I VOL. 2 



180 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



S— - 



than does that of Zizania, and all the connections of the 

 various organs show a lateral origin for the cotyledons, and 



a terminal origin for the ' ' coleoptile, ' ' 

 a structure made up chiefly of leaves 

 arising from an indistinctly differen- 

 tiated stem-tip region. 



Oryza sativa (fig. 4) is interesting in 

 the relation of the parts of the embryo, 

 the ' ' scutellum ' ' and ' ' epiblast ' ' being 

 opposite and well-balanced structures, 

 between which the prominent plumule 



(a name ex- 

 pressing the 

 real char- 

 acter of the 

 1 * coleop- 

 tile") is 

 evident. 



j 



Transverse section In bpttT- 



tina cyno- 

 sur oid e s 



5), the 



Fig. 8. 

 through cotyledon (s), show- 

 ing it embracing the plumule 

 (c) of Zea Mays: the plum- 

 ule shows three distinct 

 leaves and the terminal stem 

 tip; the succession of oppo- 

 site vascular bundles indi- 

 cates that a bundle opposite 

 that of the cotyledon is miss- 

 ing, but its rudiment is evi- 

 dent in a lower section; 

 X20. 



g- 



small cc 

 ledon ( epi- 

 blast) is less 



p r o m i - 

 nent. but its 



a — v — 



relation to the functioning cotyle- 

 don, and the relation of both to the 

 plumule are evident. 



In Leptochloa arabica (fig. 6) and 

 in Triticum vulgar e (fig. 7), the epi- 

 blast remains very small, but the 

 significant connections are evident. 



It is in the embryo of Zea Mays 

 that this reduction series reaches its 

 extreme expression in the complete 

 disappearance of the epiblast or second cotyledon (fig. 1), 

 whose position is indicated merely by more or less protuberant 



Fig. 9. Transverse section 

 through the cotyledonary plate 

 of Zea Mays: the functioning 

 cotyledon (s) does not overlap 

 a small protuberance, which 

 represents the site of the miss- 

 ing cotyledon (epiblast), as in- 

 dicated also by the appearance 

 of a procambium mass (a), 

 which is the rudiment of a 

 former vascular connection ; 

 X20. 



