578 Hatfield . — Anatomy of the Seedling and 
There is some breaking down of the pith cells, probably due to 
mucilaginization of their walls ; these collapsed cells give a ‘ stringy ’ 
appearance to both pith and pericycle, very characteristic of this portion 
of the plant. 
The stretching and ultimate collapse of these cells of the pith affect 
the xylem tracheides abutting on this region, which become bent and 
doubled up in all directions, producing an effect of extraordinary distortion 
in sections of the plant at this level. The only portion of the conducting 
system of the root which does not become involved in this distortion is 
cambium, x 3. 
the zone containing the cambium and those tracheides to which it has 
recently given rise. 
When this great distension of the hypocotyi takes place, all mechanical 
tissue tends to disappear. The wood, as we have seen, is widely separated 
by parenchyma ; the fibres of the phloem cannot be identified, while the 
lignified cells of the pericycle are also lost. Such is the structure beneath 
the cotyledonary node. 
