510 



SCIENCE 



[N. S. Vol. XLIII. No. 1110 



THE NUMBER OP STANDARD PLANTS PRODUCED PROM 

 SEED OP OPEN-POLLINATED DWAKP PLANTS 



Whether or not cross-pollination is caused 

 by wind or insects is not known, although no 

 large insects, such as bees, were seen to visit 

 the plants. Moreover, tomato pollen is dry 

 and seems better adapted to wind transporta- 

 tion. This could be easily tested by screening 

 the dwarf plants. This would not preclude the 

 possibility of cross-pollination by thrips. 



Plowers which are bagged in the bud stage 

 and left undisturbed usually do not set fruit. 

 Jarring the plant while the anthers are de- 

 hiscing generally suffices to cause pollination. 

 Tomatoes in greenhouses do not set fruit well 

 unless artificially pollinated. 



It seems from this evidence that the tomato 

 is naturally only slightly cross-fertilized. 

 Some external agency, however, is generally 

 needed for self-pollination as well as for cross- 

 pollination. 



Donald F. Jones 



Connecticut Agricultural 

 ■ Experiment Station 



SOCIETIES AND ACADEMIES 



THE AMERICAN PHILOSOPHICAL SOCIETY 



At the January meeting of tlie society held 

 January 7, Professor J. A. Miller, of Swarthmore 

 College, read a paper on ' ' The Determination of 

 the Distances of Stars from TJs." 



He sketched the attempts of Copernicus, Tycho, 

 Erache, Bradley and Sir William Herschel to find 

 a sensible stellar parallax. Perhaps the chief rea- 

 son for desiring a stellar parallax at that time 

 was that it would establish the truth of the Coper- 

 niean system upon observational rather than theo- 

 retical evidence. 



Although these men failed in their attempts to 

 determine a parallax it was while making observa- 



tions for that that Bradley discovered the aberra- 

 tion of light and Herschel established the fact that 

 a physical connection exists between the com- 

 ponents of certain double stars. 



It was 300 years after Copernicus, more than a 

 century after Bradley and a half century after 

 Herschel before the first sensible parallax of a 

 star was actually found when Bessell found the 

 parallax of 61 Cygni and Henderson a parallax of 

 a Centauri. Bessell completed his observations in 

 1S40 and although astronomers have been work- 

 ing assiduously ever since, reliable parallaxes of 

 only about 400 stars have been determined. 



At present eight American observatories are 

 working at the problem under the direction of a 

 committee appointed by the American Astronom- 

 ical Society. Most of these observatories are ap- 

 plying the photographic method devised by 

 Pritehard, of Oxford. This method has since been 

 refined and improved by various men, most notably 

 perhaps by Schlesinger. 



The Sproul Observatory of Swarthmore College 

 is one of the eight observatories mentioned above 

 and is spending most of the energies of its stafE 

 in that direction. They have determined in all 46 

 parallaxes. The program contains: 



1. All visual binaries whose orbits are well de- 

 termined. 



2. Those visual binaries, the data concerning 

 wliicb leads us to believe their orbits will be de- 

 termined in the not very distant future. 



3. Some spectroscopic binaries. 



4. Some stars of large proper motion. 



5. Some stars whose hypothetical parallax is 

 large. 



6. Other objects. 



Classes 1, 2, 3, receive most attention and the 

 measurements and reductions of 13 stars of Class 

 1 have been completed. 



Though no generalization could be made from 

 so small a number of stars as this, yet so far as 

 can be judged from these 13 stars, the orbits of the 

 binaries are comparable in magnitude to the orbits 

 of the planets. The greatest distance between two 

 components of any double star in this list (t 

 Cygni) being 32 astronomical units, and the least 

 being four astronomical units for 85 Pegasi. 



The combined masses of the two components 

 average larger than the sun. The largest mass 

 being of Lalande 9091, which is 48 times the sun 

 and the smallest being 20 Persei which is 0.26 

 that of the sun. 



