Rate of Growth and Ecesis in Lichens 157 



uncialis in a denuded quadrat on thin soil regenerated new plants 

 of full size in 4 years, from fragments thrown over the quadrat. 



Verrucaria mgrescens became established in a denuded lime- 

 stone quadrat and produced apothecia in 6 years. Placodium 

 aurellum became established on limestone and produced apothecia 

 in 4 years. Placodium micro phyllinum became established on a 

 new plane-tree board in 2 years and produced apothecia in 6 

 years. Lecanora dispersa became established on limestone and 

 produced apothecia in 6 years. Pyrenopsis schaereri and Col- 

 lema pustulatum became established on denuded limestone in 8 

 years, and Placodium sideritis became established and produced 

 apothecia in the same time. Pannaria nigra became established 

 and produced apothecia on denuded limestone in 7 years. Endo- 

 carpon pusillum grew and became established and produced 

 apothecia on limestone in 4 years. Amphiloma lanuginosum be- 

 came established on denuded sandstone conglomerate and was 

 plainly visible after 4 years. Cladonia pyxidata, C. fimbriata, 

 and C. mitrula. became established on soil in a denuded quadrat 

 and reached normal size in 5 years. Cladonia pyxidata and 

 C. cristatella became established on denuded rock and produced 

 podetia and apothecia of normal size in 8 years. Cladonia 

 subsquamosa became established on denuded sandstone con- 

 glomerate and produced podetia and apothecia of normal size in 

 8 years. 



Certain crustose lichens become established and produce thalli 

 and apothecia in denuded areas in 2 to 8 years. Foliose lichens 

 increase in diameter from 0.3 to 3.5 cm. per year. Cladoniae 

 regenerate squamules in one or two years and podetia in 3 or 4 

 years, and these plants become established by succession in 4 to 

 8 years. 



So far as external appearance goes, lichens produce apothecia in 

 their natural habitats in 1 to 8 years ; but, except in instances of 

 primary succession, it is not certain but that the primordia of 

 apothecia were present within the thalli at the time that the various 

 studies given herein were begun. From the studies of primary 

 succession, it would seem that the full development of apothecia 

 to the point when they assume their mature form requires from 

 4 to 8 years when the plants are growing in their natural habitats. 



