32 



ACADEMIC BOTANV. 



dry and leathery, but some are gelatinous, like the Lichina. 



They are 'polymorph- 

 ous (of many forms), 

 often imitating stems, 

 as in the Bearded 

 Lichen ( JJsnea bar- 

 bata). 



A lichen [Lecanora es- 

 culenta) is believed to be 

 the manna which fed the 

 Israelites in the desert. It 

 grows among flints, from 

 which its small, filbert- 



ar;Tnfire°apo«f/oil^""°'" '"'■'"'■"'■ ™ ^ '"""''• ^^R^.-^ thai lus can scarcely 



be distmguished ; and it 

 appears suddenly in such abundance that it is blown into heaps by 

 the winds. It is common in Algeria, Armenia, and Persia, but espe- 

 cially in the mountains of Tartary. One species furnishes the dye 

 called Cuthbert, or Cudbear (Fig. 23). 



Fig. 24. — Iceland Moss {Cetraria island- 

 ica). Single plant. 



57. Thallogens. — The plants 

 thus far examined, from Proto- 

 phytes to Lichens inclusive, 

 consist either of a single cell 

 like the Protococcus, Diatom, 

 and Bryopsis, or of many cells 

 united into a mass called cel- 

 lular tissue, like the higher 

 Seaweeds and the Lichens (Fig. 

 25). The growth is peripheral Ji;^'^^rp^^' ^^ Y^^! 

 (increasing at the circumference 'iiocia; g, gouidia; p, parapiiyses, or 



1 ' n \ ° 1 11 1 1 threads, surrounding the spore-Cases. 



chiefly), and usually broaden- 

 ing horizontally (Fig. 26). Observe these characteristics : 



