229 



THE VOLTEFACE OF FLORA: A REJOINDER. 



F. ARNOLD LEES, M.R.C.S., L . R . C . P . Lon d. , 



Leeds ; Author of ' The Flora of West Yorkshire.' 



Three of the personal remarks in Mr. Moss's well-arranged 

 paper on ' Changes in the Halifax Flora ' call for a reply from 

 me ; although i controversy ' over a tentative theory yet in the 

 adolescence of demonstration is as far from my liking as the 

 imputative decoy set for me on page 169 of the June 4 Naturalist/ 



No ! I do not wish to advance any such theory of substitu- 

 tion applicable to a secluded clough, as Mr. Moss implies to be 

 likely by his aggressive ' If ' ; nay, I consider his analytic par- 

 ticulars in this case to have forged a sound chain of reasoning. 

 To have substitution (even the most gradual) there must be 

 some patent — or more often hidden — change of environment. 

 Mr. Moss's facts predicate little if any ; therefore he is probably 

 right in considering that the compiler of the list in Watson's 

 History meant crocata by his fistulous CEnanthe. Not quite 

 ' certainly, for the lowland open-marsh fistulosa has got less 

 common, has been extirpated by deep drainage in Yorkshire 

 stations wherein it flourished to my knowledge in the Seventies. 

 Per contra, to my knowledge and judging from old Herbaria, 

 <E. crocata, with Typha and other things, has grown vastly 

 more abundant (if not absolutely originated) at Adel, near 

 Leeds, since the making of the dam there, and in the last ten 

 years since it has fallen quite out of use and is growing up, this 

 same CEnanthe is being choked out : to show itself at intervals 

 miles lower down the Adel-Meanwood beck where barish flood- 

 mud banks allow of rejuvenescence. Mr. Moss attributes some 

 aquatics to man's handiwork : why not this? It requires much 

 water for its tubers to ripen, it is transported readily by water- 

 ways, it will flourish in shade or the open, but it cannot stand 

 drought or vigorous competition : Typha latifolia, planted 

 amongst it, comes out victor in a very few years. 



My contention is, merely (and broadly), that as conditions 

 alter so, slowly, does the flora of a tract undergo a concurrent 

 variation ? To assert the contrary is to subvert almost every- 

 thing we know as to the limitations of soil, altitude, temperature 

 under which species flourish. Some have a strict range, others 

 a more clastic. Why do we never find the Cloudberry below 

 1200 feet, or brought down and growing by the Calder .side? 

 or Trientalis in same case? Because such spate-removal would 



uHH) August I. 



