NATURE-SrUDY AND SCIENCE NOTES 2ii 



single brood. In the long course of geographic, climatic and topographic 

 changes this early brood became broken up into many broods, and whereas 

 the date of maturity was at first synchronous for all, there followed a 

 gradually increasing divergence in this date. At present every year has 

 its brood or broods, limited as a rule to well defined areas, each reappear- 

 ing with absolute regularity. Most of the twenty broods have been care- 

 fully studied and their dates and limitations marked. The thirteen- 

 year broods are distinctly southern and the seventeen-year northern. 

 One of the common popular superstitions in regard to this animal is that 

 it has a harmful, not to say fatal sting. The evidence shows that this idea 

 is quite without foundation. The insects are very sluggish when handled 

 and can never be provoked into resentment. The author appends to his 

 account a voluminous bibliography covering a period of nearly two 

 hundred and fifty years. 



Tree Planting for Profit has hitherto not been very successful, but actual 

 statistics gathered in Illinois and published by the Forest Service show 

 actual returns of $4.28 per acre annually from larch and $15.00 from 

 catalpa. 



Swallows, according to a recent Biological Survey bulletin, are the 

 "light cavalry of the avian army." Specially adapted for flight and un- 

 excelled aerial evolutions, they are experts in capturing insects in mid§ir. 

 They eat nothing of value to man except a few predacious bugs and wasps, 

 and in return for their vast service, ask only harborage and protection. 

 Their service to the cotton grower can scarcely be overestimated, because 

 of their skill in catching prey on the wing. They get the adults weevils 

 before they have a chance to alight on the cotton bolls and lav their eggs. 



Soil Fertility. Few scientific theories have stood the test of time and 

 experiment so long and gained such universal acceptance as the Liebig 

 theory of soil fertility. Nevertheless, recent investigations seem to indi- 

 cate that this conception is likely to undergo considerable modification in 

 the near future, suggesting that the "exhaustion" of many soils may be 

 due, not so much to the withdrawal of mineral constituents as to the ac- 

 cumulation of certain organic toxic substances. 



Investigations at the Woburn Experimental Fruit Farm, in England, 

 have shown that the presence of grass in the soil about apple trees has a 

 marked deleterious effect upon the growth of the trees. It was shown 

 experimentally that this effect could not be due to rernoval of nutrient 

 materials, nor of water, nor to the exclusion of air, and it was suggested 

 that it must be caused by poisonous bodies emanating from the grass roots. 

 A similar antagonism has been shown to exist between butternut trees 

 and cinquefoil, and between peach trees and several herbaceous plants. 

 In 1904, Livingston published evidence to the effect that bog water 

 exhibits properties of a toxic nature and suggested that the xerophilous 

 character of bog plants may be due to these properties. 



In Bulletin 23, of the U. S. Bureau of Soils, it was shown that the un- 

 productiveness of certain soils examined could not be attributed to any 

 lack of available mineral matter, and that the injurious properties of the 



