260 MISS HILDA M. CUNNINGTON ON THE 
The fibrovascular bundles consist mainly of bast-fibres with walls that thicken 
relatively late (fig. 4, b). As the leaves age and disintegration sets in, the walls of the 
fibres become impregnated with brown colouring-matter, and a number of these persist 
as the bristles so prominent on the leafless parts of the rhizome. But even in this 
condition the walls are not lignified (though Sauvageau states to the contrary); they 
give a blue coloration with iodine and sulphuric acid, and do not stain with phloro- 
elucin and hydrochloric acid. 
Within the bast-fibres a small amount of phloem lies, being represented by several 
sieve-tubes with companion cells. The xylem lies within this. Sauvageau states that 
the xylem is represented by a vascular lacuna only, but in this space lie spiral or 
reticulate vessels, of which one to five are always present in the larger bundles. One or 
two vessels are present in the smaller ones, though here they are occasionally absent. 
The epidermis is devoid of stomata and has a thin cuticle. 
Between the leaves there are numerous strap-shaped intravaginal scales. These arise 
very early, and can be seen within the youngest leaf-primordia near the growing apex. 
There are usually ten to twelve intravaginal scales to each leaf arranged in a definite 
manner (text-fig. 5,7). One median scale lies on the median axil of the leaf (text-fig. 5, m), 
and the rest are arranged in descending estivation. They consist of parenchyma with | 
scattered pigment-cells (Pl. 36. fig. 5). 
Aeriferous System. 
Sauvageau describes the origin and development of the aeriferous chambers and 
diaphragms in Zostera, and says that the account applies to Hnhkalus acoroides. He did 
not, however, describe the earliest or most interesting stages or the development of the 
bundles, For this reason a complete description is given here, 
The leaf arises as a horseshoe-shaped hump near the apex of the stem. The fully 
