; 458 General Notes. [May, 
transpiration per se (theoretically distinct from the purely physi- 
cal process of evaporation, which takes place from all moist sur- 
faces and bodies, dead or alive) is especially, if not solely refera- 
ble to those particular bands of light which are absorbed by 
chlorophyll, and that such light, being arrested, is converted into 
heat, which then raises the temperature within the tissues and 
causes the loss of water. The only additional fact which I have 
here advanced, somewhat tentatively, is, that yellow light hasa 
retarding influence upon transpiration, for the reasons given 
above. That ‘life’ has a retarding influence upon evaporation as 
distinct from transpiration, I think my experiments (which I hope 
to continue hereafter) have distinctly proved.” 
It will puzzle any one to make out a good reason for using two 
terms for the process of water-loss in plants. We have it said 
that “ evaporation” is the “ purely physical process,” while the 
experiments show that what is called “transpiration ” is, after all, 
a physical process also; and when we are told, as in the last sen- 
tence above, that “ life has a retarding effect on evaporation,” the 
confusion of ideas becomes somewhat embarrassing. : 
use but one term, and that the more general one—evaporation? 
The fact of modification or control of: evaporation is so common 
a phenomenon in nature that we cannot regard it as of great 
significance. Common salt or sugar added to water retards evap- 
oration. 
~ 
r ical index to all the species. The first fifteen centuries were pub- 
. 
hope that Series 1 will carry the work up to thirty centuries i 
