Sir Francis Darwin. 
*7 
STEPHEN HALES, A REPLY TO CRITICISM. 
By Francis Darwin. 
X N the New Phytologist, Vol. XIII, p. 194, Professor Harvey 
Gibson criticises some remarks of mine in The Makers of British 
Botany. My statement “ Hales, of course, knew nothing of 
stomata” is careless, but if its context is taken into account it can 
hardly be considered inaccurate. After a comma at stomata the 
sentence continues: “but it is surprising to find Sachs in 1865 
discussing the problem of transpiration with hardly a reference to 
the effect of stomatal closure.” The words quoted by Harvey 
Gibson are also immediately preceded by a discussion on Hales’ 
observation of nocturnal diminution in transpiration, concluding 
with the words: “ This difference may be accounted for by the 
closure of the stomata at night.” So that the words criticised are 
guarded on both sides by expressions which might have shown my 
critic what was meant, viz., that Hales knew nothing of stomatal 
closure. 
I am also called to task for saying that Hales “ does not in any 
way distinguish between respiration and assimilation.” My critic 
quotes from Hales:—“we may therefore reasonably conclude that 
one great use of leaves is what has long been suspected by many 
viz., to perform in some measure the same office for the support 
of vegetable life that the lungs of animals do for the support of animal 
life; plants very probablydrawing through their leaves some part of 
their nourishment from the air.” This sentence seems to me to justify 
my contention that Hales did not distinguish the two processes in 
question.’ But here again Harvey Gibson considers I am wrong, and 
proceeds: “ Crude as was the knowledge of animal physiology in the 
time of Hales it can scarcely be believed that Hales conceived the 
lungs to be nutritive organs, and the sentence quoted therefore seems 
rather to indicate that he regarded the leaves as serving both as a 
respiratory and as a nutritive apparatus.” 
The foundation of Hales’ views on the nutrition of plants was 
the sentence he quotes from Newton, “ Dense bodies by fermenta¬ 
tion rarify into several sorts of Air; and this Air by fermentation, 
and sometimes without it, returns into dense bodies.” * 
1 I am glad to find that I am in agreement with the late J. R. Green (A 
History of Botany from the Earliest Times, Sic., p. 203) who remarks that, in the 
passage quoted, Hales “ seems to confuse the two processes of respiration and 
nutrition, but neither of these had taken shape in scientific thought.” 
2 Vegetable Staticks, 1727, p. 165. 
