Some remarks on the stelar morphology of Knorripteris Jutieri

Botany ~ Some remarks on the stelar morphology of Knorripteris ]utieri
Bertrand, and on its systematical position. By O. POSTHUMUS.
(Communicated at the meeting of January 29, 1938.)
In a memoir. shortly published. remarkable for its dear description of
details. RUDOLPH 1). studying material of unknown age. was ab Ie to give
a better insight in the anatomy of Knorripteris. He was ab Ie not only to
confirm the statement of the anatomy of the woody parts and the central
tissue. given formerly by HÖRICH. POTONIÉ and BERTRAND. but also to give
a description of the soft tissue outside the xylem. of which the position of
the phloem deserves special attention.
The chief facts are that leaf~traces in the cortex consist of 5 xylem
bundies with one phloem bundie. the xylem. as a whoie. being guttershaped.
(crescent shaped in transverse section) in the outer part. rounded in the
inner part. Towards the interior the phloem joins that of other bundies
at the bottom of one of the meshes of a lattice work of phloem bundies.
mentioned by RUDOLPH as stem phloem. The xylem bundies pass through
this gap. gradually running towards the centre and ending blind th ere.
without any fusion between each other.
The innermost portion of the groundtissue has vanished. the middle
cortex consist of lacunosa aerenchyma; this gives support to the supposition
that Knorripteris was a waterplant. with a submerged rhizome.
In a former publication. reviewing the data. given by BERTRAND and
POTONIÉ. I compared 2) this plant with Pitys. on account of the similarity
in the position of the xylem strands. which. in Pitys. run obliquely down~
wards in the pith and end there blindly. The position of the phloem of
Knorripteris and Pitys was unknown at that time. IE this comparison be
justified, Knorripteris would belong to the seed~plants and not to the
Pteridophyta. RUDOLPH. though admitting the similarity. indicated above.
is indined to consider Knorripteris to belong to the Pteridophyta. He bases
his opinion chiefly on the absence of secundary growth and the position
of the phloem.
IE we discuss these criteria. it has to be admitted that the presence or
absence of secundary growth is not sufficient to decide. whether a plant
belongs to the Filicales or not. In the Filicales secundary growth is known
from Botrychium 3) and from Botrychioxylon paradoxum SCOTT 4);
perhaps another fossil with weIl developed secundary xylem. Protopitys
1)
2)
3)
')
Palaeontographica, Bd. 82B, 143-171, pI. 14-16 (1937).
Receuil des travaux bot. néerl., vol. 21. 521-523 (1924).
BOWER, the Fems, vol. 1. 136--138, fig . 119, 129 (1923) .
SCOTT, Studies in Fossil Botany. vol. 1. third ed .. 319. fig . 142 (1920) .
149
Buchiana GÖPPERT 5) also belongs to this group. On the other hand the
Monocotyledones are devoid of secundary growth by cambial activity.
Moreover the aquatic habit may tend to its disappearance, as RUDOLPH
already admits as a possibility 6).
The value of the other criterion, the position of the phloem, is not
quite established yet. In my treatise on stelar morphology. I emphasized
that the position of the phloem is. especially in the fossil plants. less weIl
known. and. because its position appears to be more or less secundary
in regard to that of the xylem. no conclusion could yet be drawn from its
position 7); it thus cannot be considered as a decisive factor in our
considerations.
RUDOLPH only mentions the possibility of another explanation 8), which
he does not accept: Knorripteris might be derived from a plant like
Osmunda. in which the stem xylem has completely disappeared. thus
leaving the lower parts of the xylem bundIes of the leaf~strand quite free.
which bundIes afterwards extend further down towards the centre of
the stem.
It is difficult to see how. if. probably in connection with its aquatic
habit. the stem xylem disappears. the xylem of the leaf~trace bundIes
could have developed further downwards. penetrating further towards the
interior. We might expect that in such a case the reduction of both stem~
and leaf~trace xylem was more or less parallel. The structure is easier
to understand as if the reduction of the stem xylem as a whole had already
taken place beforehand and not in relation to the peculiar habit of the
plant; thus in the same way as found in the seed plants. especially as
shown. when comparing Lyginodendron with Heterangium. The occurrence
of short tracheids in the central tissue than also becomes more easy to
understand.
Also the exarch position of the protoxylem in the bundIes. resembles
more that in Heterangium. by reduction of the abaxial metaxylem; the
pres en ce of the latter is a constant feature in the Ferns.
Another point is the shape of the foliar bundIes. which. as RUDOLPH
admits 9). is more like that of Pitys than that of Osmunda.
All these characteristics plead more for an affinity of Knorripteris
with the Filicales than with the Seed~plants.
As mentioned above. though we can find some features of the xylem~
structure. which enable us. in structural remains. to distinguish Filicales
from Seed plants. this is not the case with the structure of the phloem.
lts position seems to be determined more or less indirectly by the position
of the xylem.
5)
ro)
7)
8)
9)
Receuil des trav. bot. néerl., vol. 21, 524 (1924) .
Palaeontographica, Bd. 82 B, 164 (1937).
Receuil des trav. bot. néerl., vol. 21, 281 (1924).
Palaeontographica, Bd. 82 B, 165 (1937).
Palaeontographica, Bd. 82 B, 166 (1937).
Proceedings Royal Netherlands Acad. Amsterdam, Vol. XLI, 1938.
10
150
In case the stem xylem is well developed, there is, as far as known, a
phloem surrounding it, both in the Filicales (Cheiropleuria 10), Inversica~
tenales 11» and in the Seed~plants (Heterangium 12) ). In the Pterido~
phyta we see that th is phloem attains in the more complicated forms a
greater extension, also covering the innerside of the leaf trace, penetrating
towards the inner side of the xylem lattice~work and at last surrounding
the surface of the xylem all over; thus in a transverse section of most of
the Polypodiaceae, the xylem strands, either consisting of stem~xylem or
of leaf~xylem, are surrounded by phloem. Also in the Osmundaceae the
phloem penetrates into the leaf~gap and into the funnel. ending blind
there 13).
This tendency to surround the xylem of the bundIes is not found so
clearly in the Spermatophyta; it is absent both in the living on es and in
fossil representatives as far as known to us (Lyginodendron); a tendency
to form phloem bundIes running as cortical and medullary bundles quite
separated from the woody parts, is on the other hand known in the Seed~
plants, but not in the Ferns.
,
Though, as already mentioned above, the value of the characteristics
of the phloem, is rather vague, the arguments for Knorripteris belonging
to the Seed~plants are stronger than those pleading for its affinity to the
Filicales. It is hoped that shortly more ample material, aIso including
impressions and fructifications, may throw more light on this puzzling genus.
10)
11)
12)
13)
Receuil
Receuil
Receuil
Receuil
des
des
des
des
travaux
travaux
travaux
travaux
bot.
bot.
bot.
bot.
néerl.,
néerl.,
néerl.,
néerl.,
vol.
vol.
vol.
vol.
21.
21.
21,
21,
196 (1924) .
173-194 (1924).
269 (1924).
127 (1924) .