THALLOPHYTA. 



695 



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



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

 were formerly distinguished, including Cora, Bictyonema, 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- 

 coccus-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 Scytonema-hlnmenta as Alg^. Quite 



Fig. 594.— 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-iorm 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-ceWs 

 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-iorma consist of the same Fungus growing upon Scyto- 

 nema instead of Chroococcus. In the Laudatea-iorva. 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. 



