HYBRIDS AMONG BRITISH PHANEROGAMS 269 



also redeem the subject of it from a charge of barrenness. While in 

 Salix hybrids we find fertility the rule, and in Mentha hybrids 

 sterility, there are genera in which it is not quite clear what the 

 rule is: do we, for instance, know the habits of Rosa in this re- 

 spect ? The testimony is somewhat conflicting ; and this may 

 suggest another question wanting solution : whether the rule of 

 sterility or the reverse always holds good throughout a genus, or an 

 order ? Then there are genera where it is still in question whether 

 some of the forms are hybrids or species, as in Pyrus (Sorbiis). 

 Such as these stand in need of experimental treatment rather than 

 observation. 



I am inclined to think with regard to hybridity in plant life that 

 we must not expect to be able to reduce all cases to one rigid rule ; 

 and therefore we must not draw inferences as to the habits of one 

 genus from the habits of another. The botanists of the earlier half 

 of last century either refused to believe in natural hybrids (as Sir 

 J. E. Smith with the Willows), or held that, while the cross- offspring 

 of varieties was fertile, the cross -offspring of species was always 

 sterile. They were too servile to the idea of uniformity in nature ; 

 and these prejudices long stood in the way of progress being made 

 in understanding the habits of hybrids and the part they have 

 played in the economy of nature. 



The last edition (ninth) of the London Catalogue of British Plants 

 made an attempt to distinguish the forms which were accepted as 

 hybrids with a x placed between the names of the parent species ; 

 but there was no consistency of method ; the work could not be 

 called up to date ; many hybrids still stood in the list numbered as 

 species, and some few were lettered as varieties. In the next 

 edition (tenth) it should be possible to make some advance towards 

 a complete enumeration of British hybrids, and a consistent method 

 of exhibiting them in the list. 



With this object in view, as well as that mentioned above, I 

 propose to catalogue here all the phanerogams which are known or 

 believed to be of hybrid origin in this country, and some others 

 which have been under suspicion or question, so far as I am 

 acquainted with them, in the hope that other observers may supple- 

 ment the list, remove queries, and record fertility or sterility where 

 that character is not ascertained. 



No attempt is made in this paper to represent the geographical 

 distribution of the hybrids that have been recorded for Britain. 

 Localities are referred to chiefly when only one or two are known 

 to me, or when it is doubtful whether they have been published. I 

 have to thank several friends who have given me help, especially the 

 Rev. E. S. Marshall for very numerous comments and criticisms, 

 and for all the observations here quoted from Dr. Focke's Pflanzen- 

 mischlinge; the Bev. W. Moyle Rogers for a list of Rubi; Mr. 

 Alfred Fryer for a valuable letter on Potamogeton ; Mr. Arthur 

 Bennett for a most helpful list of hybrids in the same genus ; also 

 the Revs. A. Ley and W. R. Linton, and Mr. G. C. Druce. 



Ranunculace^:. — Thalictrum. Rouy & Foucaud (Fl. de France) 

 report that Dr. Focke derives T. odoratum G. & G. from T. fcetidum 



