54 



GYMNOSPERMS 



borne in the axis of every leaf. A tangential section of a trunk of 

 Cycadcoidca shows transverse sections of the bases of foliage leaves 

 and numerous strobili surrounded by scale leaves (fig. 44). At the 

 bases of foliage leaves and entirely covering the scale leaves is a dense 

 ramentum consisting of scales several cells wide and often more than 

 one cell in thickness (fig. 45). ITiis is a dominant fern character and 

 not at all present in the Cycadales, in which the ramentum consists 



Fig. 48. — Cycadeoidea dacotensis: section of an unexpanded microsporophyll show- 

 ing, in most cases, transverse views of the two rows of loculi. At the upper right, parts 

 of two microsporangia are cut nearly longitudinally. Some of the loculi contain micro- 

 spores; X2S. — After Wiicland.**^ 



of long unicellular hairs. Occasionally there is a transverse partition, 

 but even where the ramentum is equally abundant in the Cycadales 

 the two groups could be distinguished by this character alone. 



The strobili of the Bennettitales are typically bisporangiate, with 

 leaflike microsporophylls as loosely arranged as the mcgasporophylls 

 of the living Cycas, and in the center a cone consisting of innumerable 

 small mcgasporophylls, each bearing a single terminal ovule. The 

 mcgasporophylls are slender peduncles without a trace of lateral 

 pinnae or ovules. Intermixed with the mcgasporophylls are sterile 

 leaves with a thickened top and with no lateral leaflets. 



A splendid reconstruction of the bisporangiate strobilus of Cyca- 

 deoidea ingens has been made for the Field Museum by Mr. Sella, of 



