Sense Organs for Gravity and Light. 
7 i 
difficulties in the way of this argument. It is a striking fact that 
in Viscum, which appears to have lost the power of geoperception 
falling-starch does not occur. In the same way, statoliths are absent 
in the non-geotropic root of Ivy, Hoya and Ficus, 1 but are present 
in the geotropic roots of Aroids, as Tischler 2 has shown. The last 
named author placed aerial roots of Orchids horizontal and found 
that they curved downwards, but that they did not contain falling 
starch. This seemed an adverse fact until he discovered that the 
curvature in question was apheliotropic and that the roots showed 
no downward curve in the dark. Tischler gives other facts which are 
not in favour of the statolith theory. For instance the roots of 
Pyrola and also of Pistia are apparently ageotropic and yet possess 
falling starch. The case of tertiary roots of V. faba is interesting 
in this connection : they have usually been described as ageotropic, 
yet they possess statoliths. 1 was able to show that when the 
primary root is removed the tertiaries behave like normal secondaries 
and therefore need the apparatus for geoperception. 
In a recent paper by Nemec 3 some interesting facts are given, 
showing a general correspondence between the existence of 
movable starch and the capacity for geoperception in the Hepaticse. 
Thus the sporogonium of Aneura pinguis has no statoliths and is 
apparently quite disorientated in the dark—showing that it is not 
guided by gravitation. On the other hand the vegetative shoots 
are strongly geotropic and have statoliths. 
The sporogonium of Pellia calycina is feebly geotropic and the 
starch is but slightly movable. On the other hand the capsule- 
stalk of Pellia epiphylla has well developed easily movable starch 
and is strongly geotropic. 
As making against our theory it must be stated that no 
statoliths have been discovered in Algae or Fungi. But it must be 
remembered that Noll who first brought prominently forward the 
statolith theory does not believe in starch-statoliths, but supposes 
that minute particles in the protoplasm may play their part. And 
this may conceivably be the case in the lower plants. 
The rhizoids of Chara 4 have bodies of unknown nature which 
fall to the lower end of the containing cell and may function as 
1 Haberlandt, Pringsheim’s Jahrb. XXXVIII. 
2 Tischler in Flora, 1905, Vol. 94. 
3 Flora, 1906, Vol. 96. 
V 
4 Giesenhagen, Ber. D. Bot. Ges. XIX. Nemec mentions heavy 
bodies of unknown nature in the roots of Trianea, and in the 
stems of the Characeae (Bull. Acad. Boh5me, 1904). 
