Reproduction in the New Zealand taxa ofPomaderrisLabill. (Rhamnaceae)

Abstract

Evidence is presented which shows that the diploid, Pomaderris kumeraho (2n = 24), is self fertile and reproduces sexually, whereas two triploid taxa, P. hamiltonii and P. phylicifolia var. ericifolia reproduce by agamospermy. The origin of the embryo sac in the latter is diplosporous. Although breeding experiments indicate that pol~ Iination improves seed set, endosperm chromosome counts in P. hamiltonii show that fertilisation of the endosperm nucleus does not occur. Endosperm is derived from one or both polar nuclei separately. In the tetraploid P. phylicifolia var. polifolia, reproduction is mainly sexual, but there is some indication that plants may be facultative apomicts.