ORIGIN OF FLOWERING PLANTS

Nelson Evening Mail, Volume LXI, 11 June 1927, Page 5

ORIGIN OF FLOWERING PLANTS

INTERESTING REVIEW BY DR TTLLYARD

The general state of our knowledge of the origin of the flowering plants is far behind that of our knowledge of the main groups of animals, said Dr. Tillyard in the course of his lecture Last evening. One of the great unsolved problems in paleobotany is the process of the evolution of. dicotyledons and monocotyledons. Dr. Wieland made his name as a brilliant exponent of the theory of the origin of flowering plants from cycads, of which the best known example living to-day is the Australian "Burrawang Palm," genus macrozamia. These plants look like palms, but have no real relationship with the true pirns; rather, thev are much more primitive plants having affinities with ferns and with conifers. The fossil genus Bennetites is claimed to be the connecting link between cycads and dicotyledons, and the existing types which are" said to come most closely to it are the magnolias and the water lilies. Cycads already have specialised 'parts bearing tiny male germ-cells or microsporangia and others bearing huge female germcells or macrosporangia, which in macrozamia, for instance, are larger than acorns. The former, says. Dr. Wieland. evolved into stamens, the latter into pistil, and two sets of specialised leaves came to surround these sexual organs to form the flower. All this evolutionary change took place during the mesozoic. Dr. Wieland travelled far in search of supporting evidence for this view, and during one. of his more recent journeys he collected fossil plants from the rhaetic beds of Mendoza, South America, Rhaetic being upper 'triassic would, in most people's estimation, be <far too old for any sign of true dicotyledons, but Dr. Wieland brought back half-a-dozen fossil seeds. These are claimed by him to be true samaras, closely similar to those of the ash. He showed me these and asked me to suggest a name for them, and I chose fraxinites, from the Latin fraxinns, the ash-tree. Note the ribbed wing to the seed, which allowed it, to be carried some distance by the wind, and also the definitely divided seed itself, which Dr. Wieland claims is a true dicotyledon. It is only fair to add,, however, that Dr. Jeffrey will have none of it, and makes the counterclaim that some specialised conifer might easily have had a winged seed of this kind.

Meanwhile, you might note that, when Dr. Jeffrey visited Nelson recentv f showed 'him a very fine fossil rccentlvrece.ved from Australia, and much older than Dr. Wieland's rhaetic seeds The genus glossopleris is typical of the upper permian throughout almost the whole of the Southern Hemisphere and where there is no break between primary and secondary beds, its presence or absence is used to determine them. I'M although so common, nobodv has ever found its fructification. The fronds look like those of a hart's tongue fern cmt they never carry sori as in true terns, and indeed nobody reallv knows what glossopteris was. While searching for fossil insects, Mr Pincombo, of New Uimbton, found this fine specimen and some others with curious samara-like seeds on them. Dr. Jeffrey's was immensely interested in this * find, and thinks lt quite likely that glossopteris might be shown to be the ancestral form from which all flowering plants were donved. Dr. A. B. Walkom, the wellknown Australian palaeobotanist, has taken these specimens with him to Cambridge University, where he has gone to work under Professor Seward for a year When he comes back., we may expect to hear something quite definite or. these interesting discoveries.