98 
ORGANOGRAPHY. 
BOOK I. 
filled with vasiform tissue, and representing medullary rays.* 
When the stem is dry, the woody plates separate from the 
other tissue, in which they finally lie loose. 
36 
In Nepenthes distillatoria the pith contains a great quantity 
of spiral vessels ; the place of the medullary sheath is occu- 
pied by a deep and dense layer of woody tissue, in which no 
vessels, or scarcely any, are discoverable ; there are no me- 
dullary rays ; the wood has no concentric zones ; between the 
bark and the wood is interposed a thick layer of cellular tissue, 
in which an immense quantity of very large spiral vessels is 
formed; on the outside of this layer is a thinner coating of 
woody tissue, containing some very minute spiral vessels; and, 
finally, the whole is enclosed in a cellular integument, also con- 
taining spiral vessels of small size. In this singular plant the 
outer layers are, it is to be presumed, liber and epidermis ; and 
the cellular deposit between the former and the wood is analogous 
to cambium in an organised state, belonging equally to the 
wood and the bark. What is so exceedingly remarkable is the 
complete intermixture of the vascular and cellular systems, 
so that limits no longer exist between the two. 
I have a specimen of the twisted compressed stem of a 
Bauhinia from Colombia [Jig. 37.), in which there are no con- 
centric circles, properly so called ; but in which there are cer- 
tain irregular flexuous zones, consisting of a layer of cellular 
* It will be seen that the view I now take of the analogies of the parts 
in the trunk of Phytocrene is very different from that in the first edition of 
this work. 
