FORTGESETZTE INTEUSK.ULNGEN i HEH Sl'ELTOIDMLTATIONEN 219 



Kiitslcliunj,' des (;c)nii)ii(tiiintyi)iis die sckiindiirc Kiscliciium^': die nsterc 

 Miilalion imiss dcshall) als Lrsaclu' liir die zweite aii^'enoinmen werden. 

 Schon aul (irnnd dessen lie^t es nalie aiu h liir S|)ell<)idnuitationen 

 die Erkläruni,' in Clnoniosomenkomplikationen und nicht in Faklo- 

 renniulalionen /u suchen. Indassende l'ntersuchun^'en sind noch er- 

 lorderlich, his der l'all ^'anz klar vor uns lii'j^t: es dart aher auch 

 erhottt werden, dass eine erschr)|)len(le I^rlorschun^j; der in verschie- 

 <lenen S|)eltoi(lreihen \ orkonnnenden Komplikationen einen wesent- 

 lichen iieitra^' zum \'erständnis der denetik des Weizens liefern 

 wird. — 



SUMMARY. 



In otlsj)rinii; ot the Normal ty|)e heterozyj^ous Six-Itoid mutante 

 appear, from this, aj^ain. (lonipactum heterozyf,'otes mutate, in the 

 l)roi,uiiy of which Squarehead heterozygotes appear. According to the 

 results from reciprocal crosses the relation hetween these mutants can 

 he symbolised thus: .V X A' = Normal tyi)e: S'p X A ^ Speltoid he- 

 terozygote; .SpC X A = Comi)actum heterozygote and SpYSjid^^ 

 Squarehead heterozygote (Lindh.\hd 1922 I. 



In the three last named heterozygotes the Normal, Speltoid and 

 (lompactum types form a kind of triangle not to he explained by mul- 

 tiple allelomorphism, for the hybrid between any two of these three 

 types can segregate the third in heterozygous condition. 



Preliminary investigations (by Dr. 0. Winge) of the cytology of 

 these mutants lead to the presumption that the Scpiarehead heterozy- 

 gote ^7; SpC and the Compactum heterozygote SpC X have only 41 

 instead of 42 chromosomes in the somatic cells. Accordingly the C.om- 

 pactum gamete SpC should contain only 20 instead of 21 chromosomes 

 and consist of a Speltoid gamete lacking a certain chromosome. When 

 this is finally established, the problem of the triangle will be partly 

 solved. 



Compactum heterozygotes, which are heterozygous in the factor 

 for awns also, segregate awned and awnless offspring in different 

 ratios from the two different crosses: 



A = awnless Compactum X awned Normal type, and, 



ß = awned Compactum X awnless Normal type, or 

 (when f/ = awnless and « = awned) A = USpC X iiX. According to 

 the ratio of awned offspring thi/, hybrid should produce about 8 ga- 

 metes with the composition USpC. to 1 uSpC. Conversely B = uSpC X 



