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[Vol. 2 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



cotyledon. The definition is accurate, for the epiblast occupies 

 exactly the place of a second cotyledon opposite the large and 



functional one (fig. 2). If some one had found 



an epiblast vigorous 



enough 



to establish 



< < 



Fig. 3. Embryo 

 of Leersia clandes- 

 tine!,: s, scutellum; 

 e, epiblast; c, cole- 

 optile; X 44. — 

 After Bruns. 



vascular connections, this debated structure 

 would long since have been accepted as a 

 second cotyledon, for the definition of it al- 

 ways emphasized the fact that it is a scale 

 in the right position for a cotyledon, but with 



no vascular strands." 



So obvious is the interpretation of the 

 grass embryo when an epiblast is developed 

 that Porteau in 1808, Mirbel in 1809, Turpin 

 in 1819, and Bischoff in 1834, all called the 

 epiblast a rudimentary cotyledon. The sub- 

 mergence of this idea seems to have been due 

 to Schleiden, who in 1837 dissented from this 

 view, and it disappeared from literature. It 

 reappeared in 1897, when Van Tieghem, in 



-s 



his paper on the embryo of grasses and sedges, 1 reiterated 

 based chiefly upon the study of vascular connections. 

 Any series of sections, cross 



or longitudinal, through the em- 

 bryos of grasses, shows the fol- 

 lowing facts : the so-called scutel- 

 lum or functional cotyledon 

 arising from the peripheral coty- 

 ledonary ring or sheath which 

 surrounds the apex of the em- 

 bryo, and establishing vascular 

 connections laterally with the 

 cotyledonary plate; the epiblast 

 in a similar relation to the coty- 



Fig. 4. Embryo of Oryza sativa: 

 s, scutellum; e, epiblast; c, cole- 

 optile; X 22 .—After Bruns. 



ledonary ring on the opposite side, and varying in develop- 

 ment from a structure somewhat smaller than the large 

 cotyledon, to complete suppression; and the apex of the 



1 Van Tieghem, Ph. Morphologie de l'embryon et de la plantule chez les 

 Graminees et les Cyperacees. Ann. d. Sci. Nat., Bot. VTII. 3:259-309. pi. 1^-16. 



1 Oc7 | • 



