LOCALISATION OF GEO-PERCEPTIVB LAYER 



489 



Eight dillereut determinations are given, three for Bryu- 

 phylluni and five for Nymphcea. 



TAliht: XMl. — SHoWINt; 'IHE I'dSlTlON OK THK (iEO-l'KBCKPTl VE 1 AVER A.NI" 

 OF ' STARCH SHEATH ' IN DIFFERENT SPBCIMRNS. 



•Thns in all speciraens examined, the experimentally 

 determined geo-perceptive layer coincided with the ' starch 

 sheath.' The theory of statoliths thus obtains strong 

 support from an independent line of experimental inves- 

 tigation. The statolithic theory has been adversely criti- 

 cised because in simpler organs the geotropic action takes 

 place in the absence of statoliths. There is no doubt that 

 the weight of the cell contents may in certain cases be 

 effective in geotropic stimulation ; it may nevertheless be 

 true that " at a higher level of adaptation, the geotropically 

 sensitive members of the plant-body are furnished with 

 spt-cial geotropic sense-organs — a striking instance of anato- 

 mico-physiological division of labour."* 



In the instances of Bryophyllum and Nymphwa given 

 above, the geo-perceptive layer localised by means of the 



Haberlandt — Jb\d, p. 597. 



J6 A 



