66 ON SEEDLINGS 



enabled them more easily to make their exit from the seed. 

 In that species, where the cotyledons are deeply bifid, the 

 leaves also are much cut up. In E. tenuifolia, on the contrary, 

 both the leaves and cotyledons are long and linear. Here 

 also the form probably facilitates the exit ; and one may 

 perhaps suggest that E. californica exhibits a form of which 

 E. tenuifolia represents an earlier and simpler condition. 



POSITION OF THE EMBRYO IN THE SEED. 



As a general rule, the arrangement and position of the 

 embryo in the seed is approximately the same within the 

 limits of any one genus. There are, however, many ex- 

 ceptions. 



In the genus Plantago, for instance, the cotyledons 

 sometimes have their faces and sometimes their edges to the 

 placenta. This difference is not indeed mentioned either by 



Barneoud or Decaisne in their 



A B respective monographs of the 



family. Bentham and Hooker, 

 however, say ( ' Genera Plan- 

 tarum,' vol. iii. p. 1223): 

 ' Embryo rectus v. rarius 

 hippocrepicus, hilo parallelus 

 v. in fructu monospermo 



FIG. 112. Planfago media. A, longitu- 

 dinal section of seed, x 8. B, trans- erectllS V. tranSVerSUS. 



In P. media the fruit is 

 capsular, dry, membranous, 



2-celled and 2-4-seeded. The seeds (fig. 112, A and B) are 

 plano-convex or subconcavo-convex, peltate, small, with equal 

 obtuse ends ; or with the basal end slightly the broader ; the 

 testa is thin, pale brown ; the hilum a little below the middle 

 on the ventral aspect, round, and deeper brown than the rest 

 of the testa ; the raphe tapers from the hilum obliquely 

 towards the upper end of the testa. The endosperm is copious, 

 fleshy, and white. The embryo is straight, narrow, white, a 

 little shorter than the endosperm, and embedded in it, a little 

 nearer the dorsal aspect of the seed and somewhat oblique to 

 the median axis ; the cotyledons are linear-spathulate, taper- 



