34 



SCIENCE. 



[N. S. Vol. XIX. No. 470. 



year. These two sets of isobars have now 

 been separated from each other, and the proof 

 of this statement is positive. (See 'Barometry 

 Eeport, 1901; Monthly Weather Review, Jan- 

 uary, 1903; and another forthcoming report.) 

 The prevailing stream lines, velocities and 

 temperatures in high levels have been deter- 

 mined for the United States (see ' Cloud Ee- 

 port,' 1898), and are being worked up for the 

 West Indies (report in preparation). The 

 potential temperatures can be computed for 

 both regions from the data in hand, and they 

 are such that the heat of the upper strata of 

 the temperate zones, where there is eastward 

 flow increasing with the height, is above the 

 quantity called for by the adiabatic law. In 

 the tropics, with westward velocities diminish- 

 ing upward, the heat of the upper strata is 

 probably below the adiabatic quantity, though 

 this remains to be determined. We have had 

 since December, 1902, daily isobars for the 

 United States on the three planes, the sea 

 level, the 3,500-foot, and the 10,000-foot 

 planes, and the result of the intercomparison 

 of their varying configurations throughout the 

 year is in conformity with this analysis. 

 They possess much advantage in praoticall.y 

 forecasting the areas of precipitation, the di- 

 rection of storm tracks, and the rapidity of 

 the propagation of the cyclonic areas over the 

 United States. Frank H. Bigelow. 



Weather Bueeau, 

 November 30, 1903. 



HORTICULTURAL VARIETIES OP COMMON CROPS. 



The improvement of farm crops by breeding 

 and selection has received a marked impetus 

 in recent years, due partly to the success se- 

 cured by a few pioneer workers in this field, 

 and partly to recent discoveries in the laws of 

 heredity. The present note is written for the 

 purpose of calling attention to a method of 

 improvement that has been applied to ordinary 

 field crops only to a very limited extent, but 

 which offers promise of immediate and marked 

 results. It can be best illustrated by giving 

 actual cases. Dr. A. D. Hopkins, at present 

 connected with the Bureau of Entomology of 

 this department, formerly of the West Vir- 

 ginia Experiment Station, for many years 

 grew timothy for seed. For this purpose the 



crop is ordinarily sown thinly, so that, during 

 the first harvest year, the plants are sufficiently 

 distinct to permit of the observation of indi- 

 vidual plants. Many years' close observation 

 showed that the crop consists of a large num- 

 ber of constantly recurring forms quite easily 

 distinguished. A number of plants, each 

 representing one of these forms, were taken 

 up and separated into as many parts as the 

 nature of the case permitted; in this way each 

 plant became the parent, by divisions, of a 

 large number of plants, all set side by side in 

 a plat. When seed was harvested from these 

 plats it was found that the plants produced 

 from these seeds reproduced faithfully the 

 characters of the original selection. Each 

 original selection, therefore, became the parent 

 of a variety. Several of these varieties are 

 now growing in the grass garden of the De- 

 partment of Agriculture, where they have 

 been the object of careful observation during 

 the past season. They differ markedly in 

 character of growth, earliness, size, etc. Some 

 of them are evidently far superior to the or- 

 dinary timothy as grown by farmers (which is 

 a mixture of superior and inferior varieties), 

 some for seed production, others as hay plants, 

 and others as pasture plants. 



In a manner exactly similar, Mr. A. B. 

 Leckenby, director of the Eastern Oregon Ex- 

 periment Station, has isolated ten varieties of 

 brome grass (Bromus inermis Leyss.), as dis- 

 tinct, for instance, as the ordinary varieties of 

 wheat. He has also isolated a larger number 

 of varieties of Poa pratensis, differing to a 

 remarkable degree in character of growth, and 

 consequently in agricultural value. 



This method of securing new and stable 

 varieties is probably applicable to all unim- 

 proved crops that are ordinarily close-fertil- 

 ized. In the case of cross-fertilized species, 

 a different procedure would be necessary; but 

 if Mendel's law holds in these cases, similar 

 results can be secured even in cross-fertilized 

 species by artificially close-fertilizing the 

 plants. In this case, the plants would imme- 

 diately split up into a number of stable forms 

 that could be segreg-ated as varieties by iso- 

 lating them from other forms. 



The origin of these varieties which are 



