122 General Notes. [ February, 
In the body of the catalogue a few errors are noticeable, mis- | 
takes in the spelling of foreign name are not infrequent, and 
synonomy and origin of some plants (Rubus didicertsus is given as 
a native of Canada) will require correction for another edition, 
from which no doubt further study will remove some of the 
doubtful ice credited to North America. To directors of | 
botanic gardens, or to those whose duty it is to care for such col- 
lections, the Arboretum Segrezianum will be an invaluable aid. 
A volume of plates with technical descriptions of some of the 
last and little known species in M. Lavalée’s Arboretum is prom- 
ised, and is, we believe, already in press.— C. S. Sargent. 
RESEARCHES IN REGARD TO TRANSPIRATION IN PLANTs.—J. Wies- 
ner has published, in Annales des Sciences Naturelles, an account 
of his experiments pen this subject. The following i is a state- 
ment of his conclusio 
The effect of light upon transpiration is most obvious in the 
case of plants of a green color. The comparison of green and 
etiolated maize does not leave any room for doubt. 
The functions of chlorophyll in transpiration are evident. A 
part of the light which traverses the chlorophyll is transformed 
into heat, and from this results an elevation of temperature in the 
tissues. Increase of tension of aqueous vapor in the intercellular 
space follows, and the excess of vapor passes out by the stomata. 
It is therefore easy to understand how a plant can transpire ina 
saturated atmosphere, but only under influence of light. 
ese experiments were conducted in three ways: by c 
paring green and etiolated plants, by exposing the plant to ee 
solar spectrum, and by placing them behind solutions of chlor- 
ophyll. 
"The results from these three methods agree. They show that 
the presence of chlorophyll appreciably augments the action of 
light on transpiration; that it is the rays corresponding to the 
absorption bands of the chlorophyll spectrum, and not the more 
luminous rays which excite transpiration; and finally that the 
rays which have passed through a solution of chlorophyll exert 
only a feeble influence on transpiration. 
Other coloring matters, like xanthophyll for example, act like 
chorophyll, but to a less degree. Wiesner does not deny that — 
opening of the stomata may accelerate transpiration in sunlight, 
but the very great transpiration of maize, the stomata of which 
were closed, and the feeble transpiration of Hart twegia comosa, in 
which they were largely open in the dark, suffice to indicate that 
they are not the principal cause of transpiration in the light. 
e dark heat rays act in a very appreciable manner, but less- | 
than the luminous rays. So far as the ultra-violet chemical rayi eo 
are concerned their action is xi or exceedingly sligh 
_ Whatever the nature of the bole they always os ‘i increasing a 
oo the ers of the tissues 2 
Ap rt roe ae Pete a E N eee ee ee 
Pie rae se eee Pee 
