STRUCTURE. 83 



the oval to lanceolate lamina tapers gently to a comparatively broad inser- 

 tion. Where the petals are brightly colored, the lower parts are usually 

 paler, and often yellowish, even in blue flowers. The margins of the petals, 

 as of the sepals, are always entire and are of softer texture than the sepals. 

 The inner ones are shorter and narrower than the outer. 



The structure of the basal and sepaloid portions of the outer petals of 

 N. odorata is exactly like that of the sepals, even to the presence of large 

 stomata on the back. The softer parts of these petals, and all of the 

 inner ones, are much thinner. The epidermis of both surfaces is like the 

 inner epidermis of the sepals, and has numerous hair-bases. Parallel and 

 anastomosing veins traverse the parenchyma, accompanied in the middle 

 line by idioblasts of varied shapes, but without air-canals. 



The stamens are quite characteristic in the different groups of 

 waterlilies. In Castalia, especially N. alba, all gradations are found, from 

 inner petals with a callous yellow tip or with one or two tiny anther cells, 

 to stamens with petaloid base and a small but perfect anther, and so on to 

 the innermost stamens, where the anther is large and thick and broader 

 than the filament. N. amazonum shows similar but more rapid gradations ; 

 the innermost filaments are filiform and the anthers narrowly linear. In 

 N. gigantea, however, all of the filaments are slender, and anthers narrow. 

 Lotos also shows no gradation from petal to stamen, but the outer 

 filaments are as much as half an inch wide at base ; their insertion is wide 

 and somewhat decurrent at the sides. The anther is broad and ligulate, 

 with blunt, round apex. The inner stamens are shorter and narrower, 

 ligulate in shape, and not decurrent. In all of the foregoing groups the 

 connective is not continued above the anther cells more than as a limiting 

 border to the anther, with the exception of the outermost stamens of 

 N. gigantea, which bear a tiny subulate tip. In Brachyceras, however, 

 there is a prominent prolongation of the connective at the apex of a large 

 number of the outer stamens. This is least in N. elegans (0.08 cm.), small 

 in N. flavo-virens, but may reach nearly 1.3 cm. in length in N. zanzi- 

 bariensis. In this group, also, transitional forms between petal and stamen 

 are sometimes seen. The outer filaments are ovate, often shorter than 

 the lanceolate or linear anthers ; these grade by slow degrees into the 

 innermost stamens, which are short and slender and without appendage. 

 In all species the outer stamens are colored like the petals, excepting the 

 yellow anther cells in Castalia and Apocarpiae and the reddish-brown 

 anthers of some Lotos species. The innermost stamens are wholly yellow 

 in all but N. rubra, where the reddish-brown color persists. 



