BIBLIOGRAPHY. 



117 



form so prominent a feature. There are only two represented, owing to a greater 

 number requiring more space than could be allotted for the figure ; it consequently 

 requires to be stated that they are arranged in a spiral manner. Mr. Witham described 

 these openings as containing the medullary rays, which is not the case, because what has 

 been probably taken for cellular tissue is in reality a number of small vessels (/) similar 

 to those which occupy the outer part of the medullary sheath. Although the longitudinal 

 sections do not exhibit any of these bundles springing from the vascular cylinder, their 

 proximity to this part in some transverse sections (see fig. 2), together with the fact just 

 stated, leaves no room to doubt their having constituted the leaf-cords of the plant. 

 According to Mr. Morris it would appear that Dr. Brown had ascertained this point 

 some titne since. ^ Owing to one of the openings, or vascular passages, having been 

 intersected in a portion of its course through the ligneous zone, as shown in the longi- 

 tudinal section parallel to the medullary rays in fig. 3, i)l. iv, we have displayed in a very 

 instructive manner a leaf-cord, or vascular bundle (/), traversing at right angles the 

 ligneous tissue ; a similar bundle is exhibited in the transverse section (fig. 2). These 

 two sections prove that the leaf-cords curve but very slightly in their passage through 

 the ligneous zone, as they proceed horizontally for a considerable distance. From the 

 passage being in part hollow (see fig. 4), it may reasonably be supposed that the cords 

 were accompanied in their course with a portion of cellular tissue. 



" We may now be permitted to say a few words on the comparative anatomy of 

 Anahathra. No one can help being struck with the similarity which this plant possesses 

 in some points of its structure to Sigillaria and Lejndodendroii. The width of the 

 ligneous zone is certainly greater in Anahathra than in Sicjillaria ; but there scarcely 

 appears to be a shade of difference in the character of its constituent tissue in either 

 plant ; while between Lepidodendron and Anabaihra there is in their vascular cylinder 

 the closest resemblance. It is, therefore, clear that these three plants are nearly related 

 to each other. 



" The resemblance between Anahathra and Lepidodendron in their vascular cylinder 

 has induced Brongniart to hazard a question to this effect : May not the latter be the 

 young branch, and the former the stem, of one and the same plant ? ' The hypothesis 

 involved in this question,' says its author, ' appears, however, to have little probability in 

 its favour, in consequence of there being on the outer part of the vascular cylinder of 

 Anahathra none of the prolongations which are visible on the corresponding part of 

 Lepidodendron J The prolongations here alluded to are those portions of the leaf-cords 

 which are on the point of curving off from the cylinder, to the margin of which they give 

 a sumous appearance. Mr. Witham's transverse sections of Anahathra certainly do not 

 show any sinuosities. Brongniart's objection is, therefore, so far a valid one ; but it 

 seems to me that, before Lepidodendron can be considered as the branch of Anahathra, 



1 'Transact. Geological Society,' 2nd series, vol. v, description of pi. xxxviii. See above, p. 113. 



