514 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



perature of — 1'5° C, but the pistil was liable to injury at that tempera- , 

 ture. High temperatures — 50°-55<^ G. — so long as the air was dry did 



not seriously affect the pollen, but the same temperatures with a moist j 



atmosphere caused the bursting of the grains. The pollen of tomatos 1 



and lilies did not develop well in the absence of sunshine. Lack of j 



cultivation and fertility in orchards is said to injure greatly the produc- j 



tion and fertility of pollen. Plum pollen appears to be short-lived, but ! 



apple pollen can be kept alive for six months in a dry place at a tern- | 



perature ranging from 7° to 26° 0. If the conditions are favourable ! 



the pollen soon germinates and the tube may reach the ovary of apples, | 



plums, or cherries in from nine to thirty-two hours after pollination, j 



The stigma of the apple is. receptive for from four to six days, but wet ! 



weather is fatal to it. — F. J. C. j 



Potash in Clay Soils. By F. W. Morse and B. E. Curry ! 

 (U.S.A. Exp. Stn. New Hampshire, Bull. 142; Dec. 1909).— The | 

 heavy clay and clay loam soils used for these experiments appear to | 

 have been formed from granitic rock by glacial action. They contain j 

 1 per cent, of potash. I 



The amount of potash absorbed by hay grown on a large number 

 of soils was found to be proportionate to the yield of hay. Liberal 

 fertilizing with potash produced no perceptible effect either on the i 

 yield of hay or of clover, nor on the percentage of potash absorbed i 

 by these plants. Practically by doubling the yield the amount of 

 potash in the crop is doubled. 



The amount of potash in solution in the soil moisture was found j 

 to be 80 parts of potash in the million of water, whilst the approxi- j 

 mate concentration required for the heaviest yields was 58 parts per I 

 million. 



The available amount of potash can be increased by growing 

 legum.inous crops ploughed in green or returned as manure. Lime ' 

 produced no effect, but feldspar in water treated with lime and gypsum ; 

 yielded more than double the amount of potash. Clay interferes | 

 with this process, and so conserves the potash in the soils. Experi- j 

 ments are given which show the absorptive power of clay, sandy ^ ! 

 clay, and sandy loam soils in relation to potash. Out of 1'50 gram ; 

 of potassium chloride added 0*980 gram was made insoluble in clay, i 

 0"615 in sandy clay, and 0*510 in sandy loam. The actual soil fertility I 

 is kept very nearly constant, because what is carried down in rainy ' 

 weather is carried up and left on the surface by evaporation in fair 

 weather. When potash is rendered insoluble other bases go into 

 solution. Lime has decided effects on these by-products. 



^ - ^ G. F. S.-E. 



Potato Culture in Northern Wisconsin. By E. P. Sandsten 

 and E. J. Delwiche [U.S.A. Exp. Stn. Wisconsin, Bull. 177; 1909). 

 — The sandy soils of this region are well suited to potato-growing, 

 but require manuring, for which purpose a heavy crop of clover, 

 ploughed in green, is the best, yielding 241 bushels, as compared to 



