64 Boyal Society. 



miteau by his having already described the structure of a true 

 Calamiteau strobilus from an example in which the central axis 

 retains most accurately the arrangement of tissues characteristic 

 of Calamiteau stems (Manchester Transactions, 1870). A tyjje 

 of stem to which tha author had previously assigned the provi- 

 sional generic name of Amijelon is now shown to be the root or 

 subterranean axis of Asteroj^Jii/llites, specimens being described in 

 which clusters of roo-lets are given off, in irregular order, from 

 various points of the exterior of the branching roots. The latter 

 have no medulla; but in the centres of several of them the 

 author finds the peculiar triangular tibro-vascular bundle so cha- 

 racteristic of Asterophyllites ; and remains of the same trifid origin 

 of the vascular layers may be traced in all, in the peculiar curva- 

 tures assmned by the vascular laminae as they proceed from within 

 outwards. The bark consists of two layers : the inner one is 

 composed of ordinary parenchymatous cells, often of considerable 

 size ; the outer one consists of irregular piles or columns of cells, 

 disposed perpendicularly to the surface of the bark, and vvith 

 their tangential septa in close contact and in parallel planes. The 

 lateral or radial boundaries of these piles of cells are more strongly 

 defined than the transverse septa. In tangential sections of this 

 outer bark, each of these radially disposed columns of parallel-sided 

 cells appears as a single thick-walled parenchymatous cell, whose 

 aspect, iu common \rith that of its neighbours, is that of ordinary 

 coarse parenchyma. Such sections exhibit no indication of the 

 radial elongation of these cells seen in radial and transverse ones. 

 On reexamining the inner bark, we discover the explanation of 

 these appearances. Many of the larger and more peripheral of 

 the cells of the latter are seen to be undergoing division by the 

 development \vithin their walls of secondary cell- partitions, which 

 are parallel Avith those of the radially disposed columns. It ap- 

 pears obvious that each of the latter was primarily one of the cells 

 of the inner bark, which has become elongated radially, and at the 

 same time divided into a linear series of compressed cells by the 

 growi:h of a succession of secondary divisions, all of which were 

 more or less tangential to the periphery of the stem. 



The author directs special attention to the genetic activity of this 

 inner bark ; the cells of its inner surface were obviously instru- 

 mental iu producing the successive circumferential additions to the 

 primary vascular axis, whilst those of its outer surface increased 

 the diameter of the outer bark in the way just described. 



After comparing these plants vrith living forms, the conclu- 

 sion is arrived at that the nearest parallel to the structure of their 

 stems is to be found iu Fsilotum triquetrum ; whilst their general 

 aflinities are regarded by the author as Lycopodiaceous rather 

 than Equisetaceous. The exogenous aspect of their successive 

 Avascular growths is, if possible, more conspicuous than iu most of 

 the other Carboniferous Cryptogams. 



The structure of the stems described is identical with that of 

 those found at Autun by Prof. Renault, and assigned by him to 



