STIGMARIA STRUCTURE—POOLE. 347 
Eccentrically placed within the dark and apparently struc- 
‘turless surface, about 30™™ from one side and less than ten from 
the opposite side, is anearly circular band of over thirty slightly 
wedge-shaped bundles of rectangular cells, surrounding a struc- 
tureless central circular area like the rest of the section surface 
about 11™™ in diameter. 
The bundles of cells are in radial direction from 6 to 7™™ in 
length and from less than 1 to about 2™™ in breadth, containing 
from 5 to 15 radial rows of cells, each having about 40 or more 
rectangular cells in a row. The bundles are separated by the 
uniform black material within and without the ring of bundles 
of cells, each bundle being separated by a space of more or less 
than ]™™. 
The lumen of tke cell is white (a calcium carbonate infiltra- 
tion), rectangular, 100 microns by 175 being a common size. 
The cell wall is black and thin, less than 10 microns thick. 
The smaller cells are often nearly square, 50 to 75 microns, but 
the tendency is toa greater length radially than in breadth. 
‘Cells 125 microns by 200 are the largest commonly found. The 
cells become. larger generally, as they recede from the centre, 
and the widening of the bundles in the same direction is also 
caused by the appearance of interstitial rows of cells, so that 
the bundle has a few more rows of cells across the wider than 
across the narrower end, asa rule. 
