264 



P. F. YEO 



(3) E, confusa X rostkoviana 



This hybrid is one of those listed by Warburg (1952). The specimens to be described 

 were collected in a " damp pasture near Whinlatter road, bottom of Hobcarton Gill, 

 v.c. 70," Cumberland, by S. M. Walters. 



E. rostkoviana is a tall plant of hayfields, with rather few branches and large flowers. 

 It was not collected at this locality. E. confusa is a dwarf plant with flexuous branches, 

 rather narrow, finely toothed leaves, and small flowers. The plants collected (No. 53/76) 

 represent a rather sparingly branched form. The apparent hybrid (No. 53/77) was 

 growing with it. It is long-glandular and has large flowers, 8-10 mm. long, like E. rost- 

 koviana, but has numerous slender flexuous branches and is dwarf in habit. The capsules 

 are longer and narrower than in E. rostkoviana, the leaves are smaller and narrower, and 

 the teeth of the bracts and calyces are finer. In all these characters it approaches E. 

 confusa. 



Here, the tall hayfield species, E. rostkoviana, has been modified in such a way as 

 to enable it to grow in a grazed pasture, that is, to become like E. anglica. The situation 

 is therefore the converse of that at Street. E, rostkoviana is absent from Somerset, and 

 E. anglica is absent from Cumberland. 



(4) £. rostkoviana X salisburgensis 



Specimens in Herb. Kew from fields near Innsbruck, collected by A. Kerner, show 

 clear indications of the modification of E. rostkoviana, or an allied species, by a small form 

 of E. salisburgensis Hoppe. Of the six plants on the sheet one is correctly determined by 

 Pugsley as E. salisburgensis. The others resemble this plant in their relatively short, thin, 

 wiry stems and branches and their long narrow leaves, deeply cut and with the teeth 

 directed towards the apex, but are large-flowered and long-glandular plants. 



The occurrence of this hybrid is interesting since E. salisburgensis is not closely 

 related to the other tetraploids mentioned in this paper. 



Diploid'Tetraploid Hybridisation Resulting Only in Introgression 



Where a diploid and a tetraploid hybridise in the manner suggested for £. vigursii 

 but without change of habit in the diploid, the process can be regarded simply as the 

 introgression of genes from the tetraploid into the diploid. The absence of habit modi- 

 fication may be either because the diploid and the tetraploid are the same in habit, or, 

 if they are not the same, because there is no habitat not occupied by the diploid parent 

 to which it could become adapted by acquisition of genes from the tetraploid. However, 

 even in the absence of habit modification, there might be physiological changes which 

 would alter the diploid's tolerance with respect to environmental factors other thantallness 

 of vegetation. The forms to be described now are, therefore, those in which there has 

 been introgression of ecologically neutral characters, and possibly also of characters 

 significant with respect to habitat factors not easily observed with the eye. 



The first of these to be described was found at Friday Street, Surrey. This is the 

 locality of another plant determined by Pugsley (1933) as E. anglica X pseudokerneri. The 

 specimens of this were originally collected by Salmon in 1899. They have short inter- 

 nodes, and since both E. anglica and E. pseudokerneri have short internodes they are 

 more plausibly regarded as E. anglica X pseudokerneri than the tall Piltdown plant, Salmon's 

 plant is very like E. pseudokerneri in habit and foliage, and its flowers are very large, 

 larger, in fact, than is usual in E. pseudokerneri. In 1953 I found what may be the locality 

 of Salmon's plant (grid ref. 51/132461). The only Euphrasia present apart from the 



