554 
EXPLANATION OF THE PLATES. 
taken from the vicinity of the medullary sheath : its membrane is distinctly 
perforated at the upper part with oval holes : at the lower part the place of 
these holes is occupied by glands like those of Gnetum, in fig. 5. ; or of Abies, 
in fig. 8. It would therefore seem, that the oval holes in the membrane of 
Ephedra are places from which the glands have fallen. Magnified 350 times. 
JF^. 8. A vertical radiant section of the wood of Pinus Abies, showing the 
glands upon the walls of woody tissue, magnified 520 times ; after Kieser ; but 
corrected by showing that the glands are convex, and the supposed pores in 
their centre often opaque. 
Fig. 9. The termination of a spiral vessel, extracted from the root of a hyacinth, 
by Mr. Valentine : this shows distinctly the enveloping membrane. 
Fig' 10. A fragment of a spiral vessel, bent abruptly to show that it is cylindrical 
and not flat ; magnified 500 times. 
Fig' 11. A spiral vessel, with each twist composed of four fibres, from the stem of 
Nepenthes distillatoria. This is the largest spiral vessel yet known. 
Fig. 12. A minute portion of a transverse section of an Indian tree, showing a 
medullary ray, a; the mouths of several bundles of ducts, b b b ; and the ends 
of the woody tissue, c c, d d, in which the latter are imbedded. The wood of 
this plant is exceedingly compact; evidently owing to the denseness and 
stoutness of the woody tissue. 
J^^. 13. Two vessels from the stem of Impatiensbalsamina ; magnified 130 times ; 
after Kieser ; a is a duct, with the spires broken in some places, and inoscu- 
lating in others, so as to form the reticulated vessel of this author; 6, a spiral 
vessel, with the spires broken at the top into rings. 
Fig. 14. A horizontal section of the stem of Tropaeolum majus, magnified 
130 times; after Kieser. This is to show the intercellular passages, which are 
unusually large ; at a they are empty ; at b filled. 
Fig. 15. A tangental section of Sassafras wood, magnified ISO times; after 
Kieser : a a, two banded dotted vessels ; or, as Kieser calls them, punctuated 
spiral vessels ; b b, the mouths of the medullary rays, showing how they are 
connected with the bark. 
Fig' 16. Dr. Bischoff's representation of the manner in which spiral vessels pass 
successively into annular and dotted ducts. This figure is imaginary; but 
BischofF asserts that he has actually seen^ such a vessel in the garden 
spinage {Spinacia oleracea). 
Fig. 17. Two sorts of dotted vessels from the wood of Phaseolus vulgaris, mag- 
nified 130 times; after Kieser: a, has the bands much more nearly approx- 
imated than b, in which the spaces between the bands is almost fusiform. 
Fig. 18. A bundle of ducts from the stem of a Lycopodium ; from a prepar- 
ation by Mr. Griflfith : this shows the manner in which such vessels are packed 
together when in situ, and their terminations. 
Fig. 19. Vasiform and short woody tissue from the stem of Phytocrene 
gigantea; from a drawing by Mr. Griffith, in Wallich's Plantce Asialicce, 
t. 216. 
Fig. 20. The same, from the same authority, showing that this sort of vessel is 
really composed of short cylindrical cellules, placed end to end, and opening 
into each other. 
Fig. 21. A section of the cyst, or receptacle of oil in the rind of a lemon, showing 
that it is a mere cavity built up of cellular tissue. 
