There are many plants growing round the borders of the pond, half in and half out of the water, such as the reeds and sedges, irises and the tall marsh buttercups. Watch how these plants gradually grow further and further in towards the middle of the pond. They advance with their creeping underground stems (see fig. 143), and collect mud, dead leaves, and stalks around them, gradually building up a little firm soil round their roots. Slowly these accumulations from different plants meet, and the whole gets more compact, till the plants from the shore which require soil are able to grow with them.
Fig. 144. A water channel grown over by floating plants and the advancing reeds and rushes.
In this way the shore slowly advances, the floating plants first building up some mud, and the reeds following and bringing shore plants in their train, till in the end the edges of the pond all meet in the middle, and the pond, as such, no longer exists. Only a marsh remains, till this may be gradually grown over by the ever-increasing land-plants, and an oak-tree may grow where once the water-lilies bloomed. If the advancing reeds at the edge had been kept cut back, as they often are, then the land-plants could not have taken such hold, and the pond would have remained a pond with all its “water-weeds.”
PLATE VI.
LOOKING DOWN ON A SANDY SHORE AND RIVER MOUTH