126 Â. ÂKERMAN 



AH the other plants in the plot 1917 — 965 gave rise to a typical 

 progeny, except one, which gave rise to 30 typical plants and one spel- 

 toid heterozygote with outer glumes of the same construction as those 

 of the chimaera. I have, however, not yet been able to study the 

 progeny of tiiis one. 



If one tries to give a more definite explanation of the origin of the 

 chimaeras described in the above, it lies close at hand to assume 

 that the plants originally were of normal type, and that the speltoid 

 component arose through a mutation ^ in a cell of the growing point 

 so that one of the two factors (SS) necessary for normal development 

 was changed or »fell away» resulting in a change in the genetical 

 constitution. The fact that the speltoid component in the last 

 described chimaera (from the cross Sunwheat II X Blé Balan) consti- 

 tuted the greater part of the spike does not invalidate such an interpre- 

 tation. The powerful development of the speltoid component of this 

 plant may be due to the fact that the mutation took place already 

 at an early stage in the development. The speltoid part grew stronger 

 and, lastly, became the predominant one. However, in this and in all 

 other similar cases it is not entirely impossible that the plants originally 

 were heterozygotes, arising through gamete-mutation or perhaps through 

 some complicated segregation (see Heribert-Nilsson 1916, p. 870), and 

 that in these a sector of the normal type afterwards arose through bud- 

 mutation or through a vegetative segregation. 



Additional explanations could be given. I consider, however, the 

 first mentioned to be the most acceptable one at present. 



BIBLIOGRAPHY. 



1. Bateson, VV. 1916. Root-Cuttings, Chimaeras and Sports. Journal of Genetics, 



Vol. VI, p. 75—80. 



2. Bmjr, E. 1918. Mutationen von Antirrhinum majus. Zeitschrift für induktive 



Abstammungs- und Vererbungslehre. Bd. 19. p. 177 — 193. 



3. Hehibkrt-Nilsson, N. 1918. Eine Mendelsche Erklärung der Verlustmutanten. 



Berichte der deutschen botanischen Gesellschaft. Bd. 34, p. 870 — 880. 



4. KOERNicKE, M. 1897. Untersuchungen über die Entstehung und Entv^icklung der 



Sexualorgane von Triticum. mit besonderer Berücksichtigung der Kernleilung. 

 Diss. Bonn. 



^ Of course it can also he assumed in conformity wjlli Bate.son (191(i) that 

 a kind of segregation-process has taken place. 



