Read it through once

The above description applies to bulbs and perennial plants with underground stores of food. Yet these are by no means the only plants which manage to exist in the Egyptian and Arabian desert. After a shower of rain a whole crowd of tiny annuals suddenly develop from seed; they come into full flower and have set their seed before they are killed off by a return of the desert conditions, when the effects of the rain have died away. These plants are not really desert plants at all, for they only grow during the short time that it is not a desert. They are like the Ephemerid insects which live for a summer day only.