The First Land Plants 



crop through inoculation, the evidence seems on the 

 whole distinctly against nitrobacterine. Every attempt 

 seems to have been made to make the trial as complete 

 and as fair as it could possibly be. 9 



But though all these three cultures (nitragin, nitro- 

 culture, and nitrobacterine) are found to-day not to 

 answer when tried commercially by ordinary gardeners 

 and farmers, the ideal of a tamed bacterial population 

 which one can cherish in test-tubes and sow carefully in 

 spring-time with a distinct prospect of an abundant 

 harvest will assuredly be obtained if only people will not 

 be discouraged by these repeated failures.* 



But nitrates form but one of the many salts which 

 must somehow be gathered in by the roots which have 

 to provide a constant stream of water for all the grow- 

 ing or active cells. 



The layer of soil upon which plant life depends is ex- 

 ceedingly thin. It is hardly ever more than a few feet, 

 and often is but a very few inches in thickness. But 

 one requires a touch of imagination, of sympathy with 

 bacteria and with earthworms, if one is to at all appre- 

 ciate the wonderful character of the processes at work. 

 The earth itself is porous and crumbly, made up of 

 tiny sharp-edged particles utterly irregular in shape, 

 varying in size, and of the most different constitution. 

 Some are organic, others inorganic ; there may be 

 particles of sharp quartz which have defied plant action 

 from the beginning of the world, and beside them silt 

 or sand fragments which have been devoured by worms, 

 rolled by water, attacked by acids, and utterly trans- 

 formed in every geological period from the Silurian to 

 our own days. One has first to realise the labyrinth of 



* Full details of the tubercle bacteria will be found in Chittenden, I.e. ; also 

 Bull. U.S.A. Agriculture Plant Industry, 71, 1905, and especially Jacobitz, 

 C. B. f. Bact., Jena, 1901 Nos. 22-24. 



48 



