STRUCTURE.] INTERRUPTED NODES. 167 



horizontal communication is effecting, and all the tissue is 

 more or less contracted. In many plants this contraction, 

 although it always exists, is scarcely appreciable ; but in 

 others it takes place in so remarkable a degree as to give 

 their stems a peculiar character; as, for instance, in the 

 Bamboo, in which it causes diaphragms that continue to grow 

 and harden, notwithstanding the powerfully rapid horizontal 

 distention to which the stems of that plant are subject. In 

 all cases, without exception, a leaf-bud or buds is formed at a 

 node immediately above the base of the leaf; generally such 

 a bud is either sufficiently apparent to be readily recognised 

 by the naked eye, or, at least, it becomes apparent at some 

 time or other ; but in certain plants, as Heaths, the buds are 

 often never discoverable ; nevertheless, they always exist, in 

 however rudimentary a state, as is proved by their occasional 

 development under favourable or uncommon circumstances. 

 By some writers nodes, upon which buds are obviously 

 formed, are called compound or artiphyllous ; and those in 

 which no apparent buds are discoverable, are named simple, 

 or pleiophyllous ; they are also said to be divided, when they 

 do not surround the stem, as in the apple and other alternate- 

 leaved genera; or entire, when they do surround it, as in 

 grasses and umbelliferous plants : they are further said to be 

 pervious, when the pith passes through them without inter- 

 ruption ; or closed, when the canal of the pith is interrupted, 

 as if by a partition. Pervious and divided, and closed and 

 entire nodes usually accompany each other. 



Dr. Willshire thus speaks of certain supposed interruptions 

 to continuity in the nodes of the common Miseltoe : 



" Some years ago it was stated by Dutrochet, that in the 

 node of Viscum album no true woody matter existed ; that 

 the vascular connexion of the internodal spaces was therefore 

 broken up, or was only maintained by a layer of cellular 

 tissue or pith : this doctrine was admitted, and Viscum was 

 supposed to form another illustration of what have been 

 called articulated stems. Some time after, Decaisne published 

 a small work on the woody structure of this plant, in which 

 he contradicted the statement of Dutrochet, and maintained 

 that the vascular or woody portions of the internodal spaces 



