282 
F. C. Newcombe 
must say that neither the figures in the plate nor those in the text 
can be accepted as lending evidence for the reversal of response. 
All five figures in the text, except number 4, show the roots shrivelled 
and distorted to such a degree that one used to the behaviour of roots 
must regard the figures as worthless for demonstration. Root 
number 4 in the plate is a fairly normally appearing root of Zea mais, 
but, unfortunately for the assumption of the reversal of geotropism, 
it is growing almost vertically downward. 
In the three text-figures of Vida faba roots, one root is so dis¬ 
torted as to exclude it from consideration. The placing of the other 
two figures, with the absence of any textual explanation of their 
peculiar form and appearance, prevents the reader from using them 
as an aid in forming his judgment. The three main roots of Vida faba , 
just referred to, have growing from them 14 secondary roots from 
1 to 25 mm. in length. Of these, only three can be counted as showing 
upward curvatures. The author speaks of fungi growing on his 
seedlings after two or three weeks. One must wonder why cultures 
of seedlings in damp chambers should be continued for so long a 
time; since the time of Sachs it has been published again and again, 
and it is the common experience of experimenters, that the roots of 
seedlings growing in damp chambers become distorted or unhealthy 
or die in less than two or three weeks. 
In another series of experiments. Small grew seedlings in acetic 
acid vapour in damp chambers to see whether the stem would not 
show positive geotropism. He found that seedlings of Zea mais 
would grow fairly well over 1 per cent, of acetic acid. Of the 17 
maize coleoptiles shown in the illustration, 13 bend downward 15 
to 90°. The author states that the coleoptiles were about 25 mm. 
long when the seedlings were placed in the acid vapour. As in the 
illustrations the coleoptiles are shown with about 25 mm. length, 
it must be that the downward curves were made within a few hours 
of the introduction of the seedlings into the damp chamber, unless 
growth was very much retarded. Here again the reader must wish 
that the author had given greater detail in the text. With some 
reservation because of the lack of detail, it may be said that the 
figures of the coleoptiles shown support Small’s claim of reversal of 
response. 
The series of experiments by Small and Rea was carried out with 
the notion of causing the stems of seedlings to change from their 
assumed alkaline reaction to acid by smearing the shoots with 
vaseline, thus preventing the escape of the carbon dioxide of respira¬ 
tion. The authors state that the seedlings, after being smeared with 
vaseline, “must be placed vertically in the dark for two to seven days 
to allow the carbon dioxide to accumulate if downward curvature 
