386 THE ANATOMY OF WOODY PLANTS 



the Gnetales and other gymnospermous types must be regarded 

 as somewhat doubtful. The general anatomical organization of 

 the Ranales presents some range of variety; but they do not 

 strikingly exhibit either vessels, fibers, parenchymatous distribu- 

 tion, or organization of the rays such as would be expected from 

 the study of the higher gymnospermous types and the investigation 

 of primitive regions and organs in the dicotyledons themselves 

 in primitive representatives of the angiosperms. The only strong 

 argument which can be advanced for the low systematic position 

 of the Ranales is based on their floral organization. The fact 

 that this has been deliberately disregarded in the Natiirliche 

 Pflanzenfamilien of Engler and Prantl shows that from the sys- 

 tematic standpoint it is a criterion which cannot be considered 

 as of overwhelming importance. With the ranalian origin of the 

 angiosperms is tied up the whole hypothesis of their derivation 

 from the Bennettitales. It has been pointed out that, from the 

 point of view of anatomy, there seems to be little reason to enter- 

 tain the hypothesis that the proangiosperms were of cycadean 

 origin, even if the earlier discovered impressions of the reproductive 

 remains of Mesozoic cycadean forms were originally referred to 

 angiospermous affinities by so distinguished a paleobotanist as 

 Saporta. Anatomically speaking, there seems accordingly to be 

 equally slight grounds for the derivation of the angiosperms from 

 zoidogamous gymnosperms as from ranalian dicotyledons. The 

 whole question, however, must await final and satisfactory solu- 

 tion until we are actually acquainted with the earlier angiospermous 

 types which will doubtless be sooner or later brought to light from 

 the Jurassic or from even earlier epochs of the Mesozoic. In 

 the meantime such knowledge of the general anatomical principles 

 as has been gained from the comparison of extinct and living 

 gymnosperms appears to point toward types like Casuarina and 

 its allies as representing, at any rate anatomically, the most 

 primitive conditions. 



