Moss: Changes in the Halifax Flora. 107 



a tract undergo concurrent variation ' ; with which trite dictum 

 all botanists, whether young- or old, must of course coincide. 

 It was with the theory as stated in February, when it was 

 doubtless in 'the adolescence of demonstration,' that one 'quar- 

 relled with the Deduction' ; but as in August it had taken a 

 decided step towards virility, one feels most happy in then 

 < furnishing overwhelming witnesses to the facts leading to it.' 



I do not deny that the ' substitution ' of one plant by another 

 occurs : I have simply asked for evidence of a non-supposititious 

 character. I am prepared to grant that 'substitution' by natural 

 means occurs; and that, could we find continuous and reliable 

 records over some centuries, examples would be not rare ; but 

 it seems to me that such examples are difficult to find if we only 

 extend our observations over a short period of time. No doubt 

 ' substitutions ' by artificial agencies are much more numerous, 

 and comparatively easy to find even in the course of observations 

 extending only over a few decades. 



1. Linnaius, Spec. Plant., 1753. 



2. William Hudson, Flor. Angl., 1762. 



3. (James Bolton), Catal. of Halif. Plants; Hist, of Halif., 



by Rev. Jno. Watson, M.A. 



4. R. Leyland, Herbm., in Museum, Halif., 181 5, et seq. ann. 

 S. Gibson, Herbm., in Museum, Halif., 1830, et seq. ann. 

 S. King, Herbm., in Museum, Halif., 1830, et seq. ann. 



5. Henry Baines, Flora of Yorks., 1844. 



6. F. A. Lees, Flora of West Yorks., 1888. 



7. F. A. Lees, Old Leeds Herbary, Nat., Feb. 1900. 



8. C. E. Moss, Changes in Halif. Flora, Nat., June 1900. 



9. F. A. Lees, Defence of J. Bolton, Nat., Aug. 1900. 



A Rejoinder, Nat., Aug. 1900. 



10. H. H. Corbett, Note in Nat., Sept. 1900. 

 Rev. W. Fowler, Note in Nat., Oct. 1900. 



11. R. Smith, Botan. Surv. of Scotl. , I., July 1900. 



Botan. Surv. of Scotl., II., Aug. 1900. 



12. A. Wilson, Smoke Cloud of N. of Eng., Brit. Ass., Sept. 



1900. 



13. J. Cohen, Air of Towns, Brit. Ass., Sep. 1900. 



14. C. Crossland, Note in Halif. Nat., Feb. 1901. 



15. W. B. Crump, Flora of Halif., Halif. Nat., unfinished. 



16. F. A. Lees, Note in Nat., March 1901. 



[This — the final reply — closes the discussion. — Eds. Nat.] 



1901 April 1. 



