Chemical Ivjluence of Liijlit. 85 



the sun's llglit, and producing chlorophyll and starch, would be 

 far more difficult, and it has not yet been seriously attempted. 

 Probably the investigation would be most satisfactorily pursued 

 in some of the simpler water-plants, such as the Confervoids above 

 referred to, and this in particular because the microscopist has 

 already ascertained the anatomical conditions in the successive 

 stages of growth. 



We know that green plants consume carbonic acid and evolve 

 oxygen in daylight, but when we enter into the details of the 

 chemical processes occurring here we find ourselves in complete 

 obscurity, so great indeed, that it is not agreed among physiologists 

 as to the use of the terms respiration and digestion, the process 

 or processes which it is the chief office of green parts to periorm. 

 It is not our intention to enter now into a discussion of any of 

 the other vital processes of plants, beyond the simple ve</etative 

 reproduction, dependent upon cell-development, above described. 

 But as we have directed especial attention to the importance of 

 the nitrogenous constituents of the tissues, we may mention one 

 other point connected with this and with the processes of nutri- 

 tion. The recent researches of i\I. Viile, and, a priori considera- 

 tions, such as the reflection that animals are in the last resort all 

 dependent on plants for food, render it extremely probable that 

 vegetables assimilate nitrogen directly from the air. If so, it 

 will probably be by the green parts, and hence the chemical 

 changes occurring in the protoplasm of the cells of leaves will be 

 -even more complicated than has been hitherto suspected. 



A knowledge of the ascertained facts of vegetable physiology 

 leads to a recognition of our excessive ignorance, scientifically 

 speaking, concerning the most important of the vital phenomena. 

 Here, however, if anywhere, the motto " Science with Practice," 

 should be adopted, for a large portion of the data of the science 

 have still to be established by experiment : while the many crude 

 notions that exist in the popular mind respecting the more 

 obscure processes of vegetable life, render a kind ot clearance of 

 the ground necessary before the vast mass of " observing power" 

 existing in our agricultural community can be turned to thorough 

 account. It is our hope to present to the readers of the Society's 

 Journal at a future period an account of anatomical and physiolo- 

 logical researches on some of our most important cultivated 

 plants, with a view of exhibiting the connexion of vegetable 

 physiology with the practice of agriculture. 



