58 EPIPHYTES, PARASITES, SAPROPHYTES [CHAP. 



is found within forests and in open places. In 

 the former there are two types those which 

 live on the lower branches as members of 

 the Bromeliacece, orchids without tubercles as 

 Zygopetalum, and the filmy ferns, as species of 

 Hymenophyllum. 



Secondly, there are those which grow upon 

 the summits of the trees, as Tillandsia, orchids 

 with tubers or pseudo - bulbs, coriaceous poly- 

 podys, etc. 1 



In the Savannahs or open plains the drought 

 is greater, in these, besides Tillandsias, there 

 are cactaceous plants, as the jointed leafless 

 Rhipsalis, thick-leaved orchids, and aroids. 



Without going into further details, the reader 

 will gather that this epiphytic habit, correlated 

 with corresponding structures, is totally different 

 from allied terrestrial species, as are all our 

 own English orchids ; and the question arises, 

 are they the results of spontaneous seedling 

 variations, i.e., without any influence from their 

 surroundings, and then naturally selected ; or, 

 did they arise by means of the responsive power 

 of adaptation to epiphytal conditions? Here 

 induction must suffice ; and the conclusion is 

 as in all other cases forced upon us that the 

 same natural law holds good with them as in 

 all other cases. 



Darwinians will not allow that variations 



1 Our common English polypody often takes to the habit of growing 

 011 trees by roadsides, etc. 



