570 TEAXSACTIOXS AND PROCEEDINGS OF THE [Skss. i.vir. 



shaped, fleshy, and not unfrequently asymmetrical aljoiit its 

 median line, being in these cases markedly concave near the 

 base on one lateral margin, while the opposite one is as 

 markedly convex at the same point. This want of symmetry, 

 though very distinct in most of the species of MccUrar/o and 

 in Onolrycliis, is not by any means of constant occurrence, 

 and seems to be determined in great part, if not entirely, by 

 the form of the seed, which, in its turn, may well depend 

 on the exigencies of carpel formation. 



In those genera where the cotyledons are hypogeal the 

 first part to appear -above ground is the plumule. This 

 structure lies, in the seed, between the two cotyledons, but 

 as germination proceeds it is drawn out from this position, 

 on the one hand by the elongation of its own lower inter- 

 nodes, and on the other by the growth of the cotyledonary 

 petioles, whereby the cotyledons are removed to a greater 

 distance from the axis than before. As the young bud 

 leaves the seed the apex is found in most cases to be more 

 or less closely bent down towards the base, so that here 

 again the two parts form an inverted T'. In some cases 

 the bend joining the two limbs is very sharp, and the two 

 parts of the plumule are consequently very closely applied 

 to one another. As the plumule increases in length, this 

 bend, though gradually becoming opener, does not straighten 

 out, and neither does any elongation take place in the 

 apical part till the apex itself is raised quite clear of the 

 surface by the elongation of the basal part, so that the 

 delicate plumular bud is protected from injury, being drawn 

 through the soil backwards by the elongation of what is 

 practically the first plumular internode, the first leaf being 

 generally borne somewhere near the bend. 



The first plumular leaf arises typically in a plane placed 

 at right angles to that of the two cotyledons, and in those 

 genera which have these hypogeal it is placed on the side 

 of the axis opposite to that on which the seed lies. Ft is 

 generally, but not Ijy iiny means always, simpler in 

 character than are the adult foliage leaves, being 

 frequently composed of but one leaflet if the older leaves 

 have three, or of three if the older ones have a multi- 

 foliolate pinnate arrangement, though even in these latter, 

 as in Onolrijcliif;, it is not unfrequently unifoliolate. 



