34 VAGABOND SPECIES [CH. 



p. 28), and need not be further specified. In gaps, 

 borders, and copses — half-shade — we find several common 

 grasses — e.g. 



are more likely to be met with in the deep shade inside 

 the forest. 



On the other hand there are vagabond grasses which 

 seem to show no signs of preference for one soil over 

 another — e.g. Poa annua — though in some cases these 

 ruderal plants indicate the presence of rotting substances, 

 on ash-heaps and rubbish of various kinds. 



With reference to the above, however, the student 

 must not forget that very complex relations are concerned 

 in changes of soil, shade, moisture, elevation, &c. and that 

 although experienced observers can draw conclusions of 

 some value from the presence of ivmnerotis species and 

 individuals on a given soil, no one must conclude too 

 readily that a soil is so and so, from observing solely that 

 a particular kind of grass will grow there. 



An excellent example of what may be done by applying 

 such knowledge as exists of the habits of grasses, is 

 afforded by the historic case of the planting up of shifting 



