66 The Waterlilies. 



reddish to dark crimson-brown in N. odorata, alba, tetragona and flava, 

 dull brownish in the Lotos group, and blue-purple in N. zanzibariensis 

 and gigantea. Dark brownish or blackish blotches and specks mark 

 the under surface in N. flava, caerulea, ampla, elegans and amazonum. 

 The leaves are rolled inward from the sides (involute) in venation. 

 They come up through the water in a more or less erect position, and 

 only on reaching the surface does the lamina bend over at right angles 

 i to the petiole (Frank, 1872). 



The venation, as inferred above, is in general palmate, but there is a 

 distinct midrib with pinnate branching. The lowest pair of veins turn 

 backward into the lobes, and others radiate out at various angles ; it is 

 sometimes difficult to decide whether the most anterior of these are 

 distinct or branches of the midrib. Five {N. flava, tetragona) to twelve 

 {N. zanzibariensis) veins on either side of the midrib originate thus 

 directly from the base of the leaf, and were called by Caspary (1865) 

 primary veins (Fig. 28, 1-5). They give off small branches along their 

 course, but sooner or later fork into two nearly equal parts. A strong 

 cross-vein soon connects the forks of adjacent veins, enclosing a distinct 

 area between each pair of veins. The area whose long axis stands most 

 nearly at right angles to the midrib was called by Caspary (1. c.) the 

 principal area (Fig. 28, r), and its length in relation to the radius of the 

 leaf was used as a standard measurement in all of his taxonomic work. 

 The vein below it is the principal vein (Fig. 28, 3). Beyond these 

 primary areas there is a series of similar meshes, becoming rapidly 

 smaller out to the margin of the leaf. Here the outer boundaries of the 

 ultimate meshes make an irregular, submarginal vein in all but the Lotos 

 group ; in these, three or four veinlets run together to a point in the apex 

 of each tooth of the leaf-margin. Great variety exists in regard to the 

 prominence of the veins on the under side of the leaves. In Castalia the 

 veins are easily seen, but they are marked by very slight and gradual 

 elevations of the leaf surface. In N. amazonum (Hydrocallis) the veins 

 are prominent beneath as narrow, low, but quite abruptly raised lines. 

 Among the Apocarpiae, N. gigantea has the veins quite abruptly raised 

 above the leaf surface, and standing out as a prominent reticulum ; N. 

 zanzibariensis is similar save that the ultimate veinlets at the leaf margin 

 do not project, and so we pass through N. flavo-virens to A^. caerulea, in 

 which the primary veins alone are markedly prominent, and the tertiary 

 branches are raised very little if any above the leaf surface. The Lotos 

 group, however, has an extremely prominent network of veins. The 



