Parkin, J. and E.A.N. Arber, on the origin of Angiosperms.

Peckham, Dr and Mrs, on the Attidae.

Philosophy, influence of the conception of evolution on modern.

Phylogeny, embryology as a clue to. --Palaeontological evidence on.

Physiology of plants, development of.

Pickering, spectroscopic observations by.

Plants, Darwin's work on the movements of. --geographical distribution of. --Palaeontological record of fossil.

Polymorphic species. --variability in cereals.