G. JR. Wieland — American Fossil Cycads. 305 



Art. XXXIII. — A Study of Some American Fossil Cycads. 

 Part II. The Leaf Structure of Cycadeoidea ; by G. R. 

 Wieland. (With Plate TIL) 



Introduction. 



It is generally conceded that the Cycads culminated in the 

 Jurassic, and formed the principal plant life of that time. 

 Nevertheless, the abundant and widely distributed fossil 

 remains of this vegetation consist almost entirely of discon- 

 nected and scattered trunks, leaves, and occasional fruits, which 

 have been described under separate generic and specific names. 

 So uniformly is this true that Count Solms-Laubach 9 * mentions 

 an individual of Zamites gigas, Morr., from the upper Jurassic 

 sandstone of Yorkshire, England, as the only cycad known to 

 him, whose stem with the leaves attached may be identified 

 with certainty. This specimen, now in the Paris Museum, is 

 figured by Saporta, 4 and in leaf and habit is said to recall 

 Stangeria most nearly. 



There has, therefore, been no sufficient means of correlating 

 the various genera and species founded on isolated parts, — a fact 

 which now makes especially important a determination of both 

 trunk and leaf characters when united in a single individual. 

 For this reason it is fortunate that not only the leaf and its pre- 

 foliation, but also the accompanying floral characters, may 

 be completely determined in a number of the unusually per- 

 fect cycadean trunks now in the Yale collection, though but 

 a single one is considered in this paper. 



Prefoliation of Cycadeoidea. 



The subject of the present, as well as of the preceding, pre- 

 liminary study is afforded by the type specimen of Cycadeoidea 

 ingens, Ward, a photograph of which has been already given. 

 As previously mentioned, this fine male trunk bears on its 

 summit, above the series of flower buds, a crown of young 

 leaves imbedded in fine scales, or ramentum. It would seem 

 that, having formed its blossoms, this cycad was again prepar- 

 ing to put forth its energies in the unfolding of an additional 

 series of leaves, about twenty in number. Happening to be 

 fossilized at such a critical time in its life, under the most 

 favorable conditions, there, has been preserved a wealth of 

 characters scarcely equalled by any Mesozoic plant of which 

 there is a record. This specimen alone affords all the material 

 required for a restoration. 



* The numbers refer to the list of papers given in Part I of these studies. 

 This Journal, March, 1899 ; pp. 219-226, Plates ITT, IV. 



