The First Land Plants 



hurriedly form spores and await better times. The whole 

 complex life of the soil is almost at a standstill. 



Then the rain stops, and sun and wind dry up the 

 surface so that the water evaporates and the air passages 

 become free again. Then at once, with the advent of 

 revivifying oxygen, the whole complex machinery of 

 underground life awakes again to vigorous activity and 

 is in full working order. 



Catastrophes are often blessings in disguise, as, e.g., a 

 hard frost, which not only pulverises the soil but is in 

 the end most beneficial. 



The fungi vanish, turning black at the first touch of 

 frost ; the leaves and stems of summer herbaceous plants 

 fall off or become sodden, flaccid, and horrible, and 

 nothing is left but the roots and underground stems, 

 with their carefully stored up starches and proteids. 



The bacterial population is massacred wholesale, for 

 only a few of the strongest and hardiest microbes refuse 

 to be killed. 



But when the spring comes, the new bacterial races 

 are all specially selected stocks, and the best of their 

 kind. So also are the fungi, and even the weed-seeds 

 and flower-roots. It follows that the new population 

 starts strong and efficient on another year of adventure 

 and hard work, for all its forefathers were healthy and 

 sound. 



When, for instance, such a manure as carbon bisul- 

 phide is used on arable land, the first result is a horrible 

 diminution of the bacterial population, but after a time 

 the bacteria begin suddenly to increase in numbers and 

 flourish exceedingly. This is explained by the fact that 

 all except the very strongest have been slain. 



In a recent report on the grouse disease on over- 

 stocked moors, the usual sequence of disastrous years, 

 followed by a sudden run of good seasons, seems to be 



5i 



