BOTANICAL WORK OF THE BRITISH ASSOCIATION. 473 



is how this explains the phenomena in the sugar maple, a single tree of 

 which will yield, I believe, 20 to 30 gallons of fluid before a single leaf 

 is expanded. 



We owe to Messrs. Darwin and Acton the supply of a " Manual of 

 practical vegetable physiology," the want of which has long been 

 keenly felt. Like the father of one of the authors, "I love to exalt 

 plants" (I, 98). I have long been satisfied that the facts of vegetable 

 physiology are capable of being widely taught, and are not less signifi- 

 cant and infinitely more convenient than most of those which can be 

 easily demonstrated on the animal side. How little any accurate knowl- 

 edge of the subject has extended was conspicuously demonstrated in a 

 recent discussion at the Eoyal Society, when two of our foremost chem- 

 ists roundly denied the existence of a function of respiration in plants, 

 because it was unknown to Liebig. 



ASSIMILATION. 



The greatest and most fundamental problem of all is that of assimi- 

 lation. The very existence of life upon the earth ultimately depends 

 upon it. The veil is slowly, but I think surely, being lifted from its 

 secrets. We now know that starch, if its first visible product, is not its 

 first result. We are pretty well agreed that this is what I have called 

 a " protocarbohydrate." How is the synthesis of this effected'? Mr. 

 Acton, whose untimely end we can not but deeply deplore, made some 

 remarkable researches, which were communicated to the Eoyal Society 

 in 1889, on the extent to which plants could take advantage of organic 

 compounds made, so to speak, ready to their hand. Loew, in a remark- 

 able paper, which will perhaps attract less attention than it deserves 

 from being published in Japan (Bull. College of Agric. Imp. Univ. 

 Tokio, Vol. I), has from the study of the nutrition of bacteria arrived 

 at some general conclusions in the same direction. Bokorny appears 

 recently to have similarly experimented on algae. Neither writer, how- 

 ever, seems to have been acquainted with Acton's work. The general 

 conclusion which I draw from Loew is to strengthen the belief that 

 form-aldehyde is actually one of the first steps of organic synthesis, as 

 long ago suggested by Adolph Baeyer. Plants, then, will avail them- 

 selves of ready-made organic compounds which will yield them this 

 body. That a sugar can be constructed from it has long been known, 

 and Bokorny has shown that this can be utilized by plants in the pro- 

 duction of starch. 



The precise mode of the formation of form-aldehyde in the process 

 of assimilation is a matter of dispute. But it is quite clear that either 

 the carbon dioxide or the water, which are the materials from which it 

 is formed, must suffer dissociation. And this requires a supply of 

 energy to accomplish it. Warington has drawn attention to the strik- 

 ing fact that in the case of the nitrifying bacterium, assimilation may 

 go on without the intervention of chlorophyll, the energy being supplied 



