Origin of Angiosperms 205 



sub-kingdom in the flora of our own age, including, apart from a few 

 Conifers and Ferns, all the most familiar plants of our fields and 

 gardens, and practically all plants of service to man. All recent 

 work has tended to separate the Angiosperms more widely from the 

 other seed-plants now living, the Gymnosperms. Vast as is the 

 range of organisation presented by the great modern sub-kingdom, 

 embracing forms adapted to every environment, there is yet a marked 

 uniformity in certain points of structure, as in the development of 

 the embryo-sac and its contents, the pollination through the inter- 

 vention of a stigma, the strange phenomenon of double fertilisation 1 , 

 the structure of the stamens, and the arrangement of the parts of 

 the flower. All these points are common to Monocotyledons and 

 Dicotyledons, and separate the Angiosperms collectively from all 

 other plants. 



In geological history the Angiosperms first appear in the Lower 

 Cretaceous, and by Upper Cretaceous times had already swamped 

 all other vegetation and seized the dominant position which they 

 still hold. Thus they are isolated structurally from the rest of the 

 Vegetable Kingdom, while historically they suddenly appear, almost 

 in full force, and apparently without intermediaries with other groups. 

 To quote Darwin's vigorous words : " The rapid development, as far 

 as we can judge, of all the higher plants within recent geological 

 times is an abominable mystery 2 ." A couple of years later he made 

 a bold suggestion (which he only called an " idle thought ") to meet 

 this difficulty. He says : " I have been so astonished at the appa- 

 rently sudden coming in of the higher phanerogams, that I have 

 sometimes fancied that development might have slowly gone on for 

 an immense period in some isolated continent or large island, perhaps 

 near the South Pole 3 ." This idea of an Angiospermous invasion from 

 some lost southern land has sometimes been revived since, but has 

 not, so far as the writer is aware, been supported by evidence. Light 

 on the problem has come from a different direction. 



The immense development of plants with the habit of Cycads, 

 during the Mesozoic Period up to the Lower Cretaceous, has long 

 been known. The existing Order Cycadaceae is a small family, with 

 9 genera and perhaps 100 species, occurring in the tropical and 

 sub-tropical zones of both the Old and New World, but nowhere 

 forming a dominant feature in the vegetation. Some few attain the 

 stature of small trees, while in the majority the stem is short, though 

 often living to a great age. The large pinnate or rarely bipinnate 



1 One sperm fertilising the egg, while the other unites with the embryo-sac nucleus, 

 itself the product of a nuclear fusion, to give rise to a nutritive tissue, the endosperm. 



2 More Letters of diaries Darwin, Vol. n. p. 20, letter to J. D. Hooker, 1879. 



3 Ibid. p. 26, letter to Hooker, 1881. 



