Definition of "mesembryanthemum"

The celebrated garden in which suicidal gamblers used to put an end to their troubles was overgrown with mesembryanthemum.

1933 September, H[erbert] G[eorge] Wells, “Europe in 1960”, in The Shape of Things to Come, 1st American edition, New York, N.Y.: The Macmillan Company, 2nd book (The Days after Tomorrow: The Age of Frustration), page 227

They had come out on to the coast road now, and Cornwall was out-postering itself, as usual, with rocky headlands and sandy coves and fishing villages that spilled themselves down the cliff face like cascades of mesembryanthemum.

1939, Jan Struther, “A Country House Visit”, in Mrs. Miniver‎