PLANT SOCIETIES 249 



another and noting the variations that they undergo with every change 

 of soil or climate. 



Students in cities can study ecology in parks and public squares, in 

 the vegetation that springs up on vacant lots, around doorsteps and 

 area railings, and even between the paving stones of the more retired 

 streets. A botanist found on a vacant lot near the public library in 

 Boston over thirty different kinds of weeds and herbs, and in the heart 

 of Washington, D.C., on a vacant space of about twelve by twenty 

 feet, nineteen different species were counted. Even in great cities like 

 London and New York, one occasionally recognizes among the rare 

 weeds struggling for existence with the paving stones in out-of-the-way 

 corners, some old acquaintance of fields and roadsides far away. Just 

 where all these things came from, and how they got there, and why 

 they stay there, will be interesting questions for city students to solve. 



But the country always has been and always will be the happy hunt- 

 ing ground of the botanist. All the factors considered in the two pre- 

 ceding sections can hardly be found in any one locality, but mesophyte 

 and hydrophyte conditions exist almost everywhere, and approxima- 

 tions to the xerophyte state can generally be found at some season in 

 open, sandy, or rocky places, along the borders of dry, dusty roads, and 

 on the sun-baked soil of old red hills and gullies. 



If there are any bodies of water in your neighborhood (in cities, 

 visit the artificial lakes in parks), examine their vegetation and see of 

 what it consists. Notice the difference in the shape and size of floating 

 and immersed leaves and account for it. Note the general absence of 

 free-swimming plants in running water, and account for it. Note the 

 difference between the swamp and border plants and those growing in 

 the water, and what trees or shrubs grow in or near it. Compare the 

 vegetation of different bogs and pools in your neighborhood, and 

 account for any differences you may observe ; why, for instance, does 

 one contain mainly rushes, sedges, and cat-tails, another ferns and 

 mosses, another sagittaria, boneset, water plantain, etc., and still 

 another a mixture of all kinds? Compare the water plants with those 

 growing in the dryest and barrenest places in your vicinity, note their 

 differences of structure, and try to find out what special adaptations have 

 taken place in each case. 



Draw a map of some locality in your neighborhood that presents 

 the greatest variety of conditions, representing the different ecological 

 regions by different colored inks or crayons, or by different degrees of 

 shading with the pencil. 



