XX PLANT RESPONSE 



•A(,K 



of response— (4) The effect of barium salt — (5) The antagonistic actions 

 of acid and alkali — Identity of rhythmic phenomena in animal and 

 vegetable tissues .......... 344 



PART V.— ASCENT OF SAP 

 CHAPTER XXVIII 



SUCTIONAL RESPONSE AND ASCENT OF SAP 



Inadequacy of existing theories of ascent of sap — General considerations 

 regarding cellular activity and resultant propulsion of water — The 

 Shoshungraph — Balanced Shoshungraph for determining variations of 

 suction — Hydrostatic and Hydraulic Methods of Balance . . . 359 



CHAPTER XXIX 



MODIFICATION OF SUCTIONAL RESPONSE 



Effect of temperature on suction by three methods of inquiry: (1) Un- 

 balanced method of Shoshungraph : (a) Action of cold — (b) Action of 

 moderate rise of temperature — (2) Method of Hydrostatic Balance : (a) 

 Action of cold — Reversal of normal direction of flow — (b) Action of 

 warm water — (3) Method of Hydraulic Balance — (a) Action of cold — 

 (d) Effect of warm water — Explanation of suction when the root is 

 killed by boiling water — Stimulation renews suctional activity in plant 

 whose suction has come to a standstill — Osmotic versus excitatory action 

 — Abolition of suction by poison — Suctional activity continued until 

 whole plant is killed by poison . . . . . . . . 372 



CHAPTER XXX 



THE PHENOMENON OF PROPULSION OF SAP 

 AND ITS VARIOUS EFFECTS 



The mechanics of the ascent of sap : (a) Uni-directioned flow — (/>) Initiation 

 of multiple rhythmic excitations — Connection between conduction of 

 excitation and conduction of sap — Rapidity of ascent of sap accounted 

 for by stimulatory action — Positive and negative pressures due to one 

 cause — (1) Positive pressure— (2) Negative pressure — (3) Irregular 

 variations of pressure — Direct conduction and conduction by relays — 

 Excretion of water — Excretion of nectar — Translocation of organic food- 

 substances — -Mechanical response to suctional activity — Effect of warmth 

 — Effect of cold — Explanation of the drooping of leaves during frost — 

 Explanation of response and recovery — Antagonistic actions of internal 

 energy and external stimulus 389 



