242 



POPULAR HISTORY Otf LICHENS. 



or colourless, — having finely granular or transparent con- 

 tents. They bear a resemblance to those of Pertusaria, but 

 are more irregular in form ; this irregularity is usually due 

 to the adhesion of abortive spores, which are so common in 

 this species, that of eight spores in eaot theca only one or 

 two usually attain maturity and become fertile. The sterile 

 or abortive spores of Lichens are sometimes indistinguish- 

 able in size or colour from fertile mature cells ; but they will 

 generally be found partially or wholly deficient in granular 

 or oily protoplasm, which is essential to their germination, 

 b. Apothecia variously coloured, within white. 

 t Apothecia variegate. 



8. Lecidea sph^eroides (sphm-a, a sphere or globe). 

 Thallus leprose, w r hite, covered with greenish granules, some- 

 time deliquescing into a pulverulent mass. Apothecia white, 

 becoming yellow, pale red, black-pruinose, at length black, 

 flat, marginate, or convex and immarginate, solitary, aggre- 

 gate or confluent. (E. B. 1683, var. effusa ; 2217, var. mus- 

 corum; 2547 and 2699, var. viridescens.) 



In some of its numerous varieties common in lowland 

 and subalpine districts, growing on trees, dead wood, decayed 

 moss and heather, and the ground ; some forms are peculiar 

 to moist lowland woods, others to Highland mountains. 



