400 Farmer and Hill.— Arrangement and Structure 
to a parenchymatous pith which we regard as distinct from 
the now tubular stele. The latter forms at this stage a hollow 
cylinder or siphonostele, although in using the latter word 
we do not, as already explained, attach to it precisely the 
same meaning as Jeffrey did when he originally defined it. 
Nevertheless our own view forms so simple an extension of 
that put forward by the Canadian botanist, that we have not 
hesitated to retain his terminology in preference to coining 
a new word. 
The siphonostele thus formed becomes more or less broken 
up, giving rise to those kinds of vascular arrangements which 
have been elsewhere designated as ‘polystelic ’ or ‘ dialystelic,’ 
as well as to the concomitant appearances of ‘ gamostely ’ 
or ‘ solenostely ’ as the foliar gaps are intermittently repaired. 
The earliest important change in the arrangements of the 
siphonostelar tissues results from a differentiation, in a more 
or less continuous sheet, of phloem on the internal face of 
the xylem. We have not, as already stated, succeeded in 
making out a good case for the occurrence of a regular internal 
endodermis, except as a late and purely secondary occurrence, 
and it is in this respect that our plant in its earlier stages 
departs, objectively, from the siphonostelic condition as defined 
by Jeffrey. Such a departure is not very uncommon amongst 
the Ferns. We have alluded to the case of the Osmundas, 
and Schizaea 1 supplies a similar example. The tubular 
vascular strand is not delimited from the pith by any special 
layer, nor is there any internal phloem. On the other hand, 
the young plantlet of Aneimia phyllitidis 2 only resembles 
Angiopteris in the protostelic stage. Its subsequent condition 
is solenostelic, or it might also be cited as an example of 
amphiphloic siphonostely in Jeffrey’s sense. Internal phloem 
and endodermis are, however, developed in this plant directly, 
in contradistinction to what obtains in Angiopteris , as a 
differentiation of intraxylar tissue without reference, in the 
first instance, to the external corresponding tissues of the 
1 L. A: Boodle, On the Anatomy of the Schizaeaceae. Annals of Botany, 
xv, p. 373. 3 Boodle, loc. cit. 
