SAPROPHYTISM AND SYMBIOSIS 
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FIG. 236. An orchid (Cattleya sp.) growing as an epiphyte on a portion 
of a branch of white birch. Note the aerial roots. 
FIG. 237. A thallose lichen, Physcia stellaris (L.) Nyb., growing on a 
rock. The cup-shaped structures are the fruiting bodies (apothecia). 
At the left are seen two very young plants. 
