16 



EDWARD C. JEFFREY ON 



atlantica. Running in a circular fashion through the wood is a tangential row of trau- 

 matic resin canals. It is an interesting fact that in Cedrus the lining of the traumatic 

 resin canals of the injured root is different from that found in the stem under the same 

 conditions. Instead of the glandular cells in this case being thick walled and lignified 

 as they are in the stem, they are thin walled and of pure cellulose, and in fact strongly 

 resemble in their characteristics the resiniparous lining of the normal resin canals of the 

 wood in Pinus. Figure 30, plate 5, sufficiently illustrates the structure of the traumatic 

 resin duets of the wood of the root in Cedrus atlantica. It will be seen in this highly 

 magnified representation of the canals, that they are lined with thin walled cells, con- 

 taining protoplasm and a nucleus. No resin canals are formed as a result of injury to 

 the cortical tissues of either the stem or the root in C. atlantica. Before leaving the 

 discussion of this species, reference must be made to an interesting phenomenon, which 

 occasionally is present in wounded roots. Ordinarily only vertical resin canals are 

 produced as the result of injury to the tissues of the wood in Cedrus atlantica ; but in 

 one case which has come under my notice horizontal canals were present as well. These 

 started from the vertical canals and ran for a short distance radially outward, and then 

 ended blindly. Like the vertical resin ducts of the root the}* were lined with thin walled, 

 glandular epithelium and not with thick, lignified, resiniparous cells such as are found in 

 the stem. I have not found horizontal resin canals in the stem of C. atlantica ; but this 

 is probably to be explained by the fact that my material was limited rather than to their 

 being non-existent, for I have observed such horizontal canals frequently in material of 

 Cedrus deodara, to be described below. 



In figure 40, plate 5, is seen a part of a transverse section of the wood of Cedrus 

 deodara. Crossing the lowest annual ring in the figure and in the summer wood is to be 

 seen a row of resin ducts, which we may compare with those occurring as the result of 

 injury in C. atlantica. Although the piece of wood did not actually show the presence of 

 an injury in this case, there appears to be little doubt that the tangential row of resin 

 canals occurring here is due to a wound either above or below the region from which the 

 block of wood was cut. This appears extremely probable, since traumatic resin canals 

 occur far above and below the actual spot of injurj^, as has come under my observation 

 many times in American genera of the Abietineae, and in Sequoia, in which, as has been 

 shown in the first memoir, similar conditions occur. It is further to be noted that the 

 resin ducts in C. deodara occur in the summer wood, in contrast to C. atlantica. where 

 they are found in the spring wood. The two species differ from each other in this respect 

 in the same way as do Sequoia semperncrens and S. gigantea. It is worth while to call 

 attention to the different position of the traumatic resin ducts of the two species of Cedrus 

 under discussion as it furnishes a means of distinguishing their woods. Similar differ- 



