BRIEPER ARTICLES 
CONCAVITY OF LEAVES AND ILLUMINATION 
(WITH ONE FIGURE) 
Concavity of the upper surfaces of leaves is of extremely common 
occurrence among the higher plants. WIESNER, in an important paper,’ 
has discussed this concave upper leaf surface as a characteristic of the 
peripheral leaves of woody plants, and states that the leaves within the 
shadow of the crown of trees (with concave outer leaves) are generally 
flat or nearly so. He classes these and other leaves which are capable of 
Fic. of cross-sections of leaves, taken at right angles to the midrib 
(if there is cae cau through its middle point. #. a, Astilbe decandra; b, Prunus 
persica; c, Syringa vulgaris; d, Akebia quinata; e, Citrus medica; /, Styrax japonica; 
g, Begonia semperflorens; h, Schizophragma hydrangeoides. 
some kind of temporary or permanent adjustment to the amount of light 
received as panphotqmetric leaves, regarding the concavity as useful in 
preventing injury to chlorophyll by excessive sunlight. OLTMANNS? calls 
attention to the fact that the leaflets of Robinia Pseudo-Acacia are concave 
on the south sides of trees, but flat on the north sides. 
It seemed to the writer worth while to make some notes as to the occur- 
rence of the concavity in question among various genera, particularly among 
trees and shrubs, and to take a few measurements of the amount of con- 
t WIESNER, J., Anpassung des Laubblattes an die Lichtstarke. Biol. Centralbl. 
I-15. 1899. 
2 OLTMANNS, F., Photometrische Bewegungen der Pflanzen. Flora_79:232, 233. 
1892. 
459] {Botanical Gazette, vol. 48 
