DARWINISM 95 



Linnaeus, a century before Darwin, had called attention 

 to the fact that if an annual plant produced only two seeds 

 a year, and each of the plants from these seeds, in turn, 

 produced two seeds the second year, and so on, there would, 

 if all the individuals lived, be a million plants at the end of 

 twenty years. But, few species breed as slowly as that. 

 According to Kerner, the common broad-leaved plantain 

 (Plantago major) produces 14,000 seeds annually; shep- 

 herd's purse (Capsella Bursa-pastoris), 64, 000; and tobacco, 

 360,000. The number of seeds produced each year by the 

 orchid, Acropera, was carefully estimated by Darwin at 

 74,000,000. But these figures are wholly surpassed by 

 the ferns. Professor Bower estimates the number of 

 spores produced each year by a well grown specimen of the 

 shield fern (Nephrodium filix-mas) at from 50,000,000 to 

 100,000,000, while the estimate for the fern Angiopteris has 

 been placed at 4,000,000,000 spores for a single leaf. One 

 plant may have as many as 50 or more spore-bearing 

 leaves. It has been pointed out that, at these rates of 

 increase, unrestricted, a given species of plant would, in 

 two or three years, cover an area several thousand times 

 that of the dry land. But nothing of the sort occurs. 

 There must, therefore, be an intense struggle for existence, 

 in which the vast majority of individuals perish. Darwin^ 

 gives the following illustration: 



"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 

 1 "Origin of Species" (New York, 1902 edition), pp. 83, 84. 



