June 7, 1883] 



NA TURE 



123 



this line of action directs attention to persons rather than 

 plants, and is thus out of place. 



Another point to which much more attention is given 

 now than was formerly the case is the division of a 

 county into districts. Messrs. Webb and Coleman, in 

 the "Flora Hertfordiensis " (1849), planned their divisions 

 with reference to the river drainage ; and this has been 

 carried out in the best floras of later times. If it were 

 generally adopted, and if our list of county floras were 

 complete, we should arrive at a much greater knowledge 

 of plant distribution than we have at present. The arbi- 

 trary boundaries of counties would give way to the natural 

 divisions afforded by the various river-basins, and one 

 county flora would fit into another, and form a harmonious 

 whole. This subject has lately been worked out by Mr. 

 Boulger in a careful paper " On the Origin and Distribu- 

 tion of the British Flora,'' published in the Transactions 

 of tlie Essex Field Club. No one who has not tried it 

 would suspect how greatly the floras of contiguous river- 

 basins will be found to differ from each other. 



It is time, however, to speak of Mr. Townsend's im- 

 portant contribution to our knowledge of local botany. 

 As is well known, the work has occupied him during a 

 large number of years : it has, we regret to say, been 

 retarded by the ill-health of its author, or it would have 

 been published two years since ; but Mr. Townsend tells 

 us that the delay has enabled him to improve the book in 

 various details. The county is divided into twelve dis- 

 tricts, two of which are in the Isle of Wight. A small 

 but extremely clear and useful map showing the bound- 

 aries of these is given. The usual lists of books quoted 

 and herbaria consulted are followed by a short sketch of 

 the plan of the flora. The distribution of each species 

 through the districts and subdistricts is then worked out 

 at length. We confess to feeling some disappointment 

 at the comparative fewness of the critical notes upon 

 species. Mr. Townsend's extensive knowledge of British 

 plants, especially in their relations to the Continental 

 flora, had led us to expect that we should have had a 

 good deal of additional light thrown upon some of our 

 critical forms ; but this, although not altogether wanting, 

 occupies but a small portion of the volume. Mr. Town- 

 send's notes are for the most part in the appendix — an 

 arrangement which seems to us open to various objec- 

 tions, not the least being the fact that these notes and 

 descriptions are often not mentioned in the index. Two 

 or three varieties are described and named for the first 

 time in these pages ; and occasionally a specific name 

 new to the British flora makes its appearance, as in the 

 case of Glyceria declinata of Bre"bisson, with which Mr. 

 Townsend identifies a plant which he had previously 

 considered a dwarf variety of G. plicata. 



One or two points seem to us open to criticism. " First 

 record " in books of this kind is usually taken to mean 

 first record in print ; but this is not Mr. Townsend's view 

 of the phrase. Thus under Centaurea cyanus we find, 

 " First record : Herb. Reeves, 1837." It does not seem 

 to us that the existence of a specimen in a private her- 

 barium can be considered a record of its occurrence 

 in the ordinary acceptation of the term. Sometimes we 

 do not quite understand the author's meaning, as when 

 he marks the curious and interesting Spartina Townsendi 

 as " certainly introduced," although it has as yet been 



found nowhere else in the world. Equally puzzling is 

 this sentence as to the specific rank of the same grass : 

 " I believe this plant must take the rank of a sub-species ; 

 the characters which separate it from 5 1 . stricta being so 

 important and distinctly marked. It is easily distin- 

 guished from .£ iiltemiflora." This being so, surely it 

 should be ranked as a full species? Mr. Townsend 

 admits Anthoxanthum Puclii as indigenous, but its fre- 

 quent substitution for A. odoralum by seed merchants 

 throws much doubt upon its nativity : this plant, first 

 found in Hampshire in 1874, had been collected in 

 Cheshire two years previously, but Mr. Townsend cites the 

 last-named county as one of those in which it " has since 

 been found." We can, from observation of the two plants 

 in several counties, confirm the statement of Mr. Pryor, 

 which is doubted by Mr. Townsend, that Viola Rcichen- 

 bachiana flowers about a fortnight earlier than the allied 

 V. Riviniana. Some plants are included as natives of 

 Hampshire on what seems to us insufficient evidence ; 

 Silene noctiflora is one of these, and Orchis hircina 

 another. This latter, we do not hesitate to say, requires 

 much confirmatory evidence before it can be accepted as 

 a Hants plant ; its occurrence rests solely on a manu- 

 script note of the late Mr. Reeks, who stated that speci- 

 mens had been found by a Mr. Loekart at St. Mary 

 Bourne about 1866. The number of misprints is very 

 considerable. 



Such criticisms as these — and they might easily be ex- 

 tended — do not, however, prevent the "Flora of Hamp- 

 shire '' from taking a foremost rank among works of its 

 class. A little more attention to uniformity would have 

 improved the book, and, as we have shown, there is room 

 for difference of opinion upon many of the points raised ; 

 but British botanists will be grateful to Mr. Townsend 

 for giving them a handbook to the flora of one of the 

 most interesting and beautiful of our English counties. 



James Britten 



LETTERS TO THE EDITOR 



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 or to correspond with the writers of, rejected manuscripts, 

 No notice is taken of anonymous communications. 



[The Editor urgently requests correspondents to keep their letters 

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On Real and Pseudo-Reversals of Metallic Lines 



I AM much indebted to the courtesy of Prof. Liveing for a 

 copy of a paper extracted from the Proceedings of the Cambridge 

 Philosophical Society, vol. iv. part 5, p. 256, on the circum- 

 stances producing the reversal of spectral lines of metals, by 

 Professors Liveing and Dewar. In this communication the 

 following paragraph occurs: — "Prof. Hartley has lately (Proc. 

 Roy. Soc. xxxiv. p. 84) called attention to pseudo-reversals of 

 this class, which may be produced in the c-se of a strong line 

 by over-exposure. It is well known that overexposure (solar- 

 isation, as we used to call it formerly) produces such an altera- 

 tion in the sensitive preparation of the photographic plate that 

 the over-exposed parts cease to be developable, so that a very 

 strong line may appear white in the negative where it ought to 

 be black, but with a dark border, and so give the appearance of 

 a reversed line. Prof. Hartley finds it difficult to distinguish 

 real reversals of the class we are now discussing from these 

 pseudo-reversals. His difficulty has not occurred to us, first, 

 because we have always been in the habit of taking photographs 

 in series with varying exposure, in order to get impressions both 

 of the feeble lines in some and of strong lines in others ; and 



