Chap. II] GUILDS 201 



may be found growing accidentally in the hollows of old trees ; they 

 occur however only in places where considerable masses of soil facilitate 

 the development of true subterranean roots, and they cannot in any way be 

 considered as epiphytes. 



The varied contrivances by means of which higher epiphytes have 

 become adapted to their mode of life are so closely connected with the 

 conditions of existence in rain-forests and are so characteristic of the latter, 

 that they and the forests should be discussed together. It may now 

 merely be stated that they chiefly belong to the ferns and orchids (Fig. 111), 

 and in America specially to the Bromeliaceae. 



3. SAPROPHYTES. 



Saprophytes constitute a group of plants that dispense with chlorophyll 

 and are therefore dependent on organic nutriment. They obtain this 

 nutriment from dead vegetable and animal substances, and in a more 

 or less decomposed condition according to the particular species. 



The vast majority of saprophytes belong to the Bacteria, Myxomycetes, 

 and Fungi ; the remainder are phanerogams. There are no other classes 

 of plants represented among them. In accordance with their mode of 

 nutrition, all saprophytes, except perhaps bacteria, must be derived from 

 green assimilating plants. Among phanerogams, numerous transitions 

 still exist between purely inorganic and purely organic methods of nutrition. 

 The first stage is denoted by the appearance of the mycorhiza, by means 

 of which phanerogams and ferns were first enabled to utilize the organic 

 constituents of humus. Increasing dependence on the fungus of the 

 mycorhiza, whose role has been transformed from that of a mere supplier 

 of nitrogen to that of a universal provider, has led through numerous 

 intermediate stages to the purely saprophytic mode of life. The sapro- 

 phytic habit has conferred on the plants which possess it the power of 

 occupying stations where, on account of insufficient illumination, green 

 plants can exist feebly or not at all. Like halophytes and epiphytes, 

 saprophytes are also fugitives from the struggle for existence. 



Despite the wide distribution of mycorhiza only a relatively small 

 number of phanerogams, belonging to a few families, have adopted the 

 purely saprophytic mode of life. The majority of these are monocotyle- 

 dons and chiefly orchids, but the small family of Burmanniaceae is chiefly 

 saprophytic, and that of Triuridaceae exclusively so. Among dicotyle- 

 donous plants only Gentianaceae and Monotropeae possess saprophytic 

 species. 



The change in the mode of nutrition causes a change in the structure 

 and oecology of the plant. Chlorophyll having become useless is sup- 

 pressed or transformed into other brown, yellow, or brick-red pigments 

 apparently allied to chlorophyll, and these give to saprophytes a vivid 



