PAULSON : NOTES ON THE ECOLOGY OF LICHENS. 283 
if lie had made any observations on the rate of growth of these 
plants, he sent me in one of his letters the following :— 
“ On the border tiles (stone, slate, with much mica), in my 
garden, are many fine specimens of SquamaYia saxicola. These 
are very rapid growers and develop as much as 2.5 cm. within a 
few months. They soon come into bearing apothecia, but as 
a rule do not last more than two or three years, soon becoming 
abraded in the centre, then gradually dying away, to be replaced 
by new plants. I have known this species in one situation 
(one single plant only) for 25 years. It never seems to increase 
in the slightest and is always full of apothecia. It occurs on 
a sandstone step of a stile leading into a field from the main 
road over which I should think 50 to 100 people pass daily, 
and does not appear to have suffered any accident all that time." 
“ Many Verrucariae growing about the outlets of drains, on 
backyard tiles, and in such places, and a depauperated form of 
L. coarctata, though well fruited, appear to be annual growths." 
Since I last exhibited a series of photographs that threw 
some light upon the rate of growth of lichens, there has 
appeared a paper entitled “ The Rate of Growth and Ecesis in 
Lichens "® b}' Bruce Fink. He gives the results of a series of 
measurements of the rate of growth of various lichens taken at 
two well-separated stations, some hundreds of miles apart. 
In the summary, he states that foliose lichens increase in dia¬ 
meter from 0.3 to 3.5 cm. per year. Parmelia caperata (sterile), 
measuring from 1.2 cm. across, reached in eight years 10 by 13 cm. 
As far as I have been able to take measurements of increases, 
they are as follows:— 
Exact Measurements. 
Parmelia physodes, on a fence, increased in one year from 
0.9 to 2.0 cm. in diameter. 
Parmelia physodes, on wortleberry, increased in two years 
2.0 cm. 
Parmelia fuliginosa var. Icetevirens, on elder, increased in 
two years. 1.75 cm. 
Approximate Measurements. 
Parmelia saxatilis, on plane tree, 1 year, 2.7 cm. 
Parmelia caperata, close to the sea, increased in two years 
4.5 cm. 
Ramalina cal dear is, on cone of Pinus Pinaster, in two years 
had branches 3.1 cm. in length 
6 Mycolegia, ix., pp. 138-158 (1917)* 
