28o BOTANICAL GAZETTE [October 



as O. cana. 0. pallescens, O. Lactuca, and 0. liquida. Their Lamarck- 

 mwa-like offspring are constant in their progeny. Besides the two 

 main types, they produce, as a rule, a relatively high percentage 

 of other mutants. 



2. The specimens of the parental type are on the average pro- 

 duced in about 40 per cent, the other 60 per cent being Lamarckiana 

 with some mutants; but these figures vary with the cultures and 

 with the plants according to their individual strength. They 

 may even increase, on very strong biennials, to 93-97 per cent for 

 the parental type. 



3. Dimorphic mutants of this type occur also in aUied species 

 of the biennis group, as has been discovered by Bartlett in the 

 case of 0. stenomeres mut. lasiopetala and described in this article 

 for 0. biennis Chicago mut. saligna. 



4. In the crosses with older species or with 0. Lamarckiana and 

 its derivatives, 0. cana foUows exactly the t)7pe of the analogous 

 crosses of 0. scintillans and 0. lata. 



5. In the dimorphic mutants, the special characters are handed 

 down to the next generation through the ovules only. The pollen 

 lacks these characters, and is, so far as investigated, not different 

 from that of pure 0. Lamarckiana. 



6. The dimorphic mutants constitute a group in which the 

 hereditary phenomena are evidently independent of the externally 

 visible characters of the special members of the group, but must 

 be assumed to have the same intrinsic causes in the different cases. 



Botanic Garden 

 Amsterdam 



