11 
sidered the principal inferior prolongation of the axis; thirdly, fleshy 
simple or branched perennial bodies, much entangled, tortuous and 
irregular in form, as in Corallorhiza, Neottia, &c. or nearly simple and 
resembling tubers as in Gastrodia; and fourthly of perennial round 
shoots, simple or a little branched, capable of extension, protruded 
Irom the stem into the air, adapted to adhering to other bodies, and 
formed ot a woody and vascular axis covered with cellular tissue, of 
which the subcutaneous layer is often green and composed of large 
reticulated cells. The points of these roots are usually green, but 
sometimes red or yellow. In a very few instances of leafless species, 
as Chiloschista usneoides, they become entirely green, and then appear 
to perform the functions of leaves. 
The stem is found in its most simple state in the terrestrial Ophry- 
dese, where it is only a growing point, surrounded by scales and con¬ 
stituting a leaf-bud when at rest, which eventually grows into a secon¬ 
dary stem or branch, on which the leaves and flowers are developed 
This kind of stem usually forms every year a lateral bud with a tuber¬ 
cular root at its lower end, and, having unfolded its flowers and ripened 
its fruit, perishes, to be succeeded by the stem belonging to the lateral 
bud previously prepared ; hence those species to which tins kind of stem 
belongs Jiave always a pair of tubercles, one shrivelling and in progress of 
exhaustion, the other swelling and in progress of completion. It is some¬ 
times found that the successive formation and destruction of annual tuber¬ 
cles takes place beneath an equal number of skins, the new bud and tuber¬ 
cular root being always formed within the axil of a scale-like coating 
belonging to the parent; this takes place in the genus Thelymitra and 
elsewhere. Sometimes such a stem, instead of forming a new bud upon 
its side, pushes out a slender subterranean root-like runner, which, after 
growing to some length, is arrested in its growth, and then forms at its 
extremity a new bud, which lengthens at its base into a tubercle. In such 
instances as this a kind of locomotion may be correctly said to take place, 
the plant shifting its place yearly, and to such a distance as may be 
determined by the length of the runner, which separates the parent 
plant that perishes from the young offspring which is generated. In¬ 
stances of this are common in terrestrial genera. A modification of it 
is when the tubercles are buried deep under ground, and always emit 
