OP NAIAS GRAMINEAj VAR. DELILEI. 



45 



of N. graminea (compare figs. 45 & 46 witli figs. 47-49, 



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 & 

 65), which, in the Reddish specimens, do not present that 

 contrast in the size of the cells of the superior and infe- 

 rior layers which Dr. Magnus mentions on p. 51 of his 

 'Beitrage.^ No doubt the cells of the convex side of the 

 lamina are slightly the smaller, but the difference is not 

 so marked as represented in Plate VII. figs. 31-33, which 

 are copied from the figures given by Dr. Magnus. 



There are no stomata on the leaves and no epidermis ; 

 but the surface-cells in all parts of the plant have 

 intermixed with them reddish-pink pigment-cells, which 

 become brown with age. They are probably resinous, as 

 they are the last to decay; similar cells occur in other 

 species of Naias, 



The central portion of the leaf is much thicker than the 

 sides, because at this point the two layers of the lamina 

 diverge from each other so as to enclose a central bundle 

 of small-sized cells, surrounded by a layer of six or eight 

 larger-sized cells. On either side of this central tissue are 

 Fig. 60. Fig. 61. Fig. 62. 



Fig. 64. 



Fig. 65. 



Fig. 63. 



two intercellular cavities, which greatly exceed in size the 

 cells which bound them (see figs. 60-65). 



