444 



these two forms, so dissimilar at the opposite extremities of their se- 

 ries, were scarce distinguishable in some of the intermediate examples. 

 Indeed, at this time I have a living plant before me, on which both 

 the acute and the obtuse crenatures are found very clearly shown on 

 different leaves. It is highly probable that S. hirsuta (Linn.) must 

 be sunk into the grade of a variety ; the Irish species of the section 

 remaining only two, Geum and umbrosa, and even these two running 

 almost together in hirsuta and elegans. 



10. — Glyceria plicata ("Fries") and Glyceria Jluitans (Br.). — Mr. 

 Moore kindly supplied examples of these two species, lately distin- 

 guished as such, from Hampstead. The G. plicata is likely to occur 

 in many counties, though less common than the G. fluitans, from 

 which it does not appear to have been hitherto distinguished, even as 

 a variety, by the botanists of Britain. They are certainly very similar 

 in most respects ; and if I have ever seen G. plicata in a living state, 

 it has been passed by, as only G. fluitans. All the specimens in my 

 own herbarium belong to the latter species solely. Unfortunately, 

 these grasses were not included in several of the parcels sent out in 

 January and February. 



Though other interesting species or varieties are to be found among 

 the plants distributing this year from the Society, they do not seem to 

 call for any particular notice, having been already recorded in the 

 ' London Catalogue,' or in my former paper on the Society's distribu- 

 tion of last year (Phytol. ii. 43). 



Hewett C. Watson. 



Thames Ditton, 



February, 1846. 



Thoughts on the progressive development of species. By William 



Wilson, Esq. 



In reference to Mr. Watson's remarks on this subject, I think that 

 too much has been conceded to the transitionists. To admit the pos- 

 sibility of a variety assuming the essential properties of a central spe- 

 cies, or an acquired tendency to perpetuate its own likeness prepon- 

 derating over that paternity which would induce it to return to the 

 form of the central species, seems to me very like the surrender of two 

 important principles, without which the debate cannot be profitably 

 carried on. 



