THE ANGIOSPERMAE 



1593 



It would take too long to review the various theories which have been 

 propounded to try to bring the Grass embryo into line with other Mono- 

 cotyledons, and it has been adequately done elsewhere.* We shall content 

 ourselves with indicating certain probabilities. 



Fig. 1453- — ^ea mais. 

 Longitudinal section of 

 an entire grain with the 

 embryo, which shows a 

 coleoptile, a coleorhiza 

 and the laterally attached 

 cotvledonarv scutellum. 



Fig. 1452. — ^Examples illustrating the apparent change in 

 the position of the cotyledonary middle piece. A, 

 Nolina longifolia. Attached to the apex of the cotyle- 

 donary- sheath. B, Crocus vermis. Descended to the 

 base of the sheath and now attached to the hypocotyl. 

 The sheath remains as a coleoptile. C, Smilax asperii. 

 Descending on the hypocotyl. D, Gloriosa superba. 

 Descended almost to the base of the hypocot\l, the 

 portion of which abo\e its point of junction now being 

 the mesocotyl. {After Velenovsky.) 



It should be noticed that in progressing from the apical attachment 

 of the haustorial portion of the cotyledon towards a basal attachment, as 

 described above, we have also been advancing from epigeal to hypogeal 

 germination. With the cotyledon underground the need for rapid plumular 

 development becomes more pressing and we find a correspondingly greater 

 development of the plumule before germination. Thirdly, in more advanced 

 Monocotyledons the leaves have not only a sheathing base but also a hgule, 

 which must be taken into account. 



* See a good short statement by Boyd in "Trans. Bot. Soc. Edinburgh", Vol. 30^ 1931. 



