SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 625 
Plate IV. 
Hornea Lignieri, Kidston and Lang. 
Fig. 27. Large protocormous rhizome in vertical section with three lobes, a stem arising from each lobe, 
x 14. (Slide No. 2436.) 
Fig. 28. Portion of the silicified peat, the matrix of which is composed of decayed stems of Hornea with 
spores scattered throughout. Portions of three rhizomes are shown. The largest is cut vertically and shows 
two tuberous lobes from each of which a stem arises. A stele is present in each stem. x 14. (Slide 
No. 2437.) 
Plate V. 
Hornea Lignieri, Kidston and Lang. 
Fig. 29. Vertical section through a rhizome missing the attachment of any stem, but showing the general 
parenchymatous structure and the distribution of the rhizoids. ox., outer zone ; i.c., inner tissue ; b.t., brown- 
walled tissue in the neighbourhood of the base of a stele, x 14. (Slide No. 2438.) 
Fig. 30. Portion of the lower surface of a rhizome in vertical section showing the rhizoids springing as 
protrusions of all the epidermal cells, x 33. (Slide No. 2442.) 
Fig. 31. Section of portion of the largest rhizome met with. This is a horizontal section of a rhizome 
below the bases of the steles of a number of stems which arose from it. The brown parenchymatous tissue 
in relation to some of these is seen at the points marked b.t. Lying beside the rhizome at st. is an obliquely 
transverse section of a stem. x 7|. (Slide No. 2441.) 
Fig. 32. Tangential section showing the rhizoid-bearing surface of a rhizome. The bases of the rhizoids 
are cut across at a, where they spring from the central portion of each epidermal cell. x 60. (Slide 
No. 2443.) 
Fig. 33. The tangential section of the rhizoid-bearing surface from which fig. 32 was taken, showing the 
long rhizoids extending into the peat, x 14. (Slide No. 2443.) 
Fig. 34. Small protocormous rhizome (r.') with rhizoids (rh.) springing as an adventitious growth of the 
superficial tissues of the main rhizome (r.). x 33. (Slide No. 2441.) 
Plate VI. 
Hornea Lignieri, Kidston and Lang. 
Fig. 35. Accurately vertical section of a lobe of a rhizome showing the attachment of a stem. The stele 
of this on being followed down into the rhizome shows the characteristic base in longitudinal section. The 
peat around contains spores and decayed stems of Hornea. x 14. (Slide No. 2444.) 
Fig. 36. Base of the stele shown in fig. 35. x., xylem composed of elongated tracheides ; x.' , region with 
short tracheides passing into an inverted bowl-shaped mass of brown-walled parenchymatous tissue (b.t.). 
x 33. (Slide No. 2444.) 
Fig. 37. Base of the stem-stele of another specimen showing the same features as fig. 36. x., xylem 
composed of elongated tracheides; x.', region with short tracheides passing into an inverted bowl-shaped 
mass of brown-walled parenchymatous tissue (b.t.). x 33. (Slide No. 2445.) 
Fig. 38. Vertical section of a rhizome showing good rhizoids and with the characteristic base of a stem- 
stele displaced downwards through the decay of the inner tissue, x 20. (Slide No. 2446.) 
Fig. 39. Portion of silicified peat containing fairly well-preserved stems of Hornea. These stems, one 
of which is in longitudinal section, show the structure of the lower region close to the rhizome, x 14. 
(Slide No. 2447.) 
Plate VII. 
Hornea Lignieri, -Kidston and Lang. 
Fig. 40. Slightly oblique transverse section of a small stem, probably from the upper region of the plant. 
cut., cuticle ; c., cortex with indications of outer and inner zones ; ph., phloem ; x., xylem. x 33. (Slide 
No. 2448.) 
