SAPROPHYTISM AND SYMBIOSIS 



329 



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,. 



