260 



P. F. YEO 



E. micrantha and E. vigursii were found at Pensilva, on the slopes of Caradon Hill, 

 E. Cornwall, v.c. 2 (grid ref. 20/279695-283696). They are sho™ in Plate 17, figs. 2 

 Nos. 3 and 4 respectively. The profuse branching of the specimen of E. micrantha shown is 

 due to its being luxuriant. The £. vigursii here was similar to that at Roborough. The 

 greater part of the heath had been burnt over and Ulex gallii had not yet regenerated 

 over the area as a whole, so that the vegetation consisted mainly of Agrostis setacea and 

 Molinia caerulea. E. micrantha formed a small colony in a place where Erica cinerea 

 and Calluna vulgaris were present (grid. ref. 20/282696). E. anglica was fairly common 

 in the district but it was not found nearer the E. vigursii population than about a quarter 

 of a mile. 



The rem.aining populations to be described were in W. Cornwall, v.c. 1, in the 

 neighbourhood of Perranzabuloe. At Zela Hill (grid. ref. 10 821529) £. vigursii much 

 resembled that at Roborough and Pensilva. The vegetation had been recently burnt here 

 also; the dominants v.-ere Agrostis setacea and Erica cinerea. The only other species of 

 Euphrasia present was E. confusa, but this did not occur on the same ground as E. vigursii. 



At Polgoda Down (grid ref. 10 792525) E. vigursii grew mostly in parts of the 

 heath where the \-egetation was relatively thin with Agrostis setacea and Erica cinerea 

 codominant. At this locality, E. vigursii was of an extreme form (Plate 18, fig. 3), with small 

 elliptic cauline leaves with rounded teeth, strongly suggestive of E. micrantha. It was 

 also rather small, and the anthocyanin pigmentation was strongly developed in the 

 vegetative parts. It had the usual large purplish-red flowers. Growing with the glandular 

 E. vigursii were egiandular plants which were not distinguishable except by this character, 

 though on the average the plants were slightly less vigorous and had smaller leaves. 

 Their flowers were identical with those of the glandular plant. The chromosome 

 number of the egiandular plant is n = 11. The egiandular form must therefore be 

 regarded as a form of E. vigursii. Apparently introgression of E. micrantha genes has 

 gone so far that, in a proportion of the population, suppression of gland development 

 has resulted. There was no gradation in the density of the glands between the strongly 

 glandular and the egiandular t\pes. The only other Euphrasia present at Polgoda Down 

 was E. confusa. 



A similar situation was found on a piece of heath-land about half-way between Zela 

 Hill and Carland (grid ref. 20, 837536), on the edge of Newh-n Doutls. The Euphrasias 

 occurred by paths and in other places where the vegetation was relatively thin. E. micrantha 

 w^as present and in places grew with £. vigursii. A few plants of the egiandular form 

 of £. vigursii were found growing with the normal form. 



The egiandular £. vigursii is the only egiandular Euphrasia known to me which 

 has the diploid chromosome number. 



The observations on these four populations are considered to support the idea that 

 £. vigursii is a hybrid, one of whose parents is £. micrantha, since in two of them £. 

 micrantha was present, and, at Polgoda and Newl^ni, the £. vigursii was an extreme form, 

 showing a pronounced resemblance to £. micrantha in leaf-shape, indumentum (in a 

 proportion of the plants), and habit. 



A rather distinct form of £. vigursii was found on heathy slopes above the cliflfs 

 to the south-west of Perranporth. Here the dominant plant of the heathy ground is 

 Erica cinerea. Calluna vulgaris, Ulex sp. (? europaeus), and Molinia caerulea were also 

 present. Euphrasia vigursii grew in the grassier parts of the heathy area. It had the usual 

 rather large reddish-purple flowers, and taller habit than £. anglica, but in its somewhat 

 fleshy leaves, in the shape of these leaves, and in the formation of a dense flowering 

 spike, it resembled E. occidentalis Wettst., a species which was very common in the short 

 turf adjacent to the heath. 



