The Genus Collinsia. XII. Cytogenetic Studies of Interspecific Hybrids Involving Species with Sessile Flowers

Abstract

1. Nineteen interspecific hybridizations were attempted between species of Collinsia Nutt. (Scrophulariaceae) included in the group with sessile flowers and in the groups with the anomalous species, i.e., C. corymbosa and C. multicolor; fifteen combinations succeeded. Hybridizations between C. tinctoria and four species with sessile flowers were unsuccessful. 2. Hybrids involving C. multicolor displayed one interchange complex with six or eight chromosomes; hybrids involving C. corymbosa exhibited either an interchange complex of four or six chromosomes or bivalents and univalents; and hybrids within the group with sessile flowers yielded bivalents and univalents at metaphase I. 3. The interchange complex in hybrids between C. corymbosa and either C. multicolor or C. tinctoria and between C. multicolor and C. heterophylla showed a directed orientation at metaphase I; the interchange complex in other hybrids did not. 4. Hybrids involving species with sessile flowers and either C. multicolor or C. corymbosa...