MESOPIIYTE ASSOCIATIONS. 237 



temperature ; and soft, the low stature and short life not 

 involving the development of specially rigid structures for 

 support or resistance. In such conditions, as would he 

 expected, animals are in the minority, the plants heing 

 mostly perennial and geophilous. Geophilous plants are 

 those which have the habit of disappearing underground 

 when protection is needed. This is probably the best adap- 

 tation for total disappearance from the surface and for rapid 

 reappearance (see §146). In such conditions, also, rosette 

 forms are very common, the overlapping leaves of the rosette 

 closely pressed to the ground diminishing the loss of heat 

 by radiation. It has also been noticed that these arctic and 

 alpine carpets show intense color in their flowers, and often 

 a remarkable size of flower in proportion to the rest of the 

 plant. Wherever the area is relatively moist, the carpet is 

 prevailingly a grass mat ; in the drier and sandier spots the 

 herbs predominate (see Figs. 202, 203). 



In the case of plants which can grow both in the low 

 ground and in the alpine region, a remarkable adaptation 

 of the plant body to the different conditions may be noted. 

 The difference in appearance is sometimes so great that it 

 is hard to realize that the two plants belong to the same 

 species (see Fig. 204). 



169. Meadows. — This term must be restricted to natural 

 meadow areas, and should not be confused with those arti- 

 ficial areas under the control of man, which are commonly 

 mowed. The appearance of such an area hardly needs defi- 

 nition, as it is a well-known mixture of grasses and flower- 

 ing herbs, the former usually being the predominant type. 

 Such meadow-like expanses are common in connection with 

 forest areas (see Fig. 205), but they are most character- 

 istically developed on flood-plains along streams. In most 

 cases the local meadow is probably an ephemeral society, to 

 be replaced by forest growth. 



The greatest meadows of the United States are the well- 

 known prairies, which extend from the Missouri eastward 



