THE STM^E SKTTINd 



to their cnviroiuncnt is the luihitat. Kltoii ' in his iiiteivstiiijr intro- 

 duction to ecology cU^scribes the attack on a ceilain ccolofrical prob- 

 lem in these words : 



"Suppose one is studying the factors limiting the distribution of animals 

 living in an estuary. One would need to know amongst other things what 

 the tides were (but not the theories as to how and why they occur in a par- 

 ticular way) ; the chemical composition of the water and how to estimate 

 the chloride content (but not tlie reasons why silver nitrate precipitates 

 sodium chloride) ; how the rainfall at different times of the year affected 

 the muddiness of the water; something about the physiology of sulphur 

 bacteria which prevent animals from living in certain parts of the estuary ; 

 the names of common plants growing in salt-marshes ; sometliing about the 

 periodicity of droughts (but not the reasons for their occurrence). One 

 would also have to learn how to talk politely to a fisherman or to the man 

 who catches prawns, how to stalk a bird witli field-glasses, and possibly how 

 to drive a car or sail a boat. Knowing all these things, and a great deal 

 more, the main part of one's work would still be the observation and coUeo 

 tion of animals with a view to finding out their distribution and habits." 



This gives us our approach. Our own interests, our reading, and 

 the time involved must largely determine the extent to whicii we 

 solve the ecological problems 

 of our own environment. 



Plant and Animal 

 Associations 



In making an ecological 

 study of living communities 

 we notice that one kind of 

 plant or one kind of animal 

 is never found li^-ing entirely 

 alone. Plants, for example, 

 are associated together by 

 lack or abundance of water ; 

 those living under abundant 

 water conditions being called 

 hydrophytes ; those associated 

 in a condition of moderate 



Water lilies, catta 

 (•haracteristi( 



hulriislu's 

 pliyle."*. 



1 From Elton, Charles. Animal Ecology, p. 35. By permission of The Macmillan Company. 



publishers. 



