G. B. Wieland — Origin of Dicotyls. 455 



But it is not unfair to note that this theory of dicotyledonous 

 foliage is neither more nor less than a corollary to my earlier 

 theory of the origin of angiospermous flowers expressed in 

 general terms, the only ones possible, evidence being limited to 

 Cycadeoidean fructification. For Arber and Parkin do not 

 refer to any other fossil forms directly, and draw no additional 

 conclusions from the structure of existing forms. They simply 

 iterate the well-known fact that while the angiosperms arise 

 abruptly as highly evolved forms belonging to existing orders, 

 and at once become dominant, fossil botany affords no direct 

 evidence of types of foliage understood to be transitional from 

 the groups peculiar to the early J\Iesozoic. 



Because of this very hiatus, however, no one has been able 

 to say much on the question of foliage ; though the reduced 

 condition of the flowers of Wielandiella later led me to look 

 upon that form as the nearest known approximation to the 

 hypothetic primitive Angiosperm line, despite the netted 

 venation in Dictyozamites* For I regarded those flowers as 

 offering incontestable evidence of the manner of Angiosperm 

 evolution. And furthermore this general conception of a 

 direct cycad-angiosperm relationship has also been reached 

 independently by Hallier, whose wide acquaintance with existent 

 plants entitles his views to great respect. More recently too 

 Hallier has shown that the Berberidacese may be considered 

 even more primitive than the Magnoliacese ; while he also gives 

 interpretory "figures of the essentially primitive leaf types seen 

 in Godoya, Touroulia and the Californian Lyonothamnus 

 floinbiindus.\ 



Now perforce the " small blade-like leaves " of Wielandiella, 

 a distinctly Pterophyllum-M^Q form, are the nearest known 

 approach amongst Cycadophytans to the leaves of dicotyls. 

 But after all it must be admitted that it would be a more or 

 less gratuitous guess to go on and say that Pterophyllum leaves 

 just as we know them in the Trias were extensively trans- 

 formed into magnoliaceous and other dicotyledonous types. The 

 p'oint is that however plausible such a theory, direct evidence 

 is lacking. For a change of this character going on in many 

 genera simultaneously, in others less regularly, but all over 

 the globe, must surely have left its impress so indelibly 

 stamped on the known Mesozoic record that transition forms 

 would long since have been found. 



Were it not, then, for the vast and dominating amount 

 of cycadophytan foliage in mid-Mesozoic deposits, and were 



* Wieland, G. E. Historic fossil Cycads, this Journal, p. 101, Feb. 1908. 



f Hallier, H. L'Origine et le Systeme Phyletique des Angiospermes, 

 Exposes a l'Aidedeleur Arbre Genealogique. — Extraitd. Arch. Neerlandaises 

 d. Sc. Ex. et Nat. Serie HE B, Tome I, p. 146 (1912). 



