Ch.XIV] the hysterophytes 577 



falling leaves and bark as a store of humus, as in some Ferns, 

 notably Platycerium (Fig. 128), and in another way the 

 Bird's Nest Fern (Asplenium Nidus). Pendent Epiphytes ; 

 as in Tillandsia usneoides, the Long Moss, and some Lichens ; 

 often absorbing water through stem and leaves under capil- 

 lary scales. Strangling Epiphytes; frequent in tropical 

 forests ; the seed lodges in the crotch of a tree, on which the 

 plant develops epiphytically, but it sends to the ground 

 aerial roots which then develop as stems, often crushing 

 to death the supporting tree (Fig. 385). 



A form of epiphyte is the endophyte, represented by the 

 colonies of Anabcena always present in cavities of Azolla 

 (page 500), or of certain leafy Liverworts. The significance 

 of the habit is not clear, nor have any special vegetation 

 forms been developed. 



C. The Habitats occupied by Half-parasites. 



The difficulty experienced by epiphytes in obtaining water 

 and mineral salts, renders natural the use of the supply 

 in the tissues of the stems on which those plants are sup- 

 ported. Thus originates the habit of the green half-para- 

 sites, of which the principal form is the following. 



Epiphytic Green Half-parasites; typified by the 

 Mistletoe, which is an epiphyte sending haustorial roots into 

 the fibro-vascular bundles of the host plant, whence it draws 

 the water and mineral salts used in the photosynthetic forma- 

 tion of its own food (page 86; Fig. 386). Other forms 

 have a similar habitat on roots in the ground (page 543). 



D. The Habitats occupied by Parasites and Sapro- 

 phytes, i.e., Hysterophytes. 



Autophytic plants are able to form organic food not only 

 sufficient for their own use, but in large surplus. Upon this 

 fact rests the existence of animal life, and of plant parasites 

 and saprophytes. These hysterophytes include some Sper- 

 matophytes, which have been developed from epiphytes 

 2p 



