October i8, 1900] 



NA TURE 



601 



FURTHER INVFSTIGATIONS ON XENIA 

 IN MAIZE. 

 "DROBABLY few botanical discoveries of recent years 

 ^ have aroused more interest than the remarkable 

 observations of Nawaschin upon the fusion of one of 

 the generative nuclei of the pollen tube with the defini- 

 tive nucleus of the embryo sac. Since further investi- 

 gations have rendered it not improbable that the process 

 is of general occurrence, its bearing upon some curious 

 phenomena met with in hybrids is of great interest as 

 affording an explanation, not only as to how hybrid em- 

 bryos, but also how truly hybrid endosperms can be 

 produced by crossing different races of plants. De 

 Vries' beautiful observations upon maize, which were 

 made almost simultaneously with those of Correns, have 

 already formed the subject of an article in this journal, 

 and they have recently been considerably extended by 

 some experiments conducted by Webber * in America. 

 As a result of his investigations, Webber concludes, in 

 all cases in which the hybrid corn shows a change of 

 colour, that this is due to the endosperm alone, the 

 translucent pericarp retaining, as might have been theo- 

 retically anticipated, the character properly appertaining 

 to the corn of the female parent. But in a large number 

 of instances it was found that, although the embryo on 

 germination showed that hybridisation had occurred, there 

 was no evidence of the transference of the qualities of the 

 male parent to the accompanying endosperm. On the 

 other hand, in some hybrid corns the endosperm exhibited 

 a spotted appearance, which might even {e.g. when 

 Gilman Flint was crossed with Stowell's Evergreen) be 

 restricted to only a portion of its substance. The author 

 suggests that the former case might be explained as 

 being the result of failure on the part of the generative 

 nucleus to unite with any nucleus within the embryo sac. 

 The spotted endosperms, on the other hand, might be 

 due to an independent segmentation of the second pollen 

 nucleus, which had failed to unite with the polar nuclei, 

 in which case the portion of endosperm so arising might 

 be expected to retain the characters of the male parent. 



There is no inherent improbability in such a sugges- 

 tion, nor need it necessarily affect any views which may 

 be entertained as to the sexuality of the fusion which 

 we are (perhaps rather hastily) beginning to regard as 

 general ; the investigations of Boveri and of Hertwig 

 respectively have shown that the nuclei of both male and 

 female reproductive cells of sea-urchins can be made to 

 segment by appropriate means, and even produce larvae, 

 and this without any preceding fusion of the sexual cells 

 themselves. 



It is clear, however, that much more investigation is 

 required before the points raised by Dr. Webber can be 

 cleared up, but it is to be hoped that so promising a field 

 of research will not be left to lie fallow, although the 

 work itself will necessarily prove arduous. 



PORTABLE GAS PRODUCERS. 

 A IR-GAS, as it is popularly called, consists of an 

 ^^^- admixture of ordinary atmospheric air with the 

 vapour of one of the volatile hydrocarbons, such as 

 pentane, gasolene or petroleum spirit. Travellers and 

 others having called attention to the production of a 

 natural gas in the petroleum-bearing districts, as at 

 Baku and elsewhere, it was not long before attempts 

 were made to imitate the workings of nature by pro- 

 ducing from the petroleum of commerce a combustible 

 gas. The carburetting of ordinary air by forcing a 

 current over liquid petroleum first seems to have been 

 proposed by Lowe in 1831, as in that year he took out a 

 patent for his apparatus. 



" Xenia, or the Immediate Effect of Pollen in Maize," by Herbert J. 

 Webber, U.S. Department of Agriculture, Btilletin 11, Washington, 1900. 



NO. 1616, VOL. 62] 



Air-gas producers may be roughly classified as 

 follows : — 



(i) Apparatus in which air \% forced under pressure 

 either through or over liquid petroleum, in which class 

 mention may be made of the apparatus of Jackson, 

 Miiller, Weston and Maxim. 



(2) Apparatus in which, on account of the danger of 

 using large quantities of liquid petroleum, an absorbent 

 is used to take up the hydrocarbon, either in part or 

 entirely, the air being, as in the first case, forced under 

 pressure over or through the absorbent. 



Considerable commercial importance attaches to certain 

 of the apparatus mentioned under the two classes given 

 above, both the "Alpha" apparatus of Miiller and the 

 " Sun '* apparatus of Hearson having had a considerable 

 success, both here and in America, for the lighting of 

 country houses and the like. It will be easily seen, how- 

 ever, that the necessity of having some motive power to 

 actuate the current of air introduces complex mechanism 

 which militates against the general adoption of such 

 apparatus. This disadvantage has, however, been met 

 by the apparatus comprising the third and last class of 



W^' 



^ 



Fig. I. Fig. 3. 



aero-gas generators, which possess a peculiar interest on 

 account of their simplicity and efficiency. 



In 1895 Mr. Naum Notkin, of Moscow, was struck 

 with the idea that use might be made of the physical 

 property that carburetted air is considerably heavier 

 than ordinary atmospheric air for the construction of a 

 gas-producing apparatus of extreme simplicity. His 

 method and apparatus, which are patented in Great 

 Britain (No. 20667/94), may be described as follows : — 



The apparatus consists essentially of a vessel of tin or 

 other material, with an orifice at the top and another at 

 the bottom. This simple vessel is filled with a porous 

 material which is impregnated from time to time with 

 one of the lighter hydrocarbons, and this constitutes the 

 whole apparatus. The action of the apparatus is that 

 ordinary atmospheric air enters at the upper orifice, and 

 taking up a certain proportion of hydrocarbon vapour 

 becomes heavier and gravitates through the mass of 

 absorbents, taking up more and more of the hydrocarbon 

 vapour, until it finally issues from the lower orifice in the 

 form of a gas capable of lighting, heating, and all other 

 uses to which ordinary gas is put. Not only does the 



