39 



THE ANATOMY OF WOODY PLANTS 



region of the node. Fig. 2680 shows one of these on a higher scale 

 of magnification. In the large ray and toward the bottom of the 

 figure lies the leaf trace, which is both subtended and flanked by 

 storage parenchyma. The wood on either side of the large ray 

 shows the presence of the primitive rays, which, as has been 

 pointed out on an earlier page, may be considered in a general 

 way as equivalent to the narrow rays of the conifers and similar 



forms. In Fig. 2686 is 

 seen a vertical tangen- 

 tial section through one 

 of the large leaf rays of 

 the same genus. It is 

 evident that the foliar 

 trace runs in a much 

 enlarged ray and is sur- 

 rounded on all sides in 

 its horizontal course by 

 ray parenchyma. It is 

 very clear from the con- 

 sideration of the genus 

 Leea that there are pres- 

 ent large rays in storage 

 relation to the leaf 

 traces, precisely as in 

 the oak, Casuarina, and similar forms. We may now pass to 

 the situation in Vitis, where the conditions are not so manifest, 

 but are quite intelligible by comparison with the shrubby member 

 of the Vitaceae just described. Fig. 269 shows the general topog- 

 raphy of the stem of the Concord grape in the region of the node. 

 Seven leaf traces are to be seen as darker masses. Of these only 

 one is passing into the cortex and the rest are still contained within 

 the woody cylinder. Fig. 2700 illustrates one of the foliar seg- 

 ments of the stem with a higher degree of magnification. The 

 segment in question is separated on either hand from the rest of 

 the woody cylinder by broad radial bands of parenchyma. In the 

 leaf trace itself may be found radial dark stripes, the primitive 

 rays. These are absent in the segments of the cylinder which 



FIG. 267. Transverse section of woody cylin- 

 der of Leea. Explanation in the text. 



