GERANIUM PURPUREUM VILL. AND G. ROBERTIANUM L. 

 IN THE BRITISH FLORA 



L GERANIUM PURPUREUM 

 By H. G. Baker 



Department of Botany, University of Leeds 



Geranium purpureum Vill. and G. rohertianum 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 ecologically 

 significant (or to possess a distinctive geographical distribution) are given subspecific 

 rank. They are the * ecological races ' and their taxonomic treatment is thus in accordance 

 with the principles of Clausen, Keck & Hiesey (1939). Within these subspecies, lesser 

 morphological groupings may be made, but these more or less discrete forms usually 

 differ from each other only in respect of individual qualitative characters. They are 

 accompanied by other, more or less continuous, variation in quantitative characters and 

 neither the discrete nor the continuous variation within the subspecies appears to have 

 any measurable ecological correlation. 



On this basis, British material of Geranium purpureum appears to consist of two 

 subspecies, while G. rohertianum contains three (which will be discussed in the second 

 paper of this series). That there are other non-British infra-specific groupings in both 

 species is certain and some of them will be treated elsewhere. 



In the preparation of these accounts, use has been made of material contained in 

 the following herbaria : — 



H. G. Baker (Bak.) Royal Botanic Gardens, Kew (K) 



British Museum (Natural History) (B.M.) Borrer at R.B.G., Kew (K.Borr.) 



Boswell-Syme at B.M. (N.H.) (B.M.Bosw.) Cryer at Leeds University (L.Cry.) 



Sowerby at B.M. (N.H.) (B.M. Sow.) Roper at Leeds University (L.Rop.) 



Cambridge University (Cam.) Oxford University (Ox.) 



Marshall at Cambridge University (Cam. Mar.) National Museum of Wales, Cardiff (WNH) 



Royal Botanic Garden, Edinburgh (E) C. C. Townsend (Towns.) 



Royal Albert Museum, Exeter (Ex.Hiern) Musium National d'HistoireNaturelle, Paris (Par.) 



Grateful acknowledgment is made to the authorities concerned. 



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