CHARACTERIZATION OF THE ENVIRONMENTAL DISTRIBUTION AND MORPHS OF RALFSIA-HANCOCKII DAWSON (PHAEOPHYTA) IN THE MEXICAN TROPICAL PACIFIC

The environmental distribution, growth forms of the communities where Ralfsia hancockii Dawson grows and morphs of the species are described . The species is widely distributed environmentally. It grows best in places where a combination of gradient of factors gives extreme micro- conditions such as strong wave shock at high tide with dessication and high solar radiation at low tide or under the quiet conditions of hig h midlittoral shallow pools. Under these conditions it forms extensive growths becoming the dominant species. These growths can form isolate d patches or they can be interrupted by erect thalli of different spec ies. Chaetomorpha antennina (Bory) Kutz. and Chnoospora a minima (Heri ng) Papenfuss are its principal associated species. Two morphs are des cribed in relation to the micro-conditions in which they are most freq uently found.