l6 RANUNCULACEAE 



The plant cannot be said to be common in Berkshire, and is 

 probably absent from a considerable extent of country in the upland 

 portions of the Pang and Kennet districts. In the lower parts of the 

 Kennet valley it occurs more frequently. 



R. hederaceus is recorded from all the bordering counties. 



The Batrachian section of the genus Ranunculus, which is characterized 

 hj' the carpels having transverse waved ridges and (so far as the British 

 species go) white flowers, was kept as a distinct genus in my Flora of Oxford- 

 shire^ but in the present work I have followed Bentham and Hooker's Genera 

 Plantarum in uniting them. The genus Batrachium has offered very consider- 

 able difficulties to the botanical student. The very different standard of spe- 

 cific limitation, which even British botanists have adopted, has not assisted to 

 lessen the difficulty. It must be confessed that several of the so-called 

 species appear to merge into each other, and that the differences which 

 separate one from the other are rather questions of degree, than precise and 

 definite characters. Again, I think that too much stress has been placed 

 upon inconstant characters, such as the tapering of the peduncle, the relative 

 length of the stamens and style, and perhaps the greater or slighter con- 

 tiguity of the petals, and especially upon the presence or absence of floating 

 leaves. The latter character, which is almost entirely artificial, was adopted 

 by Mr. Hiern for the purpose of separating the genus into groups, with it 

 is to be feared very unfortunate results, so far as pointing out the natural 

 grouping of the plants in question was concerned. It must be borne in 

 mind that aquatic plants are subject to conditions which greatly in- 

 crease the tendency to vary present in the majority of species. Owmg to 

 the wide distribution of the Batrachian HanuncuU under a great variety of 

 circumstances — in muddy ponds, in still quiet waters, in swiftly running 

 streams, in deep waters or in shallow brooks, the water of which may be 

 nearly free from inorganic salts, or heavily charged with lime, or brackish 

 from salt, and which may be of varying depth and temperatvire— it is 

 not at all surprising to find extreme variability, especially in leaf shape, 

 throughout the genus. At one extreme we have in E. hederaceus a species 

 with leaves only of one kind, and these nearly entire. At the other extreme 

 we have in E. divaricatus a species also with only one kind of leaves, but 

 these all submerged and cut into a number of filaments arranged in one 

 symmetrical plane. Yet but few botanists would be now content to group 

 all the varying intermediate forms under one species as E. aquatilis. In my 

 arrangement of the Batrachian genus I have tried to hit the golden mean, 

 but I am now rather afraid that my estimate of the number of species has 

 been too generous. The authors of Prod. Fl. Hispanicae and other important 

 continental authorities unite E. peltatua and E. heterojihyllus under one 

 species, and there is much to be said in support of such a view. The 

 affinities of E. trichophyllus and E. Drouetii are closer than I formerly 

 supposed. It would be interesting to learn if the two plants are ever found 

 together, or whether the former is confined to water which has but little 

 hardness except what is due to the presence of silica or which has flowed 

 through peaty soil, and the latter to water Avhich contains a large amount 

 of dissolved lime. Herbarium specimens are rarely satisfactory, partly from 

 the imperfect state in which they are preserved. 



B. sceleratus, Linn. Sp. PI. 551 (1753). Celery-leaved Buttercup, Marsh 



Croivfoot. 

 R.palusbis rotundifoUus, Ger. Em. 962 (1633). Scelerata, Apul. (1528). 



Top. Bot. 14. Syme, E. B. i. 31, t. 27. Nyman, 14. Fl. Oxf. 8. 



