NATURE 



[November io, 1904 



the pyrometer, and the electrical relations of bodies; 

 Leonhard with those on mineralogy and geology ; and 

 Schweins recorded that the " Kandidat als Pharmazeut 

 ungewohnliche Kenntnisse in der Mathematik besitzt " 

 — whatever that might imply. 



The subjects in which Mohr took his degree con- 

 tinued to interest him to the end of his days. In 

 chemistry he was no theorist ; indeed, the speculative 

 side of this science seemed to have little or no attrac- 

 tions for him ; and this is the more remarkable when 

 it is remembered that in other departments of human 

 thought he let his imagination have the fullest play, 

 as may be seen in his " History of the Earth." 

 Further, Mohr has some claim to be regarded as an 

 independent discoverer of the law of the conservation 

 of energy, as his tombstone in the old " Friedhof " 

 in Bonn testifies. 



To the historian of chemistry these letters have a 

 special interest. If, as has been said, they add little 

 to our knowledge of Liebig as a man and as a leader 

 in science, they nevertheless afford much valuable in- 

 formation concerning matters which agitated the 

 ■chemical world during some of the most stirring periods 

 ■of the last century. They have been most carefully 

 annotated by the editor and his assistants, as the 

 numerous foot-notes indicate. Many passages and 

 allusions which might have been obscure have been 

 elucidated by their patient research. We can heartily 

 -commend the book to all who are interested in the 

 personal and biographical history of chemistrv. 



T. E. T. 



THE BIONOMICS OF EXOTIC FLOWERS. 

 Handbuch der Bliitenbiologie. Begriindet von Dr. 

 Paul Knuth. iii. Band. Die bisher in ausser- 

 europaischen Gebieten gemachten bliiten-biolo- 

 gischen Beobachtungen unter Mitwirkung von 

 Dr. Otto Appel. Bearbeitet und herausgegeben von 

 Dr. Ernst Loew. i. Theil. Cycadaceae bis 

 Cornacese. Pp. 570; mit 141 Abbildungen im Text. 

 (Leipzig : Engelmann, 1904.) Price 17^. net. 



THIS valuable summary of available information 

 concerning the pollination of exotic flowers main- 

 tains the high standard of the preceding volumes, 

 though it naturally deals with knowledge essentially 

 fragmentary and only rarely founded on a statistical 

 basis. The work does not limit itself to imparting 

 information upon actual observations on pollination, 

 but in some cases includes accounts of the forms and 

 colours of flowers, the arrangement of their nectaries, 

 and even the microscopical details of fertilisation. As 

 examples of the various matters dealt with, the follow- 

 ing may be cited : — Freycinetia and its suggested 

 pollination by bats, the remarkable synchronous 

 blossoming habits of Dendrobium crutnenatuni, 

 parthenogenesis in Ficus, Kooders's work on tropical 

 geocarpous plants, the fertilisation of Rhopalocnemis, 

 the peculiar flowers of the commelinaceous Cochlio- 

 stema and their morphology, species of Yucca and 

 their relations with Pronuba. 



Among the many interesting features of the work 

 we may note that in bringing together in one work 

 NO. 1828, VOL. 71] 



the scattered observations on ornithophilous pollin- 

 ation it renders possible a survey of existing know- 

 ledge concerning the inter-relations of birds and 

 flowers. Yet the facts recorded show the rudimentary 

 stage of our knowledge as to the significance of birds 

 in the shaping of flowers. Scattered through the pre- 

 sent work we find evidence of actual or possible orni- 

 thophilous flowers belonging to a considerable number 

 of natural orders, including the Bromeliaces, Liliaceae 

 (.Aloe), Scitamincce, Orchidaceae, Proteaceae, Lor- 

 anthaceae, Ranunculaceae (.\quilegia), Capparidaceae, 

 Rosaceae (almond, peach, quince), Caricaceae, Legu- 

 minosae, Melianthaces, Balsaminaceae (Impatiens), 

 Malvaceae, Cactaceje, Rhizophoraceae, Myrtaceae, 

 Marcgraviacese, and Passifloraceae. Included among 

 these are flowers, such as the peach and almond, 

 obviously not originally ornithophilous, and others, 

 such as Passifloraceae and Aquilegia canadensis, the 

 pollination of which by birds is dubious. Still others 

 there are, such as Carica Papaya, the structure and 

 creamy tint of the flowers of which scarcely suggest 

 ornithophily. Other observations show that in 

 different parts of the earth the same species of flower 

 is visited by different animals. For example, the 

 entomophilous Japanese Eriobotrya japonica is visited 

 by humming-birds in South America, and by honey- 

 birds in South Africa. On the other hand, certain 

 natural orders, such as the Loranthaceae and Mimos- 

 aceae, markedly show pollination, or at least regular 

 visitation, by honey-birds in the Old World and by 

 humming-birds in the New World; and some flowers 

 of remarkable structure, such as those of Amhcrstia 

 nobilis and Hibiscus schizopetalus, visited by birds 

 seem to demand correspondingly remarkable methods 

 of pollination. 



The fragmentary nature of our knowledge in regard 

 to pollination is shown by the lack of published in- 

 formation in regard to some of the commonest plants. 

 For instance, Bornbax malabaricnm is not mentioned 

 in this work, yet it is very widely distributed, and even 

 common in some regions ; and in southern China I 

 know that its large red flowers are visited by small 

 birds. In some cases the omission of information is 

 due to oversight on the part of the authors ; for 

 example, there is no reference to the Vallisneria-like 

 pollination of the submarine Enhalus. The work also 

 shows that additional observations are required in re- 

 gard to some of the commonest tropical plants. As a 

 case in point, it may be said that few of those who have 

 scented Pandanus odoratissinms at distances of a 

 quarter of a mile will accept without further examin- 

 ation the view that littoral species of Pandanus are 

 anemophilous. Or, again, Knuth found that the 

 flowers Cassytha filiformis were mostly cleistogamous 

 on the coral islands of the Java Sea ; but unpublished 

 observations of my own on Dane's Island, near Canton 

 (China), sufficiently showed that this is not the case 

 everywhere. 



In regard to the printing of the work, it must be con- 

 fessed that misprints are too numerous, a brief examin- 

 ation showing the following : — Kleistoam, Magro- 

 glossa, Abitulon, Spahtiphyllum, and Bromeli- 

 aceenhliiten. Percy Groom. 



