FLORA OF THE BRISTOL COAL-FIELD. 27 



have examined the locality of late years. Nor is it 

 possible that the plant could be introduced in such 

 abundance over so wide an area. To account for 

 its resuscitation we must, I think, believe that 

 this, like some other species, may be uncertain in 

 flowering, and may require for its perfect develop- 

 ment some unusual climatal conditions. That a 

 very wet summer following the great heat of 1887 

 induced the plants, which formerly had flowered 

 but sparingly or not at all, to produce a luxuriant 

 crop, is, I think, a reasonable explanation of an 

 extremely curious circumstance. There is little 

 doubt that other plants were similarly affected. I 

 observe that whereas last spring the trees of Popu- 

 lus tremula in Leigh Woods produced abundance 

 of flowers, both barren and fertile, this year (1889) 

 not a single catkin was to be seen upon them ; and 

 much the same thing has occurred with the Horn- 

 beams in Clifton. 



