288 BOTANICAL GAZETTE _ focroper 
It was not possible in every case to obtain the per cent. of total 
illumination for the shade leaves examined. Those noted were as 
follows: (4) 2.8, (6) 2.2, (7) 4.6, (8)A 1.8, (8)B 1.1, (9) 4.6. 
It is obvious from inspection of the results obtained that the sun 
leaves are usually narrower than the shade leaves in proportion to 
their length. This is especially 
true of the leaves of Citrus, 
Olea, and Quercus; and the 
Olea and Quercus are cer 
tainly among the most xero- 
phytic of the nine species in 
$15 
Fic. 1.—Leaves of Olea europaea: a, the list above given. Fig. : 
sun leaf of very xerophytic form; B,sun leaf; _ sufficiently illustrate the differ- 
si shade leaf from another tree; D, sun leaf; nce in form of the leaves in 
E, shade leaf from another tree which is in 
° 
constant partial shade. question. 
A..other difference between 
the sun leaves and the shade leaves of many species consists in the 
manner in which the margins of the former are recurved. In many 
instances the under leaf surface of sun leaves is, strongly conc 
while that of shade leaves is nearly plane. This is well shown in 
the cross sections of jig. 6. 
In the case of Olea the sun 
leaves and shade leaves differ 
remarkably in the manner in 
which they present their sur- 
faces to the light. The latter 
are arranged in a somewhat 
horizontal manner, that is with 
the lower surface approxi- A, soo 
_Mately parallel to the ground. Fic. 2.—Leaves te - 
But the former in many - weer: am ‘a D, 
instances oe with the a sae cee tree, XO4- 
ointing almost straight rox 
Sas . downward. ts debe words, the shade leaves 7 
mately euphotometric and the sun leaves pan in 4 
not appear that the edges of the leaves are present ints of the 
and south direction more frequently than toward other pe 
