384 The Botanical Gazette. [September, 
Physiology is an experimental science, and the public must 
perforce derive its knowledge second hand without much op- 
portunity of verification. It must be admitted that, although 
a view of this portion of the res publica nature has its fascin- 
ation, yet the attainment of vantage ground for the survey is 
necessarily difficult and slow. 
The term public, when used in connection with vegetable 
physiology, needs to be construed liberally. It will include, 
without doubt, some able scientists and men of liberal education 
may be permitted to cite an occurrence to which some in 
this audience were witnesses. Some time since the subject 
of gases in plants was before the Association and induced an 
animated discussion. Probably half of those participating 
confounded respiration, which is a general function of all 
plants, as well as animals, under all conditions of existence, 
with the photosyntactic function of fixation of carbon by the 
green parts of plants in the presence of sunlight. Both pro- 
cesses have to do with oxygen and carbon dioxide, but the re- 
semblance goes no further. It is an error dating back to the 
last century, when the two processes were discovered, and 
one for which botanists themselves are by no means without 
responsibility. Another error not yet dislodged from the cob- 
webby corners of many a well-read man’s intellectual store- 
house is the old fiction of a circulation of sap, so dear to those 
who desire to find analogies in plants with the physiological 
processes of animals. It is not much over fifty years since 
the learned French Academy exhibited its ignorance of vege- 
table physiology by awarding the grand prize to an essay 
founded upon this error; and the error still lives. 
But the general ignorance of even the best established and 
most readily apprehended facts of physiology may be justly 
extenuated when the pedagogical status of the subject is eX- 
amined. Botany, as a substantial part of the curriculum, 
cannot be said to have received recognized standing in the 
American educational system until the time of Asa Gray. In 
the latter part of the decade of the thirties his first text-book, 
the ‘‘Elements of Botany,” appeared, and in the decade following 
the ‘‘Text-book for Colleges” and the ‘‘Manual,” all of which 
works showed a true appreciation of the best features of 
the science and the needs of the time. They were so We 
conceived, and so much in demand, that new editions rapidly 
succeeded one another; and to the present day they hold a 
