G, P. Wieland — Proembryo of the Bennettitece. 445 



Art. XLYII. — The Proembryo of the Bennettitece • by G. R. 

 Wieland. (With Plate XX.) 



During the course of the preparation and study of large 

 numbers of sections made from many different fossil cycad 

 trunks representing various stages of growth and fructifica- 

 tion, no more important feature has been discovered than the 

 proembryos, of which various examples have been observed in 

 several different fruits of Cyoadeoidea from the Black Hills. 

 As no developmental stage, if the archegonia of Cycadino- 

 carpus augustodunensis be excepted, has hitherto been 

 observed in any extinct plant, this discovery is of extreme and 

 novel interest. It has, therefore, been deemed appropriate to 

 present a preliminary description, to be amplified and further 

 illustrated in the writer's memoir on the Structure of the 

 Fossil Cycads, now nearly ready for publication by the Car- 

 negie Institution of Washington, under whose auspices these 

 investigations have been pursued. 



Amongst the fossil cycads in the Yale collection closely 

 resembling the so-called Bennettites Gibsonianus from the 

 Isle of Wight, but still referred by the writer to the genus 

 Cycadeoidea, the trunk numbered 393 is very completely silici- 

 fied, and bears a number of fine ovulate cones. In the various 

 longitudinal and transverse sections cut from these cones, 

 nearly all the tissues are clearly indicated, and the seed bodies 

 have reached approximately the size of those of the type of 

 C. (Bennettites) Gibsonianus, found by Solms-Laubach to 

 contain dicotyledonous embryos, nearly or quite filling the 

 seed cavity, and hence exalbuminous, or nearly so. These 

 are the only fossil embryos ever found. In the sections from 

 trunk 393, as is usually the case in silicified plants, the seed 

 cavity is often filled with more or less clear quartz, or by 

 structures and traces of structure which cannot readily be 

 interpreted. But there are in the present instance notable 

 exceptions; a considerable number of the seeds, as one must 

 conveniently call any stage of seed development which is not 

 or cannot be specified, contain well preserved large angular to 

 rounded proembryonal cells. These appear to fill the entire 

 nucellar space in some of the transverse sections. Such an 

 instance, where two adjacent seeds are finely conserved, is 

 shown on Plate XX, enlarged thirty diameters. In other 

 cases the large granular to rounded cells of the proembryo 

 appear to have been but partially preserved, or else to have 

 collapsed, carrying the nucellar wall inwards as if there had 

 been a central cavity in the large-celled mass, as usually 



