678 CLIMBING PLANTS. 



and also an insignificant little speedwell which grows in damp meadows in Great 

 Britain, and rises above the ground by sprawling over its erect and stronger 

 neighbours. This speedwell {Veronica scutellata) has long, narrow leaves which 

 in section almost resemble those of the tropical Pandanus. Like these they are 

 erect when young, and are inserted in pairs over the vertically -growing apex. By 

 the further growth of the stem they are pushed in between the gaps in the con- 

 fusion of herbage. By and by the leaves are refiexed and afford the plant useful 

 support. While the serrated teeth of the leaf-margins in other species of speedwell 

 have their apexes directed forwards, in this they are strangely directed backwards, 

 i.e. downwards towards the ground; by this means the support which these leaves 

 obtain is materially increased. In this speedwell the retro-serrate teeth of the leaf- 

 margin have undoubtedly no other significance than that of firm anchorage, though, 

 in many of the other above-named instances, the pointed teeth, prickles, and spines 

 have the additional task of protecting the foliage, and perhaps also the flowers and 

 fruit, against animals which might climb up over the stem in their search for food. 



The lattice-forming stem, (stirps clathrans) does not twine, nor indeed has it 

 any special climbing organs, and yet leaning against rock-faces or tree-trunks it 

 gradually attains to heights which it would be unable to reach without these sup- 

 ports. It clothes its supports with branches, which, in the aggregate, constitute a 

 solid lattice - work, reminding one of certain interweaving climbers, from which,, 

 however, it is distinguished by the fact that its elevation is achieved neither by 

 lateral branches projecting like spars, nor by arched shoots, nor even by reflexed 

 foliage-leaves. Lattice-forming stems occur comparatively seldom in the floras of 

 the temperate zones; the most striking example in these regions is the small and 

 dainty species of buckthorn known as Rhamnus pumila, whose lattice-work clothes 

 the steep limestone rocks here and there in the outlying Alps between Switzerland 

 and Styria, and in the Jura. Anyone looking from a little distance at a pre- 

 cipitous rocky face overgrown with this buckthorn, might think that it was ivy 

 which had spread out its stems, climbing by means of clinging roots. The foliage 

 shows, indeed, the same dark green and is about the same size as that of ivy, but 

 it is easily recognized on a nearer view that the shape of the leaf, the distribution 

 of the strands in the blade, and finally the character of the flowers and fruits are 

 quite different, and, what is especially important here, that the much-branched 

 woody stems adhering to the steep rocks have no clinging roots. It is also an 

 interesting fact that the older stems are actually wedged into the crevices of the 

 rock, and that the branches are exceeding brittle. With careless handling they 

 break and fall to the ground, and only by proceeding very carefully can one succeed 

 in detaching a complete stem with all its branches from the rocky face. We may 

 conclude that this plant would necessarily perish without the supporting back- 

 ground, since its brittle branches would break off at the first violent burst of storm, 

 and the bush would be mutilated by every tempest. 



The peculiar structure and method of growth of this buckthorn explain all these 

 striking phenonema. Here there are no strands of hard and fibrous bast deposited 



