1106 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



those of Mucor stolon if or failed to germinate with over 50 per cent., and 

 to form sporangia with over 10 per cent. In no case did exposure to 

 pure C0. 2 kill spores or mycelium. (2) Boots of Flowering Plants. — Vicia 

 sativa and Pisum sativum showed an increased growth for small quantities 

 of CO 2 , but a decrease with above 2 per cent. ; growth fell to a very small 

 rats at 30 per cent., and the roots die in a few days. (3) Stems of Flower- 

 ing Plants. — For this purpose seedlings of Sinajns alba and Trifolium 

 in carnal um, raised in sawdust, were used. Up to 2 per cent, an increase 

 in rapidity of growth was noted ; decrease at higher strengths ; ultimate 

 death at 30 per cent, in seven days for Sinapis, at 20 per cent, in eight 

 days for Trifolium. Barley showed an increase of growth of the green 

 leaf up to 3 per cent., and all proportions up to 9 per cent, gave greater 

 elongation than in the control experiment. Even 80 per cent, did not 

 arrest growth completely, though death ensued after five days here, and 

 after eight days in 60 percent. Experiments in which, after 24-48 hours' 

 treatment, air was applied, showed no evil after-effects with roots up to 

 25-40 per cent. C0. 2 , but stems showed them after 20 per cent. C0 2 . The 

 effect of CO., is only manifest after a certain interval. — M. H. 



Carbon Dioxide : The Effect of varying- amounts of this Gas 

 on the Growth of Plants. By Jost (Bot. Zeit. No. 24, Dec. 16, 1902, 

 pp. 370-371). — Remarks upon the results of experiments by H. T. Brown 

 and F. Escombe (Proc. R. S. 1902, No. 70, pp. 397-413, 5 plates), which 

 demonstrated that a considerable addition (up to 600 C0 2 in 10,000 

 instead of 2-8) to the normal amount of carbon dioxide resulted in a 

 diminution of leaf area, accompanied by some distortion, a deeper green 

 colour, and increased starch contents, while flowering was entirely sup- 

 pressed. The reviewer considers these results to imply damage in lieu 

 of adaptation, and points out that while the control plants obtained their 

 carbon dioxide normally from the air, the others were supplied from 

 vessels containing liquid carbonic acid, which might involve some dis- 

 turbing element. It is noteworthy that the abnormal quantity of gas 

 varied from 11*47 to 600 in 10,000 without affecting the extent of 

 abnormal results. — C. T. D. 



Oxygen and Chlorophyll. 



Chlorophyll, Formation of, in rarefied air and in rarefied 

 oxygen. By Jean Friedel (Comp. Bend, cxxxv. No. 23, p. 1063 ; 1903). 

 M. Palladine has shown that when detached etiolated leaves are exposed 

 to light, chlorophyll does not form unless the amount of aeration is very 

 considerable. From this fact the conclusion was formed that, for plants 

 to become green, it is necessary they should receive more oxygen than the 

 amount required for respiration. Acting on this idea, Friedel studied 

 the action of oxygen on entire plants placed under conditions where the 

 pressure of the gas could be measured. 



Lcpidium sativum was used in the experiments. Two lots of seeds 

 were sown and allowed to germinate in darkness. When sufficiently 

 developed, the plants were exposed to light ; one lot under normal atmo- 

 spheric pressure ; the second lot under half an atmosphere of pressure. 

 The plants growing under normal conditions quickly became green. 



