FORMATION OF NODULES. 
281 
at first as spherical woody protuberances, which attain some 
size, and then send out a shoot. The protuberances in early 
stages have no connection with the stem wood, and therefore 
are derived from dormant or latent buds, and not from 
adventitious buds, which arise endogenously, and would thus 
have their vascular strand in connection with the vascular 
system of the stem. Very often the spherical woody body 
produced by the continued growth of such dormant buds, 
after they have lost their connection with the wood of the 
stem, can be detected at the base of shoots developing near 
the cut surface of pollarded trees. Sections through such 
developing shoots show that they consist of wood parenchyma, 
wood fibres, tracheides, and vessels. The tracheides are 
curved and the vessels somewhat tortuous, but they are 
continuous. Later a vascular strand, consisting mostly of 
tracheides and wood parenchyma, connects the developing 
shoot with the stem wood. In the centre of the base of the 
shoot the fibres are much curved and irregular, but become 
normal in the outer layers, the irregular structure indicating 
the position of the spherical woody body from which the shoot 
developed. The vascular connection with the stem wood 
is formed by a growing point directed inwards from the 
developing shoot tissue towards the stem wood. 
Sections show that the spherical bodies are composed of 
twisted tracheides and wood fibres, with here and there a 
tortuous vessel, the several elements being interwoven in a 
highly irregular manner at the centre and becoming normal 
towards the outside. A cambium is present which produces 
a small amount of cortical tissue and latex vessels, the latter 
being determined as the product of the nodule cambium by 
their concentric disposition round the spherical body. On 
the inner side and directed towards the stem there is fre- 
quently a tapering point consisting of wood elements and 
resembling closely the vascular strand of a shoot. This 
undoubtedly represents the former connection with the wood, 
but in many cases it is entirely wanting. In some of these 
cases sections disclose the former connection completely sunk 
in the tissue of the spherical body ; the tapering point has 
ceased growth, and has been covered over by the subsequent 
6(14)17 (39) 
