Unusual behaviour of growing pollen tubes in the styles and ovules of Spinacia oleracea L.

Summary Pollen tubes of spinach, while growing in the styles, produce branches. In the ovules and the surrounding tissue, at later stages, they grow like fungus mycelium and ramify in all directions. Haustoria-like structures are produced from the pollen tubes near the micropyle of the ovule. These structures penetrate into integuments, nucellus and other tissues and produce branches. Several pollen tubes enter a single ovule and appear to bring about polyspermy. Though the functional significance of some of these phenomena is still speculative, it is likely that the persisting pollen tubes and haustoria may be responsible for the nourishment of the growing embryo.