TRANSACTIONS OF SECTION K. 769 
curvature returns on bringing the plants indoors, when the starch reappears. The 
full value of these experiments cannot be made clear without going into more 
detail than is here admissible. They are particularly interesting because, as 
Haberlandt remarks, so far as they prove the truth of the statolith theory, they 
also disprove the pressure theory. This may also be said of other experiments 
mentioned in the present section. 
We must, [ think, object on similar grounds to Némec’s observations, sugges- 
tive though they are, on the absence of geotropism in certain individual leaves 
and roots which, through unknown causes, had no statoliths.? 
The same must be said of the above-mentioned experiments of Haberlandt, in 
which geotropism is increased by rapid shaking in a vertical plane. I attempted? 
to avoid this fault in the similar experiments with a tuning-fork made inde- 
pendently, which showed that the effect of vibration in increasing reaction is far 
greater in the case of geotropism than in heliotropism, 
Haberlandt (00) made the interesting observation that plants deprived of their 
endodermis by means of an operation lose the capacity of geotropism. Here, again, 
we ought to know how the operation affects sensitiveness other than geotropic ; 
and, as Haberlandt grants, it may perhaps he said that the operation is too serious 
to allow of the foundation on it of a very convincing argument. 
The question how far the statolith theory is applicable to the root is a difficult 
one. It involves the old and apparently insoluble difficulty of distinguishing 
between the removal of the tip of the root, considered as a perceptive organ, 
and the effect of the shock of the operation. The question is, moreover, complicated 
by contradictory evidence. According to Czapek, cutting off a small part of the 
root-tip, an operation which does not remove the whole of the statoliths, interferes 
with geotropism in the same way as does actual amputation.® 
Némec, on the other hand, finds evidence for the operation depending on 
the removal of the sense-organ ; for according to him the power of geotroping 
does not return with the appearance of general symptoms of recovery, such as cell 
division and the growth of a callus, but only with the actual reappearance of 
statocytes. 
Némee’s most recent experiments‘ are confirmatory of this result. He finds 
that Lupin roots, from which } mm., 1 mm., and 1} mm. respectively are cut off, 
behave differently. ‘The $ mm. lot were clearly geotropic in seven hours, while 
no curvature occurred in the others. After a further interval of thirteen hours 
the 1 mm, lot had curved. Microscopic examination showed that statoplasts had 
appeared in these roots, but not in the 13 mm. lot, which showed no geotropism. 
It is particularly interesting that according to Némec the statoplasts appeared in a 
new growth which was visible as a slight convexity of the cut surface.° 
An experiment by Némec with the roots of V. Faba must also be mentioned. 
One millimeter was cut from the tips of each of a number of roots, and they were 
all placed horizontally. They were examined after fifteen hours, when considerable 
variety in the result of the operation was evident; some of the roots had bent 
geotropically, while others were still horizontal. On cutting sections it was found 
that the geotropic roots had statoplasts, the horizontal ones none. It may of course 
be said that the result depends on the effect of shock lasting longer in some 
individual roots, since, as Czapek has well said, the only proof of the disappearance 
of shock effect is the act of curving. But since the operation was approximately 
the same in all the roots, it is hard to believe in such a malicious coincidence as 
that the shock was smaller in all those roots which produced statoplasts. But it 
may be said that shock prevented both geotropism and statoplast-formation in 
certain roots. 
Czapek (02) quotes the experiment of Brunchorst, who found that a circular 
cut round the tip, not deep enough to free the terminal part, has the same effect as 
' Némec (01). * F. Darwin (03). 
§ Czapek’s results (02, p. 118) are in harmony with Rothert’s experiments on the 
heliotropism of Setaria, &c. * Nemec (04, pp. 46, 53). 
° This agrees, as Némec says, with Wachtel’s (99) result, who found geotropism 
returning before the whole tip was regenerated. 
1904, 3D 
