Feu. 1893.] BOTANICAL SOCIETY OF EDINBURGH. 5 GO 



111 the majority of cases the radicle grows vertically 

 downwards, branching slightly if at all, and generally 

 reaches a considerable length, often several inches, before 

 any further changes take place in the other organs of the 

 embryo, and this is especially the case in those species 

 which have hypogeal cotyledons. If, however, the coty- 

 ledons are to be epigeal, these are soon draw a out of the 

 seed-coat by the elongation of the hypocotyl. In the seed 

 this part of the axis, lying between the cotyledonary node 

 and the radicle, is very short, but when elongation is about 

 to take place in it intercalary growth is set up ; and since, 

 on account of the curved nature of the embryo, neither 

 extremity can be moved, both the root and the apex of the 

 cotyledonary part being pressed firmly against the soil in a 

 downward direction, the hypocotyl is forced by its own 

 elongation to assume the position and form of an inverted 

 U, one limb of which, that attached to the radicle, is longer 

 than the other. As it increases in length the curved part 

 of the U approaches the surface of the soil, and not 

 unfrequently appears above it. 



Very soon, however, it commences to straighten itself 

 out, and in the earlier stages of this process generally forms 

 a sickle-like bend on that part of the longer limb where it 

 is just passing over into the curve of the U, this bend 

 being directed away from the cotyledons and so formed as 

 to gain sufficient leverage to remove these from the seed- 

 coat and raise them, edge first, through the soil. 



As soon as the straightening of the hypocotyl is com- 

 pleted, the cotyledons, which till now have been closely 

 applied to one another by their upper faces, and have not 

 unfrequently retained on their apices the remains of the 

 seed-coat as a small brown cap, separate from one another 

 and become horizontally expanded at no great distance 

 above the ground. 



They are always green, and not unfrequently provided 

 with a small petiole, the base of which expands into a 

 sheathing vagina half surrounding the axis and uniting 

 in many cases with that of the opposite cotyledon to form 

 a short tube inclosing and protecting the plumular bud. 



The cotyledonary lamina is generally entire, more or less 

 broadly elliptical, though in Hippocrepis almost strap- 



