40 
REPORT ON BOTANY, MDCCCXLl : 
almost lineal, giving tlie vessel the appearance of being striped 
across. The dots are always arranged in the diagonal direc- 
tion. The dotted vessels in Zamia furfuracea and pumila, 
may be unrolled spirally, in the shape of a ribbon, as in the 
ferns ; the act of unrolling takes place in the direction of the 
dots, and from the right towards the left. Other vessels, 
which diifer but little from the spiral vessels, excepting in 
their tendency to unite themselves in their windings, are to be 
found in all Cycadece, besides the dotted vessels. The spires 
in some vessels are free, and the fibre frequently exhibits, at 
various places, slits or little branches ; the spires, in other 
cases, unite on one or on both sides, in which case the vessels 
exhibit a series of rings or bars ; the fibre, in that case, is 
difficult to be untwisted, and frequently breaks off in the ring, 
or. the bars separate themselves at the points where the spires 
unite, which usually takes place on the perpendicular sides of 
the vessel. The vessels, in other cases, are reticular, and as 
such there is a great analogy between them and the dotted 
vessels in Cycas revoluta. All these modifications are fre- 
quently exhibited in the same vessel, in Zamia furfuracea 
and pumila, which proves the correctness of Meyen’s theory, 
who reduces all these vessels to one type. The dots and bars 
are evidently the thinnest parts of the tube, and probably 
remnants of the primitive membrane of the cell, which has 
remained free from the subsequently deposited material. 
The cellular tissue of the Oycadece consists of a pretty 
regular parenchyma of prismatical hexagonal cells. The 
walls of the cells, in the above mentioned species of Zamia 
and Encephalartos, appear uniformly thick and transparent, 
without dots, but the walls of the cells, in the old stems of 
Cycas revoluta, are provided with numerous elliptical oblique 
bars, dots, or spaces, where the membrane is so extremely 
tender and transparent, that the cells seem to be perforated, 
the interstices being covered with an incrusting material, in 
the form of bands, that run one into the other. The extra- 
ordinary tenderness and transparency of the dots, or of the 
interstices, of whatever shape they may be, seem to afford 
evident proof, at those places where they are not covered by 
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