270 Bower. — Shidies in the Phytogeny of the Filicates . 
probable genetic relations with the Gleicheniaceae, but advanced on the 
one hand to the basipetal succession of the sori, and on the other to a high 
complexity of the vascular system 
The degree of closeness of those ‘ genetic relations ’ was left undefined, 
though certain species were indicated as outliers on either side of the gap 
separating the two families. On the one hand are Gleichenia linearis , 
Clarke (= dichotoma, Hk.), and pectinata , Pr., distinguished as relatively 
advanced species, both by their soral and their anatomical characters ; on the 
other hand, Alsop hila qnadripinnata , C. Chr. (= Lophosoria pruinata , Pr.), 
and A. ( Metaxya ) blechnoides , Hk., were indicated as lying anatomically at 
the base of the Cyatheaceous series. It seems desirable, as material is at 
hand, and as some further advance has already been made in the anatomy 
of the more complex Gleichenias, to examine more closely the probable 
relations of the two families, and to widen as far as possible the basis of 
the comparisons. For it is only in this way that a dependable conclusion 
can be arrived at. In discussing such genetic relations in Ferns, soral 
characters are not sufficient, nor are anatomical data sufficient. Nor should 
we be satisfied even with a combination of them. To obtain a fully trust- 
worthy result the characters of external form, of the superficial appendages, 
and of the gametophyte and sexual organs should be also used, together 
with the details of the ontogeny, while some attempt at seriation of the 
species within the genera will also assist in giving point to the comparisons. 
Many phyletic conclusions which are generally accepted fall short of this 
comprehensive foundation, and it will not be possible in the present case 
to carry out the programme fully. But it is well at the outset to visualize 
what is to be aimed at, even though a complete demonstration may not 
be actually attained at the moment. As the comparisons to be drawn will 
centralize themselves round the species above named, though with general 
references from time to time to these and to other genera as a whole, it will 
be well at the outset to become acquainted with the history, systematic 
position, and characteristics of them. Often it happens that plants which 
have a peculiar interest from a comparative point of view have in the past 
been given diverse systematic places by various authors. This will be seen 
to have been the case with one at least of the Ferns in question. Such 
a history at once suggests that the systematist has encountered a synthetic 
type. In fact the puzzles of the earlier systematists will often provide the 
opportunities of the phyletic morphologist. 
Gleichenia. 
The two species Gleichenia linearis , Clarke (= Gleichenia ( Mertensia ) 
dichotoma , Hk.), and Gleichenia (Mertensia) pectinata , Pr., have long 
been regarded as outstanding in the genus to which they belong, and 
recent anatomical observations have accentuated their aloofness from the 
