4 20 APPENDIX 



Haberlandt confirms all the above results leaves differing from one another, 

 and falling into three types. 



1. The lamina predominates. Begonia discolor. 



2. The lamina and petiole co-operate, the fine adjustment being regulated 



by the lamina. Tropaeolum and Malva verticillata. 



3. The pulvinus alone is the responsive and percipient organ. Phaseolus. 

 Haberlandt suggests that since the pressure of sunlight amounts to 0-5 mg. 



per sq. metre, according to Maxwell, it is possible that the heliotropic perception may 

 involve a power of discrimination to light pressure on the part of the plasmatic 

 membrane. It must, however, be remembered that the pressure exercised by the 

 incident light upon the peripheral surface of the transparent plasmatic membrane 

 is only a very minute fraction of the total pressure exercised upon an opaque surface. 



Phototaxis. Th. Frank (Bot. Ztg., 1904, orig., p. 162) finds that the zoospores 

 of Chlamydomonas tingens, which are negatively phototactic in strong light, and 

 positively so in feeble light, come slowly to rest in darkness without losing their vitality. 

 Light stimuli easily overcome their feeble chemotactic irritability. 



Thermotropism. Ganong (Annals of Botany, 1904, Vol. xvm, p. 631) finds that 

 leafless shoots in winter move upwards and inwards until March, and then outwards. 

 The latter movement is shown to a less degree whenever the temperature rises during 

 winter. Young shoots show the movement best, and he concludes that it results 

 from a rise of turgidity in the cells due to the direct or stimulating action 

 of temperature. It is, however, possible that the wood on the upper and lower 

 surfaces may differ anatomically and in power of swelling, as was shown by Hartig to 

 be the case in the pine. 



Lidforss, however (Jahrb. f. wiss. Bot., 1902, Bd. xxxvui, pp. 343-76) concludes 

 that the raising of the shoots of certain herbs in warm weather is due to negative 

 geotropism, and their horizontal position to diageotropism, their rapid fall at low 

 temperatures being due to epinasty. 



Chemotropism. Lilienfeld (Ber. d. D. bot. Ges., Bd. xxxm, 1905, p. 91) found 

 that the radicles of Lupinus albus curved in gelatine towards phosphates and car- 

 bonates, but away from salt and poisons, and were indifferent to KNO 3 . It may be 

 noted that alkaline (Na 2 HPO 4 ) or acid (KH 2 PO 4 ) phosphates and alkaline carbonates 

 were used, so that the curvatures may be due to the action of the acidity and alkalinity. 

 The poisons might accelerate growth on the exposed side ; and, experimenting in 

 a somewhat different manner, this author, and also Newcombe and Rhodes (Bot. Gaz., 

 Bd. xxxvn, 1904, p. 23) found that the roots of the same plant grew into slabs of 

 gelatine containing strong solutions of the feebly alkaline phosphate of sodium 

 (Na 2 HPO 4 ) and were killed. 



The local application of dilute acid or alkali does induce curvatures in roots, and 

 since these curvatures do not necessarily involve any injury, they cannot be trauma- 

 tropic in origin (Ewart and Bayliss, Proc. of Royal Soc., 1905, Vol. LXXVII, p. 64). 



Chemotaxis. According to Senn (Schweiz. naturf. Ges., July, 1904), the chloro- 

 plastids of Funaria are positively chemotactic to CO 2 and sulphates, organic acids, 

 and certain assimilatory products, but not to cane-sugar. They are negatively chemo- 

 tropic to nitrates and phosphates, and this feeble chemotropism is responsible for the 



