596 STUDIES IN FOSSIL BOTANY 



nature of the leaves referred to Cycas or Cycadttes, 

 with which the carpels are sometimes associated. 

 Professor Nathorst 1 has shown that in several species 

 from the Cretaceous of Greenland, formerly placed 

 in the genus Cycas, the vascular bundle of the pinna 

 was not single, as in the recent genus, but double, 

 and that the distribution of the stomata was also quite 

 unlike that in Cycas. He has therefore placed these 

 forms in a new genus, Pseudocycas, and no longer 

 regards them as belonging to the same suborder as 

 Cycas. It is probable that the species now placed in 

 Cycadites may prove to have similar peculiarities. 



Thus the whole question of the existence of Mesozoic 

 Cycadaceae, whether of the suborder Zamieae or 

 Cycadeae, is in an unsatisfactory position and the 

 positive evidence singularly meagre. There are a 

 great number of Cycad-like fossil remains, known only 

 as impressions and casts, the true nature of which 

 must remain doubtful until specimens showing structure 

 come to light. At present such specimens, of Mesozoic 

 age, are almost wholly limited to the Bennettiteae. 



3. Affinities of Mesozoic Cycadophyta. — The 

 Cycadophyta of Nathorst form a main subdivision of 

 the Gymnosperms, including the Cycadales, the Bennet- 

 titales, and no doubt other groups, which we are not 

 yet in a position to characterise. 2 The Cycadales 

 correspond simply to the Order Cycadaceae, with the 

 two well-known suborders Cycadeae and Zamieae ; 



1 A. G. Nathorst, "Palaobotanische Mitteilungen, r. Pseudocycas,'' Kongl. 

 Svenska Vetcnskaps Akad. Hand/, vol. xlii. No. 5, 1907. The cuticle of 

 carbonised specimens was examined microscopically. 



" Nathorst, " Beitr. /.. Kenntnis d. mesozoischen Cycadophyten,'' p. 3. 



