536 Brebner. — On the Anatomy of 
by the leaf-spiral, roughly 144°. As the roots in nearly all 
cases join the . dictyostele at or near the most peripheral 
position of the central strand, they are pretty obviously 
attached to the stem meristeles, as distinguished from the 
outgoing leaf-trace meristeles. This brings Danaea into line 
with the observations of Lachmann 1 on the behaviour of the 
roots of Ferns generally. As the result of a very careful and 
extensive piece of work, he came to the conclusion that the 
roots of Ferns were developed from the stem (stele ?) not the 
leaves (outgoing leaf-trace meristeles ?). The only case in 
which he found a direct connexion of the root with petiolar 
meristeles was that of Ceratopteris thalictroides 2 . 
The physiological meaning of the central strand is pretty 
obvious. As has been seen, it directly connects the root- 
bearing gamomeristeles at one level with the corresponding 
part at the next higher level, and so on. As the leaf-traces 
are given off from these curved plate-like masses, it is obvious 
that a considerable portion of the water absorbed can do 
what corresponds to ‘short circuiting’ in electrical termino- 
logy. But that is probably not all, for the roots, which are 
thus developed in close relation to the leaf-traces, probably 
do not reach the soil till some time after the related leaf has 
unfolded, hence the special advantage of such a central strand 
or commissural column is obvious. Finally the central strand * 
also behaves as a reparatory strand (‘ Ersatzstrang ’) helping 
to close the leaf-gap. 
Comparative Anatomy of the Marattiaceae. 
The Frond. 
The anatomy of the frond of the following species of 
Marattiaceae was examined and compared : — 
A ngiopteris evecta , Hoffm. M. alata , Smith. 
Marattia fraxinea , Smith. Danaea simplicifolia , Rudge. 
1 J. Paul Lachmann, Contribution k 1’histoire naturelle de la Racine des Fougeres. 
8°, 199 pp., 5 pi., Lyon, 1889. 
2 Cf. text, fig. 1. S. O. Ford, The Anatomy of Ceratopteris thalictroides , Ann. 
of Bot., xvi, 1902. 
