THE 
NEW PflYTOIiOGIST. 
Vol. XII, No. I. 
January, 1913 . 
[Published Jan. 31st, 1913]. 
SOME CASES OF PLANTS SUPPRESSED BY 
OTHER PLANTS. 
By C. A. M. Lindman (Stockholm). 
[With Plate 1 and one Figure in the Text]. 
I. 
E VERY botanist is well acquainted with the fact that certain 
plants of considerable size and dense growth exercise an in¬ 
fluence disadvantageous to much of the accompanying flora : the 
deep shade cast by such plants prevents many species from attaining 
a normal development and finally kills them. The common nettle 
for instance, Urtica dioica, is able to suppress other plants entirely, 
so that if a large Urtica -group is cut away, there will be seen no 
other vegetation on the central parts of the area occupied by the 
nettles, the soil being quite bare. The International Phytogeo- 
graphical Excursion in the British Isles (1911) visited the woods in 
the neighbourhood of Honley, Yorks., and the party had the oppor¬ 
tunity of admiring the gigantic form of Pteridium aquilinum , widely 
distributed in shady woods on the slate, and differing from the 
dwarf form on siliceous grasslands. 1 Pteridium also is a plant 
which grows so densely that it may exclude all herbs and grasses. 
I have seen the same species in South Brazil, where it forms 
enormous thickets very much higher than in Britain (leaves are 
met with 6 to 7 m. long; at Honley I saw leaves 2 m. long.) In 
Brazil, however, this fern grows abundantly, chiefly in sunny 
places where the forest has been destroyed 2 , and consequently it 
has there not quite the same biotic influence as ia the British 
1 See T. W. Woodhead, “ Ecology of Woodland Plants.” Journ. Linn. 
Soc., Bot., 1906, p. 368; also A. G. Tansley, “ Types of British Vege¬ 
tation,” 1911, Plate 1. 
2 Mentioned by P. W. Lund in 1835, and E. Warming in “ Lagoa Santa,” 
1892, &c. 
