168 



SCIENCE 



[Vol. LVI, No. 1441 



comparison with the hydrogen line 1215.68 and 

 with the three following lines of the same 

 series is therefore possible, with the result that 

 the wave-lengths are probably correct to one 

 or two tenths of a unit. 



The spacing of these four helium lines on 

 the frequency scale is of great interest and 

 importance, for it is found to be identical with 

 the spacing of the first four lines in the singlet 

 principal series. It may be stated therefore 

 with considerable certainty that the line 584 

 forms the first member of a principal series, 

 which, according to the notation of Professor 

 Fowler, is to be represented by oS-mP. 



Besides this series there is a single line at 

 600.5 ± .3 of a feeble and diffuse character ; its 

 origin is not entirely above suspicion. In the 

 extreme ultra-violet the arc spectrum of helium 

 appears to contain no lines in addition to those 

 just mentioned. 



The relation between the accepted values of 

 the resonance and ionization potentials in 

 helium and the wave-lengths of these new lines 

 is rather puzzling. The ionization potential 

 should certainly correspond to the limit of the 

 oS-mP series; now this limit can be accurately 

 calculated, it corresponds to 24.5 volts but the 

 experimental value is 25.3 volts. This is the 

 chief difficulty, but it is not the only one, for 

 the agreement between the wave-lengths of the 

 individual spectrum lines and the values of the 

 resonance potentials as determined by Franck 

 and Knipping is not satisfactory. A con'ec- 

 tion of about — 0.8 volts if applied to all the 

 potential measurements will bring the two sets 

 of data into fair agreement but at the expense 

 of the first resonance potential which is left 

 without any corresponding line in the spec- 

 trum. 



The matter should be of some interest to 

 , those who are struggling with the model of 

 the helium atom. 



Theodore Lyman 



Jefferson Laboratoby, 



HaRVAKD IjNlVEESrrY, 



AtTGUST 3, 1922 



THE CALIFORNIA POPPY 



It is perhaps strange that students of gene- 

 tics have not given more attention to the plant 



which is the glory of California fields, the 

 Copa d'Oro or California poppy, EsehschoUzia 

 californiea chamiso. It is a plant easily 

 raised from the seed, remarkably affected by 

 external conditions as well as subject to marked 

 variations, fluctuations or mutations, which 

 could be readily confirmed or intensified by 

 selective breeding. 



So great is the variability of this plant that 

 Greene has separated the ordinary perennial 

 form into thirty-two different "species," while 

 of the eight or nine other forms, annuals, 

 closely related to the golden poppy, but tan- 

 gibly distinct from it and from each other he 

 defines seventy-three species with some outlying 

 varieties. To this incredible list, Fedde, a Grer- 

 man botanist, adds several more. There is in 

 fact no limit if we regard every peculiar plant 

 as the type of a new species, without evidence 

 as to the origin and permanence of it-s varia- 

 tion. Such a condition, as observed by Darwin 

 among eirripeds, is attractive to us "as specu- 

 latists, however odious to us as systematists." 



The fiowers of EsehschoUzia californiea are 

 normally of a deep, rich orange, the four petals 

 with entire edges an inch and a half long. Near 

 the seashore the flowers are smallei-, of a more 

 or less clear lemon yellow, orange at base or 

 not. This is apparently "ontogenetic" varia- 

 tion, not entitled to a systematic name, because 

 likely to disappear with a changed environ- 

 ment, as the plant is not only inherently vari- 

 able but responds directly to all changes of soil 

 and season. 



Towards the end of a rainless summer, the 

 upright flower stalks wither and flowers suc- 

 cessively smaller spring from near the root- 

 stock. These are of a clear lemon yellow, some- 

 times more or less orange at base, the orange 

 fading as the flower grows smaller. 



Just now looking from my window as I 

 write over . a field golden with blossoms, I see 

 numerous variations, some of them perhaps to 

 be called mutations, as they are quite striking 

 and, occurring in patches must be moz'e or less 

 permanent. In several areas the flowers are 

 of a light creamy yeUow, the petals holding 

 their place when plucked longer than in the 

 orange form. Another group has large flowers 



