135 
Species of the New Zealand Orchidaceae. 
endodermis. Near the outer and inner limits of the cortex the cells are 
longitudinally elongated, and the walls heavily pitted with round, oval 
or slit-like pits ; in the row adjoining the endodermis the walls are usually 
reticulately marked. A few of the large central cells are covered with fine 
spiral thickening strands. Small thin-walled cells containing raphides occur 
in the two outermost layers of the cortex. The endodermal cells, which are 
large and elongated, have thick, striated, cutinized walls with numerous pits. 
When the lumina are small the nuclei are filiform. The passage cells, which 
lie opposite the protoxylem groups, are a little smaller than the other 
members of the endodermis and contain denser protoplasm. In a large root 
they may be slightly cutinized. The cells of the pericycle are elongated in 
longitudinal section, and the walls, except of those adjoining passage cells> 
are thickened and cutinized. There are usually twelve, thirteen, or eleven 
groups of xylem and phloem present. The numerous small elements of the 
former consist of diversely pitted tracheides and of spiral vessels ; the few 
larger elements are usually spiral vessels. The sieve-tubes are small, but 
at least one in each group considerably exceeds the others. Separating 
xylem and phloem area few sclerenchymatous fibres. Elongated, cutinized 
cells lie within the vascular region, while those at the extreme centre of the 
cylinder have walls of cellulose. Chlorophyll occurs in the cortex chiefly in 
the three rows adjoining the exodermis, and in two or three adjoining the 
endodermis. The larger cells contain little, if any. In the outer region the 
two small cells which lie next to the passage cells of the exodermis contain 
distinctly the most. In addition a few granules may be present in the 
cellulose cells at the centre of the cylinder, Fungal hyphae branch in 
numbers through the cells of the velamen. Eventually they pass into 
a passage cell, where they take several turns round the nucleus, and then 
proceed into the cortex. Here they seldom penetrate deeper than the fifth 
cell, where they are reduced to globular masses of disorganizing hyphae con- 
nected together through the cell-walls by mere fibrils. If the cortical cell is 
large it may contain a smaller secondary, in addition to the nuclear, mass of 
fungus. The nuclei of the cells are always larger when the fungus is present. 
The stem has a narrow cortex surrounding an irregular ring of scleren- 
chymatous fibres, within which lie the numerous large vascular bundles. 
The cuticle is heavy — at times wider than the epidermal cells. These are 
cutinized and somewhat elongated in longitudinal section. Their inner 
walls are thicker than their outer, but the former are the more heavily 
pitted. In the elongated, pointed elements comprising the cortex the 
intensity of cutinization diminishes from without inwards, while the quantity 
of starch contained increases, The cortex gives place abruptly to the 
sclerenchymatous fibres of the strengthening cylinder. These pass gradu- 
ally into the oval cells comprising the ground tissue. The latter are filled 
with dense masses of starch tetrads. The vascular strands which occur 
