254 DESCRIPTIVE CATALOGUE 



PI. XXIV, fig. 1, and text-fig. 75). They are somewhat elon- 

 gated and have approximately horizontal cross-walls, their 

 outline is very variable, and they are sometimes stout, and at 

 others squeezed and attenuated out of existence, as can be seen 

 in the radial section, text-fig. 75. They are almost universally 

 filled with very blackened contents. 



The medullary rays consist of only one kind of cell. In 

 transverse section the ray-cell is conspicuous, and may be as wide 

 or even wider than the adjacent elements (PI. XXY, fig. 1, w., 

 and text-fig. 73, m.), and averaging about 40-60 p in tangential 

 diameter. The cells are not greatly elongated radially, and 

 equal from two to four of the adjacent elements, averaging 

 about 70-100 p in radial extension. The rays are entirely uni- 

 seriate, and the end-walls are approximately straight or slightly 

 curved (PI. XXIII, fig. 1, w.). In radial section the rays have 

 very wavy walls, and the cells are arranged with considerable 

 irregularity, their waving outlines, however, fit into each other 

 (text-fig. 75, and PI. XXIV). The cells appear all alike and 

 rather thin-walled, and I have not been able to detect any 

 pitting in them. In a number of places where a ray crosses the 

 cork-like zones, the ray-cells are locally greatly thickened and 

 are often much narrower and more regular, as though the 

 regularity and thickness of wall of the cork-like layer had 

 been contagious and spread for a short distance along the ray. 



In tangential section the rays are also very conspicuous 

 (PI. XXV). The cells which compose them round themselves 

 off, leaving very definite and large spaces at the corners. The 

 cells composing the different rays vary greatly in si/e, as can 

 be well seen in PI. XXV, fig. 2, where the contrast between 

 ray x and ray y is very noticeable. The upper and lower 

 limiting cells of the ray appear quite like the others, though 

 there is often a long narrow space above and below the ray 

 before the adjacent thick-walled elements come into contact. 



The cork-lands ure narrow, composed of two, three, or four 

 rows of narrow flattened cells (text-fig. 74, n.\ These generally 

 lie between the thinner-walled elements, but may be adjacent 

 to or pass obliquely through a band of the much-thickened 

 elements. Bands of these cells can be seen at ., PL XXIV, 

 fig. 1. They have the peculiarity of cork, and appear identical 

 in longitudinal and transverse sections. 



