CHAPTER XII. 



TREE-FERNS. 



JREE-FERNS differ so much in appear- 

 ance from their humbler relatives, and 

 their cultivation involves so many special 

 cares, that we will give them a chapter to them- 

 selves. 



In Chapter I. the writer endeavored to show the 

 relation between the stem of the Tree-Fern and 

 that of ferns of lowlier habit. It remains to speak 

 of the difference caused in the growth of the fern 

 by this remarkable form of stem, and to explain 

 why Tree-Ferns demand a peculiar method of cul- 

 tivation. It is only in a large house that they can 

 be grown at all ; for although they always begin 

 with the minute spore, and pass through the pro- 

 thallus stage of development, yet, in their native 

 haunts, they sometimes reach the height of sixty 

 feet from the ground, and have a circle of spread- 

 ing fronds one hundred feet in circumference. 

 The trunk of a Tree-Fern is formed by the axis 



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