290 



NATURE 



[June i, 1916 



set of normal values and the departures for 19 13. It 

 is doubtful if this is more convenient than the old 

 plan of publishing current values and departures from 

 normal. A brief comparison between the extremes for 

 Kew and Greenwich for 1913 indicates that there is 

 less close agreement than might be expected, showing 

 that for London as a whole one outlying station is 

 totally inadequate. We notice the employment of 

 the millibar in the pressure tables, and also of. 

 absolute temperatures, but neither of these is likely 

 to popularise the work, but if the aim Be uniformity 

 we might suggest that a step in this direction might 

 be made by adopting a uniform height above the 

 ground for corresponding instruments, especially for 

 the thermographs, which are all at different heights. 



W. W. B. 



I 



RESEARCHES ON HOPS. 



N a contribution to these pages a couple of years 

 ago (Nature, April 23, 19 14, vol. xciii., p. 199) 

 it was pointed out that a good instance of that scien- 

 tific attention which is paid by certain foreign coun- 

 tries to the study of economic plants could be seen in 

 the monographic study of the hop which is being 

 made by Dr. J. Schmidt, with his staff of chemists 

 and botanists, at the Carlsberg Laboratory, Copen- 

 hagen. In that review the results were noted of Dr. 

 Schmidt's investigations into the growth in length and 

 rotational movement of the stem of the hop and their 

 diurnal periodicity. We have now to hand the results 

 of a number of further researches.-^ 



Dr. O. Winge has investigated the pollination and 

 fertilisation processes in H. Lupulus and H. japonicus. 

 The paper deals fully with the cytological and nuclear 

 phenomena, and is clearly illustrated by figures. Some 

 interesting developmental points were observed in the 

 study of a monoecious hop and of a sterile gyno- 

 morphous male. Experiments to produce a hybrid 

 between H. Lupulus and H. japonicus failed ; it may 

 be observed here that the same negative results were 

 obtained by the reviewer three years ago. Dr. 

 Winge's investigations showed that the pollen of H. 

 japonicus caused the ovary of H. Lupulus to swell 

 almost to the normal size, resulting ultimately in a 

 "fruit" of normal appearance. The hop strobile, too, 

 developed its axis and stipules. Microscopical exam- 

 ination showed that as a rule fertilisation had taken 

 place in the embryo-sac, and a small embryo was pro- 

 duced, which, however, never developed further. Dr. 

 Winge thinks that it is perhaps possible that the pollen 

 of Urtica may be able to produce " fruits " in the hops 

 in hop-gardens, as was asserted by a practical man — 

 a Bavarian hop-grower — in 1883. 



Dr. H. Schjerning gives a full summary of his 

 numerous researches dealing with the proteid sub- 

 stances of barley, both in the grain itself and during 

 the brewing processes ; for reasons of space, no further 

 reference can be made to this here. 



A new method for the quantitative determination of 

 resins in hops is described by Messrs. O. Winge and 

 J. P. H. Jensen. These ipvestigators found that, 

 contrary to what Hayduck has stated, the y resin is 

 of value to the brewer, since it gives a bitter taste to 

 the wort and helps in the precipitation of the albumens. 

 For the determination of the total resins in the hop 

 the most satisfactory method was found to be that 

 of extraction with cold ethyl ether and titration of the 

 solution with 1/20 normal potassium hydroxide solu- 

 tion. By this method the lupulin content is obtained 

 as a percentage of the dry weight of the hops ; it has 

 been employed not only for the valuation of the 



1 "Comptes Renrtus des Travaux du Taboratoire de Carlsberg," vol. x'>. 

 livr. 1-4 (7914-15)- 



NO. 2431, VOL. 97] 



various varieties of hops grown in the experimental 

 garden, but also in analyses of trade samples made by 

 the laboratory in co-operation with various breweries. 

 The relations between the bitterness of the a, ^, and -, 

 resins were found to be constant, and, respectively, as 

 10:7:4. 



Dr. J. Schmidt has a very interesting paper on the 

 aroma of hops. The author does not regard it as 

 proved that the aroma present in a hop sample, when 

 this is mixed with the wort for boiling, has anv 

 decisive influence on the flavour of the beer. This, it 

 may be noted, is in opposition to the view held bv 

 brewing experts, and the further information on this 

 subject which Dr. Schmidt promises will be awaited 

 with interest. It is pointed out that the commercial 

 varieties of cultivated hops are verv probably not 

 "true," since, being propagated by cuttings, there is 

 always the danger that these may be taken occasion- 

 ally from seedlings which have established themselves 

 in the garden. To avoid the danger, Dr. Schmidt 

 has used exclusively at his research station individuals 

 raised by vegetative propagation from one plant. This 

 group of individuals is termed a hop-clone — a clone- 

 plant being any single plant belonging to the clone. 

 In crossing experiments with two American varieties 

 and Danish male hops, proof was obtained that the 

 distinctive aroma of these American hops — which Dr. 

 Schmidt calls "turpentine-like" — was transmitted to 

 between half and three-quarters of the off^spring plants, 

 without regard to whether the hops (strobiles) them- 

 selves retained the appearance peculiar to those of the 

 mother plant. It is to be hoped that Dr. Schmidt 

 will be on his guard against attempting to ascertain 

 the true nature of the aroma of a new seedling hop 

 from the examination of the plant in its early years 

 exclusively, since there is reason to believe that this 

 may change with the age of the plant. 



Dr. Schmidt also records the results of his investi- 

 gations as to the amount of lupulin in plants raised by 

 crossing, and also their time of flowering. It was 

 found that the average lupulin content of the offspring 

 shows (with rare exceptions) a decrease, due perhaps 

 to the fact that the " wild " male plants used were 

 genotypically of a low order as regards lupulin con- 

 tent ; in every group, however, some few specimens — 

 the extreme plus varlates— occurred ; a stock of anv 

 of these new varieties with increased lupulin-content 

 can be raised for commercial use by vegetative pro- 

 pagation. Very similar results have been obtained at 

 Wye College, Kent, in the breeding of new varieties 

 of hops ; Dr. Schmidt, referring to these, writes • — 

 "Altogether, these two series of Investigations carried 

 out Independently in England and Denmark respec- 

 tively exhibit remarkable uniformity of results, and 

 the discoveries thus made appear to promise well for 

 the systematic improvement of hops." 



E. S. S. 



" TROPISMS." 



"T^HE word "tropism," first used to Indicate the 

 A growth-direction of plant-members under the 

 influence of some stimulus, has during the last fifteen 

 years become a favourite term among investigators 

 of the behaviour of animals. Those interested in 

 physiological terminology will find accounts of the 

 various meanings attached by different writers to the 

 word in two controversial articles by Mr. S. O. Mast 

 (Arch. f. Entuncklungsmechanik, xli., 1914, pp. 251- 

 263, and Biol. Centralbl., xxxiv., 1914, pp. 641-674). 

 He finds that the word Is now " used In so many 

 different senses that everj^ne finds it necessary to 

 Indicate in which sense he proposes to use it"; there- 



