CHAP. I. 
WOODY TISSUE. 
17 
Asclepiadeae, 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. 
fig. 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 be formed by the juxtaposition of two of 
these nuclei. (See also Slack, in the Trans, 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. ; Lignece fistula, 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. 1. «, S ; 2. 5. a, &c.) Slack states, that they are often met 
with open at their 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- 
lular tissue, 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 inside; 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 long 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 imbedded in fine brownish granular 
matter, which is minute cellular tissue. 
C 
