The Origin of Land Plants 117 



conditions. These new types of ferns have proved 

 themselves to be much more plastic than the other 

 pteridophytes, and many types have arisen which 

 are extremely well adapted to existing condi- 

 tions. 



In some especially favorable regions, such as the 

 higher mountains of Jamaica, and in New Zealand, 

 the number and variety of the ferns is extraordi- 

 nary, and they are perhaps the most numerous and 

 conspicuous plants that one encounters. From the 

 tiny filmy ferns, sometimes less than an inch in 

 height, to the majestic tree ferns raising their mag- 

 nificent crowns of fronds thirty or forty feet above 

 the ground, every available spot is occupied by a 

 bewildering variety of these beautiful plants. 

 Moisture-loving plants as they are, one finds that 

 they become scarcer in the drier parts of the world, 

 but many species have become adapted to dry 

 regions. For instance, there are a number of ferns 

 found in the coast regions of California, where for 

 months during the long rainless summer they be- 

 come completely dried up, and apparently lifeless, 

 but promptly revive with the advent of the first 

 autumn rains. In the moister and warmer regions 

 many ferns become epiphytes and grow upon the 

 trunks and branches of trees. These epiphytic 

 ferns are among the most beautiful growths that 

 one encounters in the tropics. A few species of 

 ferns are also aquatic in habit, but the number of 

 these water ferns is small. 



