The genus Cycas appears to be the most primitive of its order. These plants were originally relatively small tropical forest plants growing from a subterranean bulb that eventually developed an aerial stem that sometimes might develop branches.  The large compound (many vascular traces) pinnate leaves to several meters long had linear simple to dichotomous pinnae.  Reproduction was achieved on specialized leaves (sporophylls), the lower part fertile and the apical part with reduced pinnae.  Normally a fertile shoot with many sporophylls would be determinate and therefore essentially lateral.   

Since my publishing a taxonomic revision of the genus Cycas in 1998 there has been a virtual explosion in the study of this genus, particularly by Ken Hill and also by Chinese botanists.  More precisely, this began in 1992 with Hill’s work on Queensland, but I had not had the opportunity to go to Australia and look at the new material.  The European and American herbaria had but little to offer in this regard.  Now I have been to Australia and am prepared to update my revision. Cultivated material at the Montgomery Foundation in Florida has been very helpful in understanding the living species.