556 



KNOWLEDGE & SCIENTIFIC NEWS. 



[October, 1906. 



elements belongingf to independent allelomorphic pairs. 

 If the reader will turn to pagfe 556 of the current 

 number he will see that, representing the pre- 

 sence of these elements F)y the letters A and B, and 

 their absence bv a and b, out of 16 individuals there 

 will be on the average nine possessing both factors, 

 and seven having only one or neither of them. That 

 is to say, the ratio of coloured to white-flowered off- 

 spring will be as g : 7. The coloured plants, moreover, 

 are found to consist of two main classes, purples and 

 red, which occur in the ratio of 3:1, thus demon- 

 .■^trating the existence of a third allelomorphic pair, 

 the presence or absence of a blue factor, which, how- 

 ever, can only produce a perceptible effect when 

 the characters A and B are also present. In 

 the lo-week Stocks the problem is further compli- 

 cated by the fact that the hoariness of the leaves is 

 found similarly to depend upon the presence of two 

 independent factors; not onlv so, but, in general, this 

 hoariness is only produced if the colour factors also be 

 present ! This discovery of the fact that two, and 

 possiblv more, independent allelomorphic pairs may 

 enter into the composition of an apparently simple 

 character, is of far-reaching importance in affording 

 an explanation of manv results which have hitherto ap- 

 peared quite irregular and even contradictory. 



Mr. Biffen gave an account of some experiments iipon 

 breeding of wheat, which must lead to results of 

 supreme practical, as well as theoretical, value. The 

 loss which is entailed every j'ear to wheat crops 

 through the attacks of rust is only too well known. 

 Occasionally, however, there are found plants which 

 show themselves to be immune from the attacks of 

 the fungus. Mr. Biffen has shown bevond anv question 

 that this immunity is a transmissible character, in- 

 herited according to simple Mcndelian principles. The 

 raising of crops immune from rust should, therefore, 

 be onlv a matter of time. It is not necessary to dwell 

 "on the immediate practical value to agriculture of this 

 result; further, it opens a wide field for experiment as 

 to the inheritance of physiological (as distinct from 

 morohoJogical) characters in general, and gives hope 

 of the possibility of producing, by appropriate breed- 

 ing, in other plants and animals strains immune from 

 certain diseases. 



Dr. Rosenberg, of Stockholm, furnished a most 

 interesting paper upon the behaviour of the chromo- 

 somes in the formation of the germ cells in hybrid 

 plants. Although much yet remains to be done, and 

 our present evidence is largely indirect, we may look 

 forward confidently to the day when cytological work 

 will give us the key to what we may call the mechanism 

 by which segregation of characters in the germ cells 

 is brought about. 



Want of space compels us to omit all mention of 

 many other contributions both of scientific and of 

 practical value, of which full reports will be published 

 in the Royal Horticultural Society's Journal. The 

 heartiest thanks of those who had the privilege of 

 attending the Conference are due to the Ro\al Horti- 

 cultural Society and to its members for the generous 

 hospitality which was provided for all. One cannot 

 appreciate too highly the opportunity which the Con- 

 ference has afforded of meeting those who are working 

 in other countries; of equal value, too, is the recogni- 

 tion given at the Conference to the importance of com- 

 bined effort between scientific investigators and practi- 

 cal horticulturists; each can provide just that know- 

 ledge which is apt to be lacking in the other, and so 

 assist the advance along their respective paths. 



Stellar Distances. 



By T. E. Heath, F.K.A.S. 



The list of stars here given, with their magnitudes, 

 spectra, distances in light-years, hypothetical diameters 

 in miles, and sun-po\ver, is taken from my last work, 

 " Stereoscopic Star Charts and Spectroscopic Key 

 Maps," in which the authorities are given. I have 

 added four stars collected from measurements by 

 Prof. Pritchard. As my object was to show all the 

 stars to the fifth magnitude in space of three dimen- 

 sions, and as I had to use estimated average distances 

 according to magnitude and spectrum for the stars 

 for which I could obtain no measured parallax, I natu- 

 rally collected all I could. If I believed the distances to 

 be very good, I marked them **,good ", very doubtful ?. 

 I have here grouped the stars according to magnitude 

 and worked out the average distance and sun- power for 

 each magnitude, although beyond magnitude i'5 the 

 parallaxes measured are too few to make the averages 

 useful. Naturally the nearest stars only have been 

 measured where the magnitudes are small. The hypo- 

 thetical diameters in miles are calculated upon the sup- 

 position that the sun and stars, for equal surfaces, give equal 

 light, and, though this is certainly not true, form a foun- 

 dation upon which we can build ideas as to size which 

 will be greatly modified by the spectra and temperature 

 of the stars as compared with the sun. I have assumed 

 the sun's magnitude is —26-5. Readers of my first article 

 in " Knowledge " will recollect my scale for stellar dis- 

 tances. If the distance of the eaith '^rom the sun be 

 represented by one inch, then one light-year will be re- 

 presented by one mile, and the distance to the furthest 

 known planet by one pace of 30 inches. So to journey 

 mentally to Sirius you think of walking 8-| miles with 

 strides sufficient at each pace to carry you to Neptune. 



I give the mass in a few cases. It is evident in some 

 cases, as the bright star of Sirius and Algol, the density 

 is far less than the sun's; but with the darker star of 

 Sirius and of 85 Pegasi, it is much greater. 



MAGNI CUBE- 1-58 IO-050. 



Mag. spec. ^S^^ ^rv. 



12 Star* average 



