280 BOTANICAL GAZETTE [OCTOBER 
as O. cana. O. pallescens, O. Lactuca, and O. liquida. Their Lamarck- 
iana-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 4o 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 allied species 
of the biennis group, as has been discovered by BARTLETT in the 
case of O. stenomeres mut. lasiopetala and described in this article 
for O. biennis Chicago mut. saligna. 
4. In the crosses with older species or with O. Lamarckiana and 
its derivatives, O. cana follows exactly the type of the analogous 
crosses of O. scintillans and O. 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 O. 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 
