'Varietäten, Descendenz, Hybriden. 453 



Heekel, C, Sur la mutation gemmaire culturale du Solamim 

 tuberosum. (C. R. Acad. Sc. Paris. 3 Juin 1907.) 



Edouard Heekel, continuant une serie de recherches qui a dejä 

 fait l'objet d'une precedente communication, a obtenu six plantes de 

 Solanum tuberosum ä tubercules violaces, en plein etat du mutation, 

 provenant de tubercules jaunes tres petits lenticelles, originaires de 

 Burlington (Vermont, E. U.) tres voisins du type primitif proba- 

 ble. II est probable qu'on trouvera des faits semblables chez beau- 

 coup d'autres especes soumises ä la culture, en partant des formes 

 originaires sauvages. Jean Friedel. 



Loek, R. H., Studies in Plant Breeding in the Tropics. III. 

 Experiments with Maize [Zea Mays, L.). (Ann. Roy. Bot. Gar- 

 dens, Peradeniya, III. p. 95-184. 1906.) 



The phenomenon of so-called xenia in maize as well as the 

 further results of hybridisation have been studied in considerable 

 detail b}' Correns, and that author has pointed out the desirability 

 of examining the proportions in which the different kinds of germ 

 cells occur in a long series of hybrid plants, in order to discover 

 whether departures from the expected ratios have any special signi- 

 ficance, or whether they are simply to be attributed to the results 

 of random sampling. 



The evidence brought forward in the present paper seems to 

 show that in the case of the allelomorphic characters concerned it 

 is very nearly an equal chance whether one or the other member of 

 a particular pair makes its appearance in any particular gamete 

 borne on a heterozygote. 



It was found that when a starch corn is crossed with a sugar 

 corn , or when a yellow grained plant is crossed with a plant bearing 

 white grains, the heteroz3^gote grains can always be distinguished 

 from the recessive fsugary and white respectively). Taking these 

 two pairs of characters together it was found that 247 cases were 

 available in which a heterozygote, having been crossed with the 

 recessive, yielded approximately an equal number of heteroz^^gote 

 and of recessive grains. The results are expressed as percentages 

 of the heterozj^gote type. 



Total number of grains: 56,928 Heterozygotes: 55,669 Recessive. 

 That is: 50.17 per cent. of Heterozygotes (Expectation bO + 0.11). 



The individual percentages shown by the 247 samples were as 

 foUows: 



o/o.— 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 

 NO. 1 - _ ö 3 5 13.5 13.5 30 31.5 41 30 22.5 19.5 14.5 

 o/o-— 55 56 57 58 59 60 

 NO. 7 3 2 13 1. 



The Quetelet curve arising from this series of values was plotted. 

 The mode of this curve lies very nearly at 50 per cent., and the 

 mid departure found graphically from the area of the curve is 1.9. 

 The average number of individual grains borne by each of the 247 

 plants examined was 450. 



The value 1.9 is somewhat higher than the theoretical probable 

 error of random samples containing 450 individuals of two kinds 

 drawn from a stock in which the two kinds occur in equal numbers 

 such probable error being 1.6. This amount of difference seems to 

 indicate some disturbing factor at work, but is not inconsisting with 

 the view that in the majority of cases the deviations from the value 



