HYBRIDISATION OF EUPHRASIA 



261 



This suggests either that the plant is a hybrid whose parents are E. anglica and 

 E. occidentalis, or that E. vigursii arose from E, anglica and E. micrantha in the usual 

 way, and that subsequently, by the same process, there has been introgression into it 

 by E. occidentalis. The first alternative would not account for the purple flowers. The 

 second gets some support from the presence of E. micrantha in the cliff-top heath, though 

 this was found only at a point about one and a half miles from Perranport^i, and was not 

 adjacent to the E. vigursii population. 



With the glandular E. vigursii form here, an eglandular plant with purple flowers 

 was found; in one example a very few glands were present. In addition a small isolated 

 colony consisting entirely of dwarf eglandular plants with fairly large purple flowers 

 was found near the cliff- top. These may both be analogous to the eglandular E, vigursii 

 at Polgoda Down. 



At one of Davey's original E. vigursii localities, Forth Towan, the form present is 

 markedly different from that at other places in its short internodes and broad rounded 

 leaves. Davey first considered that the two forms should be distinguished as varieties. 

 Since Forth Towan is a coastal locality it seems possible that this form has been intro- 

 gressed by E. occidentalis, as suggested for the Perranporth form. 



Distribution and Status of Euphrasia vigursii 



A list of localities from which E. vigursii has been recorded is given in the appendix. 

 At several of these E. micrantha is recorded, and, at a few, E. anglica has been found.* Its 

 association with these two species supports the strong morphological evidence that it 

 is a hybrid between them. Therefore, as regards the origin of E. vigursii, I accept Pugsley's 

 view. A knowledge of the chromosome numbers of the three forms has, however, necessi- 

 tated a special hypothesis to explain this origin. 



The appendix shows that E. vigursii occurs in 7 of the 8 floristic divisions of Cornwall 

 (see Davey, 1909), and that it thus occurs widely in the two vice-counties of Cornwall, 

 as well as in part of a third (v.c. 3, S. Devon). Though in some places it is found with 

 E. micrantha or E. anglica, it can exist independently of either, I did not see E. anglica 

 at all in the Perranporth-Perranzabuloe district, and according to Rilstone (1923) itf is 

 rare in this part of Cornwall, being unknown in District 8 (Land's End) and very rare 

 in District 5 (North Coast), the district which includes Perranzabuloe. (There is, however, 

 in the Cambridge herbarium, a gathering made by Curnow and Ralfs at Tregarrest, 

 Fenzance, in District 8). E. vigursii has a distinct habitat, namely heath with Agrostis 

 setacea, and some or all of the following : Calluna vulgaris, Erica cinerea, Molinia caerulea, 

 Ulex gallii. The only other Euphrasia found with it in this habitat is E. micrantha, 

 from which it differs in chromosome number. It is morphologically very distinct and 

 easily recognisable. It thus has the appearance of being a species. Davey's description 

 of it as a species was based on his and Vigurs' knowledge of it in the field. Vigurs (1908) 

 noted the constancy of its habitat, saying : "All the known localities but one ... are 

 heathy and furzy downs and crofts." In order, therefore, to signify its species-like 

 status, I have adopted Davey's name, rather than Fugsley's hybrid formula. 



E. vigursii may have had either a multiple or a single origin. If one supposes that 

 it is of fairly recent origin, it is easier to imagine that it arose repeatedly in various localities, 

 than to imagine its having migrated from one spot to the various areas of moorland which 



• At localities not visited by me the absence of records or specimens of the presumed parents does not necessarily mean that 

 they are absent. 



t Rilstone used the name E. rostkoviana Hayne. The southern English plant known by this name was distinguished as £. anglica 

 by Pugsley in 1930. 



