232 ' Address of Prof. DeCandolle 
studying the curious phenomena of fertilization, the movements 
and direction of the stem, leaves, and parts of the flowers. Hor- 
ticulture has done much to advance the progress of physiological 
botany, but it still has much todo. The most remarkable ex- 
race These have a great scientific importance, and 
it is undoubtedly the horticulturists who are the teachers of 
It app me, however, gardens can be made still more 
useful in carrying out physiological researches. For instance, 
there is much yet to be learne e mode of action of heat, 
light, and electricity upon vegetation. I pointed out many of 
these deficiencies in 1855, in my “Géographie Botanique Rai- 
Ten years later Mr. Julius Sachs, in his recently pub- 
lished and valuable work on physiological botany,’ remarks 
much the same deficiencies, notwithstanding that some progress 
has been made in these matters. The evil consists in this, that 
when it is desired to observe the action of temperature, either 
fixed or varied, mean or extreme, or the effect of light, it is ex- 
ceedingly difficult, and sometimes impossible, when observations 
are made in the usual manner, to eliminate the effects of the 
ne variations of heat and light. In the laboratory it is 
wished to ascertain the influence of the gases diffused in the at- 
mosphere around plants, or that of the plants themselves upon 
the atmosphere. 
Place plants under a receiver, and they are no longer in a natu- 
ral condition; leave them in the open air, and the winds and 
currents, produced at each moment of the day by the temperature, 
disperse the gaseous bodies in the atmosphere. Every one is 
aware of the numerous discussions concerning the more or less 
pernicious influence of the gases given off from certain manu- 
factories. e ruin now of a manufacturer, now of a horticul- 
turist, may result from the declaration of an expert; hence it is 
incumbent on scientific men not to pronounce on these delicate 
questions without substantial proof. 
Pages 46, 49, 57, and 1346, é ; 
Handbuch der Experimental-physiologie de Pflanzen, 1 vol. in 8vo. Leipzig, 
