THE ANATOMY OF WOODY PLANTS 



nettle, chosen on account of its chalazogamous affinities for com- 

 parison with Casuarina, Betula, Quercus, etc. In the illustration 

 a leaf trace with its flanking broad rays is shown, as well as the 

 adjacent segments of the cylinder. No primitive rays are to be 

 seen in the trace, which is composed of vessels and wood fibers. 

 In order properly to interpret the slender axis of the nettle, the 

 stouter and more woody regions of the stem should be examined. 



Fig. 2760 repro- 

 duces the appear- 

 ance of a part of a 

 section through the 

 thick stem of the 

 species under con- 

 sideration, taken 

 immediately below 

 the node. The 

 trace appears as a 

 highly vascularized 

 radially directed 

 mass on the mar- 

 gin of the pith. 

 On either side of it 

 are radial bands of 

 parenchyma, which 

 correspond to 

 those shown lateral 



to the leaf traces in Fig. 275. In addition to flanking storage 

 tissue the woody region of the stem of Urtica shows a very mas- 

 sive band of radial storage tissue confronting the leaf trace, com- 

 parable to the similar structures found in the case of the oak 

 and Leea. The banded appearance of the broad foliar ray in 

 this instance is due to the presence of alternating stripes of true 

 parenchyma and substitute fibers. A region of the axis farther 

 below the node may now be considered. Fig. 2766 shows a part 

 of a transverse section of the stem some distance below the 

 node. The mass of confronting storage tissue in the region of 

 the node at the lower level has become transformed centrally 



FIG. 275. Transverse section through part of a slen- 

 der stem of the nettle. Explanation in the text. 



