JURASSIC CYCADS FROM WYOMING. 201 



Renault (Cour. Bot. Foss., I, pi. xii, fig. 3)," than like either Cycadeoidea 

 ingens or Cycadella ramantosa. That is to say, the differences between 

 these various forms are not such as in themselves may be very readily 

 used for other than specific separations. The fact is also emphasized 

 that we are here deahng with a very generalized type of leaf structure. 



Bundle pattern of the petiole. — Tlils Is iudlcated lu the youug leavcs of Cyca- 

 della ramentosa and differs markedly from that of the living cycads. 

 It is much more fern-like in being arranged like a V with a quite 

 continuous xylem and phloem region. It is desired to cut some 

 further sections before giving detailed figures. In PI. LXIII, Fig. 1, 

 there is probably shown some distortion both of the bundle region 

 and of the transverse section of the petiole, due perhaps to desiccation 

 before the process of silicification began. The leaf represented in Fig. 1 

 of the same plate shows, in the uniform contraction between the veins 

 of the pinnules, what is quite likely an abnormality due to the same 

 cause. The bundle pattern of the petiole is not to be confused with 

 that of the leaf base. The latter, of course, merges into the former. 



Number of pinnules. — Thls has uot beeu determined, since it has not 

 been thought desirable to sacrifice any of these leaves by cutting 

 them in longitudinal section, especially since number is scarcely of 

 specific value, varying often in the case of fronds from the same plant 

 and very greatly as a plant grows older and the relative size of its fronds 

 increases. The number in the present species may have been as low 

 as 30 or doubtless as high as 60. 



Form of the full-grown pinnule. — Thls may be surmlsed with no small degree 

 of confidence. The fact that in the case of the frond shown in PL 

 LXIII, Fig. 1, the number of bundles increases as successive pinnules 

 are cut, and then becomes constant, proves that the venation is 

 dichotomous after the manner of Zamia angustifolia Jacq., and shows 

 that the pinnules, though elongate, can not have had a broad base with 

 numerous veins like Dion, nor yet like Williamsonia gigas. (See PI. 

 LXII, Figs. 1 and 4.) The degree to which the tip may have been 

 acuminate and the relative width are of course not possible to deter- 

 mine from transverse sections alone. But undoubtedly the pinnules 

 of the present species presented an appearance quite like that of such 



«■ This figure is reproduced in Scott's Studies in Fossil Botany, p. 423, fig. 139A. 



