Origin of Seed-plants 209 



micropyles of the ovules were in a position to receive the pollen 

 directly, without the intervention of a stigma. It is thus indicated 

 that the Angiosperms sprang fi'om a gymnospermous source, and 

 that the two great phyla of Seed-plants have not been distinct 

 from the first, though no doubt the great majority of known 

 Gymnosperms, especially the Coniferae, represent branch-lines of 

 their own. 



The stamens of the Bennettiteae are arranged precisely as in 

 an angiospermous flower, but in form and structure they are like 

 the fertile fronds of a Fern, in fact the compound pollen-sacs, or 

 synangia as they are technically called, almost exactly agree with 

 the spore-sacs of a particular family of Ferns — the Marattiaceae, a 

 limited group, now mainly tropical, which was probably more promi- 

 nent in the later Palaeozoic times than at present. The scaly hairs, 

 or ramenta, which clothe every part of the plant, are also like those 

 of Ferns. 



It is not likely that the characters in which the Bennettiteae 

 resemble the Ferns came to them directly from ancestors belonging 

 to that class ; an extensive group of Seed-plants, the Pteridospermeae, 

 existed in Palaeozoic times and bear evident marks of affinity with 

 the Fern phylum. The fern-like characters so remarkably persistent 

 in the highly organised Cycadophyta of the Mesozoic were in all 

 likelihood derived through the Pteridosperms, plants which show an 

 unmistakable approach to the cycadophytic type. 



The family Bennettiteae thus presents an extraordinary association 

 of characters, exhibiting, side by side, features which belong to the 

 Angiosperms, the Gymnosperms and the Ferns. 



ii. Origin of Seed-plants. 



The general relation of the gymnospermous Seed-plants to the 

 Higher Cryptogamia was cleared up, independently of fossil evidence, 

 by the brilliant researches of Hofraeister, dating fi'om the middle 

 of the i)ast century ^ He showed that "the embryo-sac of the 

 Coniferae may be looked upon as a spore remaining enclosed in 

 its sporangium ; the prothallium which it forms does not come to 

 the light^." He thus determined the homologies on the female side. 

 Recognising, as some previous observers had already done, that the 

 microspores of those Cryptogams in which two kinds of spore are 

 developed, are equivalent to the pollen-grains of the higher plants, 

 he further pointed out that fertilisation "in the Rhizocarpeae and 



^ W. Hofmeister, On the Germination, Development and Fructijicution of tlie Higher 

 Cnjpto(jamia, Bay Society, London, 1862. The original German treatise appeared in 

 1851. 



' Ibid. p. 438. 



D. U 



