LECANOKA. 



221 



have found various saxicolous varieties of Z. pallescens, es- 

 pecially isidioid, variolarioid, or tartareous forms, from dif- 

 ferent habitats, — maritime, lowland, and alpine, — to yield 

 good qualities of orchill; corticolous varieties are usually 

 too thin and scarce to be so employed. Under the name of 

 " White Crottle," isidioid saxicolous forms have been used 

 by the peasantry of this and other countries, in the prepara- 

 tion of a red or crimson dye. As a general rule, the isidioid 

 or coralloid form of all crustaceous Lichens may be set down 

 as colorific. The spores of vai.jparella are large, oval, double- 

 walled, the epispore being delicate, transparent, and colour- 

 less ; the endospore, on the contrary, thick, and its contents 

 granular and oily, sometimes having a faint yellow tinge. 

 The two coats are usually more or less closely united, requir- 

 ing the use of reagents to dissociate and render them distinct. 

 After the escape of its contents, the spore appears as a large 

 pellucid or hyaline vesicle, frequently corrugated or plicate. 

 In the young state the endospore frequently contains a large 

 central, globular cell, surrounded by granular matter, mixed 

 with a considerable amount of oil-globules. The germina- 

 tion of these spores is peculiar. When first discharged from 

 the theca their outer coat is transparent, but it soon be- 

 comes opaline, a change probably due to disaggregation of 



