Studies in Hibiscus

VI. Reciprocal crosses between American herbaceous species and Asian arboreal species

Abstract

1. Intra- and inter-specific crosses were made in four arboreal species of the East Asian Group of Hibiscus, mutabilis, sino-syriacus and para-mutabilis, and six perennial herbaceous species of the North American Group, coccineus, incanus, lasiocarpus, leucophyllus, militaris and moscheutos.
2. Intraspecific crosses:
The species of the Asian Group except mutabilis showed remarkable self-incompatibility. Self-pollination yielded only a few capsules without seeds, whereas the crosses between different strains produced capsules containing many fertile seeds.
Self-incompatibility was not found in mutabilis and the American Group. Self-pollination in these species always proved highly fertile.
3. Interspecific crosses:
Reciprocal crosses between six herbaceous species of North American origin produced abundant capsules containing a number of fertile seeds with high germination capacity.
Reciprocal crosses between syriacus, sino-syriacus and para-mutabilis resulted in low percentages of capsule setting, The capsules contained few fertile seeds with low germination capacity. Mutual crosses between mutabilis and the other arboreal species were all unsuccessful.
Crosses between mutabilis and six American species were successful only when the former was the mother plant. The percentages of fruit setting, the number of seeds obtained, and the viability of the seeds were all inferior to the corresponding figures in the mutual crosses within the American group.
Reciprocal crosses between the Asian species other than mutabilis and the American herbaceous species proved unsuccessful in every case.