THE FLORAL ENVIRONMENT 57 



We have already seen that the rigours of a desert 

 climate abate in many places for a short season 

 every year. Plant life in deserts has suited itself 

 to the cHmatic conditions in many ways, of which 

 three are the most important. During the short 

 period which follows the rain annuals are common. 

 At the same season a group of perennial plants 

 which persist through the dry months dormant 

 underground produces its leaves and flowers. The 

 third principal group of desert plants consists of 

 perennials the structure of whose aerial parts is so 

 profoundly modified that they can continue their 

 vital functions throughout the year. We shall now 

 examine each of these groups more closely. The 

 first group, the annuals, is extremely conspicuous 

 after rain, so much so that for the moment the 

 desert is no desert, and the perennials, at other 

 seasons so conspicuous, cease to attract our notice. 

 The seeds of the annuals have survived a dry period 

 of months or years and have resisted terrific heat 

 and desiccation, but the stems, leaves, and flowers 

 are not anatomically modified for life in dry places. 

 The annual plants appear shortly after a fall of rain, 

 carpet the ground to a greater or lesser extent, 

 blossom in an incredibly short time, and then wither 

 rapidly when the soil and the air become dry. 

 Figs. 24 and 25, taken in the plain of Jericho in 

 February and June, show this. The spaniel dog 

 illustrates the depth and thickness of the spring 

 annuals. This ephemeral vegetation depends directly 

 upon the rainfall, and on it in turn depend a large 

 number of forms of animal life. In some parts of 



