68 Scott.— On a Palaeozoic Fern, the 
xylem ; x.i. } median island of internal xylem, destined for the axillary stele, x about 30. Scott 
Coll., 2516. 
Phot. 9. Foliar bundle, in oblique section, from the base of a petiole in connexion with the 
stem, x.e., peripheral loop ; s.v.b ., base of a secondary vascular bundle belonging to a pinna, 
x 8. Scott Coll., 2530. 
PLATE II. 
(Photographs 10-13 by Mr. L. A. Boodle, F.L.S. ; 14-16 by Mr. W. Tams.) Photographs 
10-14 from Williamson’s later specimen. 
Phot. 10. Axillary stele, from the transverse section figured as a whole in Scott, ’08, Fig. 115. 
x.i., band of internal xylem, tangential to the parent stem ; ph ., phloem ; i.c., inner cortex of the 
axillary shoot, x 34. Williamson Coll., 1919 a. 
Phots, n-13. General transverse sections. 
Phot. 11. Leaf-base prominent, st., stele of stem; l.t., leaf-trace in the act of separating from 
the axillary stele; aph ., aphlebiae, two in connexion with the leaf-base, and the third in connexion 
with the stem. The strands of other aphlebiae are seen in the cortex, x about 4. Williamson 
Coll., 1919 D. 
Phot. 12. Here the foliar bundle, l.t., and the axillary stele, a.s., have already separated. For 
details see PI. V, Fig. 13. x about 4. Williamson Coll., 1919 b. 
Phot. 13. (Reversed, as compared with Phots, n and 12.) Pet., petiole, in oblique section, 
with the axilllary shoot, not yet quite free, between petiole and stem ; a.s., axillary stele ; 
another leaf-trace, diverging from the former by f, just leaving the stele, x about 4. Williamson 
Coll., 1919 c. 
Phot. 14. Undivided leaf-trace in the outer cortex, x.e., small tracheides of a peripheral loop. 
The position of this trace is shown in the diagram, PI. V, Fig. 15, l.t. x 35. Scott Coll., 184. 
Phots. 15 and 16 from Williamson’s type-specimens. 
Phot. 15. Transverse section of a stem, showing the stele and surrounding tissues (imperfectly 
preserved), l.t., crescentic leaf-trace, as in the Shore specimen ; aph.b., aphlebia-bundle (several 
shown) ; r., root passing out through cortex, x 7. Williamson Coll., 1824. 
Phot. 16. Transverse section of the vascular bundle of the petiole and adjacent tissues, x.e., 
small-celled external xylem of the peripheral loops, x 26. Williamson Coll., 1824. 
PLATE III. 
Figs. 1, 3, and 5 by Miss G. C. Harrison. Figs. 2, 4, and 6 by Mr. G. T. Gwilliam. 
Shore specimen. 
Fig. 1. Undivided leaf-trace, after entering the cortex (level of section between that of Phots. 5 
and 6). x., large-celled xylem; x.e., small-celled external xylem of the peripheral loops; px., 
probable positions of protoxylem ; x.i., island of internal xylem, destined for the axillary stele ; 
ph., remains of phloem ; i.c., band of inner cortex between leaf-trace and stele. x about 40. 
Scott Coll., 2519. 
Fig. 2. Leaf-trace further out in cortex. Rather more than half is shown (level two sections 
above Phot. 6). Note the increased width of the middle part of the trace, in preparation for the 
detachment of the axillary stele. Lettering explained under Fig. 1. x 50. Scott Coll., 2522. 
Fig. 3. Longitudinal section of the stele of the stem passing tangentially through the * mixed 
pith ’, and showing the internal xylem, x.i., at several places, p.p., parenchymatous cells ; x.x ., 
inner edges of the outer, large-celled xylem-zone. x 100. Scott Coll., 2525. 
Fig. 4. Transverse section of arm 2 of stele (level immediately above Phot. 6). x.i., internal 
protoxylem ray, the forks nearly reaching the surface of the xylem ; aph., aphlebia-strand, given off 
from the arm of the stele, x 65. Scott Coll., 2521. 
Fig. 5. Part of leaf-trace, just detached from arm 5 of the stele (level between Phot. 3 and 
Phot. 4), showing one of the peripheral loops and an aphlebia-strand just given 'off and still in 
connexion, x.e., external xylem of peripheral loop; ph., remains of phloem; aph., the aphlebia- 
strand. x 120. Scott Coll., 2515. 
