124 J. A. Harris, R. A. Gortner and J. V. Lawrence 



It is clear that the concentration of the leaf tissue fluids 

 of trees and shrubs is higher than that of dwarf shrubs and half 

 shrubs. The freezing point lowering found in the tissue 

 fluids of both perennial herbs and winter annuals is, without 

 exception, less than that observed in either of the ligneous 

 growth forms. 



Combining the growth forms into two groups, ligneous 

 and herbaceous (Table II), the freezing point lowering of the 

 leaf tissue fluids of the herbaceous plants is seen to be less in 

 every instance than that of the ligneous species from the same 

 habitats. The percentage differences, calculated by using 

 the value of the ligneous plants as a base, range from 24 . 4 to 

 48.1. 



Unfortunately, it is impossible to group the plant species 

 of a temperate mesophytic region or of a tropical region with 

 ample moisture and uniform temperature in exactly the same 

 way as those from a subtropical desert of the type in which 

 our first investigation was carried out. Biennials, and species 

 growing as either biennials or annuals, which are so conspicuous 

 a feature of a mesophytic temperate flora are practically want 

 ing in the desert. The dwarf shrubs and half shrubs which 

 are so dominant as an element in the desert flora studied are 

 not abundant in the flora of the Eastern United States. The 

 herbaceous annuals, prominent in both the xerophytic and 

 mesophytic nearctic region, are but sparingly represented in 

 moist subtropical and tropical regions. 



A uniform classification of growth forms. is, therefore, im 

 possible. Studies on the terrestrial vegetation of the Jamaican 

 montane rain forest have shown the following results for 

 the average of species averages of the freezing point depression 1 

 (Table III). 



Without exception the values of A are higher for the lig 

 neous than for the herbaceous species. The percentage 

 differences, calculated as above, range from 22. i to 30.3. 



It is, therefore, fully demonstrated by these data from 

 two geographically widely separated and climatically very 



1 J. Arthur Harris and J. V. Lawrence: Am. Jour. Bot., 4, 287 (191?)- 



