us altogether at very high {113} temperatures, yet it serves as a very satisfactory guide to the relations between rate and temperature within the ordinary limits of healthy growth. Miss Leitch holds that the curve is not a vanãt Hoff curve; and this, in strict accuracy, we need not dispute. But the phenomenon seems to me to be one into which the vanãt Hoff ratio enters largely, though doubtless combined with other factors which we cannot at present determine or eliminate.
While the above results conform fairly well to the law of the temperature coefficient, it is evident that the imbibition of water plays so large a part in the process of elongation of the root or stem that the phenomenon is rather a physical than a chemical one: and on this account, as Blackman has remarked, the data commonly given for the rate of growth in plants are apt to be {114} irregular, and sometimes (we might even say) misleading63. The fact also, which we have already