610 PROCEEDINGS OF THE AMERICAN ACADEMY. 



resin ducts in the first annual ring, but the inner series in this case lies 

 in the primary wood. This condition is at variance with that of hard 

 pines where both are in the secondary wood. The presence of resin 

 canals in the primary wood is not unparalleled in the coniferous series, 

 — they occur in the primary wood of the root of all the Abietineae (1), 

 of the cone axis of Sequoia gigantea (2), and of certain members of the 

 Araucarineae (3). True medullary canals, such as have been de- 

 scribed in Pinus succinifera (Goepp) Conw. (4) seem to be entirely 

 absent. In the succeeding annual rings, the vertical canals are 

 smaller and less frequent. With the horizontal canals they form a 

 freely anastomosing system (Figure c). 



Figure b also shows the character of the pith. Scattered among the 

 thin walled parenchyma cells there are clusters of very thick-walled 

 sclerified elements. Such a cluster occurs in the upper part of Figure 

 b. These show a tendency to be in more or less definite horizontal 

 bands, but do not form true diaphragms. 



The medullary rays are of two sorts, — linear and fusiform. The 

 latter are frequent, and always embrace a resin canal (at the left of 

 Figure e), a leaf trace (Figure/) or both. The linear rays are much 

 more abundant, as may be seen in any of the illustrations. They are 

 usually low, and as in living pines, destitute of resinous content. The 

 walls are thin and heavily pitted. The lateral pits, as shown in 

 Figures a and 6, Plate 2, vary from one to two to each cross field ; they 

 are small, the mouths lenticular on the wall of the ray and circular on 

 that of the tracheide. Not infrequently there are indications of 

 fusion where two small pits unite to form one of medium size. At the 

 extreme lower right of Figure a, and in the upper part of Figure b, such 

 phenomena are represented. The resulting pore is rarely as large as 

 in modern pines such as Pinus strobus, though occasionally a single pit 

 occupies almost the entire cross field, as in the lower left of Figure b. 

 Both horizontal and end walls are also heavily pitted. 



In association with this parenchyma, there are longer and lower 

 cells, always devoid of contents, with bordered pits on lateral, hori- 

 zontal and end walls. That these are rav tracheides, such sections as 

 are photographed for Figures c and d, prove beyond question. They 

 may occur only on one margin of a ray, or on both, as in Figure c. 

 Rarely they are interspersed, with parenchyma above and below. 

 Projecting in from the horizontal walls, there are well marked teeth. 

 These may be seen in the lower ray tracheide of Figure c, the upper 

 one of Figure d and better in Figure c. These teeth are doubtless 

 analogous to similar appearances in hard pines, though less developed 



