6l2 EAMES 



and some of the Ranunculaceae ; the primitive monocotyledons are some of 

 the Helobiales and the primitive LiHales. The simpHcity that ranked the 

 Amentiferae as the most primitive angiosperms is the simpHcity of reduction. 

 In place of the Amentiferae, we have three or more lines of woody Ranales 

 forming a new group of basal branches on the angiosperm evolutionary tree 

 which now looks very shrub-like. We see, as yet, in these primitive Ranalean 

 plants no single stock but a group of taxa, isolated end products of an ancient 

 stock, perhaps itself complex. 



What of the age of the angiosperms? Fifty years ago, we looked upon 

 the angiosperms as the climax of evolutionary progress among plants, as the 

 taxon not merely highest in morphological structure but most recent geo- 

 logically. Now we are seriously questioning their apparent youth. Paleobotany 

 gives evidence of their presence in the Jurassic and, with little doubt, in the 

 Triassic. The study of fossil pollen is going to help greatly in finding the 

 earliest records of the angiosperms. Associated with our growing doubts as to 

 the youth of the angiosperms is the theory that the angiosperms sprang, 

 Minerva-like, from some stock in the Lower Cretaceous — presumably Cyca- 

 dophyte — and then evolved "explosively." This theory is based on too little 

 fossil evidence; it fits too well into the picture of the typical evolutionary 

 tree. Apparently, no other major taxon, plant or animal, has so evolved. The 

 diversification in Mid- and Upper Cretaceous indeed appears rapid, but no 

 more so than that of the Tertiary. 



Now that we recognize the simple, unisexual, wind-pollinated flower as 

 advanced and look at the Lower Cretaceous flora — at such genera as Populus, 

 Sassafras, Platanus — we see these genera as samples of unrelated lines, each 

 highly specialized in several characters. And when we consider the structure 

 of the flowers, inflorescences, and wood of the families to which these genera 

 belong, we cannot accept them as other than relatively well-advanced types, 

 much more specialized than the woody Ranales. 



Then consider these woody Ranales themselves. Each taxon has, along 

 with its many primitive characters of flower, node, and wood structure, some 

 advanced character: unisexuality, perigyny, solitary carpel, petaloid corolla. 

 Such diversity of structure — marked advance along different lines in these 

 otherwise so generally primitive taxa — can only mean that these, also, are 

 not the earliest angiosperms. 



Support for great age of the angiosperms has recently come from plant 

 geography and fioristic taxonomy. Analysis of the flora of Australia shows 

 that this isolated and supposedly quite different flora is not fundamentally 

 different from that of the other continents; the basic angiosperm families — 

 from which has evolved this apparently strange, but by no means primitive, 

 flora — are the same as those of the rest of the world. These families have not 

 entered Australia since Cretaceous times; the angiosperms were apparently 

 basically alike the world over in the Cretaceous. A long period of diversifica- 



