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XVIII. — Contributions towards a Knowledge of the Anatomy of the Lower 

 Dicotyledons. I. The Anatomy of the Stem of the Papaveracese. By 

 R. J. Harvey-Gibson, D.L., M.A., Professor of Botany, University of 

 Liverpool; and Minnie Bradley, M.Sc, Hartley Research Scholar, University 

 of Liverpool. (With Three Plates.) 



(MS. received December 6, 1915. Read December 6, 1915. Issued separately September 16, 1916.) 



Introductory. 



The systematic study of the cluster of orders lying at the base of the Dicotyledon 

 phylum has of late years become of fundamental importance in view of the various 

 theories advanced by different authorities as to the origin of the so-called Mono- 

 cotyledons. The anatomical structure of many of these groups has been but little 

 investigated from this aspect, and the present paper is the first of a series which 

 it is hoped to publish with the object of discovering to what extent anatomy 

 supports or contradicts one or other of views held on the phylogeny of flowering 

 plants. One such research is already far advanced, viz. on the anatomy of the 

 Magnoliacese, and another, the present contribution, deals with the stem structure 

 of the Papaveracese. Although both researches have been retarded owing to one of 

 the authors being engaged on war service, there would seem no reason for delaying 

 the publication of such observations as have been made. 



Naturally, no attempt has been made in the present paper to draw any general 

 conclusions outside the genera actually investigated ; such generalisations must be 

 postponed until the completion of other work now in progress. 



The Anatomy of the Stem of the Papaverace^. 



m According to Prantl and Ktjndig (8), the order Papaveracese includes the genera 

 usually grouped under Fumariacese, but by them placed in a section Fumarioidese. 

 Twenty -eight genera in all are described in the PJlanzenfamilien, and of these 

 twelve, represented by twenty-six species, have been investigated by us, viz. Papaver, 

 Meconopsis, Argemone, Chelidonium, Glaucium, Bocconia, Eschscholzia, Hypecoum, 

 Dicentra, Adlumia, Romneya, and Corydalis. Some of the remaining sixteen we hope 

 to discuss in a future paper, as material becomes available. 



Papaver Rhoeas, L., is placed by Leger (ll) in a subgroup Rhceades, which 



includes P. Argemone, L., P. dubium, L., and P. hybridum, L., and he selects 



P. dubium for detailed description, stating, however, that the whole group exhibits 



great similarity in anatomical structure. In the present instance P. Rhceas has 



TRANS. ROY. SOC. EDIN., VOL. LI, PART III (NO. 18). 86 



