The Physiological Anatomy of the Periderm of 
Fossil Lycopodiales. 
BY 
MABEL H. KISCH, B.Sc. 
University of London, University College. 
With Plate XXIV and twenty-seven Figures in the Text. 
Contents. 
Historical Survey 
The Species examined 
The Phellogen . 
(1) Place of Origin . 
(2) Development 
(3) Nature of the Meristem 
(4) Position relative to the Secondary 
Tissue produced 
(5) Persistence .... 
The Periderm .... 
(1) General Description . 
(2) Size and Shape of the Cells . 
(3) Character of the Radial Files 
(4) Structure and Thickening of the 
Cell-wall . . . . 
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PAGE 
(5) Cell Contents . . . -301 
(6) Intercellular Spaces . . . 303 
(7) Heterogeneous Periderms . . 304 
(8) Features of Mechanical Signifi- 
cance 309 
(9) Zonation 309 
(10) Periderm Development in relation 
to Other Tissues . . *313 
The External Manifestations of 
Periderm Development . . 314 
(1) The Tissues outside the Periderm 314 
(2) The Outside Sculpture . . 315 
Summary 317 
Literature cited £. . . .318 
Explanation of Plate . . . 320 
Historical Survey. 
T HE earliest reference to the periderm of fossil plants was made by 
Witham in his description of the classical specimen of Lepidodendron 
Harcoartii , found in 1832. ‘The tissue of the superficial layer’, he writes, 
‘ has a striking resemblance to that of the woody tissue of the Coniferae, 
the cellules being disposed in regular series and of a form approaching the 
hexagonal, but without indications of medullary rays.’ 1 This comparison 
with the wood of the Coniferae was repeated by Lindley and Hutton in 
their 4 Fossil Flora ’, but they added that a vertical section showed that the 
meshes were 4 merely sections of cellular tissue ’. 2 
In 1839 Brongniart’s monograph on Sigillaria elegans 3 was published, 
and in it appeared a more detailed and accurate description of the periderm 
under the name of the ‘ inner cortical zone \ 4 Brongniart commented on 
1 Witham (45). 2 Lindley and Hutton (17), p. 47. 
8 Now known as S. Menardi or Brardi. 4 Brongniart (8). 
Annals of Botany, Vol. XXVII. No. CVI. April, 1913.] 
