Abstract
An account is given of the flower colours, chromosome numbers and flower pigments of cultivated species and hybrids ofStreptocarpus. The origin of the garden strain is recounted and the results of breeding experiments within the strain are shown to agree with the known origin of the garden forms. The action of the flower colour genes is as follows.A is necessary for the production of anthocyanin, and alone, produces anthocyanins derived from pelargonidin.R in the presence ofA produces anthocyanins derived from cyanidin.O, is epistatic toR and in the presence ofA gives anthocyanins derived from delphinidin. ThusR adds one substituent hydroxyl (or methoxyl) group to the anthocyanidin molecule andO adds two.D produces 3 : 5-dimonoside in place of pentoseglycoside-dimonoside (d) mixtures. Seven distinct colour classes results from the combination of these genes. Methylation is complete with the delphinidin derivatives but incomplete with the cyanidin derivatives.
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