vegetable detritus(It is easy to imagine that in prehistoric ages, the quantity of decayed vegetable substances (vegetable detritus) carried into the rivers must have amounted to much more than that of the trees actually carried into them as such; for only the trees torn up from the banks and steep declivities of the rivers came into them in a perfect state, and not those which died upon the high lands and slight declivities. It was not until after these were decayed, that they could be carried away by water.google.rudimock)
