A EUROPEAN PETRIFACTION WITH FOLIAGE. 489 
this species the ramenta are of two kinds; the very large solid-walled ones 
which, curving round each other and packed together, form the pseudo-leaf- 
bases, and the interstitial ramenta, very much smaller and thinner walled, 
packing the spaces between the former and also between the true leaf-bases. 
The marked distinction between these can be well seen in fig. 5, PI. 19, 
where b represents about half a pseudo-leaf-base area, and b' part of a second, 
while ir are the interstitial ramenta. : 
Epidermis and cork cambium. See p. 496. 
There are occasional doublings and irregularities in the cells, but the 
ramenta are generally one cell-row thick, and the small ones have approxi- 
mately the same number of cells as the large ones, i. e. from about 12 to 20 
or more. The number of eell-rows in the ramentum is, within reason, a 
specific character, as was pointed out by Wieland (1906, p. 52), and the 
present species in having a single row resembles B. Gibsonianus and Cyca- 
deoide« nigra. 
Altogether there are three types of ramenta in this plant, the two types 
just described and in addition hair-like ones on the undersides of the leaves 
themselves, which will be described below. 
The rounding off of the leaf-base to form the rachis takes place rapidly ; 
in section j, for instance, one of the leaf-bases is very definitely reduced in 
area, and is rounding off, while in section his seen a rounded rachis with 
its curved horse-shoe bundle and a few pinne attached to it (P1. 20. fig. 7). 
Groups of leaflets, each belonging to one frond and still folded as in the 
bud, lie in their normal sequence round the stem and are best seen in section 
g for example, at a level high enough up to be past the apex of the axis- 
tissues, which at this level are represented only by pseudo-leaf-base ramenta. 
The /ronds on the present species are clearly not adventitious, but are its 
normal leaves, whether or not the young stem itself had ultimately originated 
as an adventitious bud. Each frond is evidently still very young, not yet 
unfolded, the pinnules being packed in regular arrangement similar to that 
described by Wieland (1906, pl. 19, and 1916, pl. 58), though on a much 
smaller scale, The natural size of. Wieland’s packed group of pinnules 
