934 



A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 919. — Convallaria majalis. Portion of a rhizome showing sympodial 

 growth and tw'o terminal leafy buds. 



Many rhizomes display an extraordinary capacity for regulating the depth 

 at which they grow. For example, if the dorsiventral rhizome of Polygonatum 

 multiflonm (Solomon's Seal) is planted too deep, the growth of new branches 

 is directed upwards until a suitable depth is reached. If it is planted too near 



¥\G. 920. — Polygonattim multiflonim. Portion of the storage rhizome 

 bearing adventitious roots and showing sympodial growth. The 

 large apical bud on the right will develop into an aerial stem. 



the surface the reverse takes place. The physiology of this peculiar response 

 is unknown, but it has been suggested that it is due to the effect of light 

 penetrating the soil. This would imply that the level of growth is a balance 

 of negative phototropism against negative geotropism. 



The apex of a rhizome is always eventually transformed into an upright 

 shoot, which becomes aerial. As this apex has to make its way through the 



I 



