1918-19.] BOTANICAL SOCIETV OF EDINBURGH 329 



separated. Plants of Vaccinium intermedium, with the 

 vegetative vigour common in hybrids, increase peripherally 

 at the expense of the neighbouring flora, by pushing out 

 creeping root-stocks in all directions. Thus the size of a 

 patch of the plant bears a simple relation to its age. The 

 various patches show considerable diff'erences in habit, size, 

 and shape of leaves and stem, flowering season and fertilit3^ 

 etc., though the plants in any one patch show a consider- 

 able degree of uniformity. This individuality, shown by 

 the various patches, would tend to suggest that each 

 patch owes its origin to a separate act of cross-fertilisation. 



As there are many upland areas in Great Britain and 

 Ireland where Bilberry and Cowberry grow together, it 

 is curious that, while the hybrid is found in very few of 

 such areas, it should be quite common in portions of one 

 of them — to wit, Cannock Chase. As upland areas are 

 peculiarly attractive to botanists, it can hardly be supposed 

 that the hybrid is really comparatively common but 

 usually overlooked. Some factor specially favouring the 

 production or spread of the hybrid must then be present 

 on Cannock Chase. 



I flrst noticed the hybrid in May 1919, and showed it 

 to Captain G. M. Vevers, KA.M.C. (since demobilised). In 

 the next few daj^s we each found several other hybrid 

 patches and compared them. Vevers pointed out that, of 

 the seven hybrid patches then noted, six were growing 

 in positions where some artiflcial and gross disturbance 

 of the ground had occurred. Thus, in three cases, patches 

 were found growing along the edges of trenches, the other 

 three being found respectively : (a) on what looked like 

 an old gun position, (b) on an area formerly used for 

 bombing practice, and (c) on a pond embankment com- 

 posed of layers of cvit peat. The remaining site showed 

 no obvious evidence of disturbance. The embankment 

 appeared to be a work of much earlier date than the 

 evidences of military training, and the hybrid patch upon 

 it was much larger than the others. Vevers suggested 

 that the violent crushing or shaking together of flower- 

 ing plants of Bilberry and Cowbeny might have resulted 

 in their cross-fertilisation. 



I have subsequently found many more patches of the 



