186 THE BOOK OF NATURE STUDY 



there, and seeds which may be blown by the wind from luggage 

 vans have a very good chance of developing. If near a new 

 railway line a record might be made of the plants that first come 

 up, then of those that follow the next season, and so on. In this 

 way some idea of the struggle for existence that goes on amongst 

 plants will be obtained. In the case of the plants that survive, 

 it will be interesting to try and find out why they can live to- 

 gether ; the depth to which their roots penetrate often suggests 

 an explanation. One may be a surface plant, the other may have a 

 deep-rooted system ; or one may afford just the right degree of 

 shade to the other ; or one may draw on certain food material 

 in the soil that the other does not want. As a rule, plants which 

 are closely allied to each other do not frequent the same habitat. 

 Primroses and Cowslips, both belonging to the same genus, are 

 not only not found together ; but where one is abundant in a 

 neighbourhood, the other is usually scarce. 



A different line of study might be followed. Instead of observ- 

 ing the plants growing together in the same habitat, all the plants 

 of an order might, as far as possible, be examined to find out some- 

 thing of the distribution of that order. The Grasses and the 

 Orchids are found in practically every kind of habitat : there are 

 wood and moor grasses, pasture and wayside grasses ; some are 

 characteristic of riversides, others of bogs. The variety of structure 

 in even such a common plant as a grass is amazing, and can only 

 be realised by putting typical grasses side by side. Some have 

 their leaves spread out, others inrolled ; some are bristly or hairy, 

 others smooth ; some have a divided sheath, others not. All 

 these differences have a meaning, which can often be explained 

 by reference to the habitat. With Orchids there is immense 

 variety. Some are adapted for life in a bog, others for life on a 

 limestone pasture ; some are found at the edges of woods, others 

 like the deep shade of the beech. 



The different species of any genus might be studied in the 

 same way ; thus one species of the Forget-me-not will be found 

 by the stream, another on the side of dusty roads. One 

 species of Ranunculus is a corn weed, another floats on ponds, 

 a third is characteristic of meadows, a fourth of marshes on 

 moors or in woods, a fifth belongs to hedges ; and all these 



