42 



PART I. THE MORPHOLOGY OF PLANTS. 



[io. 



foliage-shoots. Again, if the development of tubers be prevented by cutting 

 off the underground shoots, the buds in the axils of the leaves above the ground 

 develope into tubers. 



The Flower is another form of shortened shoot, the leaves of which, when 

 present, are arranged closely together. The morphology of the flower is 

 discussed in subsequent paragraphs. 



Shoots may grow erect into the air ; or they may grow horizontally either 

 above or below the surface of the soil. 



A shoot which grows horizontally on the surface of the soil is termed a 

 creeping shoot (Fig. 22 JJ). 



The Runner or Stolon is allied to the creeping shoot. It is an elongated 

 lateral shoot which takes root at some distance from the parent plant, and 

 which by the dying away of the intermediate portion, becomes a new individual. 

 The runner may grow either just above (Fig. 22 D), or just below the surface 

 of the soil ; it bears sometimes scaly leaves, sometimes foliage-leaves (Hieracium 

 Pilosella). Runners usually spring from shoots with limited growth, but some- 

 times from those with unlimited growth, e.g. Onoclea Struthiopteris. 



FIG. 23. J. Rhizome, with unlimited growth, of Oxalis Acetonella (Wood-Sori-el) ; n scaly 

 leaves ; I foliage-leaves ; I' remains of older foliage-leaves ; bl flower ; 7i bracts. -B Rhizome, 

 with limited growth, of Polygonatum oflicinale (Solomon's Seal) ; I scar of last year'a 

 herbaceous aerial shoot; II aerial shoot of this year, which is the anterior portion of the 

 shoot 2 ; III bud of next year's herbaceous aerial shoot, which is the continuation of 

 the shoot 3; n scaly leaves; b and b' leaves from the axils of which the shoots 2 and 3 

 have arisen ; w roots. 



When a shoot grows horizontally beneath the soil, it is termed a Rhizome. 

 It is characteristic of those plants the subterranean parts of which alone are 

 persistent. The growth in length of the rhizome is sometimes unlimited, 

 sometimes limited. When the former is the case, it continues to elongate 

 at its apex and bears either only foliage-leaves (c.<j. Pteris aquilina) ; or 

 foliage-leaves and scales in regular alternation (Fig. 23 A, /, n), in the axils 

 of which annual shoots arise ; or only scales in the axils of which annual shoots 



