12 



ON NA1AS GRAMINEA DEL., VAK. DELILEI MAGNUS. 



compare them with the slightly different figure of Braun on Plate 

 251, fig. 10. 



For drawings of the leaf-sheaths of Naias minor and N. major see 

 Plate 251, figs. 9 & 29, and compare the former with Braun's figure, 

 Plate 251, fig. 11. 



Fig. 58. 



The margins of the auricles of N. graminea, and more particularly 

 their free extremities and inner sides, are crowded with strong, 

 spiny, tawny-brown cells, similar to those on the lamina ; but they 

 occur at much shorter intervals, and the cells at the base of the 

 spines are more loosely aggregated (see fig. 58), so that there is no 

 well-defirfed series of marginal cells as in the lamina. The basal 

 cells which support the spines have their longest diameter in the 

 direction of the spine. 



Fig. 59. 



In N. flexilis (fig. 59) the cells are more loosely aggregated also, 

 but the line of marginal cells, though not so well-defined as in the 

 lamina, is more clearly apparent than it is in N. graminea. The 

 cells of the sheath, as well as the marginal cells of the lamina, of 

 N. flexilis are larger and longer than they are in N. graminea ; but 

 the two species may be distinguished by the length of the imbedded 

 portion of the spine, which in N. flexilis is less, and in N. graminea 

 is more, than one-third of its free length. The leaf-cells of N. flexilis 

 generally are larger than those of N. graminea (compare figs. 45 and 

 46 with figs. 47 to 49, and fig. 58 with fig. 59, all of which are 

 drawn to the same scale). 



VIII. — Leaf-structure. 



The anatomy of the leaves of N . graminea is simple. The margins 

 of the lamina to the extent of one-third the breadth are composed of 

 two layers of cells (see figs. 63 and 65), which in the Beddish 

 specimens do not present that contrast in the size of the cells of 



