A blue basic salt is precipitated first, which, on boiling, rapidly changes to the rose-coloured hydroxide.
Their flowers range from white to rose-coloured, yellow and blue.
Near by are the greentiled domes and walls enriched with rose-coloured marbles of the mausoleum of the beys.
Usually they are of a different colour, and may be black, brown, yellowish, or also less frequently rose-coloured, rusty-red, orange-reddish, saffron, or of various intermediate shades.
Other distinct kinds are P. campanulatus, 12 ft., pale rose, of bushy habit; P. humilis, 9 in., bright blue; P. speciosus, cyananthus and Jaffrayanus, 2 to 3 ft., all bright blue; P. barbatus, 3 to 4 ft., scarlet, in long terminal panicles; P. Murrayanus, 6 ft., with scarlet flowers and connate leaves; and P. Palmeri, 3 to 4 ft., with large, wide-tubed, rose-coloured flowers.
