part 2] COMPARATIVE REVIEW OF PLIOCENE FLORAS. 145 



4. A Comparative Review of Pliocene Floras, Based on the 

 Study of Fossil Seeds. By Mrs. Eleanor Mary Held,. 

 B.Sc, F.L.S., F.G.S. (Read March 24th, 1920.) 



I. Introductory. 



The work on which the following paper is based has been rendered 

 possible only by the help received from many botanists. If it 

 were not for a considerable private collection of seeds and fruits, 

 mounted for microscopic examination, it would have been imprac- 

 ticable, either to gain the knowledge requisite for carrying out 

 the work, or to make the preliminary determinations, which are 

 necessary before it is possible to use the great collections of our 

 public herbaria. 



The formation of this collection of seeds, though initially, and 

 essentially, due to my late husband's careful and unwearying labour, 

 has for some years passed the bounds when the work of any single 

 collector could meet the demands of the study of fossil seeds. 

 Help has, however, been received from all sides : by gifts of speci- 

 mens from Kew (both the Gardens and the Herbarium), the British 

 Museum, the Herbarium of the Museum d'Histoire Naturelle, 

 Paris, and the Gardens of La Mortola ; also by contributions 

 fi'om botanical friends, among whom I would especiallv mention 

 Mr. James Groves, Mr. C. E. Salmon, Mr. T. A. Dymes, M. Emile 

 Gadeceau, M. J. Simon, and Dr. Tokotaru Tto. 



As well as for contributions to my collection, I would also thank 

 the officers of Kew and the British Museum, for their unfailing, 

 kindness in helping while I have been at work in the respective 

 Herbaria, and in lending specimens for photography and study. 



Of late my work has been greatly furthered, particular^ the- 

 photographic part of it, by the assistance of Miss D. Minn (of 

 Newnham College, Cambridge), for whose services I am deeply 

 indebted to the Government Grant Committee of the Royal 

 Society. 



I especiallv wish to thank my friends Prof. A. C. Seward, F.R.S., 

 and Mr. James Groves, F.L.S., for allowing me always to apply 

 to them when I have wanted advice or help, and for their great 

 kindness in reading through my manuscripts. 



II. History of the Investigation. 



The study of Pliocene seeds, carried on by my husband and 

 myself between the years 1904 and 1915, 1 led us to formulate 



1 ' The Preglacial Flora of Britain ' Journ. Linn. Soc, Bot. vol. xxxviii 

 (1908) pp. 206-27 & pis. xi-xv; 'The Fossil Flora of Tegelen-sur-Meuse, &c.' 

 Verhandl. K. Akad. Wetenseh. Amsterdam, pt. xiii, No. 6 (1907) pp. 3-26 & 

 pis. i-iii ; 'La Determination de l'Age des Argiles a Briques de Tegelen,, 

 Reviver, Ryckevorsel, & Raevels ' Bull. Soc. Beige de Geol. vol. xxi (1907) 

 pp. 583-90 ; ' A Further Investigation of the Pliocene Flora of Tegelen ' 



