STRUCTURE. 77 



Nymphaea and Nuphar, the fundamental tissue of the petioles was 

 traversed by innumerable small and equal canals. Specialization has 

 enlarged some of these at the expense of others in Nymphaea, Euryale, 

 and Victoria. The distribution of vascular bundles in petioles of water- 

 leaves follows the plan laid down for floating leaves. Stellate cells occur 

 in the air-canals, but no thyll-like bodies have been found. 



The lamina is of a reddish color in Lotos and Eu-castalia, but is plain 

 green in JV. tetragona, fcnnica, and amazonum, and Apocarpiae. Its texture 

 is extremely thin and fragile in Lotos, much firmer, though still very thin, in 

 Castalia, Hydrocallis, and Apocarpiae. The upper epidermis is composed 

 of rather larger, somewhat sinuous cells, and possesses a few stomata. 

 Arcangeli noted stomata on water-leaves of N. alba in 1890 (6), but Brand 

 (1894) failed to find them, and considered Arcangeli's specimens to be 

 arrested floating leaves. Wachter (1897) corroborated Arcangeli's 

 observation by examining leaves in chloral hydrate, and extended the 

 work to N. rubra, dcntata, stcllata, and thermalis, in all of which a few 

 stomata were found on the upper surface of the leaves. The lower 

 epidermis is like that of floating leaves. Great reduction has taken place, 

 however, in the mesophyll. Arcangeli (1. c.) found the palisade layer in 

 N. alba reduced to two strata of globular or ovoid cells, and Wachter 

 found a single layer of crescent-shaped cells representing the palisade in 

 N. rubra and thermalis. The spongy parenchyma is greatly reduced in 

 quantity, and consists of loose cells with large intercellular spaces. 

 Idioblasts are present, but few in number, and the vascular network is 

 simple. The ordinary involute vernation is found in the water-leaves. 

 They are, therefore, to be considered as reduced floating leaves, and no 

 indication is offered of the wholly aerial habits which must have belonged 

 to the distant ancestors of the Nymphaeaceae. Even the large aerial 

 leaves of Nelumbo, from having stomata still restricted to the upper 

 surface, must be considered as derived from floating leaves, and in no 

 close relation to those of the probable terrestrial ancestors of the order. 



THE FLOWER, FRUIT, AND SEED. 



Few genera of plants offer such variety in size and color of flowers as 

 is found among the waterlilies. The primitive yellow, but of a rich hue, 

 is preserved in Xanthantha and the newly discovered N. sulfurea and 

 stuhlmanni; white prevails in Castalia, varying to pink in N. fcnnica, 

 odorata rosea, and alba rubra. All shades from pure white (N. dcntata) to 

 deep crimson (A 7 ", rubra) occur in the Lotos group, and from white 



