324 Earl Harrington Foote 



large and nearly uniform in size, distributed in a single or at most 

 a double row extending completely across the space between two 

 broad medullary rays. Two vessels closelj' adjoining each other 

 and even compound vessels are sometimes found (plate XIV, 

 fig. 4). Tyloses are fairly numerous in some of the preparations 

 studied. In the summer wood a few small vessels appear in 

 loose radial chains, diminishing in size toward the outer part of 

 the growth ring. Protoxylem is found next the central pith, 

 in the form of small spiral vessels grouped in definite masses 

 between the bases of the broad medullary rays. In the bast 

 there is considerable development of sclerenchyma, which in 

 young twigs occurs in the form of wavy bands just outside the 

 sieve tissue (plate XIV, fig. 1). In older stems this band becomes 

 broken. 



Tangential. The broad pith rays are frequently broken up by 

 oblique strands of wood fibers or parenchyma cells, presenting 

 a decidedly stringy appearance across the ray. These strands 

 disappear in the older wood. The uniseriate rays are straight 

 and parallel, and are rather long, being from three to thirty 

 cells in length, and averaging from ten to fifteen cells long. 

 The cells are roundish, somewhat elongated vertically. The 

 wood parenchyma cells are rectangular, being three times as 

 long as broad. The wood fibers are narrow and straight. The 

 vessels are scalariform with bordered pits, and show occasional 

 tyloses. 



Radial (plate XIV, fig. 7). The pith cells are rectangular, 

 with roundish corners, and are arranged in more or less definite 

 wavy vertical rows, being elongated sometimes radially, some- 

 times vertically. Protoplasmic connections between the cells 

 are prominent. The pith ray cells are similar in form, being 

 irregularly elongated radially. They are one and one-half times 

 as long as broad, and show conspicuous protoplasmic con- 

 nections. The wood parenchyma cells are also rectangular, 

 averaging nearly eight times as long as broad. Protoplasmic 

 connections are abundant both among these cells and between 

 them and the pith ray cells. The protoxylem vessels usually 

 show two spirals, although occasionally small vessels are found 

 with but a single spiral, and on the other hand the larger ones 

 mav have three. 



