KNOWLEDGE OF MONOCOTYLEDONOUS SAPROPHYTES. 171 
plant is very near the surface of the soil; secondly, the soil is 
light; and thirdly, the plant grows high up mountains. All 
these conditions render the substratum liable to rapidly lose 
water, and expose the plant to the risk of transpiring excessively, 
So I assume that the following process takes place :—When the 
soil is damp the roots absorb solutions, a transpiration-current 
sets in towards the growing parts and leaves in general, the 
water is carried by the small bundles of xylem into the scales 
and gradually deposited in the storage-tracheides. At this time 
transpiration is out of the question. Whether the hypodermal 
tracheides finally fill and permit liquid water to be forced out 
through the thin-walled epidermis it is impossible to say. When 
the soil dries, transpiration becomes possible. This does not take 
place from the regions covered by a layer with thick walls, but 
from those parts of the scales at which the epidermis has thin 
walls. And this process is aided by the rapid absorption of the 
exhaled vapour by the hygroscopic soil and its speedy conduction 
to regions where absorption is taking place. 
Considering the plant when it has an inflorescence-axis. There 
is a considerable current of water as evidenced by the xylem. 
The axis is coated everywhere with an epidermis with thickly 
cuticularized walls. The spots from which water can be excreted 
are the scale-leaves, the mucilage-hairs, and the parts of the 
flower. As these aerial portions are more liable to lose water 
than the subterranean portions, and as the floral parts and 
mucilage-hairs cause the plant to lose water, there is not the 
same pressing necessity for a large transpiring surface, nor for a 
large development of storage-tracheides. So we find that the 
scales dwindle in size and number and the system of hypodermal 
tracheides gradually diminishes as we ascend the inflorescence- 
axis. When the fruits form, the same holds good, for the fruits 
store up a large amount of water. 
Thus the subterranean parts are constructed so as to avoid 
being dried up and yet to permit of a regulated loss of water. In 
the inflorescence-axis the arrangements to prevent loss of water 
are much more marked than the mechanisms to permit transpira- 
tion. The plant is a unique xerophyte. 
It might be suggested that the subterranean scales are 
organs of absorption. Possibly they may be so periodically. 
But the following reasons may be urged against a view that they 
are essentially organs of absorption :—(i.) That region of them 
