EINE NICHT LEBENSFAHIGE SIPPE VON AVENA SATIVA 475 
zu sein, dass das Chlorophyll wirklich durch das Licht zerstört wird, 
entweder weil es selbst »lichtempfindlich» ist, oder infolge Ver- 
änderungen, die von dem Lichte in den Zellen verursacht werden. 
Doch ist es natürlich nicht ausgeschlossen, sondern, vor allem wenn 
man an das Verhalten des Chlorophylls in mittelmässigem Lichte 
denkt, sehr naheliegend, dass die Vergilbung durch Hemmung der 
Chlorophylibildung verursacht werden kann. Weitere Untersuchungen 
über das Chlorophyll dieser Chlorophyllsippen und über die 
Bedingungen für seine Bildung und Zerstörung in den Zellen sind aber 
nötig, um die näheren Ursachen des Vergilbens feststellen zu können. 
Svalöf, Dezember 1921. 
SUMMARY. 
Some genetical and physiological data obtained in the course of 
study of a remarkable form (f. lutescens) of cultural oat are presented 
in the above. The plant in question becomes yellow when exposed 
to bright light and dies within few weeks. It was found in 1920 in 
the F,-generation from crosses between the new Danish Novahavre 
(a Probsteier variety) and black oats belonging to the type grown in 
the middle part of Sweden (Klockhavre II and III, Stormogulhavre and 
Fyrishavre). The seedlings have at first the normal green colour but 
turn yellow after a short time when grown in the field and die within 
a few weeks. 
The parents and the F,-generation of the crosses in question were 
all green. F, showed segregation in about 1 yellow and 70 green. 
Analyses of F, and F, (tables 1—4) have shown that segregation takes 
place in the ratio 63:1. It is brought about by three homomeric fac- 
tors which show free combination each producing the green colour also 
in the heterozygous state. 
Another explanation of the segregation has also been tried, viz. 
the assumption of only two homomeric factors, A and B, which repel 
each other inducing the formation of the combinations Ab and ab 
three times the number of AB and ab (see pag. 152). This explanation, 
however, had to be rejected on account of the distribution of the 
plots in Fs. 
The plots segregation in F, in 15:1 and especially the plots 
segregation in 3:1 did not quite reach the number to be expected. 
The deficient number of the latter ones is believed to arise through the 
