iln lit.
;i
•n
8)
Mii
liowever, receives nnicli light from discoveries recently made in a n o th e r species, closely
similar to St u r ’s, h u t of which the inte rna l s t ru c tu re is known.
Among the most ahnndant and most perfectly preserved of the petrified
specimens from the calcareous nodules of the English Coal-Measures is the plant
named Lyg inod en d r on Oldhaminm by W il l iam so n . In its young condition, sometimes
fortunately preserved, the stem bears some resemblance to that of an Osmund a;
the pith is surrounded by a ilng of collateral bundles, in each of which the ])rimai'y
wood is of the type known as mesarch, the greater part having been centripetally
developed, as shown by the position of the spiral elements, while a smaller portion
Fig. 6. L y g i n o d e n d r o n o ld h a m i n m . Transverse section of a large stem, showing the
pith, containing many dark sclerotic groups; tlie strands of primary wood at tlie border ot the 7 1 4 1 ;
the broad zone of secondary wood; the phloem, pericycle, and cortex. Several leaf-trace Imndles are
seen outside the wood. On the right is the base of a root, x about 2F ,. I'Tom a nliotooTanh bv
Mr. L . A. B o o d l e . Scott Coll« 648. i » n .>
was centriiugal. In the great majority of the specimens, however, a broad zone of
secondary wood and bast, had been added, by means of a noi-mal cambium, the delicate
cells of which are sometimes preserved (Fig. G). Thus the stem, when mature
assumed a more Cycadean chai-acter; the leaf-trace bundles, as they pass out towards
the petioles, have in all i-espects the structure of the foliar bundles of living Cycads
(Figs. 7 and 8). Tlie presence of centripetal wood in the stem itself is unusual in the
recent family, but is found in certain cases in the peduncles of the cones.
The petioles, found in connection with the stem (W il l iam so n , 1890), and
formerly described as Rachi opte r i s a s pe r a , have an altogether Fern-like structure
(Fig. 9), and the whole character of the highly comiioiind leaf was that of a Fern-
frond, wdiice has proved to be identical with the type Spl ienoi i ter is H o n i n g h a n s i ,
well known in thd form of ini])ressions (see Restoration, Fig. 10). We will not
dwell longer on the remarkable vegetative
Fig. 7. Ly g i n o d o n d r o i i oldl iaiuium. Double
leaf-trace bundle and adjacent tissues in transverse
section, jv centripetal; x' centrifugal xylem; p x protoxylem;
ph ])liloem of bundles; part of phloem ot
stele; Ni secretory sacs; p d jiart of periderm, x about 40.
W il l ia m s o n Collr 1884.
structure of this plant, already
often described, and illustrated here
by the figures cited, which clearly
shows a combination of Eilicinean with
Cycadean characters, indicating, as has
long been recognized, an intermediate
])Osition between Fern and Gymno-
sperms.
Lyg inod en d r on Oldhaminm,
or Sphenopt e r i s Hon i n g h au s i (for
the two names are synonymous) was
the first of the Cycadofilices to be
recognized as a Seed-plant. The investigations
of my friend Prof. F. AV.
Ol iv e r , with whom I had the pleasure
of working in collaboration, showed
that the seed named Lagenos
t oma Lomaxi by AA'il l iam so n , was enclosed in a lobed cupnle or outer investment
(Figs. 11 and 12); this cupnle bears highly characteristic cajiitate glands, identical with
those on the vegetative organs
of Lyginodendron, with which
it always occurs in association,
but unknown in any other plant
of that period (Figs. 13 and 14).
It was further found that the
vascular bundles of the pedicel
and cupnle of the seed agree
minutely with the foliar strands
of the same plant. Comparative
anatomy and association
thus combined to prove that the
seed Lage nos t oma Lomaxi
was the longsought female fructification
of Lyginodendron
Ol d hami nm (Ol iv e r & Sc o t t ,
1903 and 1904).
The seed of Ly g i n o d e n dron
retains a special interest,
as the only case in which we
/S'tax^ir/a flofra cPoxOl-
Fig. 8. - S t a n g e r i a paradoxa. Double bundle from
the leaf-stalk of this recent Cycad, to compare with Fig. 7.
Nc stone-cell. Other lettering as in Fig. 7. x 95.
Fdg. 7 and 8. From Scott, 1900, after drawings by the
late Mr. B r e b n e r .