141 



In Figure 8i there is a portion of a single circle (straight in the picture) 

 of smaller tracheids, four or five cells distant from the well-defined autumnal 

 ones, and which evidently indicates a cold " snap," or where the growth has been 

 retarded. The manganese cavities are plainly shown, but no medullary rays are 

 visible. 



Figure 82 is portion of Figure 81 under a 210 magnification. The cells in 

 the same rows are of almost equal diameters, and on the lower radial walls of the 

 fifth row from the top, bordered pits in section can just be seen, and the torus is 

 also discernible. It will be noticed in several instances, portions of the inner cell 

 walls are detached and protrude into the cell cavity. Whether this is natural or 

 accidental in the cutting, we could not decide. It hardly appears to be a case of 

 tylosis. 



Figure 83 is an 80 magnification of a radial section of timber. The general 

 character of the parenchymatous cells of the medullary rays are rather obliterated 

 by the dark contents. However, the pictures define clearly that the outer cells 

 of the rays are of identical structure to the inner ones, and that the whole 

 group may be classed as parenchymatous. This is a distinct difference of form 

 or structure of the cells of medullary rays from some living non-Australian Pines. 

 In the same figure it will be noticed that the narrow lumina of the autumnal 

 wood are towards the right of the picture. 



The numerous bordered pits are in single rows on the medullary walls of 

 the tracheids, and are well brought out in both plates. The simple pits of the 

 medullary rays are distinctly seen at the top right-hand corner, and the bottom 

 of Figure 83. The diameter of the bordered pits varies according to the diameter 

 of the lumen, and the presence of manganese compound in the tracheids is marked 

 by the darkened content. Figure 83 has only one cell filled with manganese 

 compound, which is low down In the right hand corner, and Figure 86 has three 

 on the right hand centre of the field of observation, being the vertical views of 

 the manganese cells of Figs. 80 and 81. 



Medullary Rays. 



In addition to what has been stated under Figure 83 it may be further 

 remarked that these organs present novel features when compared with those of 

 Angiosperms. In the radial and tangential sections they are found to consist 

 entirely of narrow parenchymatous cells circular in form when viewed tangen- 

 tially in the wood. Each ray is composed of a varying number of cells arranged 

 in horizontal parallel strata only a single cell in breadth. Most of the outer and 

 inner cells are filled with manganese compound similar to the other cells, the 

 radial walls being marked by the presence of simple pits, and cells void of this 

 substance are the exception. In Figures 87 and 88 they are shown radially 

 in situ in the wood substance, the varying length is evidently due to the plane of 

 cutting, the vertical diameter varying in each case according to number of cells. 



