igoo-i.] 



Effects of Water on Foliage Leaves. 



239 



duration of the experiments, the solution had to be changed from time 

 to time. 



To learn from another point of view how a nutrient solution affects 

 the early growth of young leaves developing from the bud, a series of 

 experiments was performed with young willow twigs, during the months 

 of March and April, this being the time of the year when the process of 

 the opening of buds seems to depend only upon a favourable tempera- 

 ture. This experiment was designed also to test water absorption by 



young leaves. 



s 

 The solutions (other than nutrients) 



used in the experimental work in con- 

 nection with this paper were made by 

 dissolving the molecular weight, in 

 grams of the substance, in a liter of 

 water. This method of preparation is 

 similar to that indicated by Pfeffer* 

 (E wart's Trans. 1900, p. 146), and by 

 Detmer and Moor (p. 326), who desig- 

 nate them normal solutions. This 

 method is also that adopted by True 

 (1898, p. 410-411) and (1900, p. 185). 

 These, however, are not normal solu- 

 tions as defined by Mohrf and other 

 analytical chemists. When salts con- 

 tained water of crystallization, or 

 hygroscopic water, it was found more 

 convenient to determine the specific 

 gravity of the solution and from this 

 Calculate its concentration. A con- 

 venient apparatus for finding the 

 specific gravity of a solution was 

 arranged ; and as such apparatus may 

 be of some use in a laboratory of plant 

 physiology, a full description with 

 diagram is given (Fig. i). The stock solution once obtained, there 

 was no difficulty in preparing solutions of less concentration as occasion 

 required. The solutions of hydrochloric and of sulphuric acids were 

 normal solutions, as were those of potassium and of sodium hydrate. 

 These were procured ready prepared from the chemical supply house. 



Two small glass tubes, held in a vertical 

 position by the support P, are finely gradu- 

 ated and connected by a "T" tube to the 

 leg' of which is attached a rubber tube. One 

 of the tubes is inserted in distilled water at 

 the temperature required, the other in the 

 liquid to be measured. The stop-cock S 

 is opened and the ascent ot liquid due to 

 capillarity, A and A', measured. Then by 

 sucking on the rubber tube the liquids rise 



to D, etc. Now the sp.g. of M is t=r — 

 Dx. 



* See bibliography at the end. 

 t Titrimethode, p. 56. 



