458 THE ECOLOGY OP PLANTS. 



18. How could you distinguish between Ling, Bell Heath, Cross- 

 leaved Heath, and Crowberry, merely from leaf-bearing branches 

 without flowers ? Describe the structure of the leaf in each of these 

 four plants, and explain how the structure is adapted to the habitat. 



19. Describe the flowers of Ling, Bell Heath, and Cross-leaved Heath, 

 pointing out their differences and explaining the pollination mecha- 

 nism. 



20. Describe the flowers and fruits of Crowberry. Compare this plant 

 with the Ericaceous moorland plants. 



21. How can you explain the fact that most moorland plants, e.g. 

 Ling, Heaths, Crowberry, are protected against free transpiration, 

 although moors get so much moisture in the form of rain and mist ? 



22. Why is the vegetation of a high moor dwarfed, with no trees, 

 while low moors (heaths) are often dotted with tall trees? 



23. In what respects do many moorland plants agree with plants 

 growing on sandy coasts and in salt marshes ? How may these resem- 

 blances be explained ? 



24. What is the difference between a marsh and a bog ? 



25. Name several different species of plants that you have found at 

 the seaside and not inland. State exactly where and how each was 

 growing, and mention any characters possessed by each that you think 

 fitted it to its particular circumstances. 



26. Give an account of the vegetation of sand-dunes in any region 

 you may select, and point out the special adaptations exhibited by the 

 plants to their surroundings. 



27. Mention six plants you have found growing (a) on shingle- 

 beaches, (6) in salt marshes. Distinguish between those occurring only 

 in these habitats and those you have also found inland. 



28. Mention eight plants that you have found growing in each of any 

 three of the following situations : Cornfields, Freshwater Bogs, Shingle 

 Beaches, Sandy Heaths. 



29. What plants would you expect to find in any three of the follow- 

 ing places : (a) an open heath, (6) a salt marsh, (c) a Freshwater pond, 

 (d) chalk downs ? 



30. What would you infer as to the characters of the soils in which 

 the following plants were severally to be found growing? Spurrey 

 (Spergula arvensis), Coltsfoot, Rush (Juncus communis), Cotton Sedge, 

 Wood Sage (Teucrium), Bee Orchid. 



31. Give several examples of groups of plants which grow together in 

 the same habitat or locality and flower at about the same season. 

 Why do these plants grow side by side, what causes bind them to 

 special localities, and why do they flower simultaneously ? 



