BOTANICAL SUBJECTS. 191 



there is a third root, which emerges above the bud. At other times 

 four separate roots appear round the bud, 



10. The same occurs in the potato. Its underground stem has 

 bracts — subtending buds, with s, root fibril on each side. Frequently 

 a third fibril is given off above the bud. This, I observed, was the 

 general rule, but often root fibrils were given off all round the bud 

 like the verticillate leaflets of a Begoniajeaf, with abud at their centre. 



11. Although in an underground stem it might be an advantage 

 for roots to develop all round the bud, it is obvious that in an 

 overground erect stem any appendage which developed imme- 

 diately above the bud might interfere with the development of the 

 bud, and if tbe stem were sufficiently stiff the side roots or 

 appendages would be equally in the way, as they would not be 

 needed as tendrils ; so the only organ required would be the leaf, 

 which acts as an atmospheric root. The other roots, which, in the 

 underground stem, usually develop round the bud, would be 

 suppressed. Even the leaves themselves abort to the depauperized 

 condition of bracts, should the rhizome or stem be able to replace 

 the function of the leaves, as in Einpogium ajphijllum,^ or most of 

 the cactace93 and others -, or when some other plant furnishes the 

 needed nutriment, as in the dodder and broomrape. 



12. The aerial roots of orchids are adapted to adhering to other 

 bodies like tendrils. They consist of a woody and vascular axis, 

 surrounded by cellular tissue. They are not unlike the terete 

 leaves of Scuticaria Steeli. The leaf must be considered not only as 

 a branch system, but as an aerial root system, differentiated 

 specially for the suction of gases and the elaboration of juices under 

 the influence of light. The root is the same thing, differentiated 

 specially for the suction of liquids, containing minerals and other 

 materials in solution. When the plant is submerged, as in sea- 

 weeds, some ranunculi, Utricaria and others, the leaf probably acts 

 both as leaf and root, and the root proper may often function solely 

 as a tendril for anchorage. There are several floating plants 

 without any roots in the ground. They have only leaves on the 

 water-surface and roots in the water. The latter act as water- 

 leaves, the former as air-leaves. It may astonish the reader, 

 perhaps, to meet with the notion that a root with its fibres is 

 considered the same, morphologically, as a leaf with its veins. 

 But is it not equally astonishing to find that an axillary bud is now 

 a leafy branch and then a magnificent flower, say, of Lilium 

 speciosum or auratum, or one of the grand roses of horticulturists ? 



13. Some terrestrial orchids, such as Coryanthes and others, f 

 push forth an underground stem, which forms a bud at its extremity, 



* " Syme's Brit. Bot.," vol. 9, p. 131. 

 t " Bauer's Illuijtr.," pp. 2 and 3. 



