SAPROPHYTIC AND SYMBIOTIC VEGETATION. 51 



its nourishment solely from the air, and propagates itself chiefly by 

 the detached strands of its thread-like stems entwined and fastened on 

 the limbs and branches of the trees. Epidendron* conopseum, a hand- 

 some orchid, inhabits large magnolias and hoary live oaks in the 

 deepest recesses of the same swampy hammock lands, with numerous 

 roots closely fastened to the bark of the largest limbs of these trees. 

 Polypodium polypodioides (P. incanum Sw.) and Polypodium vulgare 

 are frequent inhabitants of trees. They are, however, found to grow 

 also upon shaded rocks and prostrate trunks. 



SAPROPHYTIC AND SYMBIOTIC PLANT ASSOCIATIONS. 



Saprophytes are colorless plants which, as far as those belonging to 

 the phanerogams are concerned, live upon the debris of the vegetable 

 world, deriving their nourishment from the organic matter resulting 

 from its decay. The largest number of saprophytes belong to the 

 fleshy fungi and some of these live upon decaying animal matter. 

 Being destitute of chlorophyll, their vascular system less developed, 

 without breathing pores, their leaves reduced to mere scales, these 

 plants are unable to elaborate the constituents needed for nutri- 

 tion or to change carbonic acid from the air into assimilated food mate- 

 rial. The number of seed-bearing saprophytes occurring in Alabama 

 is small, and widely dispersed through the deep, shady forest, as 

 Apteria Corallorhiza, and Hexalectris of the orchid family, and in 

 grassy, damp swales Burmannias. Hemisaprophytes are green per- 

 ennial herbs of the ordinary structure and habits, which for their 

 nutrition are only partially and to varying degrees dependent upon 

 organic matter. Some live in humid, peaty soils, mostly in the open, 

 for example, some of our club mosses (Lycopodium carolinianum, L. 

 cernuum) and a number of orchids (Limodorum, Pogonia, Habenaria 

 spp.), while others can exist only in a humid soil, rich in vegetable 

 matter, under cover of the forest. 



Symbiots are pale, almost colorless, plants, of waxy appearance, in 

 their organization similar to the saprophytes, and have been until 

 recently regarded as truly parasitic in their mode of living. It has, 

 however, been found that they do not subsist on decomposed vegetable 

 matter, nor are they root parasites. They are true symbiots, being 

 in their existence closely bound up with that of another plant which 

 contributes to their necessities, but is equally benefited by this con- 

 nection; Monotropa and Hypopitys, of the Indian pipe family, belong 

 to this group. Immediately after their germination the rootlets of 

 these plants are infested by the vegetative threads or spawn (mycelium) 

 of a fungus which, as the plant develops, fastens itself upon every 

 root, finally enveloping the rootstock with a thick film, the higher 

 plant drawing its nourishment solely from the elaborated food of the 

 fungus. 



