Ai'H. 1897.] BOTANICAL SOCIETY OF EDINl'.l J;< I II 53 



The medullary ray cells are of oblong rorin, the long 

 axis radial : nothing more can be made out than their form 

 or arrangement, for they are almost amorphous silica and 

 nearly structureless. 



The sinuous tvhite hands, or spurious rings, are broad bands 

 of thin walled wood parenchyma — one can just make this 

 out, for, like the rays, they are almost structureless. As to 

 their course, they run concentric to the annual rings, but 

 not continuous for any great distance ^ — crossing the 

 medullary rays and becoming continuous on the other 

 side or stopping short. Tracing one of these bands : it 

 starts from the perivascular parenchyma, stretches across 

 to the next medullary ray, which may thicken somewhat 

 to meet it. Across the ray it may not be continuous, or it 

 may have bifurcated each arm passing on. Tn this course 

 it may alter its dimensions, broadening oui here and 

 thinning out there, and is by no means straight, but a 

 series of zigzag. At the next vessel it may bifurcate and 

 start again on the opposite side as one. 



Structurally, they consist of a mosaic of closely packed 

 polygonal cells without intercellular spaces. The cells are 

 large and thin walled, and quite distinguishable from the 

 other wood elements. They are broadest radially in the 

 spring wood, 0'20 mm., and farther apart 0-40 mm. While 

 the largest here consist of 7 to 8 breadths of cells, radially 

 there is great variation even in the same band, sudden 

 thinning being common. At the outer limit of the year's 

 wood, the radial breadth of the band is 0-12 mm., and they 

 are separated by a distance of 0'14 mm. 



This metatracheal parenchyma and the medullary rays 

 conjointly divide the wood into a series of what are oblong 

 or square areas. These last are largest in s]iring, and 

 smallest in autumn wood. 



The bulk of each area is composed of woody fibres, with 

 very thick walls, so much so that in some cases the lumen 

 is almost obliterated. Around these, and separating it from 

 the rays on the radial sides and the false rings on the 

 tangential side, is a single layer of thin-walled cells, 

 which appear to be fibrous parenchyma. < >ccasionally the 

 whole square appears composed of this last. 



Si/stematic Position. — The points of special impoi'tauce to 



