THALLOPHYTA. 



695 



few genera of Pyrenolichenes, including Verrucaria, Ephebe, Endocarpon, and 

 Sphcerophorus. 



Basidiolichenes. These occur only in tropical countries, and a number of genera 

 were formerly distinguished, including Cora, Dictyonema, and Laudatea. Cora 

 pavonia, the best-known form, consists of a greenish-yellow, fan-like, concentrically- 

 striated thallus which produces its basidia on the under surface and contains Chroo- 

 coc<ms-cells as its Alga; Dictyonema, on the other hand, consists of thin plates of 

 rather felty consistency, in which the radiating character of the strands is very 

 apparent; these delicate plates, blue-green in colour, stand out from the tree-branch 

 to which they are attached. Laudatea, though resembling Dictyonema, is a crus- 

 taceous form. Both the latter forms have $c2/o7iema-filaments as Algae. Quite 



Fig. 394. Lecanora esculenta. 



recently it has been shown by A. Moller, a naturalist who resided several years in 

 Brazil, that all these supposed distinct Lichens are different growth-forms of one 

 and the same Lichen. In addition to finding each of these forms in connection 

 with the other so that there is no doubt of their continuity he found attached to 

 the Cora-form the Fungus growing free from all trace of the Alga; this Fungus is 

 one of the Telephorese (cf. p. 688), and when it is supplied with Chroococcus-ceHs 

 grows into the Cora-form. This seems to be the only well-ascertained instance in 

 which a Lichen-fungus has been found growing wild independent of an Alga. The 

 Dictyonema- and Laudatea-iorms consist of the same Fungus growing upon Scyto- 

 nema instead of Chroococcus. In the Laudatea-Horm the Alga seems to get the 

 upper hand and to determine the growth of the thallus. Cora and its various 

 growth-forms is certainly the most interesting, as it is also the most beautiful of all 

 Lichens of which we have any knowledge. 



Gasterolichenes. A Lichen from the Gasteromycetes has also been recognized; it 

 is a little, shortly-stalked, puff-ball-like form resembling a Lycoperdon (cf. p. 690). 

 The Alga (a Palmella) is restricted to the peripheral portions of the Lichen, which 

 is named Emericella variecolor. 



