STRUCTURE OF MODIFIED SHOOTS 127 



Such underground stems are known as rhizomes ; that of 

 the Lily of the Valley (Fig. 79) is a very instructive 

 one to study. Observe the nodes with their scale-leaves 

 and also the branched fibrous roots springing from each 

 node in a circle. Such an arrangement of members is 

 termed a whorl. Carefully dissect a bud and compare it 

 step by step with the parts found in other buds you have 

 examined. Notice the different kinds of scale-leaves : 

 the tough outer ones, forming a protective coat ; further 

 inwards some which are rather fleshy ; then the foliage- 

 leaves. If the bud is a large one, look for the inflorescence 

 in the centre. Which of these structures come above 

 ground ? How is the further growth of the axis continued 

 underground ? Compare this mode of growth with that of 

 the Beech, Hazel, Elm, or Willow. Is the axis monopodia! 

 orsympodial ? The following examples of rhizomes should 

 be studied and their parts compared : Garden Mint, Colts- 

 foot, Dog's Mercury, and Wood Sorrel. In all these cases 

 the end bud emerges from the soil, and growth is continued 

 underground by means of a lateral bud. 



Rhizomes as land-winners. The rhizomes of some plants, 

 such as the Marram-grass, Sand-sedge, and Horsetails, 

 grow to a great length, often many yards, and this habit 

 makes them useful for reclaiming our sandy shores. Fig. 80 

 shows how the Marram-grass is planted on the sands. 

 Round the tufts wind-blown sand accumulates, and the 

 shoots by elongating keep their leaves above the surface. 

 Below the ground long rhizomes are formed, from the 

 nodes of which very long, slender roots arise and grow 

 deeply in search of water, the two producing a tangle, 

 and serving effectually to hold the sand together. At 

 the same time the old and decaying shoots, by adding 

 humus to the sand, begin the formation of a soil upon 

 which other plants can grow. Similar uses are made of 

 rhizome-bearing plants to hold together the banks of 



