This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
And indeed this naturally leads up to the next plan, and that is to collect or examine any fresh or dried specimen unknown to one, and by aid of the knowledge already gained to refer it to its genus, order, etc, and then to the species. If the first plan is carried out on systematic lines, by taking a common plant of each natural order (there are 90 odd British orders, and at least 300 or 400 well-known common plants, so there is plenty of scope for choice), then the reference to the natural order should not be difficult, assuming some knowledge already of orders, genera, etc, as advised previously. The whole plan of this work, apart from its ecological basis, is to help the beginner with this end in view. The large number of beginners who, foiled in their early attempts, give up systematic botany in despair may indeed provide ample reason for the production of this work, apart from its other, and, I trust, not less laudable objects, which have been followed out in response to a widespread demand.
Having followed the two plans suggested for making progress in identification, the botanist, as he or she may now be termed, having gone through a preliminary botanical course, may take more definite steps to name species. A method largely in vogue is to run down the species by a process of elimination, by aid of the various analytical keys to orders, genera, and finally species, to be found in many floras which describe the whole, or most, of the British Flora. Bentham and Hooker's work for this purpose is invaluable, and another and more modern work is Babing-ton's Manual, where, however, the analytic key stops at genera, as do many others. For readily identifying species, Druce's edition of Hayward's Botanists Pocket-book is invaluable. The specific characters are brief and therefore easy to compare. The method of using a key is well explained in Bentham and Hooker's Handbook of the British Flora, and the student may be referred to it. Other larger works, to be used later, which have also analytical keys to genera, and sometimes to species, are given in the Bibliography. Until the student is well advanced, Bentham and Hooker will however suffice. Finally, so far as identification goes, there remains the process of comparison with descriptions of species in any of the standard floras, such as the above, perhaps a more natural method than the arbitrary use of analytical keys, which are artificial.
Though not to be recommended in the first resort, comparison with figures may be advised where descriptions, as too often happens, lack the power of expression of the meaning of differences or separate characters. Only an illustration or specimen can properly convey an idea of size, colour, relation of parts, habit, and form-structure as a whole.
For the same reason that illustrations are more helpful than descriptions, especially in the case of closely-allied species, comparison with herbarium specimens may be recommended.
In each case comparison should follow, not precede or replace, an effort to identify a plant by means of descriptions or the use of a key.
Not until the botanist has made some progress in the identification of plants, and has gained some confidence, will he, if wise, undertake definite survey work on any extensive scale. When, however, the time has come to study any particular area, say a county, it will be of interest to discover the distribution of the plants observed. For a single county the county flora will suffice to give the desired information, and any.plant found, which is not included in that work, or a supplement to it, will constitute a new county record (N.C.R.), and proud will be the botanist, in a well-worked area, if he or she can make any noteworthy additions to the list. If the flora is an old one this will not be so difficult for such critical genera as Rubus or Hieracium; for the older botanists only knew the aggregate species, and were unacquainted with the new segregates; and, as has been seen, since 1835 some 600 species have been added to the British plant list.
If, moreover, the botanist elects to travel about and to botanize in a number of counties, it will be more difficult to discover if a plant is new to any particular district or not, without some knowledge of distribution generally.
In Vol. I some general remarks have been given upon distribution, and a summary and map of the botanical districts or vice-counties into which the country-was divided by H. C. Watson. The latter was indeed the pioneer of plant geography in this country. His Topographical Botany is a summary of the flora of each county, and to this work, and his other works, everyone interested in this branch of botany must turn. The data given in Vol. II-V as to distribution are based upon this and other works quoted below. Watson's Topographical Botany, 3rd Edition, with the supplement compiled by Mr. Arthur Bennett, extends to 1903. Additions since that date are to be found in the Reports of the Botanical Society and Exchange Club of the British Isles, edited by Mr. G. C. Druce, or in the Journal of Botany; whilst if the flora of a county be a recent one, that work should include all recent additions up to the date of its publication.
For Ireland, R. L. Praeger's Irish Topographical Botany should be consulted. Three useful papers on Irish distribution have been published by the Rev. E. S. Marshall, viz. Review of Irish Topographical Botany, On the Probable Status of some Irish Plants, Remarks on the Cybele Hibernica. Ed. 2.
The distribution of Rubi in Great Britain is dealt with in a paper by the Rev. W. M. Rogers, 1902. Comital Census Numbers, by G. C. Druce, 1909, deals with the estimate of counties throughout the British Isles, where each species has been observed, as given in the Oxford Plant List. The London Catalogue of British Plants also cites the census numbers for each species.
The distribution of plants in the British Isles is of interest from a broader point of view, viz. the European range of each species. According to their British range, Watson placed plants in groups, such as Germanic, Atlantic, etc, and these terms have been used to denote the general range of a species in relation to the Continent or their possible origin. There are divergent views as to the origin of the British Flora, as expounded by Dr. Clement Reid and Dr. Scharff (see Vol. I).