HALONIA. 93 



Pig. 3 (magnified twenty diameters) represents the centre of one of the areolae, 

 showing the vascular bundles in the middle, with a zone of orthosenchyma, which has for 

 the most part disappeared, as is generally the case, and a regular zone of parenchyma 

 very similar to that exhibited in fig. 5 of Plate XVI, as occurring in specimen 

 No. 35. 



§ 4. Specimen No. 37, Halonia regularis. Plate XVII, figs. 4, 5, 6. 



Specimen No. 37 (fig. 4, natural size) is another example of Halonia regularis, also 

 from the Upper Brooksbottom seam of coal. Like the last described specimen, it is 

 partly imbedded in a matrix of limestone. The portion exposed shows the main stem, or 

 rather root, immediately before it dichotomizes, and parts of the forking branches. The 

 transverse section of the former is irregularly oval, measuring one eighth of an inch 

 across its major and rather more than half an inch across its minor axis. The two 

 portions of the fork are nearly circular, and each measures about five eighths of an inch in 

 diameter. The depressed areolae, so well shown in specimen No. 36, are not equally 

 displayed in this, but there is sufficient evidence to prove that it belongs to Halonia 

 regularis. 



Pig. 5 (magnified five diameters) is a transverse section of the specimen, showing the 

 medulla composed of orthosenchyma, and a woody cylinder composed of large scalariform 

 tubes in the interior of the broken circle, and lesser utricles or cells next the exterior. The 

 division of the woody cylinder might at first sight have been taken for an accidental 

 disruption before the specimen was fossilized ; but, as it occurs just before the root 

 dichotomizes, and is not the only example of the kind in my possession, I am led 

 to believe that it is the first commencement of the division of the woody cylinder into two, 

 as previously described at length in specimens No. 32 and No. 33. Outside the woody 

 cylinder the delicate parenchyma has, for the most part, disappeared ; but evidence of four 

 vascular bundles, partly showing structure, is seen in the mineralized portion ; and, where 

 the parenchyma becomes stronger and passes into prosenchyma, indications of more bundles 

 are seen. 



The exterior presents a thick epidermis, similar to that described in the last specimen 

 (No. 36) ; and the two are so much alike in structure that it is impossible to distinguish 

 the one from the other. 



I am aware that the vascular bundles last named, as well as those in Nos. 35 and 

 36, have been generally described as intruding rootlets of Stigmaria which have penetrated 

 the stem. No doubt they do appear larger, especially on their outsides, than we should 

 expect to find in such a root ; but the delicate tissues of those parts have nearly 

 always been much distended, whilst the vascular bundles in the centre remain generally 

 of the same size. Whether they be taken for the vascular bundles of the root, 



