[Illustration: Fig. 145. A Sand-dune by the sea with the Marram grass in tufts, and the Carex tufts coming up in straight lines from their underground stems.] One of the first plants to follow the marram is the sea-star grass, or carex. You have probably seen its little tufts following in lines across bare banks of sand (~see~ fig. 145). This appearance is due to the underground stem, which runs very great distances in nearly straight lines, sending up groups of leaves at short intervals as well as side-stems, which form lines crossing the main line. Often a bank may be covered with lines of this plant. A little piece of the plant is shown in fig. 146, where you can see that the structures are on very much the same plan as those described for the marram grass. There are many other plants with this kind of habit, which enables them to live on the sandy shores and dunes. Look at all the plants you can find on the sand-hills, and you will see that in some way they have their parts adapted to suit the conditions. Very long roots and a running stem are the commonest characters, and these you will find on almost every plant you try to dig up. [Illustration: Fig. 146. A small piece of the underground stem of Carex, with tufts of leaves coming above the level of the sand; (~s~) stem, (~r~) roots (cut off) with small side roots, (~sc.~) scale leaves underground.] Sometimes the stem can grow up and up, even though it is continually buried by the shifting sand, as you can see very well in the case of the sea holly. You may dig for more than a dozen feet before you come to the end of the vertical stem of what seemed to be quite a small plant (~see~ fig. 147). [Illustration: Fig. 147. Sea Holly, showing the plant at the surface, and the long stem below the level of the sand (~s~).] Along the shore are other plants of quite a different kind, which have also special characters to help them to conquer a region which seems to be very inaccessible to land plants. Many curious plants live in the mud-flats that are frequently covered by the tides, and which can therefore only get salt water. You remember that salt kills ordinary land-plants, so that these must be specially built to be able to stand it. Most of them have very thick, fleshy leaves, and rather bushy stems, while others have leathery leaves covered with a kind of wax, or with hairs, which make them look grey. Look at the sea-daisy, and you will see that the leaves are very thick and juicy; so are those of the sea-blite and salt spurry. The boldest of all these plants, the marsh samphire, which goes furthest out to sea, and may grow on bare mud covered by every tide, has not leaves at all, but very thick, fleshy stems, which are green and do the work of leaves (~see~ fig. 148). [Illustration: Fig. 148. Marsh Samphire or Glasswort, a plant with swollen green stems which do the work of leaves.]