CONTENTS. 



Page. 



Introduction 255 



Historical 255 



Species of Potamogeton investigated 260 



General survey of life conditions of the species investigated 261 



P. americanus 261 



P. amplifolius 261 



P. heterophyllus 262 



P. perfoliatus 263 



P. crispus 264 



P. zosterifolius 264 



P. obtusifolius • 265 



P. filiformis 265 



P. pectinatus 265 



P. Robbinsii 267 



Summary of cultural features 268 



Natural and artificial propagation 268 



Propagation by tubers 269 



Propagation by tuberous rootstocks 272 



Propagation by subterranean stems not tuberous 273 



Propagation by winter buds 273 



Propagation by bius 274 



Propagation by fragments of stems 277 



Propagation by seeds 278 



Production of seeds and vegetative propagative structures 279 



Economic aspects of Potamogetons 281 



Species of Potamogeton and the animals foraging upon them 284 



Conclusion 285 



Bibliography 286 



Explanation of plates 289 



19371°— vol 33—15 17 253 



