300 
is made to prevent the entrance of water, and to facilitate its 
fall from the leaves to the roots. Ifyou will take a leaf from 
the Bamboo and plunge it into water, and hold it there, vou will 
find on drawing it out, that the underside of the leaf is absolutely 
dry. Now Bamboos are great pumps; they consume much 
water, but instances are found where they absolutely weep, and 
keep the ground beneath them quite moist. M. Carriere has 
noted this in Algiers, and in Gregory’s account of the Great Rift 
Valley in Tropical Africa, he tells of some thickets of gigantic 
Bamboos, whose “ upper foliage interlocks into an impenetrable 
thatch, which is always sodden with moisture,” and amongst them 
would grow nothing, ‘‘except mosses, but in places the soil was 
covered with Iceland Moss (selaginella) and the Maiden-hair 
Fern,” and ‘a mist hung over the Bamboos and kept the 
vegetation sodden with moisture, and made the soil as saturated 
as a sponge”—Great Rift Valley—1—290. That is one way in 
which “the wilderness is made into a standing water, and 
water-springs in a dry ground,” and is an instance of the way in 
which thirsty plants can supply themselves with water in a dry, 
tropical country. I will give you another example from a very 
different climate. In the Death Valley of California, the rainfall 
does not exceed five inches in the year, yet the district has really 
an abundant vegetation, chiefly, however, of low trees and shrubs, 
with Cacti and Yuccas. The problem is how this five inches 
can be made to answer for the support of the vegetation, and the 
problem is thus solved by nature. The trees and shrubs are low 
and far spreading, and so the evaporation from the earth is 
reduced as much as possible; the roots spread to enormous 
distances, and so are able to suck up every particle of moisture ; 
and the transpiration is reduced to a minimum partly by some 
leaves not transpiring at all, partly by the leaves being 
clothed with a thick, and in many cases a woolly epidermis; and 
partly by the leaves falling very early, and so stopping at once 
the leaf transpiration. This isa most curious example of the way 
