70 



POPULAR HISTORY OP LICHENS. 



these generally become fused into a homogeneous mass, 

 which is frequently of an oily nature. The spores are lightly 

 agglutinated to each other by the mucous protoplasm from 

 which they were first developed, but at no period of their 

 development are they attached to the walls of the theca or 

 its spore-sac. Where they exist to the number of eight or 

 upwards in a theca, they have appeared to us to be arranged 

 usually in a spiral manner. From the disappearance of 

 the thecal walls prior to the maturity of the spores, they 

 sometimes appear naked, or extra thecal. When mature 

 they escape from the theca by rupture of its apex ; they 

 then find their way to the surface of the thalamium, in gym- 

 no carp on s species, whence they are removed by the winds or 

 rains. In the Angiocarpi they accumulate in the cavity of 

 the thalamium, and issue by the terminal pore or fissure ; 

 in some species, by their agglomeration, they form pulveru- 

 lent or scobiform masses on the surface of the thalamium, 

 which appears covered with a bluish-black dust. In germi- 

 nating, one or both ends of the spore usually become lighter 

 in colour : gradually a bulging takes place, apparently by 

 projection of the endospore, or inner membrane, through a 

 rupture or solution of continuity in the epispore, or outer ; 

 this bulging is prolonged into a filament, whose ramifications 



