SEASONALDIMORPHISM OF CHAMAEPHYTES 215 



values are attained in March and April at the end of the season of extensive 

 growth and the minimum values for most of the plants are reached in the 

 autumn and early winter when a great part of the older summer leaves 

 have been shed and the new growth of the autumn and winter branches 

 and leaves after the first rains have only just started. 



Table i 

 Relative seasonal body reduction of desert and Mediterranean chamaephytes 



The values for the relative seasonal body reduction, i.e. the decrease in 

 weight of the transpiring body during the summer expressed as a per- 

 centage of the weight in spring, are presented in Table i . This shows that 

 the values for the desert plants are higher than those for the Mediterranean 

 ones, while Artemisia monosperma, which is a desert sand dune dominant, 

 is intermediate between them. Table i also shows that no marked differences 

 between the values for 1957 and 1958 could be found although the values 

 for 1958 tend to be somewhat higher. On the other hand the amount of 

 new growth for the desert plants in 1957 was higher than that in 1958, as 

 seen from Table 2, in which the values for the weight of the transpiring 

 body of the plants in the spring of 1958 are expressed as a percentage of the 

 corresponding values for 1957. No clear-cut differences were found between 

 the amounts of new growth of the Mediterranean plants in the two years. 



TRANSPIRATION RATES 

 The transpiration rates of the chamaephytes were measured during 1950 

 and 195 1 in the field by the cut leaf quick-weighing method. Because the 

 15 



