134 Mr. J. Miers on Ephedra. 



for the ligneous fibres of the several internodes which enclose the 

 pith, and which constitute the wood, all converge to form a 

 sort of plexus or solid diaphragm across each node, much after 

 the manner of the stem of a Bambusa, 



This pith is quite homogeneous, consisting of oblong, square, 

 parallel cells (hexagonal in their transverse section), with very 

 thin transparent walls, which are pitted with few, minute, opake 

 dots. The wood is hard, formed of fine, simple, indurated 

 fibrous tissue, closely compacted ; these longitudinal fibres, under 

 a powerful microscope, appear marked by dark glands lying 

 across them at irregular distances, which are either transversely 

 linear or oblong, thus giving them almost a scalariform appear- 

 ance, the walls themselves being pitted with minute and almost 

 invisible specks ; these are crossed by very numerous transverse 

 medullary rays of similar structure, which extend from the pith 

 to the bark. In the first two or three rows of the longitudinal 

 fibres or ducts next the pith, the markings are so very close 

 that they have much the appearance of uncoilable trachese ; but 

 I have nowhere been able to find any true spiral vessels. Inter- 

 spersed among the longitudinal woody fibres, are the many hol- 

 low air-tubes before mentioned, of three or four times their dia- 

 meter, which appear uninterrupted throughout the entire length 

 of the internode : their walls are extremely thin and translucent ; 

 and it is upon these only that we find the large circular spots 

 (apparently fenestrations), which are well shown in Lindley's 

 * Introduction,' pi. 2. fig. 7. It will hence be seen that there is 

 no analogy between this structure and that of the ConifercB, 

 where the annular disks, which so conspicuously mark the Gym- 

 nospermous families, are always found upon the ligneous fibres 

 themselves, and not upon the air-passages, as in Ephedra. The 

 structure is equally different from that of the young branchlets 

 of Casuarina, where the pith crosses the nodes and is continuous 

 throughout the branches. 



There is a peculiarity in the bark of Ephedra that may be 

 worth recording : it is filled with strong ligneous fibres, as in 

 Urticacea, which, being always united in bundles, give rise to 

 its finely striated surface ; it is covered by a thick, tough epi- 

 dermis, of the texture of parchment, and which follows the si- 

 nuosities of the striatures. Upon the ridges of the striae a 

 number of prominent horny excrescences occur, which occasion 

 its scabridity ; and in the hollows between the ridges are seen a 

 number of black longitudinal specks, which appear almost like 

 stomata that have become closed by a deposit. 



Thus far it has been endeavoured to show that the order 

 Gnetacea is not allied to any of the Gymnospermous families, 

 with which it has been associated by most botanists. It will 



