CHAP. II. 
STEM. 
79 
M. Diitrochet calls by the name of embryo-buds (fig. 24.) those 
nodules which are so well known in the bark of the Beech, 
and some other trees, and which are externally indicated by 
small tumours of the bark. According to this author such 
bodies are at first very small and globular, in the tissue of the 
bark, near its surface ; he has found some not larger than a 
pin’s head, and thinks they are born in the parenchymatous 
tissue. They are at first completely free, and isolated in 
the bark, have a peculiar bark of their own, which is united 
with that of the parent tree, but which may in the Cedar be 
easily distinguished by the direction of its fibres. 
The form of such nodules is variable ; sometimes they are 
rounded, sometimes conical, &c. When in the progress of 
developement, the woody nodules born in the thickness 
of the bark, bring their wood in contact with that of the tree 
which bears them, the intermediate bark disappears, being 
destroyed by the pressure to which it is subjected, and then 
the wood of the nodule becomes adherent to the wood of the 
tree. This adhesion sometimes does not take place for several 
years. The wood of the nodules is arranged in concentric 
zones around a common centre, and has both pith and me- 
dullary rays ; and, however irregular, the form is evidently in 
all cases a genuine sphere ; it has all the elements of organisa™ 
