46 



The Waterlilies. 



The endo-cortex contains some starch. The ground tissue of the central 

 core of the stem consists of spherical cells with large intercellular spaces, 

 as in N. alba candidissima, and is densely filled with starch, even in a 

 large vegetative stem taken up in autumn and otherwise destined only to 

 decay. In N. flava (Fig. 21) the endo-cortex and ground-tissue are 

 constituted as in N. alba-candidissima, but the cortex cells seem more 

 crowded together than the central tissue of the core, and more densely 

 laden with large starch grains. Stellate cells are occasional in the central 

 core, and very plentiful in the cortex of this species. 



The trabecular which cross the medio cortex (Fig. 16) are composed 

 for the most part of tissue similar to the endo-cortex, but at the outer ends 



they gradually take on the character- 

 istics of the exo-cortex. The number 

 of trabecular in a cross-section is about 

 5 in N. flava, 7 or 8 in N. odorata, 

 8 in N. tuberosa, 14 to 15 in a very 

 large rhizome of N. alba candidissima, 

 1 5 or 1 6 in a large caudex of N. lotus. 

 On stripping off the exo-cortex of 

 a stem o{ N. odorata, I found eight 

 bands of trabecular tissue running 

 longitudinally throughout the length of 

 the portion studied, connected by trans- 

 verse or oblique cross-trabeculae at 

 intervals of a half-inch or more. The 

 petioles and peduncles are always 

 situated over a longitudinal trabecula, 

 in which the vascular bundles travel to join the central vascular plexus ; but 

 these leaf and flower insertions stood in no discoverable relation to the 

 transverse and oblique trabecular ; in two cases carefully dissected there 

 were no cross-trabeculae near the insertion of the leaf. In N. flava slender 

 trabeculae divide the medio-cortex into fusiform areas, each lying with 

 its longer axis horizontal and tangential to the stem ; a leaf or flower 

 or stolon stands over each such area, and a stout vertical trabecula 

 crossing the short diameter of the area bears the central leaf trace 

 to the vascular cylinder of the stem, while the lateral traces travel 

 inward near the points of the fusiform area, surrounded by a thin layer of 

 dense cortex. Caspary (1857 b) states that such a division of the spongy 

 cortex into areas is common to Victoria, Euryale and Nymphaea. 



Fig. 18. Caudex of N. caerulea; transverse sec- 

 tion. Heavy lines represent vascular tissue; e, 

 exo-cortex ; /, peduncle ; m, medio-cortex ; n, endo- 

 cortex ; p, petiole ; r, root ; 8, stipule. Natural size. 



