8 Introductory 



' barren fields ' are also part of the great world's farm, 

 an outlying part, it is true, where the produce is not 

 large: but, such as they are, the crops are needed, 

 for there are glacier-fleas and other live-stock even 

 here, and these tiny vegetables supply them with 

 food. 



Nature's labourers are such zealous and thrifty hus- 

 bandmen that they are always on the watch to occupy 

 every inch of space where anything can be grown the 

 moment it is vacated, and even before. They will 

 overrun our gravel paths, and grow grass in our streets 

 if allowed, and they will take but a very short time 

 to convert the most highly cultivated garden into a 

 wilderness without any trace of a path in it, if it be 

 given up to them. This is true even in such temperate 

 climates as our own, but in warmer latitudes the 

 incessant struggle of the wild crops to invade and 

 recover the ground which they have lost is still more 

 marked. 



At Pard, in Brazil, for instance, we are told that 

 every lane, yard, and square is a battle-ground. Even 

 the roofs and cornices of some of the public buildings 

 are occupied by plants or small trees, which wave their 

 feathery heads aloft like flags of triumph in defiance of 

 the enemy. The city is hemmed in by a wall of tropical 

 forest, consisting of giant trees, palms, and tangled 

 creepers, which ever and anon send out skirmishers to 

 try and effect a lodgment in the enemy's territory ; and 

 so well do they succeed where circumstances favour 

 them, that a large square, which was cleared and turfed, 

 but left unguarded, was covered in five years' time with 

 a tangled mass of vegetation fifteen feet high, and 

 denser than the virgin forest. 



