34 



THE WATERLILIES. 



this divides into two smaller ones. Occasionally the angle is formed not 

 by a single cell but by three partition cells which meet at a point and are 

 connected by beveled ends. In N. flavo-virens, N. tuberosa, and to some 

 extent in N'. niarliacea-chromatclla, all of these cells are greatly rounded 

 out and turgescent, but their areas of union with one another (common 

 wall) are narrow and bounded by slightly curved lines ; in transverse 

 sections these lines give the appearance of small tubular and branched 

 cells lying between larger rounded cells ; longitudinal sections reveal the 

 true state of affairs. The contents of the medio-cortex cells may be very 

 small indeed, as in N. flavo-virens and N. elegans X zanzibariensis, or there 

 may be starch in the inner parts, as in N. tuberosa and N. marliacea- 

 chromatella, or the whole medio-cortex may be loaded with starch, as in 

 N. flava. N. marliacea-cJiromalella is intermediate in this respect between 

 tuberosa and flava. The grains of starch are rounded and simple or 

 elongate and double. 



The endo-cortex is an ill-defined layer, most distinct in N. flava 

 and N. elegans X zanzibariensis ; in the former it consists of one or two 

 cell-layers, in the latter of but one ; it is composed of small cubical 

 cells, and has rather large intercellular spaces, both between its own 

 cells and between these and the endodermis on the one side and the 

 medio-cortex on the other ; it should not, perhaps, be separated in the 

 description from the medio-cortex. 



Bounding the cortical tissues on the inner side, an endodermis with 

 thickened radial walls may always be recognized. Its circular outline 

 is interrupted by occasional slight sinuosities ; it is most evident in 

 N. lotus, odorata (Fig. 8) and elegans x zanzibariensis, least so in N. flavo- 



vircns and tuberosa. Its cells contain starch 

 in N. flava and marliacea-chromatella. 



A typical radial bundle system passes 

 along the middle of the root. Its outer- 

 most cell-layer constitutes the pericambium. 

 Against this the xylem and phloem patches 

 abut ; their number in different species is 

 shown in the accompanying table. 



In the center of the bundle an area 

 of pith remains ; this may extend over 

 one-third of the diameter of the bundle in 



N. odorata and lotus, one-fourth in N. flava, tuberosa, and marliacea-chroma- 

 tella, or one-sixth in N. elegans X zanzibariensis. In a general way this 



