OLIVER ON THE STEM OE DICOTYLEDONS. 
257 
F. J. F. Neues system Pflz.-Physiologie, 1837, tab. iii. 6-8.— 
Zamia integrifolia. Brongniart, A. Obs. sur la Structure interi- 
eure du Sigillaria , &c. Arch. du Museum (1839) i. 425, tab. 
xxxiv. The wood-cylinder consists of narrow, irregular, radiating 
series of vessels, marked with transverse or reticulate bars, sepa¬ 
rated by medullary, parenchymatous plates.—Don, D. Linn. Soc. 
Proc. 1840, 53. ISTo distinction of wood and liber in the vascular 
bundles. Cyccis has a large central pith, and several thick, 
alternating layers of cellular and fibro-vascular tissue. In Zamia 
and JEncephalartos there are but two very thick layers surround¬ 
ing the pith, one fibro-vascular, the other and exterior, parenchy¬ 
matous. The wood-mass consists of two kinds of vessels, viz., 
slender, transparent tubes, without dots, &c., and dotted, reticu¬ 
lated and spiral vessels, capable of unrolling: the former identical 
with the fibrous or woody tissue, the latter comparable to the 
strictly vascular tissue of other plants. The dotted ‘ vessels * of 
Cycads may have 1-2 to 5 rows of dots, not always confined to 
two vertical sides; in some cases seeming to follow the entire 
circumference of the vessel. No generic distinction can be 
drawn from the character of the vessels. The dots are always 
arranged obliquely. The cellular tissue of Cycadeae consists of 
tolerably uniform elements. All Cycads have numerous gum- 
miferous canals, often of great length, and with thick walls. 
—Miquel, F. A. ~W. Monographia Cycadearum, 1842. Anato¬ 
mical Structure, p. 3.—Bischoff. Lehrbuch ii. 61, 64,—Meyen, 
F. J. F. Neues Syst. Pfi. Physiol, tab. iii.—Morris, J. Bemarks 
upon Becent and Fossil Cycadeae, Ann. Nat. Hist. vii. 110.— 
Miquel, F. A. W. Ueber den Bau eines gewachsenen Stammes 
von Cycas circinalis, 3 plates. Linnssa, 1844, 125. Ann. Sc. Nat. 
iii. Ser. 5, 11. Silliman’s Journ. Sept. 1846. Four concentric 
belts are distinguishable in a transverse section of an old trunk, 
(i) Exterior and (2) interior cortical parenchym ; (3) wood, 
formed of unequal, irregular layers (6-8 in an old stem), more or 
less interrupted by confounding with adjoining layers or dividing 
into two; these are separated by zones of cellular tissue: the 
cells of the wood are all dotted: and (4) pith.—Endlicher and 
Unger. Grundziige d. Botanik, 92.—De Yriese, W. H. De¬ 
scriptions et Figures des Plantes Nouvelles, &c. Leide, 1847. 
C. circinalis (with figs).—Griffith, Notulae, iv. 2.— Zamia muri- 
cata. H. Karsten. Organographische Betraehtung der. Ab- 
handl. d. K. Ak. Wiss. Berlin, 1856, 193. Observations on the 
development of the ligneous zone, &c. Spirals and liber fibres 
are absent from the pith.—Schacht, H. Pflanzenzelle, 284. 
Scattered vascular bundles are found in the pith.—Uenfrey, A. 
Micr. Diet. ‘Wood’ (fig.). The wood is composed of pitted 
prosenchyma, without vessels or ducts, except in the medullary 
sheath. Its zones are separated by alternating, parenchymatous 
layers. 
N. H. R.—1863. 
S 
