Fig.
15.3-14. Transverse section of Robinia
pseudoacacia (black locust or false acacia). Most
of the vessels here are plugged with tyloses. They had cavitated at
some point, and subsequently the adjacent paratracheal parenchyma cells sealed
them with tyloses. This plugging is not confined to just this level of the
vessels; if a longitudinal section were available, almost all the length of the
vessel would be seen to be plugged.