[Vor. 1 
2 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
(4), Swingle (21), and others. Moreover, with the exception 
of incidental references, we wish to deal at this time only with 
its physiological action in prolonging the vitality of leaves 
and plants. 
During the first years of the use of this spray mixture it was 
natural that any increased vitality of the sprayed plants would 
be attributed merely to the action of the fungicide in restrain- 
ing fungous or insect pests. Indeed, we find no authentic 
suggestion of any other effect than that mentioned for eight 
or ten years after the discovery of this fungicide. Since 1892 
there have been frequent observations indicating beyond any 
reasonable doubt that in the absence of all disease-producing 
organisms there is often prolonged vitality of the sprayed 
plants as contrasted with the unsprayed. The increased 
longevity is partieularly noticeable in plants like the potato, 
in which, under normal conditions, the foliage frequently dies 
in advance of the first killing frost. Nevertheless, lengthened 
life in leaves of deciduous trees, notably of the apple, has like- 
wise been reported. It is not always possible to state definitely 
to just what extent any apparent increased vitality is to be 
attributed to the physiological action of the fungicide rather 
than to the control of pests, and it must be said that the fre- 
quency of the phenomenon and the reliability of the observers 
alone preclude the possibility of constant errors in this matter. 
In practical field experimentation the most significant differ- 
ences in yield and vitality as a result of spraying with Bordeaux 
mixture have been evident in the case of the potato, and with 
this crop it is a matter of common observation both in Europe 
and America. In recent years the consecutive reports on 
potato spraying by F. C. Stewart (19) and his associates at 
Geneva, New York, suggest in a decisive way the probable 
magnitude of the Bordeaux influence when disease is a minor 
factor. In general, observers are perhaps liberal in their 
estimates of the gain from fungous suppression. 
It will be pertinent to note a few observations and comments 
from the reports of the work done at Geneva. In 1904 the 
increase in yield from spraying potatoes five times was 233 
bushels per acre. ‘Spraying prolonged the life of the plants 
25 days. Late blight was the only trouble.” In his experiments 
