140 



PRACTICAL BOTANY. 



are attached to the supporting surface by a very small 

 area and rise from it with branching treelike forms. 

 Such Lichens are called fruticose. (Fig. 79, A.) 



The sexual reproduction is known to exist in Lichens, 

 at least in some species, but is as yet imperfectly 

 understood. 



By the asexual method of reproduction, spores are 

 produced in sacs. (Figs. 77 and 81.) These sacs are 



Fia. 79. A, Usnea barbata, a fruticose Lichen; B, Sticta pulmonacea, a 

 foliaceous Lichen ; a, a, a, in both figures, apothecia. (Goebel.) 



sometimes wholly inclosed in the tissues of the Lichen ; 

 sometimes they are grouped in circular masses that show 

 conspicuously as disks on the surface of the thallus. 

 (These may be seen in Figs. 78, 79, and 82.) They 

 are to be studied by making sections through these disks. 

 Material for practical work may be kept in the dry 

 condition indefinitely ; upon being wet, the dried Lichen 

 resumes its active existence. 



