INVESTIGATIONS ON RUBBER-BEARING PLANTS: IV. CYTOGENETIC STUDIES IN ASCLEPIAS (TOURN.) L.

Abstract

The chromosome number of eight species and varieties of Asclepias (A. syriaca, A. incarnata and variety pulchra and forma albiflora, A. Sullivantii, A. tuberosa, A. curassavica, A. speciosa) was found to be 2n = 22.Various interspecific pollinations were attempted without success. A cross of A. incarnata with forma albiflora was successful.Possible natural hybrids between A. syriaca and A. speciosa and between A. incarnata and var. pulchra and forma albiflora are described. Two unusual chimaeral plants of A. incarnata that produced several stems of forma albiflora are described.