58 



LECTURE V. 



developed from various places on the shoot-axes, or even from leaves, and which 

 cannot be looked upon as metamorphosed shoots or leaves. In the Roses and 

 Brambles they are known to every one ; among the American speeies of Solanum, 

 many are remarkable for conspicuous brightly coloured prickles, e. g. Solanum pyra- 

 catitha and alro-sanguineuin ; many Palms, on the other hand, have very long and 

 hard ones resembling those of a porcupine. 



Among sub-aerial shoots the filiform, often very long runners, which usually 

 spring from the base of an upright leafy shoot and bear a few inconspicuous 

 leaf-scales on their long internodes, deserve even if only passing mention here. 



Fig. 53-— a potato plant grown from seed. ;- primary root; c/ cotyledons ; //foliage leaves; ** lateral shoots, 

 with leaf scales c' c' ; tb the tubers at the ends of these shoots (after Duchatre). 



These produce, at some distance from the mother-plant, a rosette of foliage leaves, 

 from which spring, downwards, a tuft of roots, and upwards, flower shoots. 

 The Strawberry affords a very good example. Runners of this kind are funda- 

 mentally organs of multiplication, since from each rooted tuft of foliage leaves at 

 the end of a runner, the filiform part of which perishes later, a new independent 

 plant arises. Very many other plants behave in a similar manner; their runners 

 or stolons grow forth as horizontal fibres beneath the surface of the earth, and 

 produce from their terminal bud a new rooted plant, often far removed from the 

 mother-plant. This is the case for example in the Umbellifer JIjgopodiu?n poda- 

 graria, in the common Valerian ( Valeriana oßcinalis), and in many labiate plants 



