26 



NATURE 



[September 12. 1918 



hybrid are more distim tl; 

 than thosi ■ H subrhomboideus. In othei cases 

 cross annuals with perennials havi re- 



il failure, ;is has 1 1 . 1 p j > 1 • 1 1 > • 1 1 uh'-n cro-sini; 



//. anmius <>n //. pumilus; in attempts to repeal the 

 cribed above, which was erroneously inter- 

 l. In other cases seeds were obtained from the 

 pollen ol perennials used on annuals, and the resulting 

 plants were indistinguishable from the annual parent. 

 Seeds received from Mr. L. Sutton from England, 

 representing the F„ of a cross between the red II. 

 annum and the perennial //. rigidus, also gave plants 

 entirely of the annuut type. 



Babcock and Clausen, in their recenl (1918) admir- 

 able work, "Genetics in Relation to Agriculture," 

 have (chap, xii.) discussed those remarkable cases in 

 which the F, generation of a cross gives plants 

 resembling the original species crossed, with greatei 

 or less fertility. A ven ingenious and plausible ex- 

 planation is given. Collins and Kempton recently 

 found that in crossing two distinct genera of grasses, 

 Triosacum and Euchlasna, they obtained plants agree- 

 ing with the pollen parent, the F.uchlaena. They call 

 this patrogenesis (Journal of Heredity, vol. vii., No. 3, 

 1916). One of the explanations offered by them is 

 that the male nucleus may have developed in the ovary 

 to the complete exclusion of the female, " representing 

 in a way the counterpart of parthenogenesis." It 

 appears quite possible that in some hybrids, and perhaps 

 other heterozvgous forms, particular pairs of homo- 

 logous determiners do not both function or develop, 

 so that in respect to certain characters the organism 

 is simplex, not in the sense of the old "presence and 

 absence theory," but in the sense of not being a hybrid 

 at all in respect to particular features. 



T. D. A. COCKFRELL. 



University of Colorado, Boulder, Colorado, 

 August 6. 



THE NITROGEN PROBLEM IN RELATION 

 TO THE WAR. 



PROF. ARTHUR A. NOYES, of the Massa- 

 chusetts Institute of Technology, who is 

 chairman of the Committee on Nitrate Investiga- 

 tions of the National Research Council of America 

 — a body which owes its existence to the war — 

 recently delivered a lecture before a joint meeting 

 of tin Washington Academy of Sciences and the 

 Chemical Society of Washington, a report of 

 which, under the above title, is published in the 

 Journal of the Washington Academy of Sciences 

 for June 19. The lecture dealt with the vital im- 

 portance of an adequate supply of nitrogen com- 

 pounds, particularly of nitric acid and ammonia, 

 in connection with the war, and gave a brief de- 

 scription of the various efforts America was 

 making in order to meet the demand. Nitric acid 

 enters, directly or indirectly, into the composition 

 of all the more important explosives, such as 

 smokeless powder, picric acid, ordinary black 

 powder, dynamite, trinitrotoluol, and ammonium 

 nitrate. The last-named substance is now used 

 on so enormous a scale that the demand for am- 

 monia is scarcely less urgent than that for nitric 

 acid. 



The main sources of these two nitrogen com- 

 pounds are: (1) Chile saltpetre; (2) by-product 

 gas from coke-ovens ; (3) atmospheric nitrogen, 

 which is "fixed" by (a) the cyanamide process, 

 NO. 2550, VOL. I02] 



('») the cyanide process, (c) the arc process, and 

 (d) the synthetic process. 



For its supply of nitric acid the United States, 

 like ourselves, has hitherto mainly depended 

 upon imported sodium nitrate (Chile saltpetre), 

 which is now recognised as a rather precarious 

 source, as it depends upon adequate shipping, and 

 is liable to be affected by enemy machinations in 

 interfering with production, destroying plants, or 

 blowing up the reservoirs of oil needed for fuel. 

 Hitherto all attempts on the part of the enemy 

 to establish a submarine base on the Pacific Coast 

 have been foiled. But even if this source con- 

 tinues to be efficiently safeguarded, America 

 realises that it is impracticable to get through 

 imported nitrate the huge amount of nitric acid 

 thai will be needed for her Army, and that it will be 

 necessary to supplement thissupplv by other means. 



The demand for ammonia has led, as with us, 

 to a complete revolution in coke-oven practice, 

 and the old wasteful "beehive" oven is rapidly 

 becoming a thing of the past. "By-product" 

 ovens, in which the coal to be coked is heated in 

 what are practically closed retorts, and the evolved 

 gases passed through scrubbers and condensers 

 whereby the ammonia and inflammable gases are 

 recovered and utilised, are, under the spur of 

 necessitv, being everywhere established, to the 

 permanent benefit of industry. The preference of 

 the iron-smelter for the hard-coke produced in the 

 "beehive" oven was no doubt the reason why a 

 process of coking which wasted all the nitrogen 

 and much of the calorific energy of the fuel has 

 continued so long, both here and in America. The 

 war, however, has effectually broken down what 

 is, after all, a prejudice, and there can be little 

 doubt that "by-product" coking will shortly be- 

 come the universal practice. Indeed, it is now a 

 question of practical politics whether, in the in- 

 terests of national economy, the employment of 

 "by-product" ovens in coking, to the exclusion 

 of the old form, should not be made compulsory. 

 Si • urgent is the demand for ammonia in con- 

 nection with the war that Germany is incidentally 

 producing far more coke than she can use imme- 

 diately, either in metallurgy or as fuel, and enor- 

 mous stocks are being accumulated. 



As regards "fixation" processes, America is 

 now working, to a greater or less extent, all the 

 methods which have been developed during the 

 past fifteen years. Even before the war the 

 American Cyanamid Co. at Niagara Falls was 

 producing about 20,000 tons of cyanamide a year, 

 largely for use in agriculture. By the action of 

 steam upon this substance it is practicable to get 

 substantially all the original nitrogen in the form 

 of ammonia. This process is capable of a great 

 extension, and has already reached considerable 

 proportions in Germany, where it competes with 

 the Haber process. The American Government is 

 building" a cvanamide plant with a capacity of 

 110,000 tons of ammonium nitrate at Muscle 

 Shoals, Alabama, and a third plant has been 

 authorised for the production of another 1 10,000 

 tons in Ohio. The cyanamide process has the 



