WEEDS AND WEED-CUTTING 351 



preserved, while those which do not usually hold any 

 great number of nymphs, shrimps, etc., should be 

 ruthlessly cut away. 



It might be convenient here to set out for the 

 information of the reader the 

 Suitable and unsuit- weeds among those generally 

 able weeds. present which are most favour- 



able and those which are less 

 favourable. Probably the best of all the usual chalk- 

 stream weeds is the water celery {Apium inundatum), 

 as it always contains great numbers of dun nymphs, 

 shrimps, caddis, and other forms of animal life. The 

 water starwort {Callitriche vernus or C. autumnalis) 

 is a weed usually containing a fair quantity of food 

 for the fish. The water crowfoot {Ranunculus aqua- 

 tilis) is a very prominent water-weed, and generally 

 holds a considerable quantity of caddis and a few 

 Ephemeridae nymphs. It is a somewhat curious cir- 

 cumstance that in an aquarium used for observing the 

 habits of these insect larvae and nymphs the presence 

 of water crowfoot in any great quantity is, as a rule, 

 fatal to the dun nymphs. The so-called American 

 weed {Elodea canadense) is not good for any stream. 

 It tends to choke up the water, and does not seem 

 favourable for the food affected by the fish. Ribbon- 

 weed (Sparganium ramosum) is the home of the 

 larvae and pupae of Simulium and other smuts in the 

 chalk-streams. 



When dealing with comparatively deep and slow 

 water it is advisable to adopt the system of weed- 



