Rate of Growth and Ecesis in Lichens 



147 



thalli averaging 0.25 to 9 mm. across in various directions. Some 

 of the plants were in groups of 2 to 15 or 20; and the individual 

 plants of the groups were often too small to be seen without the 

 hand lens. All the plants left were sterile. After 10 months the 

 plants had grown but little, the largest one being but n mm. 

 across. After 4 years 1 plant was found 13.7 by 14.3 mm. across 

 and another 11.3 by 12.5 mm. across. The remainder of the 

 plants averaged for most part from 0.4 to 1.5 mm. across in 

 various directions. All were still sterile. 



Ohio, area 13, a quadrat 19 cm. square, plotted on a boulder 0.7 

 m. high, 2 m. from a brook in a damp wood. The quadrat was 

 thoroughly scraped with a knife blade, and only minute particles 

 of Physcia endochrysea, Leptogium lacerum, and the small num- 

 ber of mosses and leafy hepatics interspersed were left adhering 

 to the surface of the rock. After 1 year Physcia endochrysea 

 was returning in 30 areas, varying in size from those barely dis- 

 tinguishable under the hand lens to others 1 mm. across. 

 Leptogium lacerum was returning in several spots in the quadrat ; 

 but the plants were visible only under the hand lens. Bryophytes 

 were also returning and gave a green coloration to portions of the 

 quadrat not covered by lichens ; but their gross structure was dis- 

 tinguishable only under the hand lens. After 2 years Physcia 

 endochrysea was found growing in 60 spots in the quadrat ; and 

 the plants varied from 0.2 to 1.5 cm. across. Some of them were 

 visible 60 m. distant. The other plants showed little change. 

 After three years the largest Physcia endochrysea was 1.75 cm. 

 across, and 10 others were 1 cm. across or larger. The 

 bryophytes covered a considerable portion of the remaining area, 

 and the plants were as large as those surrounding the quadrat. 

 The remainder of the quadrat was covered mainly by Verrucaria 

 nigrescens sparsely fruited. Poorly developed thalli of this lichen 

 were probably present when the quadrat was plotted, but were 

 covered by other lichens and bryophytes and grew rapidly only 

 after the cover plants had been removed. At this time and at 

 later periods only 3 or 4 minute centers of Leptogium lacerum 

 were found within the quadrat. After 7 years Physcia endo- 

 chrysea and the bryophytes covered about three- fourths of the 

 quadrant in approximately equal areas, and Verrucaria nigrescens 



