Thomas Johnson (botanist)

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There were two Thomas Johnsons who were both botanists

Thomas Johnson attended Elmfield College and was Professor of Botany at University College, Dublin from 1890 to 1926.

The other Thomas Johnson has been called "The Father of British Field Botany" but has been largely neglected, no doubt largely due to the very scanty records of his life which have survived. Such as there are, moreover, in any cases confuse rather than help the biographer, owing to the popularity of the name Thomas Johnson.

Kew and Powell (1932) describe him as a "learned, amiable, brave man." Their first chapter is devoted to a list of Johnson's publications and of other works to which the authors referred during their investigations.

The second chapter provideas a chronological account of Johnson's life and work. With regard to the date of Johnson's birth (which almost certainly took place at Selby in Yorkshire, although he is also said to have come from Barton on Humber) the authors are forced to admit that they have not advanced beyond the statement made by Trimen and Dyer in 1869, that "it was probably at the beginning of the seventeenth century." His early years are equally obscure, and it is not until the first of his famous journeys (to Kent in 1629), when he was an apothecary practising at Snow Hill, that we obtain any clear picture of his activities. These journeys are here vividly described, and mention made of many of the plants found by him and his fellow apothecaries. The authors quote from the "somewhat free" account of the Kentish journeys which appeared in The Phytologist for 1848 Those interested in the byways of Victorian botanical literature might well read the whole of this article, and especially the severe editorial censure called forth by certain passages, harmless enough to our modem ears, on the refreshment taken by Johnson and his companions during their journey (The Phytologist, 3, 125. 1848). From this date (1629) until the beginning of the Civil War, Johnson led an exceedingly active life, combining his practice as an apothecary with further botanical excursions, and the publication of those works on which his fame rests. In the Civil War he fought for the King and was mortally wounded in 1644 at the siege of Basing House, in which he distinguished himself by conspicuous bravery and of which the authors give an absorbing account compiled from contemporary reports. In the third chapter Johnson's place in the investigation of the British Flora is reviewed and it is here that the authors make their most important contribution to botanical history. Hitherto it has been generally accepted that the first British Flora was How's Phytologza Bvitauc?zica, published in 1650. It is pointed out, however, that Johnson's Mevcz?,vizcs Bota?zicz6s (published in two parts, 1634 and 1641) contains not only a list of the plants found by him on his journeys in the West of England, but also an enumeration of all the then known indigenous British plants, and that it should therefore displace Reviews the Phytologia, which was largely compiled from it, as the first British Flora. The fact that its claim has been so long overlooked is probably due to its rarity, and subsequent historians have relied on the statement by Pulteney (who only saw one part of the Mevczcvzzcs) that How's was the first Flora of Britain. The final chapter discusses the various genera which have been named Joh?zso?zia in honour of the subject of this biography. The book is illustrated throughout by drawings and facsimile pages from Johnson's works and deserves to be widely read by all interested in the history of British Field Botany. J. s. L. G. The Mechanism of Creative Evolution. By C. C. HURST, Ph.D., F.L.S. Pp. xxi + 364, with a frontispiece and 199 figures in the text. Cambridge University Press, 1932. 21s. Dr Hurst's book gives an account of evolution regarded from a cytological point of view. It is concerned entirely with the genetic mechanism and makes no attempt to deal with the relations between the organism and its environment, either with regard to the possible origin of mutations or to subsequent selective processes. The first chapters deal with the original genetical and cytological discoveries which were the starting points of the modern sciences of genetics and cytology. The author then proceeds to enumerate in considerable detail and with numerous examples the various cytological and genetical mechanisms which have been established up to the present time as playing integral parts in evolutionary change. The book is confident in tone, perhaps too much so, in that the difficulties yet remaining are almost ignored. One example is the treatment of the origin of doqinance, for though the author in his chapter on "Genes and Characters" when considering the genetics of rabbits and of man assumes that dominance is prevalent in the wild species, no attempt is made to account for this either on Fisher's theory of dominance or on any other theory. The possibility of the existence of further mechanisms and the limitations of existing theory are not discussed and it is difficult at times for the reader to distinguish between established fact and unproved theory. In particular the concept of "genetical species" is open to criticism. Emphasis is rightly laid on the contribution that genetics and cytology can make to taxonomy, in relation particularly to the species concept: the statement is made that "On this view a species is no longer an arbitrary conception convenient to the systematist, a mere new name or label, but rather a real specific entity which can be experimentally demonstrated genetically and cytologically." This treatment of a species as a genetical entity divorced from its environment is as pernicious as the practice of regarding a species as a convenient herbarium unit equally divorced from its environment. The question as to whether "species " exist would seem to depend primarily on two things (apart from such species as have arisen through polyploidy and hybridisation), viz. the size of mutations and the time during which mutations have been taking place in any group. For if it is believed that evolution occurs mainly by mutations of a single character and such mutations are taking place with any considerable frequency in all organisms all the time, the stability of species in nature will depend on elimination from among such mutations and this must in turn depend on environmental conditions and geographical isolation, in which case the concept of the "genetical species" can have little relation to actual fact. If, on the other hand, such mutations occur with considerable frequency only at considerable intervals of time, and if evolution takes place during such periods with subsequent stabilisation of species by the environment (and on the evidence at present before us, one would judge this to be the case) then the species is an entity determined in part by inheritable