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Kisch . — The Physiological Anatomy of 
(7) Heterogeneous Periderms. 
Bearing in mind the general nature of the periderm cells as described, 
one may now turn to the species in which the secondary cortical tissue is not 
quite homogeneous. 
( a ) The simplest variation from the ordinary type consists in the 
occurrence in the periderm of many cells which have become chambered by 
horizontal, and occasionally also by vertical septa 1 (Text-fig. 16). These 
Text-fig. 16. Chambered cells in the periderm of a Lepidophloios sp. A, tangential section 
showing both horizontal and vertical septa. U. C. L. Coll., A 39 g. B, transverse section near the 
outside of the periderm, a, cells divided by vertical septa ; c, outer cortex. U. C. L. Coll., A 39 a. 
C, obliquely radial section from the outer border of the periderm. U. C. L. Coll., A 39 d. x 90. 
have been found in a species of Lepidophloios and also in a Lepido- 
dendron. Of the former there are transverse (Text-fig. 16, b) and obliquely 
radial (Text-fig. 16, c) as well as tangential sections, from which it is 
seen that the chambered cells occur chiefly in the outer layers of the 
periderm. 
( b ) In the second case, as found in two forms of ribbed Sigillaria , one 
of which is referred to 5 . reniformis , there are the same chambered cells to 
be seen in tangential section, but they are arranged in definite vertical 
groups (Text-fig. 17), and are rather wider and lighter in colour than the 
rest of the periderm. The septa here seem to be all horizontal. 
1 The cells recall somewhat the chambered bast and libriform cells of recent plants, but the 
transverse walls are not specially thin. 
