329 



some attention at his hands. His investigations were rather with earlier growth 

 than the mature material with which, however, we are more directly concerned, 

 as it serves more the technological side, and so it is on the latter that the following 

 remarks are based, the secondary wood being more particularly dealt with here. 



A cross-section through a portion of two seasons' growth (Figure 237) shows 

 the lumina of the tracheids of the xylem to be of varying diameters, whilst the 

 cell walls are fairly thickened, those of the autumnal period being more so. 



The outer walls of the tracheids are seen in this picture to be irregularly 

 hexagonal in shape, but mostly circular or oval internally. It will be noted that not 

 many of the tracheids contain a dark-brown substance, — the manganese compound, 

 and these are all well defined in Figure 237. The medullary rays are two in 

 number here, situated three and four rows from the left and right side respectively, 

 and extend the whole length of the specimen from top to bottom ; the particular 

 point of interest is that they are entirely empty, and this fact should be noted, 

 as throughout the whole series of plates it is an important generic, specific, and 

 phylogenetic character — this almost entire absence of cell content in the parenchy- 

 matous cells of the rays in t\\e Araucaria. Figure 238 shows, however, at the top 

 of the figure the manganese compound substance in three of the rays, and in the 

 case of the left one, a portion has come out of the cell and bent over in the form 

 of an obtuse angle. 



Attention might also be drawn to this dark-brown cell content of the 

 tracheids in the spring growth, for in this respect it is similar, with the exception 

 of Podocarptis, to all Australian living Conifers, and other living representatives 

 of the Conifer family. In this connection one might mention the researches of 

 Professors Jeffrey and Chrysler in Palseo-Botany, who have found similar features 

 in fossil and living pines of North America. Figure 239 shows the intrusion of a 

 traumatic resin cavity between the two seasons' growth ; a similar feature has 

 already been recorded imder Adinostrohus pyramidalis (Figures 208-211), the 

 dark-cell contents of the tracheids are here much in evidence in the upper portion 

 of the picture in the spring wood, whilst the other parts are almost quite free 

 from this manganese compound. There are two medullary rays, one in the centre 

 and one midway between it and the left edge, and it should be noted that both 

 contain none of this substance. 



The tangential section in Figui'e 240 shows the emptiness of the medullary 

 cells more clearly depicted, for practically no dark-brown coloured cell contents 

 can be seen in them. In this view the linear outline of the rays is clearly defined 

 as they intrude between the tracheid walls, and in no instance are they more than 

 one cell in width, whilst the number of horizontal cells in each ray varies from 

 two to over twenty. The dark patches in the lumina of the tracheids correspond 

 to the dark-cell contents referred to in previous Figures (237-9). Several of thr 



