194 



NATURE 



[January 2, iyo8 



strong in detection of movement, catches the images 

 of objects moving laterally. The tapetum would thus 

 be put out of action by " blinkers," and, on the other 

 hand, would aid carnivores both by detecting move- 

 ments of their prey and by bringing these movements 

 to the analysis of the central vision. 



The third problem discussed in this pamphlet is 

 (hat of colour-vision amongst insects. Insects are 

 chosen because there seem good a priori grounds for 

 believing that they possess colour-perception. The 

 problem is raised in this form : Is any morphological 

 peculiarity in the structure of these presumably colour- 

 perceptive animals associated with this faculty, and 

 can we picture their colour-field? The author points 

 out the well-known composite nature of the rhabdoms 

 or rods in the higher Crustacea and insects, how they 

 arc composed of denser and more refractive plates 

 alternating with feebly refracting layers, and how 

 white light becomes broken up, partially absorbed and 

 partially resolved into interference colours. He con- 

 cludes that diurnal insects must view objects as we 

 should see them through a tinted glass. Those 

 coloured with the like tint would stand out from the 

 rest, the majority would be blurred, and the whole 

 field would be dim in any but a strong light. Hence, 

 the author infers, the activity of diurnal lepidoptera 

 only in very bright weather. Some of the suggestions 

 made in this speculative essay are of great interest. 

 .\llied species often exhibit very different choice of 

 stations, and comparison of their eyes may throw 

 some light on why they do so. Again, the form of 

 the rods of diurnal insects is certainly broadly different 

 from that of nocturnal insects; the former are clear, 

 the latter suffused with red pigment. But, on the 

 other hand, both kinds of insect-eye show a similar 

 lamellar structure, and it would require a far more 

 rigid demonstration than is given by the author of this 

 work before we could accept the view he takes, 

 fascinating and suggestive as it is. 



A LANCASHIRE FLORA. 

 The Flora of West Lancashire. By J. A. Wheldon 



and A. A. Wilson. Pp. iii + 511. (Liverpool: J. A. 



Wheldon, 60 Hornby Road, Walton; Ilkley : A. 



Wilson, 4 Eaton Road, 1907.) Price i2jr. 6d. 

 V^HEN the ravages of the jerry-builder are fast 

 obliterating the comparative solitudes on the 

 outskirts of our great cities, and the equally destruc- 

 tive, though more localised, irruptions caused by dock 

 and railway extensions and industrial enterprises 

 are slowly exterminating the flora of our country- 

 sides, it is a matter for congratulation that there are 

 to be found men like the authors of this flora, pre- 

 pared to sacrifice hours of leisure and recreation in the 

 task of cataloguing for future reference the plant in- 

 liabitants of such botanically doomed districts. As the 

 authors point out, Lancashire is sadlv deficient in 

 such records, and the present result of their pains- 

 taking efforts is to be welcomed for that reason, if 

 for no other. 



The volume is, in the main, a catalogue of the 

 plants of the district known in Watson's "Topo- 

 graphical Botany" as "Vice-County No. 60," em- 



No. 1992, VOL. yjl 



bracing the West Lancashire spurs of the Pennines, 

 the coast district between Carnforth, Morecambe and 

 Lancaster, and the extensive flat lands reaching from 

 the estuary of the Lune to that of the Ribble. The 

 catalogue is prefaced by a summary of the general 

 topographical and botanical features of the district, 

 by a chapter on meteorology and climate, and a brief 

 synopsis of the relation of plant distribution to lati- 

 tude and to edaphic factors. The flora follows, as 

 the authors say in their preface, " the conventional 

 models," yet one could have wished that they had 

 departed from these models — at least in a few funda- 

 mental particulars. 



One of the most remarkable features' of recent 

 British floras is the inclusion of gymnosperms under 

 the head of dicotyledons. It is incomprehensible to 

 the general botanist that a taxonomy so archaic 

 should be repeated so persistently in successive 

 editions of the London catalogue, in local floras like 

 the present, and even in the latest list of British 

 plants compiled by Britten and Rendle. 



Again, the value of this flora would have been 

 greatly enhanced had the authors deemed it advisable 

 to add some critical notes on local forms and varieties 

 special to the district, on the model of Townsend's 

 excellent flora of Hampshire. 



Although they do not profess to give " a botanical 

 survey " of the West Lancashire area, the authors 

 have devoted nearly a quarter of the volume to what 

 is to all intents and purposes a digest of that aspect 

 of their subject — to the general reader by far the most 

 interesting part of the book. Moreover, this section is 

 illustrated by fifteen most excellent photographs, of 

 characteristic ecological features. One does not wish 

 to depreciate the value of records of " first finds," 

 nor the claim to recognition of the " first finders," 

 but there reinains a lingering desire for a more 

 succinct treatment of such records — which, after all, 

 can be only of local interest — and a fuller statement 

 of the main general topographical features, a state- 

 ment which the authors are, apparently, so well 

 qualified to give. 



It has been customary, for some unexplained 

 reason, to include in local (and even general British) 

 floras only dicotyledons (including — saving the mark I 

 Coniferae), monocotyledons, Pteridophyta and Chara- 

 ceae. Messrs. W'heldon and Wilson have had the 

 courage to include mosses, Hepaticje and lichens, on 

 which groups, if we mistake not, one at least of the 

 writers is an acknowledged authority. It is unfor- 

 tunate that they have not been able to enlist the aid 

 of a fungologist and algologist, and so present us 

 with a complete flora of the area. 



It seems almost ungracious to direct attention to 

 the many typographical errors, especially in the first 

 quarter of the volume (over and above the few 

 errata mentioned), and, too, the haphazard dis- 

 tribution of commas and full stops, authorities for 

 species, and so on, but these criticisms are made 

 with no intention of depreciating the merits of the 

 work under review, but rather of indicating what 

 we think are deficiencies and blemishes on what is 

 otherwise a valuable contribution to the field botany 

 of a hitherto neglected district. 



