CHAP. I. AVOODY TISSUE. i7 



Asclepiadese, has made it the subject of more extended observ- 

 ation. According to this gentleman, such nuclei not only 

 occasionally appear on the cuticle of some plants (Plate III. 

 %. 9.), in the pubescence of Cypripedium and others, and in 

 the internal tissue of the leaves, but also in the cells of the 

 ovule before impregnation. It would seem that Brown con- 

 siders stomates to^e formed by the juxtaposition of two of 

 these nuclei. {See also Slack, in the Tram. Soc. Arts, xlix.) 



Sect, II. Of Woody or Ligneous Tissue. 



This {Vasa fibrosa, Lat.; Petits tubes, Mirb. ; Tissu cellu- 

 laire allonge or ligneux, Fr. ; Vaisseaux propres fasciculaires, 

 Mirb.; LignecB fistulcB, Malpighi; Fasergefdsse, or Bastrohren, 

 Germ.) consists of very slender transparent membranous 

 tubes, tapering acutely to each end, lying in bundles, and, 

 like the cellular tissue, generally having no direct communi- 

 cation with each other, except by invisible pores. (Plate II. 

 fig. l.a,b;2. 5. a, &c.) Slack states, that they are often met 

 wTth open at theh- extremities; " which probably arises either 

 from the membrane being obliterated where it was applied to 

 another fibre, or ruptured by the presence of an adjoining 

 cell, as we sometimes find the conical extremity of another 

 tube inserted into the aperture." 



Many vegetable anatomists consider it a mere form of cel- 

 lidar tissuc^in an elongated state. However true this may be 

 in theory, woody tissue may be known by its elongated figure 

 and extremely attenuated character*; usually it has no sort 

 of markings upon its surface, except occasionally a particle or 

 two of greenish matter in its hiside; but sometimes it is 

 covered with spots that have been mistaken for pores, and 

 that give it a peculiar character (Plate II. fig. 3. and 4.) ; 

 and I have remarked an instance, in Oncidium altissimum, of 



* The distinction between cellular tissue and woody fibre is more pro- 

 nounced in the Ions club-shaped aerial radicle of Rhizophora Candelaria, 

 than in any plant with which I am acquainted. It there consists of large, 

 very long," transparent tubes, lying unbedded in fine brownish granular 

 matter, which is minute cellular tissue. 



C 



