1904] BERGEN—RELATIVE TRANSPIRATION OF LEAVES 451 
leaves that live only about fifteen months, while those of others live 
more than two and a half years. 
2. All of the leaves studied reach their maximum area consider- 
ably before they attain their full thickness. 
3. The leaves of six out of the eight species studied transpire more 
for equal areas when fifteen to eighteen months old than they do 
when they have just reached their maximum area (i. ¢., at three or 
four months). 
4. Transpiration for equal weights of leaves is generally more 
active for leaves of fifteen or more months than for those of three 
months or a little older. 
5. Epidermal transpiration bears a much smaller ratio to total 
transpiration in leaves of three months than in those of fifteen months. 
Naptes, ITALY, 
