152 On the Irritability of the Fronds of Asplenium bulbiferum. 



Graphically, this is shown in fig. 4, where a curve for the rise and fall of 

 the statolith apparatus would practically correspond with that of response to 

 gravity — certainly more nearly than with any other. The result of this 

 work may therefore be held to support the view that the possession of 

 statoliths is causally connected with graviperception in plants. 



All acknowledgements will be made on the completion of my work on the 

 cytology of the statolith apparatus in plants. 



LITERATUEE CITED. 



(1) Darwin, C. and F. (1880). ' The Power of Movement in Plants.' 



(2) Darwin, C. (1904). " On the Perception of the Force of Gravity in Plants,'' ' Brit. 



Ass. Rep.,' Cambridge. 



(3) Dehnecke, C. (1880). "Ueb. niehtassimilirende Chlorophyll-Korper," ' Bot. 



Zeitung.' 



(4) Prankerd, T. L. (1915). " Preliminary Observations on the Nature and Distribu- 



tion of the Statolith Apparatus in Plants," ' Brit. Ass. Rep.,' Manchester. 



EXPLANATION OF PLATE. 



Photomicrographs of transverse sections of a frond of Asplenium bulbiferum a little 

 younger than (3) in text-fig. 7. 



(1) is taken above the second pair of leaflets, and within the curl. The chloroplasts are 



scattered in the cells, and there is no trace of statoliths. 



(2) cut just above the first pair of leaflets. The ground tissue is transitional between 



(1) and (3) ; statoliths are beginning to be formed. 



(3) from below the first pair of leaflets— nearly all the cells of the ground tissue are 



statocytes. 



