176 . À. AKERMAN 
circumstance that the uni-factorial heterozygotes are less vital than 
than the rest of the combinations. The validity of this belief is 
strengthened by the fact that the chlorophyll becomes partially 
destroyed in a certain period of the development of the plants causing 
yellow spots. This naturally weakens the plants. However, the normal 
green colour is recovered after some time. 
The fact of a real change in dominance here presented increases 
the interest of the observations. 
The distribution of the different factors in the parent types has 
not yet been determined. The light green colour of Novahavre is 
supposed to indicate the presence of only one chlorophyll factor in 
this type. 
No plants defect of chlorophyll have been found in the crosses 
made between other Probsteier varieties and the black oats from the 
middle part of Sweden (see pag. 164), or between these Probsteier 
varieties and Novahavre, a fact which goes to show that the ordinary 
white Svalof varieties contain at least two of these chlorophyll factors. 
The fact that lutescens-plants have not been found until now in 
Svalöf is easily explained if the assumption made by the writer that 
the Novahavre is uni-factorial while the black oats in middle Sweden 
are di-factorial is correct. Probsteier varieties or black oats from middle 
Sweden have in most cases been used in the combination work, at 
least as one of the parents. The fact that lutescens-plants have not 
yet been obtained as so called loss mutation is also believed to be 
due to the homomeric nature of this chlorophyll character. 
Experiments performed at varying light intensities have further 
shown that the yellowing of the lutescens-plants takes place only in > 
bright light. In subdued light, for instance */,—'/, of the intensity 
of the direct sunlight, the green colour is retained although somewhat 
less dark than in plants with normal green colour. The quantity of 
chlorophyll in these plants — even in light of very low intensity — 
has also been found to be less than in the normals. This is true 
not only of the green colouring matters but also of the yellow. 
ZITIERTE LITERATUR. 
1. CORRENS, C. 1918. Zur Kenntnis einfacher mendelnder Bastarde. Sitzungsb. 
d. preuss. Akad. d. Wiss. 1918, S. 221—268. 
2. — 1919. Vererbungsversuche mit buntblättrigen Sippen. I. Capsella bursa 
pastoris albovariabilis und chlorina. Ibid. 1919, S. 585—610, 
ee ht 6 : 
