824 ON NAIAS GRAMINEA DEL., VAR. DELILEI MAGNUS. 
and in the middle fruit of figure 86. This division of the beak into 
two branches is a constant character, and very clearly distinguishes 
it from the four-rayed beak of Naias flewilis (fig. 87). 
\ 
\. 
Fig. 86. Fia, 87. 
One other point of differentiation between Naias graminea and 
N. flewilis rests in the shape of the fruit. In the former the ends 
are more abruptly narrowed into the base and the beak than they 
are in the latter, poo gradually narrowing ends; compare 
figs. 86 and 87. Cesati’s figures in ‘Linnea’ xxxii., Plate 2, 
confirm this conclusion 
The perianth easily separates from the fruit; 
is represented in fig. 88. The portion which cov te 
the body of the fruit consists of a single layer of cells. 
XV.—Tue Roors. 
The roots are of great length, creeping in the soft 
black mud of the bed of the canal; they are given 
off = the nodes in verticils. Bhs are capillary, 
rig: ben 
aterm structure they bear some resemblance 
to the stems. There is a central channel surrounded 
to form a . 
central cells ; from this row of cells numerous short branches are 
given off which enclose intra-cellular cavities, similar to those 
