Triglochin maritimum , L. 85 
of 4 mm., while in the more apical regions a diameter of 8 mm. 
is quite common in well-grown plants ; the reason of this lies 
in the fact that here the cells are younger, and consequently 
more turgid. 
The younger parts of the rhizome are covered, especially 
around and just below the apex, with the persistent bases of 
old leaves, which are quite chaffy in character. The rhizome 
frequently forks into two branches, each end bearing a crown 
of leaves and possibly flowers, 
A transverse section of an old rhizome shows a structure 
such as is diagrammatically figured in Pl. VI, Fig. 1. From 
this figure it may be seen that the underground stem is 
bounded by a mass of brown cells, to the inside of which suc¬ 
ceeds a layer of sclerotic elements, which are lignified and 
extremely hard. These cells are much pitted with simple 
branched pits. It will also be observed that these strongly 
lignified cells occur in various other places, the more central 
regions of the axis of the older parts of the rhizome being 
always occupied by cells of this character. 
The cortex consists of rounded cells loosely arranged in 
a somewhat radial manner, with numerous intercellular air¬ 
spaces (Fig. 2). The cells of the cortex of plants collected in 
the winter and spring are densely packed with starch-granules, 
and so also are the parenchymatous cells of the central 
cylinder. 
The endodermis is represented in Figs. 2 and 3, PI. VI : 
in the older parts of the rhizome it is extremely well marked, 
forming a continuous ring of cells much thickened on their 
radial and inner walls ; this layer, in fact, is remarkably similar 
to the endodermis such as is met with in the roots of Dracaena 
or Iris. 
The endodermis in the younger parts of the rhizome is not 
easy to make out in the ordinary stained microscopic prepara¬ 
tions, but its presence can easily be demonstrated by means 
of the usual test of iodine and sulphuric acid. 
The central cylinder has a large number of vascular bundles, 
which, when fully developed, resemble those of the concentric 
