18 



EDWARD C. JEFFREY ON 



In figure 46, plate 6, is a cross section of the root of Cedrus atlantiea. The 

 center of the primary wood is occupied by a resin canal of considerable size, which 

 is surrounded, as in Pseudolarix and Abies, by thin walled cells of the secretory paren- 

 chyma. The walls of the gland cells in Cedrus are of pure cellulose. The presence 

 of a median resin canal in the root of this genus has already been described by 

 De Bary ('84) . The secondary wood of the root in the various species of Cedrus con- 

 tains no resin ducts except in the case of injury. There are no sclerifications either 

 in the bast or in the cortex, and mucilage cells are absent as well. In the smaller 

 roots which have been mainly examined there were no cortical resin canals, although 

 these are abundant in the stem. 



The leaf trace of Cedrus is described by Bertrand (74) as showing some evi- 

 dence of duplication by the presence of a very distinct median medullary ray. In 

 the cortical course of the leaf trace it is obviously double, as in the case of the other 

 Abietineous genera described above. 



This condition is shown in figure 47, plate 6, which represents the foliar trace of 

 Cedrus atlantiea as it is passing through the cortical tissues on its way to the leaf. 

 A similar state of affairs has been made out in the leaves of seedlings of Cedrus libani. 

 It will thus be seen that in its outgoing leaf trace Cedrus is no exception to the 

 condition of affairs described above for the other Abietineae. Although the foliar 

 trace in this genus is geminate in the middle and outer cortex, it nevertheless 

 leaves the central cylinder of the axis as a single strand. 



Tsuga. 



In figure 48, plate 6, is shown a transverse section of an injured stem of Tsuga 

 canadensis. There are four normal rings of wood present and part of another. The 

 injury took place obviously in the early summer of the fifth year of growth of the 

 branch represented in our figure. From the mode of formation of the traumatic 

 wood it is clear that the injury must have been very severe, for the first ring 

 of woody tissue formed subsequently to this event extends only half way around 

 the stem. Although the magnification is not great, it is obvious that resin canals 

 are present in the usual tangential row, which is characteristic of the traumatic 

 canals in the Abietineae in general. The resin ducts are situated in the early 

 formed part of the traumatic wood. The usual position of the resin ducts in 

 the injured wood of T. canadensis is in the later formed portion of the spring 

 wood. This is clearly seen in the case of large wounds in thick steins, where a 

 number of years is necessary for the closing over of the exposed surface by 



