■44-4 



EDWAKD C. JEFFKEY ON 



fact that the resin ducts end upwardly in resin pockets of considerable size. Figure 10, 

 plate 69, illustrates the structure of the reproductive axis proper as seen in cross section 

 at a height much above any of the foregoing. The resin ducts have reappeared in the 

 wood close to the medulla, which in the present figure presents an elliptical outline due 

 to the fact that two fructiferous scales of the cone derive their fibrovascular supply from 

 the central cylinder of the axis in this region. The resin canals are particularly well 

 developed around the bays corresponding to the departing traces of the fructiferous 

 scales. The figure includes only part of the first annual ring of wood. In the repro- 

 ductive axis of S. gigantea there are two annual rings of wood only, in the portion 

 corresponding to the cone proper, and as a consequence growth does not continue 

 after the second year when the seeds are ripe. The additional annual rings which are 

 characteristic of the peduncle of the cone gradually die away in the transitional region 

 between the peduncle and the axis proper. It is to be noted that there is no connection 

 between the resin ducts of the peduncle and those of the proper axis of the cone, a condi- 

 tion quite similar to that described above for the successive longitudinal annual segments 

 of the more vigorous vegetative branches of adult trees. I have not yet found any cone 

 of S. gigantea in which the resin canals were absent from the first year's growth of the 

 wood. 



In figure 11, plate 69, is seen a transverse section through the woody portion of the 

 base of a cone scale, including all of the first annual ring of growth and a narrow zone 

 of the second. On the lower side of the first annual ring, resin ducts appear near the 

 medulla. These form the direct continuation of the resin ducts of the axis shown in 

 figure 10, plate 69. In figure 12, plate 69, is represented a section through a somewhat 

 higher region of another fructiferous scale. In the center appears the medulla, above and 

 below it is the wood of the fibrovascular system of the scale. The most interesting- 

 feature of this figure is the large number of resin canals present in the wood. Of these 

 there are two series : the one composed of larger and less numerous ducts nearer the 

 pith, and the other made up of smaller and more numerous ducts, farther out in the wood 

 of the scale. Both series of ducts tend to become divided by radial partitions, and the 

 two systems are not infrequently united by radial anastomoses as well, comparable to the 

 radial canals running in the medullary rays of most of the Abiethieae. The last two 

 figures present extreme conditions in the modes of occurrence of resin canals in the wood 

 of the fructiferous scales. Where the ducts are least abundant they are confined to the 

 lower side of the scale as in figure 11, plate 69, and form a single series. They may also 

 extend as a single series to the upper side of the scale. When the system of ducts is 

 double, it may be double on the lower side of the scale only, or on one or other wing of 

 the scale as well, or finally as in figure 12, plate 69, the double series may extend all 



