THE CHROMOSOMES OF OENOTHERA LAMARCKIANA. 513 



of mutants obviously correspond, at least essentially, to the three 

 large chromosomes and the four small groups to the four smaller 



Central chromosome 



Lata chromosome & %^\ Scintiiians chromosome 



Pallescens chromosome 



Cana chromosome 



Liquida chromosome \ ^% JW / Spathalata chromosome 



Figure 1. Diagrammatic view of the seven haploid chromosomes in Oenothera 

 Lamarckiana, to each of which, except the "central chromosome", is provisio- 

 nally assigned one of the groups of 15-chromosome mutants. 



chromosomes. We may then put the results of our investigation in 

 the form of the scheme given above (figure 1). In this scheme the 

 position and relative size of the chromosomes have been drawn in 

 accordance with figure 28 of Cleland, but the axis of the figure has 

 been turned a little so as to make it more clearly symmetrical. Of 

 every pair only one rod has been reproduced. 



Our central chromosome obviously corresponds to the chromosome 

 I of Shull (1921), which in the contrasting gametes of Oe. Lamarckiana 

 carries the factors for the characters of velutina (I a) or those of 

 laeta (I b). The new mutants funifolia and pervirens constitute also, 

 according to the description of this author, members of the central 

 group of mutant characters. 



The lateral chromosomes have been given the names of their 

 primary, dimorphic mutants, the sesquiplex and rarer mutants in 

 each group being considered as of secondary importance. 



Of course our scheme is only a provisional and in part an arbitrary 

 one. But it is corroborated by the quite analogous results of Blakeslee 

 with Datura. Many smaller arguments could be given to support 

 it, as will be seen from the detailed description of our researches. 

 We will here only adduce a single point, relating to the 21-chromo- 

 some types or semigigas. These proceed from Oe. Lamarckiana, 

 with its two kinds of gametes, as well as from simplex, all the sexual 



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