No. 544] BOTANICAL SOCIETY OF AMERICA 



223 



Mesozoic was long called "the age of cycads," so far as 

 its vegetation is concerned. These characteristic Meso- 

 zoic forms are known now as the Bennettitales, and their 

 resurrection from rich Mesozoic deposits of America is 

 due to the skill and patience of our American colleague, 

 Dr. Wieland. They retained many of the primitive fea- 

 tures of the Cycadofilicales, but departed from them 

 chiefly in the development of a strobilus. Not only so, 

 but the strobilus is peculiar among gymnosperms, all of 

 which have strobili except the fern-like Cycadofilicales. 

 The strobilus of Bennettitales is bisporangiate, and the 

 two sets of sporophylls are related to one another as they 

 are in the flowers of Angiosperms. With the investment 

 of sterile bracts, the strobilus as a whole bears a remark- 

 able structural resemblance to such a flower as that of 

 Magnolia. This resemblance has proved to be very se- 

 ductive, for it has led to the claim that Bennettitales rep- 

 resent the ancestral forms of angiosperms. It is not the 

 province of the present paper to discuss this claim. It 

 has in it as a basis just enough of structural resemblance 

 and of historical timeliness to make a plausible argu- 

 ment, but hardly enough to carry conviction to those who 

 must take other facts into consideration. In any event, 

 the Bennettitales are a notable group, and paleobotany 

 has revealed them to us. 



Along with them, the true cycads, or Cycadales, began 

 to appear, apparently never a dominant group, and they 

 have persisted in the tropics to the present time. The 

 cycads as we know them, therefore, are the modern rep- 

 resentatives of an old phylum, which included Bennetti- 

 tales in the Mesozoic and Cycadofilicales in the Paleozoic, 

 a phylum aptly called the Cycadophytes. The cycads 

 present us with that paradox with which students of phy- 

 logeny are familiar, namely, they are structurally very 

 primitive, but historically modern. So far from being 

 the oldest of living gymnosperms, they are younger than 

 the conifers and the ginkgos. 



The Cordaitales of the Paleozoic had already developed 



