680 CLIMBING PLANTS. 



tree-trunks as supports, particularly those of palms. At first they adhere very 

 slightly, and lean on them only to a certain extent. All the shoots of these 

 Clusiaceae are thick and beset with opposite leathery leaves; they remain green 

 for a very long time, and are still unlignified when they develop lateral shoots 

 from the leaf -axils of their erect branches, and when the cortex is wounded, a thick 

 adhesive juice like gamboge makes its appearance. The leaves are so heavy that 

 the outstretched lateral branches are bowed under their burden, and sometimes 

 even hang downwards. It is therefore unavoidable that many of these lateral 

 branches should intersect and come into contact with each other, and that at the 

 places of contact the epidermis should be wounded by the friction. But at such 

 places an actual fusion of the branches occurs, and since this process is many times 

 repeated, a lattice-work results, as shown in fig. 169. The individual portions of 

 the latticed stem remain soft and pliant, and thus mutually supporting one another, 

 the whole possesses a bearing capacity adequate to enable the erect shoots to rise 

 higher and higher from this scaffolding. The lattice-work is additionally strengthened 

 by the production of aerial roots from the older intemodes. These, like the stems, 

 fuse where they intersect. From their general external similarity it is often diffi- 

 cult to distinguish between the two sets of elements comprised in an old lattice-work. 

 In cases where the inclosed stem increases in thickness, the latticed sheath becomes 

 tightly stretched. Often, in Clusia, many of the branches die in consequence of this 

 tension. Still, new shoots generally arise from the stumps, and repeating the already- 

 described method of growth, become interlaced into a lattice-work. Sometimes the 

 adherent stems become flattened and girdle-like, whilst aerial roots developing at 

 many points become inextricably interwoven in the lattice-work till it is impossible 

 to see the original palm stem. On the banks of the Rio Guama in Brazil, Martius 

 saw whole groves of the Macaw tree {Acrocomia sclerocarpa) covered with Clusia 

 alba. The Clusia formed an absolutely closed sheath bearing flowers and foliage, 

 whilst 10 metres above the stately crown of the palm-tree projected. 



The tivining stem (stirps voluhilis) is able to reach considerable heights by 

 attaching itself to various objects and twisting spirally around them. In a state 

 of nature, erect stems or even those of other climbing plants may serve as supports, 

 whilst in gardens, sticks, sti-ings and wires are utilized in this way when it 

 is desired that twining plants shall cover walls, arbours, &c. We find by experi- 

 ence that even very fine threads form excellent supports, while thick posts and 

 bulky tree-trunks are less adapted for this purpose. In the case of many annual 

 twining stems, props of even 20-25 cm. diameter are too thick for the plants 

 to twist around. Those perennial and lignifying stems called lianes are sometimes 

 found round pillars of 30-40 cm. diameter, e.g. those of Glycine Ghinensis in the 

 avenues of the park at Miramare, near Trieste. In the tropics, twining plants 

 are seen embracing the trunks of trees as much as 40-50 cm. thick, but in such 

 instances it is probable that the trunk did not possess this thickness when it 

 was first entwined, and only attained it later on. Of course this can only happen 

 under particularly favourable circumstances, for most perennial, twining stems 



