more 
nearly flat, thus.exposing a larger surface. The. rolling under of 
the blade and the growth of hairs on the lower surface form a pro- 
tected cavity which, in a measure, regulates the amount of evapor- 
ation through the stomata, but still the air has free access to the 
whole surface. Here again are the raised stomata, but much 
fewer in number. In one respect, however, this leaf is better pre- 
pared for extremes of temperature, namely, the enormous thickness 
of the cutinized outer wall of the upper epidermis, which even 
exceeds that of Cowrvadii in most instances. : 
The leaf is the first organ where we should expect to find 
changes for the accommodation of the plant to a changed environ- 
ment. It is primarily the organ for the individual uses of the 
plant, for through it is obtained food material from the air, and in 
it the chief processes of metabolism are supposed to take place. 
Again, it is the metamorphosed leaf which is used for the a 
productive processes of the plant. Here the leaf gives up its 
function as the servant of the individual and its energy is turned to 
the perpetuation of the species. In the whole life history of 4 
plant species the leaf is the inconstant organ, changing its form 
and function for the varying needs of the individual and the 
species. The stem, on the contrary, is the constant organ. It is, 
therefore, to the anatomy of the stem, rather than that of the leaf, 
that botanists attach the first importance in the determination of 
relationship. In the same genus only the slightest variations are 
expected in the anatomy of the stems of the different species. 
In the two species under discussion the stem of Conrad 
agrees with that of C. aléa in all particulars, showing the ae 
deviations from the normal dicotyledonous type. The leaf of 
Conradii has all the peculiarties of a/éa shown in the raised 
stomata, the two sorts of hairs, the extremely thick cuticle, and 
the unusually large epidermal cells with the strengthening proj. 
tions of the cellulose wall. It disagrees in ways which indicate 
adaptation to environment rather than difference in origin. 
Therefore, the result of the comparative study of the tissues 
favors the classification already made of these two species. 
In view of the resemblance between the orders, a compariso? 
