Read it through once

Thus these half-desert countries are by no means without interest from a botanical point of view. The conditions of life are no doubt hard both for plants and animals. The scent so richly produced depends upon the strong sunlight and pure air. It is very useful, partly because it attracts those useful insects which carry the pollen, but also because such odours are distasteful to grazing animals. The gums, incenses, thorns, and spines are all of great use to the plant in its dangerous struggle for existence with hungry camels and thirsty soil.