62 
James Small . 
intumescences, the effects of acids, alkalies and salts on plants and 
animals in general and on the permeability of protoplasm in 
particular and possibly also to epharmonic variation. It provides 
an explanation, not only for the normal polarity of growth in plants, 
but also for the changes in geotropic response and in colour which 
occur in flower buds and other organs. The adsorption of ions by 
the Brownian particles, which is postulated, furnishes an 
explanation of the stimulus/response ratio of the Weber Law as 
modified (24-25) by Waller. 
EXPLANATION OF PLATE I. 
Fig. 1. Three beans with secondary roots showing negative geotropism. 
Fig. 2. Main roots of the bean showing the same. 
Fig. 3. Main roots of the maize showing the same. 
Fig. 4. Adventitious roots of the maize ; two show slight upward curves 
Fig. 5. The same, five days later, with more pronounced upward curves. 
Fig. 6. Maize stems with unbroken coleoptiles showing positive 
geotropism. 
Fig. 7. Controls in a neutral atmosphere : the top specimen has recovered 
after growing down as in Fig. 6. (specimen on the right). 
Fig. 8. Maize stems, showing cytolysis and fungal infection after 
downward curving had taken place. 
Fig. 9. Maize stems showing positive geotropism, the lower specimen 
did not react at all, either positively or negatively. 
Fig. 10. Three of four stems showing the same. 
Fig. 11. Four stems all positively geotropic. 
BIBLIOGRAPHY,, 
1. Bose, J. C. Plant Response. London, 1906. 
2. Clowes, G. H. A. On the electrical resistance and permeability of tumour 
tissues. Proc. Soc. Exp. Biol, and Med., 15, p. 107 
1918. 
3. ,, ,, On the action exerted by antagonistic electrolytes on 
permeability of emulsion membranes. Ibid, 15, 
p. 108, 1918. 
4. Fischer, M. H. and Hooker, M. O. Physical Chemistry of Emulsions. 
Science, 43, p. 468, 1916. 
5. Fischer, M. H. On the swelling of gelatin in polybasic acids and their 
salts. Jour. Amer. Chem. Soc., 40, p.272, 1918. See 
also Science, 46, p. 189, 1917. 
6. „ ,, The colloidal-chemical theory of water absorption by 
protoplasm. Jour. Amer. Chem. Soc., 40, p. 862, 
1918. 
7. Free, E. E. A colloidal hypothesis of protoplasmic permeability. 
Plant World, 21, p. 141, 1918. 
8. Haas, A. R. The Acidity of Plant Cells as shown by Natural Indicators. 
Jour. Biol. Chem., 27, p. 225, 1916. 
The excretion of acids by roots. Proc. Amer. Nat. Acad. 
Sci., II, p. 561, 1916. 
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