144 Curtis . — The Anatomy of the Six Epiphytic 
coriaceous, dark green, often spotted with purple. Peduncles 1-4 from the 
axils of the lower leaves, slender, i-s-J in. long, 5-15 flowered. Flowers 
J-Jin. in diameter, green spotted with purple. 
The velamen consists of two or three rows of cells, the outer of which 
are large, thin-walled and covered with fine parallel radial strands 
(PL XII, Fig. 89). The cells within this row are irregular in size, devoid of 
thickening strands, and cutinized in the walls which adjoin the exodermis. 
The protective cells of the latter layer are much larger than the passage 
cells. Spirally thickened water-storage cells occur in numbers from exo- 
dermis to endodermis, and raphides are not uncommon throughout the same 
region. The cortex as a whole contains an unusual amount of chlorophyll. 
The walls of the endodermis are so heavily thickened that only narrow 
radially elongated lumina remain. Near the passage cells, which occur 
singly, the walls of from one to three of the pericycle cells are of cellulose. 
From ten to thirteen vascular strands are present. In the conjunctive 
tissue the degree of cutinization diminishes towards the centre of the cylinder, 
where a little chlorophyll may occur. 
A thick cuticle covers the stem. The cortex is nearly one-third of the 
radius in depth, and is composed of small assimilatory cells and numbers of 
irregularly scattered large raphides cells. The vascular bundles are well 
developed, and the sheaths, especially of those near the edge of the vascular 
region, contain many sclerenchymatous elements on the side of the phloem. 
Chlorophyll is present in the pitted cells comprising the ground tissue. 
The strength of the thick leaf is dependent upon its succulent nature. 
No sclerenchyma is present except that in connexion with the vascular 
strands. The sheaths are seldom complete, and only those of their 
elements which adjoin phloem have heavily thickened walls. Large 
raphides cells abound. Chlorophyll granules occur from upper to lower 
epidermis, although in fewer numbers in the upper cells. Xylem and 
phloem contain numerous elements of regular size. 
Summary. 
1. The velamen consists of one row of cells in Bulbophyllum pygmaeum 
and B. tuberculatum and of two or three rows in Sarcochilus adversus ; the 
number in the two species of Earma and in Dendrobium Cunninghamii is 
more variable, ranging from three to five, or more. 
3. The greatest amount of chlorophyll, in proportion to the size of the 
root, occurs in Sarcochilus adversus , and next in the two species of Bulbo- 
phyllum. Less is present in the Earinas and in Dendrobium Cunninghamii . 
3. A great number of spirally thickened water-storage cells are present 
in the cortex of the root of Sarcochilus adversus ; they are also to be seen, 
though less frequently, in the two species of Earina. 
4. Fungal hyphae are present in the roots of all ; they penetrate to the 
