FIFTY YEARS OF PALEOBOTANY, I906-I956 



597 



Fig. 3. SelaginelUtes crassicincttis Hoskins and Abbott. — 1. Megaspore of S. 

 crassicinctus, proximal surface. — 2. Detail of flange and adjacent wall of mega- 

 spore. — 3. Transverse section of sporangium wall showing the numerous buttresses 

 which may easily be mistaken for cell walls. — 4. Tangential section of sporangium 

 wall. The cells are irregular polygons and possess numerous buttresses on radial 

 and inner tangential walls. — 5. Megaspore, distal surface. — 6. Detail of flange and 

 adjacent wall of megaspore. — 7. Semi-diagrammatic drawing of a megasporophyll 

 and sporangium; megaspores are shown in axial section. — 8-12. Microspores of S. 

 crassicinctus. — 8. Proximal surface. — 9. Axial view. — 10. Distal surface with "clover- 

 leaf" depressions. — 11. Axial view showing flange, lips, and wall ornamentation of 

 both proximal and distal surfaces. — 12. Outline of axial section showing relative 

 size and position of flange and lips. — 13. Ligule (not that shown in 7). — 14. Apical 

 portion of megaspore in which the flange, lips, and reticulations of both proximal and 

 distal surfaces have separated as a unit from the remainder of the exospore. (This 

 is best seen in spores freed by maceration.) (For details see Am. J. Botany 43:36- 

 46, 1956.) 



