687 



chemical power resided. He found that the green matter did not 

 possess it in itself, that it operated in the cells of the parenchyma, 

 and that the vessels and pores of the cuticle have a useful influence 

 in the phenomenon, so as to increase the quantity of oxygen gas 

 disengaged. When solar light is received on the superior surface 

 of leaves immersed in spring water, the quantity of oxygen gas dis- 

 engaged is, in the same time and under similar circumstances, two 

 or three times greater than when it is received on the inferior sur- 

 face. The same difference may be observed in the diffused light, 

 by means of the leaves of Camellia japonica, Portugal laurel, and 

 some others which, when kept during some time in the dark in 

 spring water, give out, when brought into the light, bubbles of oxy- 

 gen gas through the central vessels of the footstalk. 



The following is a brief recapitulation of the facts which the 

 author has attempted to prove in this paper : — 



1. The theories advanced to explain the curling up of tendrils, 

 do not agree with the experiments made on those of the Tamus 

 communis, this phenomenon being the result of a vital irritability 

 acted upon by chemical agents. 



2. The direction of the green parts of plants towards the light is 

 not the result of an attraction properly so called. 



3. The bending outv/ards of slit stems is due to the elongation of 

 the cellular tissue by endosmose of water and the resistance of the 

 cuticle. 



4. The quantity or rapidity of endosmose is not influenced by heat 

 or light. 



5. Light is the only agent of the natural position of leaves and 

 of their turning over when inverted. The blue are the most, the 

 red the least active rays. 



6. Light does not act in this case by a physical attraction or re- 

 pulsion, properly so called. 



7. The turning over of leaves takes place sometimes by a torsion 

 of the footstalk, sometimes by a curling of the fiat part. 



8. The blue rays appear to be the most, and the red the least 

 active in operating the turning over of leaves. 



9. The exhalation of leaves is much increased when their inferior 

 surface is exposed to light. 



10. The decomposition of carbonic acid and the disengagement 

 of oxygen gas are, under the same circumstances, considerably di- 

 minished. 



6. " On the Solution of Linear Differential Equations." By 

 Charles James Hargreave, Esq., B.L., F.R.S., Professor of Juris- 

 prudence in University College, London. 



I. By the aid of two simple theorems expressing the laws under 

 which the operations of differentiation combine with operations de- 

 noted by factors, functions of the independent variable, the author 

 arrives at a principle extensively applicable to the solution of equa- 

 tions, which may be stated as follows: — ''if any linear equation 

 (p(a.^,D).w=X have for its solution z<=;/>(a%D).X, this solution being 



