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well as individuals makes it more difficult for a species 

 to flourish than in a section where the stress is less. The 

 young fern finds that the ground is literally all taken 

 with no signs of " standing room only " to be seen. It 

 must, therefore, find a foothold elsewhere or perish. 

 Thus it happens that many respectable fern families 

 have been obliged to take to the " upper story of the 

 woods " for refuge. 



It is interesting to note the ways in which various 

 species have attempted to secure advantages not pos- 

 sessed by their neighbors. The lack of space for all on 

 the ground has resulted in numerous curious forms being 

 evolved. In some parts the trees are ferns, the climbing 

 vines are ferns, the thorns that pierce and the brambles 

 that scratch are ferns, the epiphytes are ferns, and the 

 very moss on the trunks seem turned to ferns. 



With the exception of some mountain tops covered 

 with Dicksonia in Eastern Pennsylvania, I do not remem- 

 ber any such vast areas covered with a single fern as I 

 saw in Jamaica. The bracken and various species of 

 Gleichenia claim whole hillsides for their own and grow 

 in perfect thickets. This, I hasten to add, is the excep- 

 tion and not the rule. These two species live in locali- 

 ties so dry that no other species want them — at least no 

 other species that are strong enough to take them — but 

 in the forest one is at once impressed with the large 

 number of species in proportion to the number of indi- 

 viduals. I believe that in a three-mile walk in the 

 vicinity of Morce's Gap I could collect nearly a hundred 

 species without going out of the path more than six 

 feet. Xature has filled up the forest as a man would fill 

 up a trench with gravel — using all sizes. Just as the 

 small stones fill the chinks between the larger ones, so 

 do the small ferns find an existence upon and between 

 their larger relatives. 



When we speak of the climbing fern in the Northern 

 States, we have a very definite species in mind, but not 

 so in the Tropics. It is true that the Lygodiums, faithful 



