224 



HEREDITY AND EVOLUTION IN PLANTS 



senting 12 tribes, demonstrated the presence of the rudi- 

 mentary cotyledon (epiblast) in 29 of the genera, repre- 



FIG. 106. Diagram of longitudinal sections of grass-embryos (Gram- 

 ineae) to illustrate the rudimentary cotyledon (epiblasl). A-C, E-G, 

 redrawn from J. M. Coulter, after Bruns; D, from nature. A, Zizania 

 aquatica; B, Leersia clandestina; C, Lcplochloa arabica; D, Trlticitm vul- 

 gar e; E, Sparlina cynosuroides; F, Triticum vulgarc; G, Zea Mays; 

 s, scutellum; c, colcoptile; e, epiblast. 



senting nine tribes; later studies by Van Tieghem (1897) 

 disclosed the presence of an epiblast in 61 out of 91 genera 

 examined. From these figures we max reasonably infer 



