GERANIUM PURPUREUM VILL. AND G. ROBERTIANUM L. 

 IN THE BRITISH FLORA , 



II. GERANIUM ROBERTIANUM 



By H. G. Baker 

 Department of Botany, University of Leeds 



Geranium rohertianum L. is a commoner and more variable species in the British 

 flora than G. purpureum which was dealt with in the previous paper of this series (Baker, 

 1955). Experiments, which will be described elsewhere, have demonstrated that some 

 of this variability is the direct result of the influence of environmental factors while the 

 remainder, some of which is important taxonomically, is genetically determined. Al- 

 though populations of the species are often relatively uniform, there may be striking 

 differences between populations. Part of the intra-population uniformity can be related 

 to the prevailing self-pollination in this species (as in G. purpureum) (Baker, 1952). 



This classification, which relates genetically determined morphological and ecological 

 character- differences to each other, cuts right across the groupings made simply on the 

 basis of the hairiness of the various plant parts even though such characters remain 

 constant in cultivation. To take a single example - Druce^s varietal name hispidum 

 (Druce, 1917) was applied by its author to maritime material from Berry Head, South 

 Devon and to hillside plants growing near Buxton in Derbyshire (Druce, 1924). On the 

 other hand, glabrous plants grow on the shingle at Shoreham, Sussex and at several 

 inland stations on Carboniferous Limestone, corresponding with those where the hirsute 

 Derbyshire plants grow. Between these extremes a complete series may be made out 

 in maritime and woodland populations. 



The subdivision of British material of Geranium rohertianum into varieties was 

 attempted by Wilmott (1921) and three taxa with this status are listed by Warburg 

 (1952) as " the more distinct forms " in a variable species " which is probably divisible 

 into several ssp." In the present paper the division is made into subspecies in accordance 

 with the principles of Clausen, Keck and Hiesey (1939). 



The type subspecies is a race inhabiting woodlands, hedgebanks and patches of 

 soil among rocks as well as on moist walls. Maritime material, usually found growing 

 in relatively stable beach shingle, belongs to the subsp. maritimum, while subsp. celticum 

 represents an ecoclimatic race apparently restricted to unshaded limestone rocks in the 

 west. This last subspecies appears to be endemic to the British Isles. 



Geranium robertianum L. (1753), Sp. PL, 955 



G. ROBERTIANUM Subsp. ROBERTIANUM 



G. rohertianum var. incisum St. Hil. (1825), Fl. Bras, mer., 1, 82. 



G. rohertianum var. alpinum Gaud. & var. fiore alho Gaud. (1829), Fl. Helvet., 4, 417. 



G. rohertianum var. mosquense Ledeb. (1842), Fl. Ross., 1, 474. 



G. rohertianum var. genuinum Gren. et Godr. (1848), Fl. France, 1, 306. 



G. rohertianum L. sec. Jord. ex Boreau (1851), Fl. Cent. France, ed. 3, 2, 131. 



G. rohertianum f. suhglahrum Grognot (1861 ?), PI. vase. Saone et Loire, 139. 



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