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EDWARD C. JEFFREY ON 



enclosed incompletely on the opposite side by wing-like extensions of the secondary 

 xylem. These are in turn completely covered by a thick zone of very dense transfusion 

 tissue. The phenomenon just described is not of very common occurrence and in all 

 probability no very great morphological importance is to be attached to it. 



The Seedling of 8. gigantea. 



Figure 17, plate 70, reproduces a transverse section of the woody portion of a five 

 year old seedling of 8. gtgantea, collected by Prof. Asa Gray in the famous Calaveras 

 grove of Big Trees, during his visit to California in 1872. I owe this duplicate, specimen 

 to the kindness of my colleague, Prof. B. L. Robinson, curator of the Gray herbarium. 

 Four annual rings are shown in the figure. The resin cells which are so conspicuous in 

 the wood of the adult stem are much less strikingly present in the seedling, and resin 

 ducts are entirely absent even from the first annual ring. Through the kindness of Dr. 

 Joseph L. Goodale, I have had the opportunity of examining several other seedlings 

 of S. gigantea, grown on his estate at Ipswich. In none of these did I find any indi- 

 cation of the presence of resin canals in even the first annual ring of woody growth. 



Effects of Wounds on the Woody Tissues of 8. gigantea. 



Figure 18, plate 70, represents part of a transverse section of a wounded root of 8. 

 gigantea, in which the wounded area has become completely callused over. Towards the 

 right in the figure, may be seen a mass of callus tissue. In the ring of growth just below 

 the callus, is to be made out a long row of traumatic resin ducts stretching completely 

 across the figure. The annual ring containing the resin canals, although axial to the 

 callus, was formed subsequently to the wounding of the tissues, as was made out by 

 examining the whole line of injury. The resin ducts are quite similar to those occurring 

 normally in many of the Abietineae, and are generally surrounded by but a single layer 

 of cells. Of these cells some are normal glandular cells, such as usually surround the 

 lumen of resin canals where they occur in the wood of the Abietineae, while others are 

 " resin cells," and are distinguished by their thick and strikingly pitted walls. In figure 

 19, plate 70, is represented part of the outer margin of the wood in a transverse section 

 of the peduncular portion of the cone of 8. gigantea. Very large resin canals appear 

 along the inner border of the vernal wood in the last annual ring. These are surrounded 

 by secretory cells ; but as the figure was made from dry material the latter have almost 

 completely collapsed. The formation of true resin canals in this case was due to the 

 same cause as in the root just described above. I have seen a large number of instances 



