VI 



The Web of Life 97 



it seems much more true of plants than of animals that 

 between those of the same kind the struggle for existence 

 in a crowded area is very keen. For plants cannot migrate 

 nor combine in mutual aid ; in a crowd the slightly weaker 

 must be smothefed. 



In this matter Darwin is again ready for us with exact 

 observation and experiment. "From observations which I 

 have made it appears that the seedhngs suffer most from 

 germinating in ground already thickly stocked with other 

 plants. . . . The more vigorous plants gradually kill the 

 less vigorous, though fully-grown plants ; thus out of twenty 

 species growing on a little plot of mown turf (3 feet by 4) 

 nine species perished, from the other species being allowed 

 to grow up freely. . . . Seedlings also are destroyed in 

 vast numbers by various enemies ; for instance, on a piece 

 of ground 3 feet long and 2 wide, dug and cleared, and 

 where there could be no choking from other plants, I 

 marked all the seedlings of our native weeds as they came 

 up, and out of 357 no less than 295 were destroyed, chiefly 

 by slugs and insects." 



Perched Plants or Epiphytes. — In temperate climates 

 the only perched plants are those mosses and lichens which 

 sometimes clothe the stems and branches of trees, but in 

 tropical countries many Orchids, Aroids, and other flower- 

 ing plants have this habit. Entirely isolated from the 

 ground, and yet not parasitic on their bearers, how do they 

 live ? In part, of course, like other green plants, on the 

 air and the power of the sunlight ; and it is interesting to 

 notice that they flourish best on trees, such as Cassia and 

 Csesalpinia, whose crown of branches is in the dry season 

 bereft of leaves. For water and mineral matters the 



a lecture entitled "How Plants maintain themselves in the Struggle 

 for Existence," dehvered at Newcastle, September 1889. See abstract 

 in Nature, September 1889. 



H 



