MAN'S FOOTPRINTS. 277 



these would quickly perish from off the earth if 

 left to themselves. 



There is, however, a class of plants which 

 indicate man's presence in the forest, although 

 they are never planted by him. Wherever a 

 clearing is made, no matter how far it may be 

 from others, certain species come to the front 

 that are never to be found in the virgin forest. 

 Among them may be mentioned the silver fern 

 (Gymnogramma calomelanos), certain thorny 

 solanums, grasses, and scrambling vines. These, 

 like the weeds of more populous countries, follow 

 man wherever he goes, but do not spread outside 

 the forest region to any great extent. In presence 

 of the great army of cosmopolitan weeds of the 

 tropics they are obliged to give way, but in their 

 own particular environment they flourish to per- 

 fection. It sometimes appears as if their seeds 

 have lain dormant in the earth for indefinite 

 periods perhaps centuries and are only brought 

 to the surface when the soil is disturbed, otherwise 

 it is hard to say how they came into the new 

 clearing. An orchid (Catasetum discolor) is found 

 in great numbers about old charcoal pits, and here 

 we have another example of the result of turning 

 up the soil. Similar behaviour has been noticed 

 in certain wild flowers which grow in the woods of 



