HYBRIDISATION OF EUPHRASIA 



263 



on the one hand and E. nemorosa on the other (Plate 17, fig. 2 No. 6). Its commonest form, 

 however, was intermediate between the extremes, being tall but with little anthocyanin, 

 and very distinctive in appearance. It grew in long grass where Pteridium aquilinum 

 was present, with the fronds well spaced out. The variation of the apparent hybrid 

 might be due either to selection in response to habitat variation, or to phenotypic responses 

 to different conditions. Probably both causes operate. , 



The glandular plant from Lane End Common has the diploid chromosome number, 

 and at meiosis two of the larger chromosomes quite frequently occur as univalents, 

 instead of as one bivalent. 



The glandular plant at these two localities is presumably derived from E. anglica, by 

 crossing with the form of E. nemorosa present, since it distinctly resembles the latter in 

 its more extreme modifications. £. anglica is presumed to be the diploid parent because 

 it is the only diploid species known in southern England. The modification of E. anglica 

 is comparable in extent to that which E. vigursii shows, and it enables the glandular 

 plant to grow in communities in which normal E. anglica would not be expected to occur. 

 The hybrid populations are thus closely analogous to E. vigursii. 



Like E. vigursii, the Sussex plant has rather large flowers, and this evidently led 

 Pugsley to regard it as a hybrid between E. anglica and E. pseudokerneri. The nearest 

 place to Piltdown where the latter is likely to occur is the South Downs, six miles away. 

 E. pseudokerneri is therefore much less likely to be the parent than E. nemorosa. Owing 

 to the unpredictable results of the process of crossing involved, the parentage of these 

 fertile hybrid-populations should be inferred from the species associated with them, and 

 not from the hybrids* morphology alone. 



(2) E, anglica X brevipila 



At Street Heath, N. Somerset, v.c. 6, two forms were found (grid ref. 31/396461). 

 One is Euphrasia brevipila, a plant with long internodes, rather few branches, short- 

 stalked glands on the leaves, and medium-sized flowers (6-7-5 mm. across the lower 

 lip). The other is a long-glandular plant, similar in habit to E. brevipila, and attaining 

 a very large size and having very large flowers, 7-11 mm. across the lower lip. The 

 plants were found in moderately long grass, in two separate clearings, about 50 yards 

 apart, in the fen carr which occupies most of Street Heath. E. brevipila was found by a 

 peat cutting, the other plant in a relatively acid spot, with Myrica gale, Erica tetralix 

 and Calluna vulgaris. The long-glandular plant is similar to E. rostkoviana Hayne, but 

 the fine leaf- and calyx-teeth of some plants suggest that it is a hybrid. 



Mr. C. C. Townsend has kindly sent me specimens of a plant collected at Street 

 Heath and reported as E. anglica in Proc. B.S.B.I., 1, 59 (1954). These plants resemble 

 E. anglica in habit and flower size, but appear somewhat modified in habit, and more 

 distinctly so in the fine teeth of the leaves and calyx. These plants tend to confirm that 

 the very tall and large-flowered plant is in fact E. anglica X brevipila. 



The hybrid parallels E. vigursii in having larger flowers than either parent, and in 

 having a modified habit and habitat, as compared with E. anglica. 



Two records of this hybrid from the Somerset peat moors have been obtained from 

 herbaria. They are : (1) Sharpham, near Street, with E. brevipila, in low peaty pasture, 

 V. S. Summerhayes, 19/7/1928 (Herb. Kew) ; (2) " Carex evoluta enclosure," Turfmoor, 

 with E. brevipila and more or less normal E. anglica, H. S. Thompson, 1922 (Herb. Univ. 

 Cantab, and Herb. N. D. Simpson). These two gatherings are probably both from the 

 same place, which is probably the Sharpham Reserve of the Society for the Promotion 

 of Nature Reserves. 



