342 SM1TB LPPLICA I'KiN OF TDK THBOBY OF 



show Itself. It must be stated at once that under natural 

 conditions the two factors of intense light and low humidity 

 are bo constantly associated that no very decisive evidence 

 is to be obtained on this point. Neither is it easy to arrange 

 experiments in which a plant of considerable size shall be 

 subject to different degrees of humidity with constant light, 

 or to constant humidity with varying Light. Some little 

 evidence has however been obtainable on this point in the 

 following way : — 



Kraut hemum cinnabarinum is a shrubby plant whose shoots 

 grow sufficiently rapidly for reliable measurements to betaken 

 at intervals of two hours. The curves of growth for the day- 

 time always show markedly the effect of lower humidity by 

 either very slow growth or cessation of growth altogether. 

 The shoots were measured on several fine days and always 

 showed this effect . that while the curve of growth rapidly fell 

 during 1 he morning along with the curve of humidity, yet after 

 about I p.m. the growth always began to increase. The curve 

 of growth in fact after 1 p.m. rises previous to the rise of the 

 curve of humidity and rises much more sharply. 



This increase of length which clearly preceded the increase 

 of humidity showed that some other factor was assisting to 

 cause the slow growth of the period before 1 p.m. It was 

 noticed that at about I P. m. t he bush which had hit herto being 

 exposed to the full sun came into the shade of an avenue of 

 talipol palms close by. There is no doubt that the change 

 from full sun to the less intense though still very bright diffuse 



light in the shade had an effect on the growth of the shoots 

 and allowed growth to commence though the humidity did 

 not increase but rather diminished. This effect was also 

 noticeable in Capparis Etoxburghii. The shoots measured 

 "I, two different bushes which received direct sunlight 

 at different times of the day. It was observed that though 

 t he humidity of 1 he ail would be pi act ically the same for each . 

 -hi 1 e they were only about ten yards distant from each other, 

 the period of actual contraction of the shoot varied and 



