THE BATTLE OF LIFE AMONG PLANTS. 83 



In a previous set of experiments the Giessen professor had ascer- 

 tained that the particular plants under observation grew equally well 

 in all the varieties of soil in which they were placed, provided due 

 care was taken to prevent the growth of intruding weeds. Having 

 arrived at this result, Prof. Hoffmann next left the several plants to 

 themselves, with a view of ascertaining how they would comport 

 themselves, without assistance, against the inroads of weeds. The re- 

 sult was, that the weeds completely gained the upper hand, as might 

 have been expected from their known habit. The species which held 

 out longest was Asperula cynanchica. This plant, after having been 

 grown in a bed for three years, and protected from weed-invasion by 

 the use of the hoe, was then left to take care of itself. It held out for 

 four years, but was ultimately elbowed out by the intruders. Acting 

 on the principle of " set a rogue to catch a rogue," Prof. Hoffmann 

 then set himself to observe the results of the internecine struggle 

 between the weeds themselves, thinking that the ultimate survivors 

 would perhaps prove to have special affinities for the soil in which 

 they grew. 



Thus left to themselves, the beds became so densely covered, that, 

 in a square foot, the professor counted 460 living plants, and the rem- 

 nants of many others, which had succumbed in the encounter. Every 

 year, in July, the plots were examined, and every year the number of 

 species was found to have diminished. Melilots, at first abundant, 

 gradually disappeared ; Artemisia vulgaris succumbed after two or 

 three years ; and so on, till at length only a few species were left, and 

 these not only persisted, but slowly gained ground from year to year, 

 and ultimately remained in possession of the plot. The plots under 

 observation were 2 metres 30 cents, long, 1 metre broad, and all as 

 nearly as possible under the same conditions, save that the soil was 

 varied, in some cases consisting of the ordinary soil of the garden, in 

 others of an admixture of lime, in others of sand, or of sand and lime, 

 and so forth. 



Of the 107 species under observation, all, or nearly all, found the 

 most essential requisites of their existence equally well in all the vari- 

 eties of soil ; so that, other conditions being equal, the nature of the 

 soil was indifferent. The species which remained victors, all the 

 others being ultimately dispossessed, were Tritieum repens (couch), 

 Poa prate?isis, Potentilla reptans, Acer Pseado Platanus (sycamore), 

 Cornus sanguinea, native plants ; and Aster salignits, A. parviflorus, 

 .Euphorbia virgata, and Prunus Padus, derived from other portions 

 of the garden. 



It may, therefore, be inferred that the district in which these ex- 

 periments were made would, in process of time, if no obstacle were 

 afforded, become covered with meadows and woods meadows in the 

 low ground and woods in elevated places. Again, the experiments 

 show that the survival of certain plants has not been influenced by the 



