448 EDWARD C. JEFFREY ON 



occur in long tangential rows in l)()tli the last-named species. T have myself examined 

 a number of species of the genus Abies, and have found resin canals of verv frequent 

 occurrence under conditions to be more fully descrilx'd on another occasion. For the 

 present, however, it may be stated that re.sin ducts are extrenu'ly apt to be present in 

 the female reproductive axis of various species of Abies, even when the}' are quite absent 

 from the woody tissues of the ordinary vegetative stem. For example, in Abies cjrand'is^ 

 according to Penhallow, there are no resin ducts present in the wood. Figure 20, plate 

 70, shows the general structure of the woody axis of the upper portion of the female cone 

 of A. grandis. The specimen from which the figure was made, was secured at the Gray 

 herbarium, and as a consequence the tissues have suffered a good deal from long desicca- 

 tion. Nevertheless, indubitable resin ducts can be clearly made out in large numbers in 

 practically the whole circumference of tlie woody cylinder of the cone. They are of quite 

 the normal type and are surrounded l)y glandular cells which still retain the remains of 

 their protoplasm. The section through the small upper end of the cone axis was chosen 

 because it permitted of showing the structure of the whole of the ligneous portion of the 

 tissues of the cone on a sufficient scale of magnification to make clear the presence and 

 mode of distribution of the resin canals. In figure 21, plate 70, is seen a similar view of 

 the woody tissues in the cone of Abies balsamea. This species is devoid of resin ducts 

 not only in the wood of the vegetative axis but also in that of the cone. The figure in 

 this case was made from material wliich had been properly presei'ved. Figure 22, plate 

 70, is made from a section through an iiijni-ed root of a small tree of Abies balsamea 

 growing in the Botanic garden of Harvard university. The figure includes all the xylem 

 as well as a portion of the phloem of the injured root. There is an interruption of con- 

 tinuitv in the latter tissue on the lower side, due to an incised wound which was made in 

 all probability by a spade used in digging the soil about the tree. The woody tissue is 

 likewise interrupted in the same region as the phloem, and on one side the last annual 

 ring is separated for some distance from the tissues below. There is a considerable forma- 

 tion of resinous tissue along the inner margin of the last annual ring on both sides of the 

 wound, which takes the form of resin cells. Farther away from the wounded portion, on 

 the left, the resinous tissue gives place to a tangential row of resin ducts continuous 

 through almost half the circumference of the root, and passing on tlie right into a narrow 

 zone of resin cells, wdiich are in turn continuous with the thick mass of resinous tissue 

 on the immediate border of tlie wound. The center of the root is occupied by a resin 

 duct surrounded by resinous cells, such as is conunonly found in the axial wood of the 

 root in the genus Abies (de Bary, Comp. anat., 1884). My investigations on this genus, 

 although not yet complete, show that resin canals occm" very frequently in the female 

 reproductive axis, even when they are (juite al)sent from tlie wood of the vegetative stem 



