76 THE GEOGRAPHY OF PLANTS. 



titute of almost all the beauties of tropical 

 vegetation. Many of the features we have 

 described under the last zone are common to 

 this also, especially where the moisture, etc., is 

 such as to admit of the development of vegeta- 

 tion to the extent the climate will allow. In 

 some portions of the zone, especially the south- 

 ern, palms, bananas, mangroves, orchideaceous 

 parasites, and rope-like climbers, also are found. 

 Tree ferns, and plants allied to the convolvulus 

 and pepper tribe, are some of its most striking 

 features. 



The tree ferns frequently have a stem forty 

 or forty-five feet high, and bearing at the top 

 a beautiful crown of those peculiarly graceful 

 leaves for which the ferns are so remarkable. 

 Some species have trunks no thicker than three 

 inches in diameter, but twenty to twenty-eight 

 feet high, with a cro\vn of fronds, each eight or 

 nine feet long, of the most elegant and feathery 

 form, and from their extraordinary delicacy 

 put into tremulous motion by the gentlest wind. 

 It will thus be seen that they bear a consi- 

 derable external resemblance to the palms ; 

 and, in fact, so close is the similarity of the 

 stems, that a number of fossil trunks, which 

 have been discovered in the quarries of our 

 more northerly regions, and which were con- 

 sidered as palms, have been proved by later 

 investigations to belong almost exclusively to 

 tree ferns and cycadeas. 



The tree ferns chiefly prefer moist, and espe- 

 cially island situations. On some of the East 



