CULTURE AND HYBRIDIZATION STUDIES ONGIGARTINA PAPILLATA(RHODOPHYTA)1

Abstract

ABSTRACTThe foliose red algaGigartina papillata(C. Ag.) J. Ag. was studied in culture to determine its life history and possible relationship to the life history ofPetrocelis middendorffii(Ruprecht) Kjellman. Carpospores cultured from individual female plants gave rise to either crustosePetrocelis‐like plants that reproduced by tetraspores, or to another generation of foliose female (cystocarpic) plants that reproduced by carpospores. Apices cultured from blades of individual field‐collected female plants produced either papillae with many procarps that developed cystocarps only when crossed with male plants, or papillae with few procarps that produced cystocarps in the absence of male plants. The results are interpreted to demonstrate that two types of life history occur inG. papillata:one, a sexual life history involving a crustose tetrasporophyte; the other, a possibly apomictic life history involving only cystocarpic plants. Hybridization experiments demonstrated, thatG. papillatais interfertile withGigartina‐phase gametophytes cultured from tetraspores ofP. middendorffii.Sexual plants of G.papillataare postulated to represent the naturally‐occurring gametophyte ofP. middendorffiiin California. The possible relationships of the sexual and apomictic plants ofG. papillataare discussed.