ANATOMY AND PHTLOGENY OP THE CONIFERALES. 



in a two year old branehlet from a, cone-bearing branch of a. different s|)ecimen of A. mag- 

 nified. Resin canals are clearly present in the first annual ring and absent in the second. 

 No injury to the tissues could be made out in the case of this branch any more than in 

 the case shown in figure 17 of plate In figure L9 ? plate 3, is shown a cross section of 

 the internal region of the woody ring of a vigorous branch from a nourishing specimen 

 of A. magnified, between 8 and LO meters high, growing in the Hunnewell pinetum at 

 Wellesley, Mass. Resin ducts are present here as well as in the other cases. In less vig- 

 orous branches from the lower part of the tree the resin ducts do not appear. In figure 

 20, plate 3, a portion of a section from the same branch as that appearing in figure 19 is 

 represented more highly magnified to show the nature of the resin ducts and of the cells 

 forming their walls. It will be seen that the ducts under consideration are quite close 

 to the primary wood. They are obviously surrounded by the same thick walled, resinipar- 

 ous cells as occur normally in all the annual rings of Larix. The magnification is suffi- 

 cient to show the presence of nuclei in four or five of the parietal cells of the ducts. The 

 nuclei present in the remaining cells have been missed by the plane of section. To sum- 

 marize, resin canals surrounded by thick walled, epithelial cells, such as are found about 

 the ducts in the annual rings of Larix, occur in the first annual ring only of vigorous 

 branches from vigorous trees of Abies magnified. 



In longitudinal section the pith of branches of A. magnified presents a curious 

 appearance, which is shown in figure 21, plate 3. The medulla is crossed by diaphragms 

 consisting of sclerotic tissue, and alternating with these are segments of soft parenchyma, 

 which tend to break down, thus producing a fistular medulla, such as occurred in many 

 of the Cordaites. Sir J. William Dawson ('88) was the first one, so far as I am aware, 

 to call attention to this feature in the genus Abies. It is referred to here because it 

 appears to have a certain significance in connection with other facts to be described and 

 discussed at a later stage. Noticed by Dawson first in the case of A. bedsamea, it seems 

 to be thoroughly characteristic of the genus, but occurs also in the curious Cedrus-like 

 species, sometimes united under the subgeneric name Keteleeria. 



In figure 22, plate 3, is seen a transverse section of a root of Abies nobilis, a species 

 somewhat closely allied to A. magnified. The root of the latter species differs from it 

 only in unimportant details. The most striking feature of this root is the presence of a 

 resin canal in the center of the primary wood. This peculiarity has been noted by De 

 Bary ('84) as being common to the genera Cedrus and Abies. To these Strasburger ('91) 

 adds the so called Chinese larch, Pseudolarix. The central resin canal in the case under 

 discussion is surrounded by several layers of delicate parenchyma cells, the innermost of 

 which functions as the resiniferous epithelium. There are normally no resin canals 

 present in the secoudary wood of the root of Abies, and the examination of a consider- 



