The Anatomy of Matonia sarmentosa, Baker. 303 
the internal tissue is composed of parenchyma, but opposite each 
protoxylem there is a considerable mass of fibres with narrow 
lumina. 
The protophloem, consisting of small angular elements, is 
almost continuous round the exterior of the bundle. The main 
sieve-tubes, however, are localised chiefly on the flanks of the 
bundle, and round the ends of the horse-shoe. They do not extend 
into the interior region, but whether they are here replaced by the 
above-mentioned fibres, or whether these latter are not true phloem 
structures could not be determined. 
sclerenchyma. 
Further away from the base of the petiole changes take place 
in the vascular strand. The arms of the bundle separate somewhat, 
so that the internal parenchyma becomes continuous through the 
gap with the external tissues. At the same time the central group 
of sclerenchyma disappears. It forms a tough connection between 
the sclerised tissues of the rhizome and the base of the petiole, and 
no doubt functions mechanically as an additional resistance to the 
tearing-off of the frond at its base, where the greatest strain must 
fall. 
