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-oiiig on a struggle for the mastery, or even for life itself, and 

 the weaker necessarily succumb. Some species no sooner spring 

 up than they are smothered or devoured ; others just manage 

 to live, but in a half-starved state ; or they may thrive sufficiently 

 to retain possession of certain spots, but not be able to extend 

 themselves to any distance. These circumstances -will in part 

 account for some plants being so very common and generally 

 distributed, whilst others are local and rare. Or it may happen 

 in the case of certain plants that, though they cannot spread far 

 Avhere they were first located, the seeds may be transported by 

 winds, or water, or birds, or some other means, to more distant 

 parts, where they are under fewer disadvantages. We then have 

 the case of local plants, growing perhaps in several different 

 localities, but these localities more or less for removed from each 

 other. Sometimes, as we know, seeds carried in one of the above 

 ways, will lie dormant for years, springing up, whenever, from 

 •some change in the circumstances under which they are placed, 

 growth becomes possible. I will not here dwell upon the various 

 means employed by nature for the dissemination of the seeds of 

 plants — sorr^e depending upon the structure of the seed itself— as 

 they are familiar to many of us, and it would take us too far from 

 our subject. But I will just state one fact recorded by Darwin 

 in his " Origin of Species," in connexion with the dispersal of 

 aquatic plants, which have generally wide ranges, and the seeds 

 of which he thinks are occasionally transported long distances 

 through the mud of ponds, &c., adhering, sometimes in considerable 

 quantities, to the feet and beaks of aquatic birds. He says, " I 

 do not believe that botanists are aware how charged the mud of 

 ponds is with seeds : I have tried several little experiments, but 

 will here give only the most striking case. I took in February 

 three table-spoonfuls of mud from three different points, beneath 

 water, on the edge of a little pond ; this mud when dry weighed 

 only 6| ounces ; I kept it covered up in my study for six months, 

 pulling up and counting each plant as it grew ; the plants were 



