LIKNEA.N SOCIETY OP LONDON. IxxV 



is a methodical summary of recent observations (his own and others') 

 on the mutual relations of the sexual elements in plants, and more 

 especially the means by which the cross fertilization of separate indivi- 

 duals by insect agency, "or otherwise, is effected, preceded by a short 

 sketch of the history of the subject. Christian Conrad Sprengel, to- 

 wards the close of the last century, in a remarkable work, long forgot- 

 ten, but now recalled to our notice by Darwin, Hildebrand, Delpino, 

 and others ('Das ontdeckto Geheimniss der Natur, &c.', " The dis- 

 closed secret of Nature in the structure and fertilization of flowers"), 

 first announced, as a fact, that the majority of flowers which secrete 

 honey are incapable of self-fertUization, but are cross-fertilized by 

 means of insects which visit them in search of that honey, illus- 

 trating this proposition by more or less detailed obsex'vations on be- 

 tween four and five hundred plants. Similar observations, on the 

 evident impossibility in so many flowers of the stigma being acted 

 upon by the pollen of the accompanying stamens, appear to have 

 been brought forward by Hcnsclicl in 1820, in the attempt at refu- 

 tation of the established doctrine of sexuality in plants ; but all 

 these observations were generally disbelieved or ridiculed, for as yet 

 no plausible hypothesis had been brought forward connecting the facts 

 observed with the general economy of reproduction. But when Darwin 

 had once pointed out, in his ' Origin of Species,' the true tendency 

 of these curious provisions, and graphically delineated some of the 

 more complicated ones in his ' Fertilization of Orchids,' naturalists in 

 various parts of the world set to repeating his experiments, and 

 many detached papers on the subject have been published by Hilde- 

 brand himself as well as by others. The present memoir, in which 

 the facts thus elicited are collected and systematized, affords a fair 

 starting-point for future inquiries on the same subject under differ- 

 ent conditions and in different climates. 



Very few botanical monographs of any importance have been 

 recently published in Germany. Ilanstein has completed his review 

 of Gesneraceoe in the ' Linnaea ' ; F. W. Klatt has illustrated the 

 genus Lysimachia, with detailed descriptions and several plates, in 

 the Transactions of the Natural-History Society at Hamburg, and 

 completed his revision of Irideae in the * Linnaea ' ; and Batka has 

 given a very elaborate monograph of the few species constituting 

 the Sennet group of the genus Cassia. Wimmer has published a 

 monograph of European Willows ; and Milde has completed, in the 

 Nova Acta Academies Naturae Curiosorum, his very full and copiously 

 illustrated monograph of Equisetum. 



