116 



POSSIL PLANTS. 



terminations (see figs. 3 and 4). The whole of their walls are marked with fine trans- 

 verse lines or bars, which in general are parallel to each other ; but occasionally they 

 divide as is represented in fig. 5. All the tubes have their walls of a uniform thickness, 

 so that Anahathra displays no appearance of the concentric rings which are found in the 

 wood of ordinary exogenous trees. The ligneous zone appears to have been intersected 

 by numerous narrow medullary rays, judging from the interspaces which are marked d 

 in figs 2 and 4. 



"The vascular cylinder is composed of elongated tubes which on the transverse 

 section are irregularly angular, and somewhat variable in their proportion. Those of the 

 greatest diameter are a little larger than the tubes composing the marginal strip of the 

 ligneous zone, and they constitute the inner four fifths of the cylinder ; while the 

 smallest, into which the others gradually pass, occupy the remaining or outer portion. 

 At the margin of the cylinder the vessels have become so diminished in size as to 

 resemble the small ligneous tubes wdiich immediately circumscribe them ; occasionally a 

 small vessel is to be seen among the larger ones. With the exception of their being 

 placed somewhat according to size, as just stated, the tubes of the medullary sheath possess 

 no order in their arrangement. The tissue of this part appears to be shorter than that of 

 the ligneous zone, as there are several terminations displayed on a longitudinal section 

 (see h, fig. 3) ; but I am strongly inclined to believe that the shortness is more apparent 

 than real : it ought rather to be said that the tubes in their longitudinal direction are 

 very flexuous and twisted round each other. This circumstance, by causing a longi- 

 tudinal section to display certain of the tubes obliquely cut, and others deviating 

 from each side of the plane of the section would produce, it is conceived, the 

 appearance as if these cuts and deviations were so many terminations. The walls of the 

 tubes are marked with transverse lines or bars, which difi'er somewhat from those on the 

 ligneous tissue, inasmuch as they are closer to each other, and they are often seen coming 

 in contact, which gives them an anastomosed appearance (see fig. 6, pi. iv). In none of 

 the large vascular tubes are the lines so disposed as to form a spiral, either broken or 

 continuous ; probably this is the case in the smallest, but the section is not sufficiently 

 thin to allow of its being seen. The vascular cylinder is in close contact with the 

 ligneous zone ; and in no part does it display the least appearance of openings or 

 medullary rays. 



" The pith appears to have been formed of fusiform cells, analogous to those which 

 Brongniart describes as belonging to the corresponding part of Lepidodendron. It may 

 be doubted, however, that what I have considered as forming a portion of the pith of 

 Anahathra did in reality belong to this part, since it is simply a portion of fusiform tissue 

 crossing the centre of one of the transverse sections. 



" Reverting to the ligneous tissue, and adverting to the longitudinal section repre- 

 sented in fig. 4, pi. iv, which is at right angles to the medullary rays, and through the 

 marginal strip, our attention must now be directed to these large openings (<?) which 



