178 SECTIONAL ADDRESSES. 
The Rhyniacee, at all events, were leafless and rootless plants. In 
one species of Rhynia and in Hornea the aerial stems are entirely 
without any appendages, while in the other Rhynia there are hemi- 
spherical swellings, which have been identified by Arber with certain 
states of the spines in Psilophyton. The emergences of R. Gwynne- 
Vaughani have been interpreted as nascent leaves, but more recent 
observations, showing their late histological origin, have rendered this 
hypothesis very doubtful. 
In Asterorylon, a higher plant altogether, the stem is clothed with 
quite distinct leaves, though they are somewhat rudimentary as regards 
their vascular supply. Have we, in these plants, and others of con- 
temporary date, the first origin of the leaf from a mere non-vascular 
emergence, or had reduction already begun, so that in Rhyniacez, for 
example, the leaves were in the act of disappearance? In the former 
case we should be assisting at the birth of Lignier’s phylloids, the 
microphylls of the Lycopod series, though, as just mentioned, the out- 
growths in Rhynia Gwynne-Vaughani may have had nothing to do 
with leaves. 
But the opposite view may also be tenable. We have already 
seen that these plants have been referred both to the Pteridophytes and 
the Thallophytes; they also show signs of Bryophytic affinities, and T 
understand that it has even been proposed to include them in the 
Bryophyta, in which case every possible view will be represented. The 
Sphagnum-like structure of the columellate sporangium or sporogonium 
of Hornea and Sporogonites may justify the Bryophvtic attribution, and 
it is then, of course, easy to extend it to Rhynia. If we were to adopt 
this opinion, we should probably have to regard these simple Devonian 
plants as representing stages in the reduction of the sporophyte to a 
sporogonium, the leaves being already nearly or quite lost, while the 
branched thallus was still much in excess of the simple seta of the 
modern Moss or Hepatic. Naturally we know nothing of the gameto- 
phyte, so that the material for comparison is limited. Kidston and 
Lang, however, have recently pointed out that the presence of spore- 
tetrads clearly indicates the existence of a gametophyte. 
I make no attempt to decide between these views. There can 
be no reasonable doubt that the Psilophytales generally represent an 
earlier phase of Cormophytic life than any of the groups previously 
recognised. But we must not assume that all their characters were 
primitive. It has been pointed out that the Rhyniacee were peat plants, 
and that the peat-flora is apt to be peculiar. Under such conditions 
it is not improbable that a certain amount of reduction may have 
already been undergone, though this is not the view taken by the 
investigators. 
There is one more point in connection with the Rhynie plants which 
may be mentioned, as it is of purely morphological interest, and may 
be more in place here than at a later stage of the discussion. 
In Hornea, as Kidston and Lang have shown, the terminal 
‘sporangia evidently arose by the transformation of the tips of certain 
branches of the plant.’ 
They are, in fact, very little modified as compared with vegetative 
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