Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.

(N/A) $\Rightarrow$ It is an anatomical abnormality. It is an irregular type of secondary growth where the regular fascicular cambium or cork cambium does not function under normal conditions.
$\Rightarrow$ In the case of old tree trunks,irregular secondary growth is produced by the activity of the cortex and the formation of anomalous vascular bundles.
$\Rightarrow$ Consequently,these extra or subsidiary vascular bundles create an appearance as if the trunk is formed by the fusion of several smaller trunks.