556 



NATURE 



[October 8, 1903 



HUE BRITISH ASSOCIATION. 

 SECTION K. 



Opening Address by A. C. Seward, F.R.S., Fellow and 

 Tutor of Emmanuel College, late Fellow of St. 

 John's College, Cambridge; Lecturer on Botany in 

 THE University, President of the Section. 



In 1883, the date of the last meeting held by the British 

 Association at Southport, the late Prof. Williamson, of Man- 

 chester, delivered a Presidential Address before the Geological 

 Section, in which he reviewed recent progress in palaeo- 

 botanical research, with special reference to the vegetation of 

 the Coal period. It would have been an interesting task to 

 traverse the same ground to-day, in order to show what a 

 vast superstructure has been built on the foundations which 

 Williamson laid. In alluding to the controversies in which 

 he bore so vigorous a part, Williamson spoke of the conflict 

 as virtually over, though still reflected, " in the ground- 

 swell of a stormy past." Now that twenty years have 

 elapsed we are able to recognise with no little satisfaction 

 that his views are firmly established, and that the debt which 

 we owe to his able interpretation of the relics of Palaeozoic 

 plant-life is universally acknowledged. Williamson's labours 

 demonstrated the possibilities of microscopical methods in 

 the investigation of Carboniferous plants ; but at the time 

 of publication his results did not receive that attention which 

 their importance merited, and it is only in recent years that 

 botanists have been induced to admit the necessity of extend- 

 ing their observations to the buried treasures of bygone ages. 

 We have been slow to realise the truth of the following 

 statement, which I quote from an able article on Darwinism 

 in the Edinburgh Review for October of last year : " The 

 recognition of the fact that in every detail the present is 

 built on the past has invested the latter with a new title to 

 respect, and given a fresh impulse to the study of its his- 

 tory." The anatomical investigation of extinct types of 

 vegetation has done more than any other branch of botanical 

 science in guiding us along the paths of plant-evolution dur- 

 ing the earlier periods of the earth's history. 



I cannot conclude this brief reference to Williamson's work 

 without an expression of gratitude for the help and 

 encouragement with which he initiated me into the methods 

 of palaeobotanical research. 



Floras of the Past : their Composition and Distribution. 

 Introduction, 



It is by no means easy to make choice of a subject for a 

 presidential address. There is the possibility — theoretical 

 rather than actual — of a retrospective survey of modern de- 

 velopments in the botanical world, and the opportunity is a 

 favourable one for passing in review recent progress in that 

 department of the science which appeals more especially to 

 oneself. In place of adopting either of these alternatives, I 

 decided to deal in some detail with a subject which, it must 

 be frankly admitted, is too extensive to be presented ade- 

 quately in a single address. My aim is to put before you one 

 aspect of palseobotany which has not received its due share 

 of attention : I mean the geographical distribution of the 

 floras of the past. In grappling with this subject one lays 

 oneself open to the charge of attempting the impossible — a 

 not unusual characteristic of British Association addresses. 

 I recognise the futility of expecting conclusions of funda- 

 mental importance from such an incomplete examination of 

 the available evidence as I have been able to undertake ; but 

 a hasty sketch may serve to indicate the impressions likely 

 to be conveyed by a more elaborate picture. 



One difificulty that meets us at the outset in approaching 

 the study of plant distribution is that of synonymy. " The 

 naturalist," as Sir Joseph Hooker wrote in his " Introduc- 

 tory Essay to the Flora of New Zealand," " has to seek 

 truth amid errors of observation and judgment and the re- 

 sulting chaos of synonymy which has been accumulated by 

 thoughtless aspirants to the questionable honour of being the 

 first to name a species." Endless confusion is caused by the 

 use of different generic and specific names for plants that are 

 in all probability identical, or at least very closely allied. 

 Worthless fossils are frequently designated by a generic and 

 specific title : an author lightly selects a new name for a 



miserable fragment of a fossil fern-frond without pausing to 

 consider whether his record is worthy of acceptance at the 

 hands of the botanical palaeographer. 



