of Vascular Strands in Angiopteris evecta . 381 
out commonly through one of the diamond-shaped orifices 
on the lower surface of the siphonostele. But the great 
majority of the roots originate from the latter itself. 
Attention has been directed by several writers to the 
similarity between the root-traversed cortex of Marattiaceae 
and the structure, apparently similar, of the fossil plants in- 
cluded in the genus Psaronius. In these plants the roots 
also seem to have passed through a parenchymatous tissue, 
and this fact has been utilized to strengthen the evidence 
based on other considerations of a possible affinity between 
Psaronius and Marattiaceae. Mettenius 1 also briefly alludes 
to the comparison between the vascular systems in the two 
groups, but concludes that the resemblance in that respect 
is but slight. And on further comparing the fine series of 
illustrations which accompany Zeiller’s 2 splendid monograph, 
we find ourselves inclined to draw the same conclusion, in 
which we have been further strengthened by a study of 
preparations of Psaronius Renaulti , Will., and Ps. asterolithus , 
for which we are indebted to the kindness of Dr. Scott and 
Professor Oliver. 
In the first place, without attaching too much weight to 
the abundance of the sclerenchyma in Psaronius , and its 
absence from the stems of Marattiaceae 3 , the distribution 
of this tissue in the fossil stems is somewhat remarkable 
both as regards its position and its relations to the leaf- 
traces. The region traversed by the roots is very sharply 
delimited from the central tissues by a strongly defined 
ring of sclerenchyma, which is only broken here and there, 
at points where leaf-traces are in the act of passing out 
of the central region 4 . At these places the roots are ab- 
sent, and it might be perhaps argued that the peripheral 
sclerenchyma, within the root-zone, really represented the 
1 Mettenius, loc. cit., p. 517 (footnote). 
8 R. Zeiller, Bassin houiller et permien d’Autun et d’^pinac, fasc. ii, Flore 
fossile, 1890. 
3 Cf. R. Kuhn, Ueb. d. anatomischen Bau von Danaea, Flora, 1890. 
1 Cf. especially Zeiller, loc. cit., PI. XVIII, Fig. 2 ; XIX, Figs. 1, 2, 3; XX, 
Fig. 4 - 
