ANATOMY AND PHYLOGENY OF THE CONIFERALES, 



18 



tative shoots of the genus under consideration have I ever Found resin duds in the first 

 annual woody ring, such as occur in Abies magnifica as described above, and in Sequoia 

 (jhjantea described in the former memoir. 



The root of Pseudolarix closely resembles that of Abies, for if has the same central 

 resin canal in the primary wood and numerous mucilage cells in the cortex as well. The 

 sclerotic nests which are characteristic of the cortical tissues of Abies are absent in the 

 present genus. Figure 28, plate 4, sufficiently illustrates the truth of the statements 

 made above. The dark cells appearing in the cortex contain tannin, while the Large 

 empty ones are those which in life contain mucilage. En figure 2!), plate 4, a part 

 of another root is represented. In this instance the section was treated with chrome 

 alum, in order to render the mucilage insoluble in the aqueous dyes employed in staining. 

 In one of the mucilage cells on the extreme right of the figure the contents, although 

 rendered insoluble by the use of chrome alum, have come out bodily, and are lying 

 over some of the other cells. The central resin canal, which is always present in the 

 root of Pseudolarix, is surrounded by parenchymatous cells with thin walls of unmodified 

 cellulose, and thus closely resembles that of Abies. 



In figure 30, plate 4, appears a transverse section of the ligneous portion of an 

 injured root from a seedling from Pseudolarix. The magnification is sufficient to show 

 a semicircle of resin ducts running off from the margins of the wound. There is 

 no corresponding formation of traumatic resin canals in the cortical tissues, which 

 like those of the stem are normally entirely without resiu ducts. I have had no 

 opportunity of examining the reaction of the root in the mature plant of Pseudo- 

 larix when injured, but there seems no reasonable doubt that the result would be 

 the same as in the stem of the seedling described above. 



Figure 31, plate 4, shows the structure of a three year old branch of Pseudo- 

 larix as seen in transverse section. The material in this case came from a large 

 tree growing in the Hunnewell pinetum at Wellesley, Mass., which has produced cones 

 abundantly for a number of years. From the seed of this tree a number of seedlings 

 have been grown by Mr. Jackson Dawson at the Arnold arboretum of Harvard 

 university, so that there can be no doubt as to its vigor. There are no resin canals 

 present, either in the cortex or in the wood. The empty spaces seen in the former 

 tissue are the mucilage cells referred to above. In figure 32, plate 4, is a transverse 

 section through the bracteolate portion of the peduncle of a female cone of the spe- 

 cies under consideration. Resin canals are equally absent in both wood and cortex. 

 The mucilage cells of the cortex in this case are much fewer in number than they 

 are in the vegetative axis, and in the higher portion of the peduncle they disappear 

 entirely. 



