44- FORMS AND DISTRIBUTION OF BATIIACHIUM.
botanists with reference to their specific distinctness, many of the names have been used in different senses and with different impressions of the range of forms lo be included under them.
After stiidying the phints botli in the living state and in the herbarium, I conclude, taking into consideration the intricate network of connecting links that seem to me to break down specific characters in several direc- tions, that the best and most philosophical course to follow is to unite all the forms under one aggregate species. Nor am I alone in this opinion, for Spenner, in his ' Flora Friburgensis,' published in 1829, adopted such an arrangement and called the collective species by the name of Ranun- culus hydrochm-'is, describing at the same time several varieties ; this name I adopt.
Again, Drs. J. D. Hooker and T. Thomson, in the first volume of their 'Flora Indica,' published in 1855, expressed their willingness to unite all the segregate species known to them into one ; and Mr. Bentham, in the first edition of his ' Handbook of British Botany,' did combine all the British forms into one species. It is right, however, to mention that in his second edition of the same work, Mr. Bentham reverted to the decision of LinnfEus and allowed two species ; and also that Dr. Hooker, in his recent ' Students' Flora of the British Islands,' has recognized three species, namely, R. aquatilis, R. Lenormandi, and R. Jiederaceus.
Such, however, are the variations and remarkable differences presented by many of the forms that it is desirable, and almost necessary, in order to understand the plants, at least for the purposes of local floras, to men- tion, and as far as possible define, the principal forms and give them dis- tinctive names.
For this purpose I have drawn up an artificial key for referring any given specimen to the name which most nearly applies to it ; this I have tried to make as practically useful as possible, but the reticular bond of union which prevails in nature amongst the members of this group is so complicated and involved as to render any such ready method impossible in some cases and difficult in several ; and the difficulty has been increased in consequence of the large number (35) of ultimate forms that have been included.
Concurrently with the ultimate forms, I have cited several names of a comparatively collective meaning, which can be used when further deter- mination caimot be reached. Thus botanists of whatever views with reference to specific values, will be enabled to stop at will and help them- selves, consistently with the nature of the case, to whatever name they please.
In nearly every case I have employed already published specific names for the forms, whether aggregate or segregate, which I recognize. One new form only I have named as of co-ordinate value with the rest of my ultimate forms, namely, No. 3, Lobbii. This is a native of California and Oregon, and is interesting as occupying a place under the hederaceiis group, and yet making some approach to the aquatilis group.
In a paper on this subject read before the Cambridge University Natural Science Society on October 25th, 1864, I attempted a geometrical repre- sentation of the British species in the following manner. Each species was placed in a given plane with reference to two axes of co-ordinates, the abscissa being the same number of units of length as the normal number of stamens, and the ordinate being the number of veins on each
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