368 



RHINANTHACEAE 



L. REPENS X VULGARIS = i. sepium, Allm. in Proc. Irish Acad. ii. 



(1844) 404. 



Under the above name may be grouped several different hybrids of 



the above species which have been found in Berkshire. 



. 2. Ock. Near Didcot on ballast by the loopline and also near the 



railway station. Near Upton. Near Cholsey. 



3. Pang. On the downs above Moulsford on arable ground. 



Abundantly near Shooter's Hill, Beading. Pangbourn. On 



railway ballast near Reading. 



5. Loddon. Near Henley. 



The hybrids oflfer an almost unbroken chain of intermediates between the 

 two species. They may, however, roughly be arranged into four groups. 

 The first, which is the commoner one, and which comprises at least three- 

 fourths of the individuals, is that in which the repens parentage is prepotent, 

 so that there is about a quarter of the vulgaris as opposed to three-quarters 

 of the repens strain. The flowers are slightly larger than in true repens, but 

 the spur, the colour of the flowers, and the striations on them, all show that 

 the L. repens is the predominating factor. 



A second group may be made up of plants in which the influence of 

 L. vulgaris is more evidenced by the larger and paler- coloured flowers ; in 

 this about two-thirds of L. repens are present to a third of L. vulgaris. 



The two next groups consist of plants which are better expressed as 

 L. VULGARIS X REPENS. The flrst of these (which is even less frequent than 

 the second groiip alluded to) shows that the L. vulgaris parentage is largely 

 present by the increased size and prominence of the yellow palate, the 

 broader leaves, and in the shape and direction of the spur ; to this series 

 belongs L. sepium, AUman. The last group consists of individuals which are 

 near to L. vulgaris^ from which they chiefly differ in the faint striations on 

 the yellow corolla, and by the narrower leaves. To this I gave the name 

 X L. Baxterii in the Rep. of Bot. Exch. Cluh (1893) 421. 



The occurrence of these plants at Oxford affords an absolute proof (if such 

 were needed) of their hybrid origin. Up to the year 1890, Linaria vulgaris 

 only occurred. About that date a space of ground between the Great 

 Western and the London and North-Western Railways was filled up with 

 chalk rubble, which had been brought from the chalk district of Berkshire 

 near Upton. With the chalk, the seeds of many chalk plants were introduced. 

 In the year 1890 the chalk was covered with a profuse growth of Iberis 

 amara, Picris Hieracioides, and less plentifully with Thymus, Daucus, Linaria 

 repens, Centaurea nigra, Verbascum Thapsus, Campanula glomerata, Festuca 

 rubra, Bromus erectus, &c. Linaria vulgaris, which had previously existed in 

 the vicinity, was also common, but no hybrids were seen that season. In 

 the following year, however, hybrid plants occurred in great quantity, but 

 they belonged almost exclusively to the first two groups described above. 

 In 1892 the remaining two groups occurred, so that in going over the ground 

 an almost unbroken chain of intermediates between L. repens and L. vulgaris 

 could be found. A botanist unaware of the history oi L. repens and L. vulgaris 

 might have been excused if he had described them under one species. The 

 year 1893 marked the maximum quantity of the hybrids, which have since 

 become much diminished in quantitj- ; the native vegetation of Oxford now 

 threatens to destroy the settlers. Instead of the white Iberis, the red 

 Centaurea, and the blue and yellow Linaria and Picris, the surface is 

 beconung covered with grasses ; probably a few years only will elapse before 

 this object-lesson will be a thing of the past, the chalk plants extirpated under 

 the stress of stronger competitors, and the covering of the chalk by dead 

 vegetable matter, garden refuse, and soil from the immediate neighbourhood. 



