272 



H. G. BAKER 



workers (vide Rouy, 1897) who believe that the equally glabrous plants which they call 

 graniticarum are restricted to siliceous soils. 



The partial albino (f. leucanthemum Dum.) has rather yellower-green foliage but 

 otherwise differs from the type only in having white petals. It occurs quite commonly. 

 On the other hand, the complete albino (which lacks anthocyanin any^vhere in the plant) 

 is very rare in Britain and appears to have been found only once; as a true-breeding 

 weed at Newport, Isle of Wight (Long, 1936). 



In some Carboniferous limiestone areas of the south-west (e.g. in the Cheddar Gorge 

 and around Pontsticill, Breconshire) plants show less than the usual amount of antho- 

 cyanin in stems and petioles and the leaves are of a lighter green. The flowers may show 

 white stigmata. In these characters they show a transition towards the subspecies celticum. 

 The interpretation of this transition is not clear and there are alternative possibilities of 

 introgression and parallel differentiation. 



Similarly, in the vicinity of the River Camel, in Cornwall, many of the plants of 

 G. rohertianum have lemon-yellow anthers instead of the normal orange -red and they 

 breed true for this character which is likely to have been obtained by introgression from 

 G. purpureum which is common in the same hedgebanks. 



Of the ecads (the forms which are the results of direct environmental modification), 

 the shade-form is often seen (f. umbraticum Westerl.) This has broad leaflet-segments, 

 relatively little vegetative anthocyanin and a rather upright habit due to the prolonged 

 development of the leading shoot from the rootstock. 



Contrasting with this is the exposed form. In inland rocky regions Geranium roherti- 

 anum may be found growing in the open, sprawling over the rocks. It is often reddened 

 where it is exposed to wind and sun (and such plants have often been called var. ruhricaule 

 by British botanists). This coloration develops particularly in plants growing on walls. 

 The plants are usually dwarfed. 



At the end of the summer, plants may be found bearing small flowers with dull 

 yellow anthers. These have been mistaken by some observers for hybrids with Geranium 

 purpureum or even with G. lucidum. Nevertheless, fruits from these plants produce 

 perfectly normal plants in cultivation. In unusually cold weather a laciniate -leaved 

 condition is produced, just as it is (more easily) in Geranium purpureum, and this form has 

 been reported quite frequently by naturalists. It seems, however, that morphologically 

 similar but genetically determined forms also exist (e.g., Stephenson, 1920; Druce, 

 1927, etc.). 



G. ROBERTiANUM subsp. MARiTiMUM (Babington) comb. nov. 



G. rohertianum L. var. purpureum sec. Pauquy (1831), Fl. Somme, 76. 



G. purpureum Vill. sec. Bouch. (1833), FL d'Abheville, 61; non Vill. 



G. rohertianum L. var. ruhricaule Hornem. (1837), Dansk. Oec. PL, 2, 226; sec. 



Willk. & Lange (1878), Prodr. FL Hisp., 3, 531 (at least in part). 

 Rohertianum vulgare var. purpureum sec. Picard (1838), £t. Geran., 42. 

 G. rohertianum L. var. maritimum Babington (1851), Man. Brit. Bot., ed. 3, 62. 

 G. rohertianum L. var. purpureum sec. Syme (1864), Eng. Bot., ed. 3, 2, t. 307, 204. 

 G. purpureum Vill. var. littorale Rouy (1897), FL France, 4, 98. 

 G. rohertianum L. var. hispidum Druce (1917), Rep. Bot. Soc. & E. C, 5, 406 



(partim). 



G. rohertianum var. intermedium Willmott (1921), /. Bot., 59, 99 (including the 

 " Kingsdown form "). 



Type locality : Shingle beach, Shoreham, Sussex, England. 



