Landwirtschaftliche und forstliche Biologie. 195 



Landwirtschaftliche und forstliche Biologie. 



454) Briggs, L. 3., and Shantz, H. L., Relative Water Requirement of 

 Plants. In: Journ. of Agr. Research, Vol. III, No. 1, S. 1—64, Oct, 1914. 



This paper deals with the measure of the water requirement of plants at 

 Akron, Colo., U. S., in the central portion of the Great Plains. The term "water 

 requirement" is here used to express the ratio of the water absorbed by a plant 

 during its period of growth to the dry matter produced. The experiments were 

 conducted in such a way that the loss of water was practically confined to that 

 taking place through transpiration, and the entrance of rainfall as a disturbing factor, 

 was almost wholly prevented. The detailed results given in the paper comprise 

 measurements of many species and varieties for a period of three years. In order 

 to facilitate comparison, the plants have been arranged under three main heads: 

 "Grain crops", "other crops" and "native crops". Under the heading "Other crops" 

 are included principally the legumes, cucurbits, crucifers, sugar beets, cotton, 

 and potatoes, as well as some of the introduced grasses. Under the heading "Native 

 plants" are listed indigenous species, as well as certain introduced species which 

 have become thoroughly established. The grain crops fall rather naturally into 

 two sections: Those of low water requirement — proso, millet, sorghum, and 

 com — and those of high water requirement — wheat, barley, oats, rye and 

 flax. The plants with a comparatively low water requirement are late-maturing 

 crops, which make their best growth during the hottest and driest portion of 

 the summer. The plants having a comparatively high water requirement mature 

 during midsummer and make their best growth during the earlier, cooler period 

 of the year. Varieties of the same crop often differ widely in water requirement. 

 In the case of barley, the variety having the highest water requirement was 8 per 

 cent. above the lowest; oats, 11 per cent.; wheat, 18 per cent.; proso 27 per cent.; 

 com, 31 per cent.; vetsch, 35 per cent.; alfalfa, 48 per cent.; sorghum, 60 per 

 cent.; and millet, 70 per cent. This wide ränge in water requirement among the 

 varieties of many crops encourages the belief that strains may yet be secured 

 which are still more efficient in the use of water than those now in dry-land re- 

 gions. Pearl. 



455) Swingle, L. D. ? The Life-History of the Sheep-Tick. In: Univ. of 

 Wyoming Agr. Exp. Sta. Bul. No. 99, S. 1—24, 1913. 



The egg is fertilized and developes through the embryonic and most of the 

 larval stages within the body of the female tick. It is laid as a larva without 

 changes into the pupa stage about 12 hours later. (For convenience the term 

 pupa is used to designate the offspring from the time it was born until it was 

 hatched.) 



Pupae require during the summer months from 19 to 23 days to hatch. 

 In the winter from 19 to 36 days are required in case the sheep are kept in 

 the barn. Were they turned out doors in the cold wind, the probability is that 

 in some cases the period might increase to 40 or 45 days. The period of incu- 

 bation is greatly affected by the temperature, and therefore, by the distance the 

 pupa are laid from the skin of the sheep, especially in the winter. 



The time required for females to reach sexual maturity is variable. Gene- 

 rally it is from 14 to 30 days. Males and females are capable of copulating 

 within three or four days after hatching. The whole life of the tick is spent on 

 the sheep. They will not live more than a few days off their host. Female ticks 

 were followed for five and one-half months. Some probably live much longer. 



13* 



