26 



NA TURE 



[November 9, 1905 



careful discrimination. The effects should not be 

 lumped together as due to suddenness. 



A good deal of space is devoted to what the author 

 terms "true stresses." He takes the well known 

 strain equations Ee, = S, - --AS., — AS,, &c, and, because 

 Etj is of the same form as stress in terms of ex- 

 tension, he calls He | the "true stress" due to the 

 "apparent stresses" S r S 2 , S,. This is to use the 

 term " stress " in a totally new sense. The real 

 stresses which balance the external forces are only 

 "apparent stresses"; an imaginary stress which is 

 greater is the " true stress." It is impossible here to 

 follow the author to the curious results he arrives at, 

 which involve a revision of all the ordinary formulas 

 of strength. It is not difficult to see from what point 

 he has drifted. He throughout implicitly assumes 

 that the condition of security in a structure depends 

 on the maximum stress. He nowhere discusses the 

 other views which have been taken. Now one of 

 these is that security depends, not on maximum stress, 

 but on maximum strain. What the author does with 

 his equations is to make security depend on tin- 

 maximum strains e,, &c. ; but this does not justify 

 him in calling I'> 1 a true siress. 



I HANDBOOK OF FLOWER lilt > / .< H . V. 

 Handbuch dcr Blutenbiologie. Vol. iii. Part ii. By 

 Ernst Loew, assisted by Otto Appel, completing 

 the work commenced by Paul Knuth. Pp. v + 6oi. 

 (Leipzig: Wilhelm Engelmann, 1905.) Price iSs. 

 net, in paper cover. 



T'HE work which the late Prof. Knuth projected 

 and commenced — a " Handbook of Flower- 

 Biology," to replace Hermann Midler's " Fertilisation 

 of Flowers " — is now complete. It runs as follows :— 

 vol. i., an advanced text-book of flower biology; 

 vol. ii., an account of observations made in Europe 

 (two parts); vol. iii., an account of observations made 

 outside Europe (also two parts). 



Ernst Loew, who, after Knuth's death, undertook 

 the completion of the work, appends to the lasl pari 

 a review of the collected extra-European observations. 



There can be no doubt of the preeminent fitness 

 of Dr. Loew for his task ; but the result on close 

 criticism is found just a little disappointing on account 

 of omissions, e.g. Willis's observations on Phacelia, 

 Monarda, and Ixora, and Keeble's on Loranthus, in- 

 correcl citations at (In- rate of one per page in the 

 literature-list an imperfect index, far loo many 

 printer's errors, and illustrations not always, I believe, 

 drawn from the living flower. 



Dr. Percy Groom (Nature, vol. lxxi. p. 26) re- 

 marked on omissions and printer's errors in review- 

 ing the preceding part of this work. 



Of the body of the work, it is to be said that, besides 

 abstracting all pertinent publications that have fallen 

 into Dr. Loew's hands, it gives to the world a con- 

 siderable number of original observations made by 

 Knuth in Java, Japan, and California, and a few of 

 Loew's made in the Berlin Botanic Garden, and 

 that the names of North American insects have been 

 subject to a revision by Prof. Robertson, of Carlin- 

 ville, Illinois. 



NO. 188O, VOL. J 3) 



Of the review, it is to be explained that it centres . 

 on a discussion of the fertilising agents in countries- 

 outside Europe. I greatly appreciate the vast amount 

 of labour which Dr. Loew has put into it. He could! 

 hardly have made greater use of the fragmentary 

 material to hand. But the account of fertilisation in 

 the tropics wants atmosphere ; it is such as a man 

 would write who had no particular experience of their 

 vegetation. Twelve pages of the review are given 

 to this account : first, Dr. Loew borrows from Prof. 

 Warming a description of the vegetation of Lagoa 

 Santa, in Brazil; then he goes on very successfully 

 to discuss the part which birds play in fertilising 

 flowers. In the place of the description of Lagoa 

 Santa, one had hoped to find a more general de- 

 scription of tropical seasons. Nearly twelve pages 

 are given to an account of fertilisation in New 

 Zealand and the Antarctic islands — chiefly to a com- 

 parison of Arctic and Antarctic flowers, wherein 

 Loew sees less agreement than does Delpino. Four 

 and .a half pages are given to South Africa with 

 Madagascar — an ill-assorted union, three to the cactus 

 region of N. America, six to the Arctic region in- 

 cluding Spitsbergen, and twenty-six to the forest 

 belt of N. America. I have here set down the 

 number ol pages devoted to each region because they 

 rightly indicate the proportion in which the regions 

 have been studied. 



In dealing with the forest belt of N. America, Loew 

 depends, of course, on Robertson's excellent work;, 

 there alone he really finds facts enough to enable 

 him to work in the statistical methods which he has 

 used so extensively in his writings regarding Euro- 

 pean flowers. 



A time will come when the botanists of North 

 America ask for a handbook of North American 

 flower biology. Loew's work shows how far from 

 readiness is material for it, and how very much 

 further from readiness is material for a handbook 

 ol flower biology lor any other part of the world. 

 Until we get such handbooks, Loew's volume of 

 Knuth's work will remain very useful on account of 

 its suggestions, its references, its information, and 

 especially as a companion in travel. I. H. B. 



.1 FRENCH BOOK OX SPORT AND 



TRAPPING. 

 Chasse, Elevage ei Piegeage. By A. de Lesse. 



Encyclopedie Agricole. Pp. xii + 532; illustrated. 



(Paris: J. B. Baillierc and Son, 1905.) Price 



5 francs. 

 T'lIE volume before lis is one of a series dealing not 

 1 only with subjects pertaining to agriculture in 

 its proper and more restricted sense, but likewise with 

 practically everything connected with country life 

 which has any bearing at all on that pursuit. In the 

 present instance, the subject of the trapping and 

 snaring (piegeage) of animals, which, in the case of 

 noxious species is, of course, a matter of consider- 

 able importance to the agriculturist, serves to 

 establish a connection between sport (especially in 

 the French sense of that terml on the one hand and 

 agriculture on the other, and thus justifies the in- 

 clusion of the volume in the series. In connection 



