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Fic, 438.—I. Transverse section through the rhizome of the common brake, Pzerzs 
aqutlina, showing the distribution of the vascular bundles (natural size); II. a 
part of the preceding figure; o epidermis ; rR’ thick-walled, r” thin-walled coer- 
tical tissue; S vascular bundle-sheath ; x cells with the wall thickened on one 
side outside the latter ; s¢ bundles of fibriform cells (x 110), 
