252 BOTANICAL GAZETTE. { October, 
ence Phellem; von Mohl made a distinction between the 
 plate-formed cells, that is, those of short radial diameter, and 
the longer ones, naming the former cork, the latter periderm 
cells:; this distinction being considered unscientific, inasmuch 
as both are developed alternately from the same layer, De 
Bary,® who wished to retain the term periderm, determined 
to refer to this word all that tissue originating from the phel- 
logen layer. So that, as the terms are now used, periderm 
consists of two kinds of tissue, that developed from the phel- 
logen, found on the outside of this layer, which is named 
determinate in a sense generally applicable to all cases, 
and that this is owing to the number of transition forms be- 
tween it andthe superficial. He does not give the exact 
position of the phellogen layer of the internal periderm. 
Joseph Moeller,1° in his Anatomie der Baumrinde, gives four 
classes of superficial periderm, considered with reference 
the exact position of the phellogen layer. These, he say*s 
may be reduced to three, when genetically considered. \ 
these three, the first is when the phellogen layer is the epl 
dermis ; the second, when it is situated in the primary rind 
the third, when in the phloem of the vascular bundles. This 
last; he says, may be considered a transition form betwee? 
the superficial and the deep-seated. For the latter, it must 
be inferred its place is in the phloem of the secondary growth, 
wale A eg ee 
*Comparative Anat. of Phanero, d 544. 
2 gams and Ferns (Eng. trans.), pp. 114 aD 
10 nal : perlin 
1882. Anatomie der Baumrinden. Vergleichende Studien von Dr. Joseph Moeller. seat 
