182 Plant Life and Evolution 



in the ocean. Struggling for light in the fierce 

 competition in the tropical zones, climbing plants 

 of many types have been evolved, and many epi- 

 phytes, or air plants, may be seen perched almost 

 at the very tops of lofty trees. Some species, like 

 the giant Rafflesia, are parasites of the most ex- 

 treme type, and pass nearly their whole existence 

 within the tissues of their host, exactly as a fungus 

 does, and like the fungus they expand their repro- 

 ductive parts in the air. A still larger number are 

 more or less completely saprophytic, extracting their 

 nourishment from the organic debris of the forests, 

 much as the toadstools and other larger fungi do; 

 but it may be stated that in order to do this they 

 seem obliged to call in the assistance of a true 

 fungus, with which they always seem to be asso- 

 ciated. These are but a few of the manifold 

 adaptations shown by this protean plant-type. 



SUMMARY 



While the early history of the angiosperms is 

 wrapped in obscurity, the evidence at hand indicates 

 that the first angiosperms probably appeared rather 

 suddenly towards the end of the Mesozoic. Whether 

 they arose from gymnosperms, possibly allied to 

 cycads of the Mesozoic, or whether they were de- 

 rived more directly from some fern-like ancestors, 

 must for the present remain unanswered. The re- 

 markable uniformity in their essential structures, 



