766 REPORT—:1904. 
analogy drawn from animals gives any support to the theory for plants. The 
study of sense-organs in plants dates, I think, in its modern development, at least, 
from my father’s work on root-tips, and on the light-perceiving apices of certain 
seedlings. And the work on the subject is all part of the wave of investigation 
into adaptations which followed the publication of the ‘ Origin of Species.’ It is 
very appropriate that one of the two authors to whom we owe the practical 
working out of the statolith theory should also be one of the greatest living 
authorities on adaptation in plants. Haberlandt’s work on sense-organs,' especially 
on the apparatus for the reception of contact stimuli, is applicable to our present 
case, since he has shown that the organs for intensifying the effect of contact are 
similar in the two kingdoms. No one supposes that the whisker of a cat and the 
sensitive papilla of a plant are phylogenetically connected. It is a case of what 
Ray Lankester called homoplastic resemblance. Necessity is the mother of 
invention, but invention is not infinitely varied, and the same need has led to 
similar apparatus in beings which have little more in common than that both are 
living organisms. 
But, whether we are or are not affected in our belief by the general argument 
from analogy, we cannot neglect the important fact that Kyreidl proves the possi- 
bility of gravisensitiveness depending on the possession of statoliths. We must 
add to this a very important consideration—namely, that we know from Némec’s 
work? that an alteration in the position of the statoliths does stimulate the stato- 
cyte.® Such, at least, is, to my mind, the only conclusion to be drawn from the 
remarkable accumulation of protoplasm which occurs, for instance, on the basal 
wall of a normally vertical cell when that wall is cleared of statoliths by temporary 
horizontality. The fact that a visible disturbance in the plasmic contents of the 
statocyte follows the disturbance of the starch-grains seems to me a valuable 
contribution to the evidence. 
There is one other set of facts of sufficiently general interest to find a place in 
this section. I mean Haberlandt’s result,’ also independently arrived at by myself, 
that when a plant is placed horizontally and rapidly shaken up and down in a 
vertical plane the gravistimulus is increased. This is readily comprehensible 
on the statolith theory, since we can imagine the starch-grains would give a 
greater stimulus if made to vibrate on one of the lateral walls, or if forced into 
the protoplasm, as Haberlandt supposes. I do not see that the difference in the 
pressure of the cell-sap on the upper and lower walls («e., the lateral walls 
morphologically considered) would be increased. It would, I imagine, be 
rendered uneven; but the average difference would remain the same. But in 
the case of the starch-grains an obvious new feature is introduced by exchanging 
a stationary condition for one of movement. And though I speak with hesitation 
on such a point, I am inclined to see in Haberlandt’s and my own experiments a 
means of distinguishing between the pressure and statolith theories. Noll,° how- 
ever, considers that the shaking method is not essentially different from that of 
Knight’s experiment, and adds that the result might have been foreseen. 
Distribution. 
As far as I know, the development of statop/asts® has not been made out. Are 
they at first like ordinary immovable amyloplasts; and, if so, by what precise pro- 
cess do they become movable? Where the two forms of starch are seen in close 
juxtaposition the difference between them is striking, and it is hardly possible 
to doubt that these differently situated bodies have different functions. In a seed- 
ling Phalaris canariensis the apical part has only falling starch-grains, while 
lower down both forms occur. It suggests a corresponding distribution of 
! Haberlandt (01). 2 Némec (01, p. 153). 
3 Td est, the cells containing statoliths. 
4 Haberlandt (03) and F. Darwin (03). 
5 Noll (03, p. 131.) 
6 T would suggest the word statoplast in place of the cumbersome expression 
movable starch-grains. 
