Fibres with intrusive cavities were present in Alchornea sidifolia, Al
chornea triplinervia, Croton floribundus, Sapium glandulatum, and Seba
stiania serrata (Euphorbiaceae). These cavities are the result of an i
ntrusive growth of fibres which detour when they encounter a cellular
obstacle, form either a fork or a concavity around the obstacle, and s
ubsequently unite. The term 'intrusive cavity' is proposed for this st
ructure.