66 PLANT LIFE. 



exactly at the proper level. Ranunculus bulbosus, 

 which has a little fleshy corm, behaves in a similar 

 way, and is periodically hauled down by its contractile 

 roots. 



One of the most curious cases is that of the Rasp- 

 berry. If a series of young plants are carefully pulled 

 up, it will be found that the roots have thrown them- 

 selves into spiral coils ; after the branch has reached the 

 soil the rootlets fix themselves at the tip, and then, by 

 their contraction, pull down the young shoot, coiling 

 themselves like tendrils in the process. 



It is especially in the loose, light, leaf-mould of woods 

 that these subterranean colonisers are most abundant. 

 The underground system of any of the following plants 

 is well worth attentive study, as nothing can give so 

 clear and definite a picture of the struggle that goes on 

 for every cubic inch of fertile soil. Dog's Mercury 

 {Mercurialis perennis) has a system of tough, horizontal 

 runners which root and give off flowering stems at 

 every node. As the internodes are from 3-10 cm. 

 long, and as perhaps twenty tough, slanting, anchoring 

 roots trend downwards from every node, the whole 

 system is very firmly attached, and may produce from 

 16-40 erect foliage-shoots on every square foot of 

 ground. A single plant of the Wound wort {Stachys 

 silvaticd) may occupy a circle two feet in diameter and 

 possess 18-20 robust, leafy and flowering stems. The 

 young creeping rhizomes, which end in the upright 

 stalks, are, in both cases, beautifully adapted to insinuate 

 themselves through the soil to a new ground ; but, once 

 established, the strong and closely set stems make it 

 impossible for any other plant to grow beneath them. 

 (Compare also the Woodsage {Teua^uin Scorodonia)). 



These subterranean rhizomes and roots being full of 



