59 



diaceae both annuals and perennials. These plants do not 

 die or go to rest till the autumn. SCHIMPER calls such plants 

 "Ground-Water Plants". 



Another group of plants satisfy their water-requirements 

 from the precipitation of the winter and spring, the melting 

 snow and rain-water which is stored in the upper layers of 

 the soil. When the dry hot time comes (in May June) most 

 of the available water (Chresard) from these strata evaporates, 

 and they become very dry. What water remains becomes 

 more concentrated and saline through evaporation (BERNATSKY 

 p. 209), and as the plants dependent on the water in the 

 upper layers the Spring-Plants -- are not xerophilous 

 or only slightly so, the increasing heat soon makes them 

 wither. Before this takes place, however, their development 

 is finished, and they have dispersed their seeds. Most of the 

 spring-plants are annuals or ephemerals, as VOLKENS terms 

 them, but there are also some bulbous plants and other 

 perennials, especially in the more favourable localities. These 

 perennials go to rest when summer comes, and assimilate 

 and bloom only in spring. 



This distinction between a spring-vegetation and a sum- 

 mer-vegetation has long been known for many deserts and 

 steppes. (It is also present, though perhaps less pronounced, 

 in the whole region of temperate winter-rains). GRISEBACH 

 (1872 I p. 449) has already recorded Artemisia as one of the 

 few perennials ("Stauden") which vegetate through the sum- 

 mer, and he also states that most annual plants die quickly 

 during the spring, whereas some annual Chenopodiaceae live 

 through the summer, blossom in the autumn, and do not 

 die till the frost sets in. The spring-flora of the South- 

 Russian steppe has been described among others by GRUNER 

 and TANFILJEW, that of Egypt by VOLKENS, and that of the 

 desert-territory of western North-America by MAC DOUGAL, 

 THORNBER and others. Here we find two maxima of ephe- 

 meral plants corresponding to the two rainy seasons of winter 

 and summer. 



We shall first describe the Transcaspian Clay-desert in 

 its Spring aspect, and afterwards attempt to present a picture 

 of the more sombre aspects of Summer and Autumn. 



