186 INTERNATIONAL BOTANICAL CONGRESS. 
and it is quite impossible for him to study their complete development 
during the whole year. The notes taken by the most intelligent 
naturalist are so affected by these fatal circumstances, that it is seldom 
they add anything to that which a dried specimen can teach the seden- 
tary botanist. 
It is horticulture, then, which brings before us a multitude of exotic 
plants in a condition best adapted for study. Thanks to the variety 
of species it accumulates and successfully cultivates, the botanist can 
investigate the most difficult questions, and pursue his researches in 
families g are not indigenous in Europe. In the herbarium 
more minute observations can be made than is generally supposed ; 
nevertheless, for certain researches, it is absolutely necessary to have 
the living plant, particularly for those relating to relative disposition, 
the origin and development of the several organs, as well as for study- 
ing the curious phenomena of fertilization, the movements and direc- 
tion of the stem, leaves, and parts-of the flowers. Horticulture has 
done much to advance the progress of physiological botany, but it still 
has much to do. The most remarkable experiments of physiologists— 
viz. those of Hales, Duhamel, Knight—have been made in gardens. 
Also the long series of experiments of the younger Geertner, and, more 
recently, of M. Naudin, on hybridization, which relate to the cardinal 
subject of the species. As much may be said of the numerous trials 
which are made, in horticultural establishments, to obtain new races 
or varieties. These have a great scientific importance, and it is un- 
doubtedly the horticulturists who are the teachers of botanists on these 
subjects. 
It appears to me, however, gardens can be made still more useful 
in carrying out physiological researches. For instance, there is much 
yet to be learnt on the mode of action of heat, light, and electricity 
upon vegetation. I pointed out many of these deficiencies in 1855, in 
my * Géographie Botanique Raisonnée.’* Ten years later, Mr. Julius 
Sachs, in his recently-published and valuable work on physiological 
botany,f 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 
B * Pages 2. n. s and 1346. 
I t = anon Erperimental-Physictogia der Pflanzen,’ 1 vol. 8vo. 
