KNOWLEDGE OF MONOCOTYLEDONOUS SAPROPHYTES. 177 
earlier in the latter, in the exocortex the mycorhizal hyphe 
remain distinct for a lengthy period. 
Within the exocortex there lie about eight layers of paren- 
chymatous cells which are isodiametral in transverse section. 
Of these five to six outer layers form the mediocortex, and con- 
tain glistening yellow mycelial masses. The remaining two or 
three layers have no mycelia, and form an endocortex. The cells 
composing the endocortex contain starch, which is found nowhere 
else in the root. 
There is a well-marked endodermis. Its cells are longitudinally 
elongated. Outside the phloém the walls (Pl. V. fig. 1) are more 
thickened. Some of the cells opposite the xylem are passage- 
cells with large nuclei and very thin suberized walls (fig. 1). 
The pericycle is composed of a single layer of brick-shaped 
cells, Some of these cells have thin cellulose walls and rich 
protoplasmic contents. But typically the cells of the pericycle, 
which are on the radii between the bundles of xylem and phloém, 
have lignified, thick, pitted walls. 
The root is pentarch, the whole of the tissue within the 
pericycle is lignified excepting the bundles of phloém. 
Outside each bundle of xylem lie, in transverse section, 
about three pericycle-cells with thin unmodified walls. As the 
ground-tissue cells radiating out from the xylem towards the 
pericycle on each side are lignified, each bundle, in transverse 
section, looks as if it were forked outwards. At certain spots 
these lignified forks are interrupted by cells with thinner, but 
still lignified walls, so that they permit of communication between 
the phloém and the pericyle which is outside the xylem. 
The conducting elements of the xylem are made up of tracheides 
with transverse pits, and towards the interior there are in addition 
fibro-tracheides with fewer pits, which are, however, bordered. 
Outside each bundle of phloém there lie, in transverse section, 
about three pericycle cells, of which the two lateral, or all 
three, have lignified walls. The phloém consists of a mass of 
delicate tissue with thin cellulose-walls: sieve-tubes with oblique 
terminal plates, companion cells with strap-like nuclei, and elon- 
gated parenchymatous cells with wider lumina and oval nuclei. 
The whole of the conjunctive tissue and the pith is converted 
into longitudinally elongated cells with thick, pitted, lignified 
walls. 
Within the whole root the intercellular spaces are small. 
