486 SUMMARY OF CURRENT RESEARCHES RELATING TO 



receive outside, so that the results of experiments conduetecl uuder 

 cover would not be perfectly trustworthy, the author arranged that 

 the jdants experimented on shouM bo exposed to the free air in line 

 weather, but removed under shelter in bad weather. As a proof of 

 tho difl'ercnces produced by the now arrangements, the results of 

 experiments are given which show that not only was the total yield 

 of barley greater, but that the weight also of the grains harvested 

 was greater in free air and direct sunlight than in diffused light. 

 Barley plants were grown under cobalt glass, which allowed of tho 

 passage of the red and green rays as well as of the violet, and 

 yellow carbon glass in which the violet and blue were extinguished, 

 with the result, that under the influence of the blue light less ash 

 and more organic matter were i)roduced than uuder the yellow. The 

 2)lants under the blue glass grew well, whilst those under the yellow 

 seemed to be retarded in their growth, and when shaded were long in 

 the interuodes, and the leaves were thin and delicate. Taking this 

 experiment in conjunction with another somewhat similar one, the 

 author comes to the conclusion that plants arc not very sensitive to 

 moderate changes in the composition of the light which falls on them, 

 consequently that the light as altered by the roof and walls of a 

 glass-house cannot have any serious detrimental influence on tho 

 plants. 



In plants grown uuder glass shaded by cylinders so that the light 

 could reach them in a vertical direction only, he found that the stems 

 grew lengthy and rapidly, being thin and w^eak : the lower leaves 

 were jiale ; those of the pea reddish. Under the influence of lateral 

 shades the growth is somewhat abnormal, and this is the more marked 

 the narrower the shading cylinder. Under all these disadvantages, 

 however, the plants fruited, but under all conditions those plants 

 which were not shaded produced the most fruit, and, as the cylinder 

 narrowed, the yield of grain decreased, while the chaff and the straw 

 (peas excepted) increased. It was also remarked that under the 

 medium-sized shades with the upper opening of the same size as tlie 

 pots, although the other conditions were so various, the amount of 

 dry matter in the plants was approximately tho same. 



As regards the warmth necessary for tlie proper growth and ripen- 

 ing of plants, tho experiments arc detailed very fully, but it will 

 suffice to state the results obtained. For the growth of four-rowed 

 barley, the average daily temperature during the first lialf of tho 

 period of vegetation should be about 15° C, in the latter half, 

 when the blossom forms, &c., the average must be 17-18°, and tho 

 average of tho whole season 16°. The average of the mid-day during 

 the first period should be 20^, during the second period about 25°, 

 the average during the whole season about 21°. 



Evaporative Surfaces of Plants and Influence of Moisture in 

 Soils on Plant Growth.* — Dr. H. Hellriegcl's previous experiments 

 have convinced him that plants so dissimilar as beans and barley have 



* Bled. Centr., 1884, pp. 834-49. See Journ. Chcin. Soc— Abstr., xlviii. 

 (ISS.")) p. 421. 



