Article: Williamsoniella lignieri: its pollen and the compression of spherical pollen grains

The type specimen of the Bennettitalean flower Williamsoniella lingnieri (Nathorst) on reinvestigation proved to have an intact pollen sac yielding vell-preserved pollen. The pollen grains resemble Exesipollenites scabratus. Most of the grains are distorted by crushing and the distortion of outline is related to folds on the surface. Hollow balls made of various materials were compressed between flat surfaces and their various secondary distortions are described; one kind of ball mimicked the forms seen in W. lignieri pollen and other balls with different mechanical properties mimicked the distortions of miospores of other plants. When compressed in a matrix (whether itself compressible or not) the hollow balls distorted differently. There is scope for further experimental study of compression in a matrix.