434 



NA TURE 



[September 8, 1898 



for such a purpose. We should have welcomed a few 

 observations on the best means of preventing fading in 

 museum specimens, which is another crying evil, from 

 so experienced a conservator as Mr. Rowley, 



R. L. 



KNUTWS TEXT-BOOK OF FLORAL 

 BIOLOG V. . 

 Handbuch der Bluienbiologie unter zugrundelegung von 

 Hermann Miiller^s iverk : '■''Die Befruchtung der 

 Blimien durch InsektenP Bearbeitet von Dr. Paul 

 Knuth, i. Band, ii. Band, i Theil. Pp. xix + 400 and 

 697. (Leipzig : Wilhelm Engelmann, 1898.) 



DR. KNUTH is to be congratulated on carrying out 

 an excellent idea in a masterly manner. It is now 

 twenty-five years since Hermann Miiller's " Befruchtung 

 der Blumen " appeared, and although the English trans- 

 lation of 1883 contains a good deal not to be found in the 

 original book of 1873, yet it too is becoming antiquated. 

 A book, therefore, like Knuth's " Handbuch," founded on 

 Miiller, and incorporating the mass of work accumulated 

 in recent years, is very welcome. Dr. Knuth is well 

 known as an active and successful worker in the domain 

 of floral biology, and has therefore the chief requisite for 

 success— a first-hand knowledge of his subject ; he also 

 makes it clear that he has gone thoroughly mto the 

 literature. 



The book is to be in three volumes, of which vol. i. and 

 the first part of vol. ii. are now published. It is sum- 

 marised by its author as follows : — 



I. Introduction and literature.^ 

 II. The Floral-Biology of European and Arctic plants. 



Part i. Ranunculacese to Compositse. 

 Part ii. Lobeliaceae to Coniferae. 

 III. The Floral-Biology of Extra-European Plants. 



The first volume begins with the history of floral- 

 biology, to which I shall return later. It then goes on to 

 the different forms of reproduction occurring in flowering 

 plants, e.g. Xenogamy., Geitonoganiy and Autogamy, 

 under which heading a useful list of self-fertilised and 

 self-sterile plants is given. The author passes on to an 

 excellent account of the biological classes into which 

 flowers are grouped— such, for instance, as the Anemo- 

 philous and Entomophilous divisions. Among animal 

 visitors the bird, and even the bat, are shown to be 

 of importance : the powers of the snail in this line 

 are respectfully discussed ; while further evidence is 

 demanded for the suggestion that the kangaroo fertilises 

 Dryandra. 



Next comes a good discussion of the elements that go 

 to make up the floral machinery — protection of pollen — 

 conspicuousness through odour or colour, nectar and 

 nectar guides, protection against unbidden guests, &c. 

 Then comes a fuller discussion of flowers in relation to 

 insects, in which a well-known biological classification is 

 adopted, flowers being grouped in an ascending series 

 beginning with those nectarless kinds which are visited 

 for the sake of their pollen, and then into various types of 

 NO. 1506, VOL. 58] 



honey-supplying species, in which the protection of the 

 nectar increases in complexity. Next, wehavean account 

 of the specialisation of flowers for certain groups of 

 insects, and their classification as fly-flowers, butterfly- 

 flowers, bee-flowers, &c. Lastly, a full account of the 

 structure of insects in relation to flowers, a subject origin- 

 ated and brilliantly treated by H. Miiller. The author has 

 done wisely in giving a general account of floral-biology 

 with so much fulness. The student who proposes to go 

 on to vol. ii. comes to the study of special mechanisms far 

 better prepared by Dr. Knuth's vol. i. than a reader who 

 attacks for the first time H. Miiller's " Fertilisation of 

 Flowers." 



A valuable feature in Dr. Knuth's book is the excellent 

 account of the method which Hermann Miiller intro- 

 duced and used with such signal success— namely, the 

 study of an exact record of the species of insects which 

 visit each kind of flower. This, commonly known as the 

 statistical method, gave astonishingly interesting results 

 in Miiller's hands, supplying as it did a solid basis of 

 incontrovertible fact to his generalisation on the re- 

 ciprocal interaction of insects and flowers, the evolution 

 of the flower in general, and other interesting points. The 

 statistical method has been largely taken up by the 

 modern school of floral-biologists, and especially by 

 MacLeod, Loew, Knuth and Kirchner on the continent, 

 and by Willis, Burkill and Scott-Elliot in this country, 

 with results which go to swell the lists of insect visitors 

 given for each species in vol. ii. Space does not allow 

 me to deal with the points of general interest which occur 

 in this section ; I may, however, call the reader's atten- 

 tion to the clear and useful account of MacLeod's method 

 of treating the observed facts. 



The growth of floral-biology is well illustrated by the 

 admirable list of literature given by Dr. Knuth, and for 

 which he deserves the thanks of all serious students. 

 D'Arcy Thompson's list (1883) contains 814 entries, which 

 seemed to contemporary readers a sufficiently striking 

 proof of the growth of the subject, but it is a trifle to 

 Knuth's literary index, in which are found 2871 entries. 

 It should be mentioned, too, that in vol. ii. the literature 

 is carefully given under each species. This part of the 

 work is fully illustrated with Miiller's excellent drawings, 

 as well as figures from other sources, and a certain 

 number of original illustrations. Dr. Knuth has intro- 

 duced an improvement over H. Muller's arrangement by 

 prefacing each natural order with a general sketch ot 

 the characteristic mechanisms ; this seems a better 

 arrangement than Muller's "retrospects," which were 

 placed at the end. 



'Dr. Knuth has shown so much ability in the treatment 

 of the part of the work already published that students may 

 look forward to his completion, with equal success, of 

 what will be the standard treatise on the subject. The 

 only point in which I have any adverse criticism to 

 offer is Dr. Knuth's treatment of the Knight- Darwin 

 law. In common with some other modern writers on 

 floral-biology, he takes what seems to me a mistaken 

 view of the bearing of this law. The subject does not 

 lend itself to treatment in a brief notice ; I hope, how- 

 ever, to deal with it at length elsewhere. 



Francis Darwin. 



