STRATOSE THALLUS 91 



Pannoparmelia anzioides, a. species from Tierra del Fuego (Fig. 51). A some- 

 what dense interwoven felt of hyphae occurs also in certain parts of the 

 under surface of Parmelia physodes^. 



This peculiar structure, regarded as a hypoth alius, is probably of service 

 in the retention of moisture. The thick cell-walls in most of the forms 

 suggest some such function. 



E. Structures for Protection and Attachment 



Such structures are almost wholly confined to the larger foliose and 

 fruticose lichens and are all of the same simple type ; they are fungal 

 in origin and very rarely are gonidia associated with them. 



a. Cilia. In a few widely separated lichens stoutish cilia are borne, 

 mostly on the margins of the thallus lobes, or on the margins of the apo- 



Fig. 52. Usneaflorida Web. Ciliate apothecia (S. H., Photo.). 



thecia (Fig. 52). They arise from the cortical cells or hyphae, several of 

 which grow out in a compact strand which tapers gradually to a point. 

 Cilia vary in length up to about i cm. or even longer. In some lichens they 



' Porter 1919. 



