PALYNOLOGICAL RELATIONS BETWEEN THE GENER A ECHIUM L (SECT GIGANTEA, DECAISNEA, SIMPLICIA, AUBERIANA) AND LOBOSTEMON LEHM (BORAGINACEAE)

Within the Macaronesian taxa of Echium and the South African Lobostemo n, palynological diversity as measured, by size, ornamentation and ult rastructure of the exine, shows two extreme forms (primitive and deriv ed) with their intermediates. The ornamentation demonstrates a morphol ogical series from microperforate type to microreticulate with the abs ence or presence of foveola and rugulate walls. Equally ultrastructure shows another series from infratectum rudimentary to structure colume llate. These series are continuous and are interpreted as evolutionary trends which suggest a strong affinity between certain of the Macaron esian Echium taxa and the genus Lobostemon.