of Vascular Strands in Angiopteris evecta . 383 
Is it possible that these cells of the supposed cortex belong 
to the periphery of the roots themselves, and are really of 
the nature of hairy outgrowths which have become woven 
into a pseudo-parenchymatous tissue? Whilst retaining an 
open mind on this question we are inclined to see in the 
suggestion a solution of some difficulties, which, in the face 
of the evidence we have been able to collect, appear to us 
to render the commonly accepted interpretation somewhat 
inconclusive. Such a weaving of hairy tissue does actually 
occur to a limited extent in some tree ferns of the present 
day ; and if the roots really did enclose the stem, instead 
of traversing its tissues, the mechanical advantage of such an 
arrangement would be obvious, ajid at the same time the 
elaborate sclerenchymatous system which appears as a mecha- 
nical anomaly in the centre of a stem at once becomes intel- 
ligible, if the outer sclerenchymatous band really marked the 
external limits of the young stem. 
We do not raise the question as to the affinity, or the 
reverse, of Psaronius with the Marattiaceae generally, but 
only desire to point out some of the difficulties at present 
in the way of accepting the equivalent character of the root- 
zone in the two cases as having been satisfactorily demon- 
strated. 
Internal Structure of the young Sporophyte 
of Angiopteris evecta. 
The stem terminates below in a primary root containing 
a diarch vascular strand or stele (Fig. 8). The phloem is not 
always clearly marked from the pericycle, although with care 
the distinction can commonly be made out. The whole stele is 
surrounded by an extremely well-marked endodermis. Some- 
times the protoxylem does not directly abut upon the 
endodermis, but may be separated from it by a layer of 
parenchymatous (pericyclic) cells, and the same feature may 
also recur in connexion with the structure of the few first- 
formed lateral roots, in which also a diarch or tetrarch 
character is retained. In the greater number of roots, how- 