An enthusiastic specialist is apt to exaggerate the value of 

 his material, and to forget that lists of plants should be 

 based on evidence that can be used with confidence in inves- 

 tigations involving a comparative treatment of the floras of 

 the world. As Darwin said in the " Origin of Species "' : 

 " It is notorious on what excessively slight differences many 

 palaeontologists have founded their species ; and they do this 

 the more readily if the specimens come from different sub- 

 stages of the same formation." It would occupy too much 

 time to refer to the various dangers that beset the path of 

 the trustful student, who makes use of published lists of local 

 floras in generalising on questions of geographical distribu- 

 tion during the different eras of the past. Such practices as 

 the naming of undeterminable fragments of leaves or twigs, 

 the frequent use of recent generic names for fossil specimens 

 that afford no trustworthy clue as to affinity, belong to the 

 class of offences that might be easily guarded against ; there 

 are, however, other obstacles that we cannot expect to re- 

 move, but which we can take pains to avoid. An author in 

 naming a fossil plant may select one of several generic 

 names, any of which might be used with equal propriety ; in- 

 dividual preferences assert themselves above considerations 

 as to the importance of a uniform nomenclature. The per- 

 sonal element often plays too prominent a part. To quote a 

 sentence from a non-scientific writer : " The child looks 

 straight upon Nature as she is, while a man sees her re- 

 flected in a mirror, and his own figure can hardly help com- 

 ing into the foreground." 



In endeavouring to take a comprehensive survey of the 

 records of plant-life, we should aim at a wider view of the 

 limits of species and look for evidence of close relationship 

 rather than for slight differences, which might justify the 

 adoption of a distinctive name. Our object, in short, is not 

 only to reduce to a common language the diverse designa- 

 tions founded on personal idiosyncrasies, but to group closely 

 allied forms under one central type. We must boldly class 

 together plants that we believe to be nearly allied, and resist 

 the undue influence of considerations based on supposed 

 specific distinctions. 



The imperfection of the Geological record was spoken of 

 by one of England's greatest geologists, in a criticism of the 

 " Origin of Species," as " the inflated cushion on which you 

 try to bolster up the defects of your hypothesis." On the 

 other hand, Darwin wrote, in 1861 : " I find, to my astonish- 

 ment and joy, that such good men as Ramsay, Jukes, Geikie, 

 and one older worker, Lyell, do not think that I have in the 

 least exaggerated the imperfection of the record." No one 

 in the least familiar with the conditions under which relics 

 of vegetation are likely to have been preserved can for a 

 moment doubt the truth of Darwin's words : " The crust of 

 the earth, with its embedded remains, must not be looked at 

 as a well-filled museum, but as a poor collection made at 

 hazard and at rare intervals." 



As a preliminary consideration, we must decide upon the 

 most convenient means of expressing the facts of geo- 

 graphical distribution in a concise form. The recognised 

 botanical regions of the world do not serve our purpose ; we 

 are not concerned with the present position of mountain- 

 chains or wide-stretching plains that constitute natural 

 boundaries between one existing flora and another, but 

 simply with the relative geographical position of localities 

 from which records of ancient floras have been obtained. In 

 the accompanying map I have divided the surface of the 

 earth into six belts, from west to east. The most northerly 

 or Arctic Belt includes the existing land-areas as far south as 

 latitude 60°, comprising — i, Northern Canada; 2, Greenland 

 and Iceland ; 3, Northern Europe ; 4, Bear Island and Spitz- 

 bergen ; 5, Franz Josef's Land ; 6, Northern Asia. The 

 North Temperate Belt, extending from latitude 60° to 40°, 

 includes — 7, South Canada and the northern United States ; 

 8, Central and Southern Europe ; 9, Central Asia. The 

 North Subtropical Belt comprises the land between latitude 

 40° and the Tropic of Cancer, including — 10, the Southern 

 States of North America ; 11, Northern Africa, part of Arabia 

 and Persia; 12, Thibet and part of China; 13, Japan. The 

 Tropical Belt, embracing the land-areas between the Tropics 

 of Cancer and Capricorn, includes — 14, Central America and 

 the northern part of South America ; 15, Central Africa and 



NO. 1 77 1, VOL. 68] 



