GERANIUM PURPUREUM VILL. AND G. ROBERTIANUM L. IN THE BRITISH FLORA I.

Geranium purpureum ViII. and G. robertianum L. form a valuable pair of species for ecological and cytogenetical comparison. One is a rare species whose British occurrences are at the northern limit of its Mediterranean type of distribution while the other is a widespread species with a considerable range of ecological tolerance. Since 1945 they have been grown, observed and hybridised in the Experimental Gardens of the University of Leeds. The genecological results of this study will be published elsewhere; in the present papers the subspecific units which have been established in each species as a result of the experimental and field studies are treated taxonomically and their British distributions are mapped. A great many infra-specific taxa have been described for these two species by those who have only observed their plants in the wild. Cultivation experiments show that some of these have no genetical basis (and are modifications induced directly by the environment). Only those distinctions which are maintained in cultivation in the uniform conditions of a garden are to be considered worthy of nomenclatural recognition. With this principle in mind, those morphologically distinct forms which appear to be ecologicall