139 
Species of the New Zealand Orchidaceae. 
are somewhat thickened and the outer are slightly mucilaginous. Stomata 
are confined to the lower surface of the leaf, and are not numerous. Spiral 
vessels occur occasionally in the xylem, but tracheides are the more usual 
elements. 
Dendrobium Cunning kamii , Lindl. Bot. Reg. sub t. 1756. 
Stems usually much branched, slender, rigid, wiry, terete and polished, 
1-4 ft. long ; usually pendulous, but small specimens growing on rocks or in 
exposed places are often erect. Leaves numerous, distichous, alternate, 
f-3 in. long, in. broad, linear-lanceolate, acute, rigid, and coriaceous, 
striate and more or less conspicuously 3-nerved ; sheaths truncate, grooved, 
and transversely corrugated. Flowers -f in. in diameter, white and pink. 
The root as a whole, and all the cells individually, are large (PL IX, 
Fig* 47)- Of the usual four rows in the velamen, the three outer are more 
or less alike, while the inner is elongated radially and has its outer walls in- 
clined to one another. Root-hairs are often present. In transverse section 
the elements of the velamen immediately over a passage cell look like two 
or three triangles of different altitudes, standing on a common base, one 
within the other, and having their apices connected by a zigzag line to the 
centre of the base. In longitudinal section the walls of these cells resemble 
portions of concentric circles. Except in these walls the fine thickening 
strands of the velamen are radial. The exodermal walls may have several 
striations. They are all cutinized, even the inner tangential. The elements 
of the cortex are thin-walled and regular in shape. In the central region 
and near the endodermis they are usually round. Chlorophyll is present, 
but not in great quantities. Small round pits occur frequently, but spiral 
bands are seldom to be seen. As in the preceding genus the cortical cells 
adjoining the endodermis are reticulately pitted. The endodermis is well 
marked. Its cells are large, radially elongated, and heavily cutinized. The 
passage cells, which are small, occur about every sixth cell. They are 
distinctive in being elongated in longitudinal section. The walls of pericycle 
and conjunctive tissue are cutinized, but the lumina are large. Ten or 
more strong alternating vascular groups are present. A number of small, 
and one or two much larger, elements occur in the xylem. The tracheides 
usually have reticulate or regular equidistant pits. A few fibres may 
be present in the phloem. 
Stem and branch resemble each other closely. A thick cuticle sur- 
rounds a peripheral sheath of sclerenchymatous fibres which extends to 
a depth of about one-fifth of the radius. The cortex is narrow, and consists 
of thick-walled cells containing a little chlorophyll. Here and there the 
sheaths of the outer vascular strands join one another. Chlorophyll may 
also occur in the somewhat thin-walled elements of the ground tissue. 
