54 THE BOOK OF NATURE STUDY 



(b) By the banks of streams, rivers, and lakes. The Upright- 

 leaf association. 



(c) In ponds, lakes, and in the river. The Floating-leaf 

 association. 



(d) In marshes. Often a combination of pasture and aquatic 

 plants will be found. 



(e) Submerged plants, found in ditches and shallow pools. 

 The special organ to observe in detail is the leaf, the structure 



of which varies considerably. 



II. The difference in the leaves of the same plant when in 

 water, and when out of water. The Brooklime and the Water 

 Crowfoot are typical plants to observe in this connection. 



III. The absence of hairiness in water plants. There are a 

 few plants growing by water which are undoubtedly hairy. A 

 list should be made of these, and compared with the same species 

 growing inland, in order to ascertain whether the plants growing 

 by the water are more or less hairy than those inland. The 

 Meadow-sweet and the Forget-me-not give good results. 



IV. The effect of growing land plants submerged in water. 

 This may be observed under natural conditions, as in the over- 

 flowing of a pond or river ; or under artificial conditions. The 

 seedlings of plants, which normally grow in damp places, might 

 be grown in an aquarium or large tank, and the results noted. 

 Similarly, the result of growing water plants out of water may 

 be tried, and the one set of results compared with the other. 



V. The influence of man, seen in 



(a) The draining of marshy districts, with the result that 

 certain species are becoming extinct. 



(6) The altering of the level of lakes ; or the creation of 

 lakes. 



(c) The pollution of rivers, especially in country districts, where 

 sewage arrangements are sometimes non-existent. 



(d) The abandoning of mills and of brick-ponds. Under 

 these circumstances, nature is left undisturbed, and there will 

 probably be a succession of Plant associations. This kind of 

 observation is practicable for class work in those localities which 

 have mills, or brick fields, within easy reach of them. 



VI. The effect of running water on Hedgerow vegetation. 



