Read it through once

Looking down on the seashore, you will notice the high-water mark, a yellowish brown line of floated rubbish which is quite distinct even at a distance. If you now go down and examine it closely (not a particularly pleasant operation, seeing that so much is in a decomposing condition) you will find many seeds amongst the corks and bits of straw, seaweed, and objectionable, if lively, animalcula, and very likely also pieces of plants, such as willow branches, which might quite easily take root.