200 MR. H. HAMSHAW THOMAS AND MISS N. BANCEOFT ON 



in the spreading out of the woody lamellae at the poles into an almost continuous 

 investment without the characteristic thin patches. The relations of the guard-cells 

 to the surrounding epidermal cells also seem to be another important feature of 

 difference. 



It would seem, then, from the foregoing study, that the characters presented by the 

 stomata and epidermal cells of the Gymnosperms can be regarded as important as 

 indicating to some extent their relationships. In the Cycadean alliance we find some 

 charactej's which have undergone comparatively little modification in the ages which 

 have elapsed between Jurassic times and the present day, and we are consequently 

 entitled to regard stomatal structure as being the expression of ancestral characters 

 rather than of purely local and temporary conditions of environment. Of course, 



r 



further study of other groups is needed, and we hope that it will be possible in the 

 future to make further researches upon this line of enquiry. 



In conclusion, may we express our thanks to Professor A. C. Seward for his help and 

 advice during the course of this work, also to Professor Nathorst and other friends who 

 have given us information and assistance. 



BiBLTOGKAPHY. 



(1908).— "Nathor 



cutinised portions of Fossil Plants.'* 



il. Mag., Dec. v. vol. v. p. 454. 



W. (191 1).— Maryland Geological Survey. Lower Cretaceous. Baltimore. 



( 



(1856). — " Ueber organisclie Reste der Lettenkohlengruppe Thiiringens." Leipzig 

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■' Scharlach B : a Micro chemical Test for Oils." New Phvtolosrist. vol. xi. n. 72 



Karzel, R. (1908). — "Pie VerholzuDg der Spaltoffnungen bei Cycadeen." Wiesner-Festschrift, 



p. 510. 



Kraus, G. (1866). — « Ueber den Ban der Cycadeenfiedern." Priugs. Jahrb. vol. iv. p. 305. 



LiGNiEK, O. (1894). — '^ Structure et Affinites du Benneitites Morierei, Sap. et Mar.*' Mom. Soc. 



Normaudie, vol. xviii. Caen. 



191 2). — " Stomates des Ecailles intcrsemlnales chez le Bennettites 

 Bull. Soc. Bot. de France, vol. lix. p. 425. 

 F. E. (1908).—" The Physiology of Stomata." Carnegie Institute. 



Morierei (Sap. et Mar.) 



Mahlert, a. (1885). — "Beitrage zur Kenntnis der Anatomic der Laubblatter der Coniferen, rait 



besonderer Beriicksichtigung des SpaltoflFnungs-Apparates." Bot. Centralbl. vol. xxiv. p. 54. 



880}.—" Berattelse etc." 



** 



No 



(1907).—^^ Palaobotanische Mitteilungen 1 & 2/' K. Sveaska Vet.-Akad. HandL Bd. xlii. No. 5 



8). — ^^ PalUobotanischc Mitteilungen 4. 



yj 



No 



— (1909).—" Ueber die Gattung Nihsonia, Brongn." K. Svenska Vet.-Akad. Handl. Bd. xliii. 



No. 12. 



(1912). — "Einige palaobotanische Untersuchuugsmethoden." Palaobotanische Zeitschrift, 



Bd. i. p. 26. 



Nestler, A. (i895).~''Ein Beitrag zur Anatomic der Cvcadeenfiedern." Prings. Jahrb. vol. xxvii. 



p. 341. 



Phillips, J. (1829).— Illustrations of the Geology of Yorkshire. York. 



