The cercaria swims freely for a time and either encysts directly on grass or weeds or it enters a second host which may be another mollusc, an insect, crustacean or fish, and then encysts.
Think of the possibilities if we could reduce pollination of weeds and intrusive vegetation.
The lawn, if it could be called that, was overgrown with weeds and sadly in need of mowing.
In these districts and others the number has become much reduced, owing doubtless in part to the fatal practice of catching the birds just before or during the breeding-season; but perhaps the strongest cause of their growing scarcity is the constant breaking-up of waste lands, and the extirpation of weeds (particularly of the order Compositae) essential to the improved system of agriculture; for in many parts of Scotland, East Lothian for instance, where goldfinches were once as plentiful as sparrows, they are now only rare stragglers, and yet there they have not been thinned by netting.
A more rational system of cropping now began to take the place of the thriftless and barbarous practice of sowing successive crops of corn until the land was utterly exhausted, and then leaving it foul with weeds to recover its power by an indefinite period of rest.
It is nowhere muddy, and a casual observer would say that there were no weeds at all in it; and of noticeable plants, except in the little meadows recently overflowed, which do not properly belong to it, a closer scrutiny does not detect a flag nor a bulrush, nor even a lily, yellow or white, but only a few small heart-leaves and potamogetons, and perhaps a water-target or two; all which however a bather might not perceive; and these plants are clean and bright like the element they grow in.
All grass and weeds must be kept down, and the crust must be broken after every rain, but these seem to be the only principles upon which all agree.
The seventh year's fallow prevented the exhaustion of the soil, which was further enriched by the burning of the weeds and spontaneous growth of the Sabbatical year.
If it isn't the skunks and opossum killing the chickens, it's the weeds taking over the garden.
They burrow in the sands of every shore; they throng the weeds between tide-marks; they ascend all streams; they are found in deep wells, in caverns, in lakes; in Arctic waters they swarm in numbers beyond computation; they find lodgings on crabs, on turtles, on weed-grown buoys; they descend into depths of the ocean down to hundreds or thousands of fathoms; they are found in mountain streams as far above sea-level as some of their congeners live below it.