A natomy of Solenostelic Ferns . 707 
a marked influence upon many subsequent investigations. 
Stenzel 1 > however, was entirely unaffected by it, and was the 
first to declare that even the central strands of the stem 
were cauline, although he admits that branches are given 
off from them which run out into the centre of the petiole. 
The Monocotyledonous comparison was also rejected by 
Mettenius 2 , although he still describes the central strands 
of the stem as running out direct into the petiole, sending 
branches to the margin of the leaf- gap as they pass through. 
The point was carefully reinvestigated by Trecul 3 in 1869, 
who reverts to the opinion of Stenzel, and concludes that 
none of the central strands of the stem pass out as such into 
the petiole, and that therefore all the vascular bundles of the 
leaf-scar arise from the margin of the leaf-gap. De Bary, in 
his text-book (1. c., p. 291), follows Mettenius, so that the 
question may be regarded as still an open one. 
Cyathea Brunonis , a Tree-fern with comparatively simple 
once-pinnate leaves, was examined by me, and will serve as 
a good example in which to describe the relations that exist 
between the internal accessory strands and the leaf-traces. 
In this plant the ordinary stelar cylinder is a dictyostele 
consisting of two or three large band-shaped meristeles 
separated by relatively small leaf-gaps. A large number 
of separate leaf-traces arise from the outwardly turned margin 
of each leaf-gap, and these are so arranged in the petiole that 
a figure is produced in transverse section easily recognizable 
as a modification of the outline given by the gutter-shaped 
trace so often met with in Fern petioles. In this case, 
however, the margins of the gutter are strongly curved 
towards within, and there is also a deep tuck or fold along 
each of its sides (Fig. 15). In consequence of this, certain 
of the petiolar strands come to lie some distance within 
the others, and these are the central strands, the origin and 
1 Uber Verjiingungserscheinungen bei den Farnen, Verhandl. d. Deutsch. Acad, 
d. Naturforsch., Bd. xxviii, p. 18, 1861. 
3 l.c., p. 525* 
3 Remarques sur la position des trachees dans les Fougeres, Ann. des Sc. Nat., 
5® ser., yoI. xii, p. 274, 1869. 
