454 



NATURE 



[October 6, 1910 



liverworts have been the subject also of several mono- 

 graphs, of which Pearson's is the fullest. 



Among the Thallophyta, certain groups have been more 

 satisfactorily treated than others — e.g. the Discomycetes, 

 the Uredinere and Ustilagines, the Myxomycetes, and 

 certain others among the fungi, and the Desmidiacese 

 among the algae ; but the Thallophyta as a whole are 

 much in need of thorough revision to place them on a 

 footing either satisfactory or comparable to their treat- 

 ment in other countries. 



Of the Thallophyta, many more of the smaller species 

 will probably be discovered within our islands when close 

 search is made, if we may judge by the much more 

 numerous forms already recorded in certain groups abroad, 

 and which almost certainly exist here also ; but among the 

 higher plants it is not likely that many additional species 

 will be discovered as native, yet even among these some 

 will probably be found. It is, however, rather in the 

 direction of fuller investigation of the distribution and 

 tendencies to variation within our islands that results of 

 interest are likely to be obtained. 



The labours of H. C. Watson gave a very great stimulus 

 to the study of the distribution of the flora in England 

 and Scotland, and the work he set on foot has been taken 

 up and much extended by numerous botanists in all parts 

 of the British Islands. It is largely owing to such work 

 and to the critical study of the flora necessary for its 

 pro.secution that so many additions ha\e been made to 

 the forms previously known as British. Many local works 

 have been is_sued in recent years, often of a very high 

 standard of excellence. Besides these larger works, scien- 

 tific periodicals and transactions of field clubs and other 

 societies teem with records, some of them very brief, 

 while others are of such size and compass that they might 

 have been issued as separate books. A few of both the 

 books and papers are little more than mere lists of names 

 of species and varieties observed in a locality during a 

 brief visit ; but usually there is an attempt at least to 

 distinguish the native or well-established aliens from the 

 mere casuals, if these are mentioned at all. In respect 

 of aliens or plants that owe their presence in a district 

 to man's aid, intentional or involuntary, their treatment 

 is on no settled basis. Every flora admits without ques- 

 tion species that are certainly of alien origin, even such 

 weeds of cultivated ground as disappear when cultivation 

 is given up, as may be verified in too many localities in 

 some parts of our country. Yet other species are not 

 admitted, though they may be met with here and there 

 well established, and at least as likely to perpetuate their 

 species in the new home as are some native species. 



Comparatively few writers seek to analyse the floras of 

 the districts treated of with a view to determine whence 

 each species came and how, its relation to man, whether 

 assisted by him in its arrival directly or indirectly, whether 

 favoured or harmfully affected by him, its relations to its 

 environment — especially to other species of plants and to 

 animals, and other questions that suggest themselves when 

 such inquiries are entered on. It is very desirable that 

 a careful and exhaustive revision of the British flora should 

 be made on these and similar lines. In such a revision 

 it is not less desirable that each species should be repre- 

 sented by a good series of specimens, and that these should 

 be compared with similar series from other localities within 

 our islands, and from those countries from which it is 

 believed that the species originally was sprung. Such 

 careful comparison would probably supply important 

 evidence of forms being evolved in the new environments, 

 differing to a recognisable degree from the ancestral types, 

 and tending to become more marked in the more distant 

 and longer isolated localities. An excellent example of 

 this is afforded by the productive results of the very careful 

 investigation of the Shetland flora by the late Mr. W. H. 

 Beebv. 



Within recent years excellent work has been done in the 

 study of plant associations, but the reports on these studies 

 are dispersed in various journals (often not botanical), and 

 are apt to be overlooked by, or to remain unknown to. 

 many to whom they would be helpful. The same is true 

 in large measure of the very valuable reports of work done 

 on plant-remains from peat-mosses, from lake deposits, 

 and from other recent geological formations, researches 



XO. 2136, VOL. 84] 



that have cast such light on the past history of many 

 species as British plants, and have proved their long abode 

 in this country. Mr. Clement Reid's " Origin of the 

 British Flora," though published in 1899, has already (by 

 the work of himself and others) been largely added to, and 

 the rate of progress is likely to become still more rapid. 

 Among the fruits and seeds recorded from inter-glacial 

 and even from pre-glacial deposits are some the presence 

 of which could scarcely have been anticipated, e.g. 

 Hypecoum procumbcns, in Suffolk. Some of the colonists, 

 or aliens now almost confined to ground under cultivation, 

 have been recorded from deposits that suggest an early 

 immigration into the British Islands. While much re- 

 mains to be discovered, it is desirable that what is already 

 established should find a place in the manuals of British 

 botany. 



Apart from the descriptive and topographical works and 

 papers on our flora, there is a serious lack of information 

 gained from the study of our British plants. Although a 

 few types have received fuller study, we have little to 

 compare with the work done in other countries on the 

 structure and histology of our plants, on the effects of 

 environment, on their relations to other species and to 

 animals, and on other aspects of the science to which 

 attention should be directed. On these matters, as on a 

 good many others, we gain most of what information can 

 be had, not from British sources, but from the literature 

 of other countries, though it is not wise to assume that 

 what is true elsewhere is equally true here. It is as well, 

 perhaps, that for the present such subjects should find 

 scanty reference in the manuals in ordinary use ; but, 

 when trustworthy information has been gained within the 

 British Islands, under the conditions prevailing here, these 

 topics should certainly not be passed over in silence. 

 Students of the British flora have as yet no such works 

 of reference as Raunkjaer's book on the Monocotyledons 

 of Denmark or the admirable " Lebensgeschichte der 

 Bliitenpflanzen Mitteleuropas," at present being issued by 

 Drs. Kirchner, Loew, and Schroter. 



In a complete survey of the British botany there must 

 be included the successive floras of the earlier geological 

 formations, though they cannot as yet be brought into 

 correlation with the recent or existing floras. In the 

 brilliant progress made recently in this field of study our 

 country and the British Association are worthily repre- 

 sented. 



The present provision for the study of the British flora 

 and the means that should be made use of for its extension 

 appear to be these : — 



Much excellent work has already been accomplished and 

 put on record towards the investigation of the flora, but 

 much of that store of information is in danger of being 

 overlooked and forgotten or lost, owing to the absence of 

 means to direct attention to where it may be found. A 

 careful revision of what has been done and a systematic 

 subject-index to its stores are urgently required. 



The systematic works treating of the flora are in great 

 part not fully representative of the knowledge already 

 possessed, and require to be brought up to date or to be 

 replaced by others. 



Great difliculty is caused by the absence of an authori- 

 tative synonymic list that would show so far as possible 

 the equivalence of the names employed in the various 

 manuals and lists. There is much reason to wish that 

 uniformity in the use of names of species and varieties 

 should be arrived at, and a representative committee might 

 assist to that end ; but, in the meantime, a good synonymic 

 list would be a most helpful step towards relieving a very 

 pressing obstacle to progress. 



There is need for a careful analysis of the flora with 

 the view of determining those species that owe their 

 presence here to man's aid, intentional or unconscious; 

 and the inquiry should be directed to ascertain the periods 

 and methods of introduction, any tendencies to become 

 modified in their new homes, their subsequent relations 

 with man, and their influence on the native flora, whether 

 direct or by modifying habitats, as shown by Lupinus 

 nootkalensis in the valleys of rivers in Scotland. 



Those species that there is reason to regard as not 

 having been introduced by man should be investigated as 

 regards their probable origins and the periods and methods 



