On the Presence of a Parichnos in Recent Plants. 
BY 
T. G. HILL, F.L.S. 
Lecturer on Biology in the Medical School of St. Thomas's Hospital London. 
With Plates XIX and XX. 
T HE term Parichnos was used by Bertrand 1 to designate the thin- 
walled parenchymatous strand of tissue, occurring in Lepidodendron 
Harcourtii , which accompanies the leaf-trace on the posterior side during 
its outward journey. It is described as originating in the middle cortex, and 
during its passage through the suberized zone — i. e. the outer cortex — the 
strand bifurcates, the two branches diverge, and eventually occupy a 
position one on each side of the foliar bundle, forming the well-known 
lateral prints on the leaf-scar, as seen on casts. 
These facts were corroborated by Hovelacque 2 for Lepidodendron 
Selaginoides and by Williamson 3 . 
Essentially the same features occur in Syringodendron. Renault 4 has 
described the presence of two large lacunae, which accompanied the leaf- 
trace one on each side in Sigillaria spinulosa . He subsequently showed 
that these spaces were originally filled with a delicate tissue, traversed by 
secretory canals, and that each parichnos-strand was surrounded by a 
sheath of radially elongated elements. 
Maslen 5 , in his work on Lepidostrobus oldhctmius , found that the 
parichnos was represented by an empty space of considerable size ; there 
was no indication of branching, and, as regards this last point, he remarks 
that, * this difference may perhaps be correlated with the small width of 
the proximal end of the pedicel, as compared with that of the leaf-base in 
the vegetative region.’ 
1 Bertrand, Remarques sur le Lepidodendron Harcourtii de Witham. Travaux et Memoires des 
Facultds de Lille. T. ii, 1891. 
2 Hovelacque, Recherches sur le Lepidodendron Selaginoides, Stemb. Mem. Soc. Linn. Nor- 
mandie, xvii, 1892. 
3 Williamson, Organization of the Fossil Plants of the Coal Measures, part xix, Phil. Trans. Roy. 
Soc. Lond. B., 1893. 
4 Renault, Flore fossile d’Autun et d’^pinac. 
5 Maslen, The structure of Lepidostrobus. Trans. Linn. Soc. Lond., 2nd ser., Bot., vol. v, 1899. 
[Annals of Botany, Vol. XX. No, LXXIX. July, 1906.] 
