Apr. 1S97.] T^OTANICAL 80CIKTY OF EDINBURGH 51 



Looked at with the naked eye, the foUowiug are the 

 points noticeable : — The annual rinr/s are not distinctly 

 marked, still one can make out on the specimen a con- 

 centric series of about twelve such growth marks (whether 

 annual rings, so called, or not is an open question). In the 

 uninjured part the ring measures, on the average, 10 mm., — 

 a very rapid growth if each increment be annual ; in the 

 crushed part it is diminished to one-half the size. Each 

 ring appears marked off from its successors by an area 

 devoid of pores. 



The Medullary Rays. — These appear as sharp white 

 radial lines, running sinuously and continuously through 

 the uninjured part ; they can be traced readily through 

 several rings of the crushed part of the stem, despite a 

 certain amount of lateral displacement. The rays visible 

 to the unaided eye are of fairly uniform size, and occur 

 pretty close together. 



Pores (Vasa). — These are arranged approximately in 

 radial rows, and while all the vasa in any one row are 

 practically visible to the naked eye, these in the first part 

 of each annual ring — "the spring pores" — are characterised 

 by their comparatively large size, in fact the calibre of the 

 pores diminishes as they are traced out radially. Similarly, 

 also, their distribution alters. They are most abundant in 

 the spring, and gradually diminish in numbers as they pass 

 out, until at the limit of each growth-increment occurs an 

 area where they are very scarce and small, or altogether absent. 



The next and very interesting point is a series of sinuous 

 or zigzag tangential lines, white in colour, like the rays 

 running concentrically in the yearly increments and pro- 

 ducing a series of " spurious rings." 



With the naked eye, they are seen to form a series of 

 concentric rings stretching irregularly from vessel to vessel. 

 Sometimes they are continuous across several rays, with a 

 straight or zigzag course, at other times they do not 

 correspond on opposite sides of the same ray. They 

 bifurcate to enclose the smaller vessels or pass on the 

 outer or internal border of the large vessels. While these 

 spurious rings are broader and farther apart in the spring 

 wood, they gradually become narrower and closer approxi- 

 mated outwards to the limit of the " annual ring." An 



