ISOETES. 
235 
submerged grass, that the inexperienced eye would pro- 
bably pass it by unnoticed. It has a fleshy tuber, of a 
nearly globular form, white, and of compact texture in- 
ternally, but spongy and of a dark-brown colour externally. 
In the centre is a small nearly pellucid part, which 
appears to be the growing-point, since it is from this 
point that the leaves have their origin. From these 
tubers are produced the long semipellucid tubular roots, 
which strike downwards almost perpendicularly. The 
leaves spring from the crown of the tuber, and grow erect 
to the height of four or six inches, or more. They are 
persistent, and of an olive-green colour, and their general 
form is awl-shaped. The basal portion is dilated and 
furnished with membranous margins ; above this dilated 
base they are bluntly quadrangular, being formed of four 
parallel hollow tubes, which tubes are subdivided at irre- 
gular distances by transverse partitions, while towards the 
apex they taper off and terminate in a sharp point. The 
transverse partitions above mentioned, being visible through 
the texture of the leaf, give it a jointed appearance. 
Owing to their brittleness, they not unfrequently break off 
at one of these joint-like points, their basal parts and the 
decaying remains of the older leaves continuing to encircle 
