Freshly cut leaves of Kohleria eriantha and K. Γ "Longwood" were exposed to a wide range of gamma irradiation doses and allowed to root and form adventitious buds. K. Eriantha could not be successfully propagated from leaf half cuttings. "Longwood' produced a small number of adventitious plantlets as compared to other Gesneriads. Colchicine treatments reduced leaf half survival in "Longwood' by more than 50%. Leaf halves exposed to low and moderate doses of gamma irradiation showed increased overall plantlet production compared to nonirradiated leaf halves.
Of the mutation parameters calculated, the 'number of mutants per 100 surviving leaf halves" appears to be the most useful since it relates the number of mutants within a dose to the number of surviving leaf halves, the number of mutants to the number of plants produced, and the number of mutants within doses to control values.
Using the criteria, ~number of mutants per 100 surviving leaf halves', optimum production ofalt mutants, of useful and of dwarf mutants was obtained at 2.5 kR for noncolchicine treated leaf halves and 1.5 to 3.0 kR for colchicine treated leaf halves.
Of the adventitious plantlets produced, 13.8 % were classified as mutant types. Mutant plants were found in radiation dose levels up to 5.5 kR. The array of mutants produced was skewed toward "plant habit' and ~flower characteristic' mutants with several qeaf characteristic', "lethal', and "polyploid' mutants observed. A high tYequency of mutants, 10 of 93 plants, occurred in the nonirradiated controls. Four sectorial chimeras were identified from both control and irradiation exposed groups. Several potentially useful flower color and dwarf mutants have been selected tot further study. Adventitious buds may have developed from callus at petiole and leaf-vein bases. Colchicine treatments severely inhibited adventitious plantlet production and because of this could not be used as a criterion to identify the origin of adventitious buds. Conclusive determination of the organogenesis of adventitious buds from 'Longwood' leaf halves could not be made. Mutant plantlets formed from adventitious buds on detached leaf halves of'Longwood' appear to arise from single cells as has been found with other Gesneriads.