518 KEPORT— 1880, 



general tesult was tliat a smaller proportion of both the total nitrogen and the total 

 carbon was accumulated bj' the middle or end of June than in the case of the wheat ; 

 tliough the actual amount of nitrogen taken up by the beans was much greater, both 

 before and after that date. The nitrogen of this leguminous crop increased in a 

 much greater proportion during the subsequent stages of growth than did that of 

 the gramineous crop ; but the carbon increased in a larger proportion still, three- 

 fourths or more of the total amount of it being accumidated after the middle of June. 



I should say that determinations of carbon, made in samples of soil taken from 

 the wheat field at diflerent periods during recent years, indicate some decline in the 

 percentage of carbon in the soils, but not such as to lead to the supposition that the 

 soils have contributed to the carbon of the crops. Besides the amount of carbon 

 annually removed, there will, of course, be a further accumidation in the stubble 

 and roots of the crops ; and the reduction in the total carbon of the soil, if such 

 have really taken place, would show tliat the annual oxidation within it is greater 

 than the annual gain by the residue of the crops. 



Large as is the annual accumulation of carbon from the atmosphere over a given 

 area in the cases cited, it is obvious that the quantity must vary exceedingly with 

 variation of climatal conditions. It is, in fact, several times as great in the case of 

 tropical A"egetation — that of the sugar-cane for example. And not only is the 

 greater part of the assimilation accomplished within a comparatively small portion 

 of the year (varying of course according to the region), but the action is limited 

 to the hours of dajdight, whilst duiiiig darkness there is rather loss than gain. 



But it is remarkable that whilst the accumulation of carbon, the chief gain of 

 solid material, takes place under the influence of light, cell-division, cell-multipli- 

 cation, increase in the structure of the plant, in other words, what, as distinguished 

 from assimilation, vegetable physiologists designate as (/rowth, takes place, at any 

 rate chiefly, during the night ; and is accompanied, not with the taking up of carbonic 

 acid and the yielding up of oxygen, but with the taking up of oxygen and the giving 

 up of carbonic acid. This evolution of carbonic acid during darkness must obviously 

 be extremely small, compared with the converse action during day-light, coinciden- 

 tally with which practically the whole of the accumidation of solid substance is ac- 

 complished. But, as tlie product of the night action is the same as in the respiration 

 of animals, this is distinguished by vegetable physiologists as the respiration of plants. 



I suppose I shall be considered a heretic if I venture to suggest that it seems in a 

 sense inappropriate to apply the term f/i-oicth to that which is associated with actual 

 loss of material, and that the term respiraiinn sliould be applied to so secondary an 

 action as that as the result of which carbonic acid is given ort' from the plant. It 

 may, I think, be a question whether there is any advantage in thus attem.ptiug to 

 establish a parallelism between animal and vegetable processes ; rather w^oidd it 

 seem advantageous to keep prominently in view their contrasted, or at any rate 

 complementary characteristics, especially in the matter of the taking up of carbonic 

 acid and the giving up of oxygen on the one hand, and the talcing in of oxygen 

 and the giving up of carbonic acid on the other. 



But it is obvious that in latitudes where there is comparatively contmuous 

 daylight during the periods of a egetation, the two actions — designated respecti^-ely 

 assimilation and growth — must go on much more simultaneously than where 

 tliere is a more marlced alternation of dayliglit and darkness. In parts of Norway 

 and Sweden, for example, where, during the summer, thei-e is almost continuous 

 daylight, crops of barley are grown with only from six to eight weeks intervening 

 from seed-time to harvest. A.nd Professor Schlibeler, of Christiania, after making 

 observations on the subject for nearly thirty years, has recently described the 

 characteristics of the vegetation developed under the influence of short summers 

 with almost continuous light. He states that, after acclimatisation, many gar- 

 den flowers increase in size and depth of colour ; that there is a prevailing tinge 

 of red in the plants of the fjelds ; that the aroma of fruits is increased, and their 

 colour well developed, but that they are deficient in sweetness ; and that the deve- 

 lopment of essential oils in certain plants is greater than in the same plants grovni 

 in other latitudes. Indeed, he considers it to be an established fact that light bears 

 the same relation to aroma as heat does to sweetness. 



