NATURE 



{June 7, 1877 



to undergo repair during the intervals of darkness. The 

 aesthetic superiority of the analytic colours over black, 

 white, and grey is explained by considerations analogous 

 to those which have just been mentioned in the case of 

 musical tones and noises ; while harmony of colours is 

 treated in the same way as harmony of sounds. A some- 

 what curious speculation is ventured to explain the appa- 

 rent deficiency of the red-perceiving elements. " It is 

 clearly desirable that the eyes of the frugivorous animals 

 should be pleasiirahly stimulated by reds, oranges, and 

 purples ; and the simplest contrivance for effecting this 

 end would be to give the greatest possible rest to such 

 elements as answer to stimulations of these orders. Ac- 

 cordingly, they ought only to be excited by comparatively 

 powerful s imulations of their proper kinds." 



Adopting Mr. Spencer's view ^ as to the ideal being a 

 faint central stimulation of such nerve-fibres as would 

 receive strong peripheral stimulatioti by the reality, Mr. 

 Allan carries his analysis to the limit where " Physio- 

 logical yEsthetics " must end, and where Psychological 

 Esthetics ought only to begin. Space, however, will not 

 allow us to follow him into this division of his subject. 

 Enough has been said to show that his work deserves the 

 attention of psychologists ; and it may be added that as 

 he throughout clearly explains both the physics and the 

 physiology of his subject, his entertaining little treatise 

 will prove instructive to any general readers who may be 

 desirous of observing the intimacy of those relations 

 between psychology and the lower sciences, which the 

 magnificent generalisations of recent years are now every 

 day bringing into clearer prominence. 



George J. Romanes 



OUR BOOK SHELF 



Select Plants readily Elit:,ible for Industrial Culture or 

 A'atm'alrsation in Victoria, with Indications of their 

 Native Countries and some of their Uses. By Baron 

 F. von Mueller, C.M.G., F.R.S., &c. (Melbourne : 

 McCarron, Bird, and Co.) 

 This is another form of Baron Mueller's, numerous and 

 widely-spread contributions to the Acclimatisation .Society 

 of Victoria- -numerous we say, because the Baron's pen 

 is always at work upon botanical matters, the considera- 

 tion of useful plants being apparently one of his favourite 

 themes, and widely spread, because these papers on 

 " select plants " seem to have been freely distributed not 

 only in Australia and in this country, but also in America, 

 where indeed some portion, if not all, have been repub- 

 lished. The present issue. Baron Mueller tells us. is a 

 rearranged and largely supplemented form, which has 

 been taken up by the Government of Victoria, and pub- 

 lished under their authority. The book, which numbers 

 some 293 pages octavo, contains references to an im- 

 mense number of plants, the information attached to each 

 being brief but withal accurate. The generic and specific 

 names are arranged alphabetically from beginning to 

 end, and this arrangement is perhaps the best for general 

 use. After the scientific name, the vernacular name is 

 given, then the geographical distribution or habitat, fol- 

 lowed by a note as to the nature of the plant, whether a 

 tree, shrub, or what not, and finally a brief description of 

 its properties and uses. As a proof that Baron Mueller 



^ Here, as indeed in most other places, Mr. Allan does not express his 

 obli^alioi.s. Doub:le>s, having a psychological public in view, he thought 

 it superfluous to state the sources from which such well-known conceptions 

 have sprung ; but as his work is in all other respects adapted to badly- 

 informed readers, it would have been desirable, on their account, to have 

 supp'ied the c onvssi^ns. 



has corrected this latest issue of his papers, down quite 

 to the present time we may mention that under Nicotiana 

 tahacum, Lattakia tobacco is included, and it is only within 

 a comparatively recent date that Mr. Thiselton Dyer has 

 shown this to be right, nearly all previous writers having 

 attributed it to N. rustiea. At the conclusion of the book 

 a very good plan is adopted of classifying the plants 

 mentioned under distinct heads referring to their uses ; 

 thus, under alimentary plants, the generic names of all 

 such are placed ; the same under dye plants, fibrous 

 plants, and so on. A good index is given of vernacular 

 names only, which is quite sufficient when it is remem- 

 bered that the scientific names are arranged alphabeti- 

 cally throughout the book. 



Notes on the Ancient Glaciers of Neiu Zealand. With / 

 Map. By J. C. Russell. Reprinted from the "Annals | 

 of the Lyceum of Natural History." (New York : 

 November, 1876.) 



Mr. Russell was attached to the U.S. Transit of Venus 

 Expedition, and finding himself stationed on the shores of 

 Lake Wakatipu among the snow-fields and glaciers of the 

 South Island of New Zealand he read what had been 

 written on the ice-work of that region and supplemented 

 his reading by the personal observations recorded in 

 these notes. Though he does not add any important 

 new fact to our previous knowledge he gives an interest- 

 ing resumi: of the physical geography of the glacier region, 

 pointmg out the evidence for the former greater extension 

 of the ice-fields of New Zealand, and dwelling especially 

 on the proofs of enormous erosion shown by the valleys 

 and lake-basins. 



LETTERS TO THE EDITOR 



\_The Editor does not hold hitnself respotisibte for opitiions expressed 

 by Ms correspondents. Neitlier can he undertake to return, 

 or to correspond with the writers of rejected manuscripts. 

 No notice is taken of anonymous communuations. 



The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on /lis space is so great that it 

 is impossible otherwise to ensure the appearance even ef com- 

 munications containing interesting and novel facts.'] 



Nectar-secreting Glands 

 I HAVE briefly described in vol. xv. of the Linn.Tean Society's 

 fournal, the nectar-glands found at the base of the fronds of the 

 brake fern (Pteris aqidlina) which are visited by ants for the sake 

 of their sweet secretion. This case seemed to me to show in a 

 striking manner that extra-floral nectar-glands are not necessarily 

 proteciive in function, because the fern has, in England at least, 

 extremely few enemies. The following extract of a letter lately 

 received from Fritz Miiller (of St. Catharina, Brazil) is of con- 

 siderable interest in relation to this subject. He states that 

 " the honey-glands on our Pteris aqidlina serve, without doubt, 

 to protect the ferns from the depredations of the leaf-cutting 

 ants (dcodoma), as is the case with Passiflora, LufTa, and many 

 other plants. The glands of the Pteris are eagedy visited by a 

 small black ant, Crematogaster, of which the CEcoioma seems 

 to stand in great dread. On the other hand, when no protecting 

 ants are present, I have seen (Jicodoma gnawing the young 

 fronds ; here, as in other cases, it is only the young leaves that 

 stand in need of protection, the older ones not being attacked 

 by the leaf-cutting ants." This fact might, no doub', be used 

 as an argument by those wh-j believe that all nectar-glands were 

 originally developed as protective organs, and this argument 

 would have great force it it could be shown that Pteris aquilina 

 is a form which has arisen in countries where protection is 

 needed ; but even in that case there would remain the difficulty 

 of accounting for the continued function.il activity of the glands 

 in districts where no such protection is required. Or it may be 

 said that in past ages the glands on our European I^teris served 

 as a protection against enemies which have now become extinct. 

 But here we are again met by the difficulty of accounting for 

 the continued activity of the glands. It is characteristic of evo- 

 lution that great changes occur in the functions of organs, and I 

 think that it will generallv he allowed that even tha most beauti 



