io8 
THE ESSEX NATURALIST. 
is fairly common, only stiff aerial leaves are formed. Plants 
living in deep running water produce only ribbon leaves, which 
may be from two to four feet long. When growing with those 
of Arrow-head, they can be easily confused with them, but the 
Bur-reed leaves have a weak midrib, and are traversed by 
from eleven to thirteen parallel veins, enclosing short rectangu¬ 
lar air chambers. Many runners grow out from the base of the 
stem; some lie along the bottom of the pond or stream, and are 
green, others, buried in mud, are white. They are stored with 
starch, and are provided with an abundant system of air chambers 
which are in communication with the air-space in the leaves. 
No conspicuous perianth is ever developed in the Reed-mace 
family, to which Sparganium belongs, but the round yellow heads 
of stamens and the pale balls of pistils are showy objects in 
summer amongst the shining bright green leaves. 
The larger Bur-reed, Sparganium erectumL. (or S. ramosum 
Huds.) grows by the lake in Wanstead Park, in the Roding,and 
in some of the larger forest ponds. It is stouter in all parts 
than S. simplex and the leaves are strongly keeled nearly to 
the tip. Submerged ribbon-leaves seem to be very rarely 
formed. 
These two species, as well as the graceful Sparganium natans 
L., whose leaves are all either submerged or floating, and which 
has not, I think, been recorded for Essex, are very widely 
