STIGMARIA STRUCTURE POOLE. 347 



Eccentrically placed within the dark and apparently struc- 

 turless surface, about 30 mm from one side and less than ten from 

 the opposite side, is a nearly 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 ll mm in diameter. 



The bundles of cells are in radial direction from 6 to 7 mm in 

 length and from less than 1 to about 2 mm in breadth, containing 

 from 5 to 15 radial rows of cells, each having about 40 or more 

 rectangular ce)ls 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 l mm - 



The lumen of the 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 to a greater length radially than in breadth. 

 Cells 125 microns by 200 are the largest commonly found. The 

 <jells 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, as a rule. 



