PROBLEMS OF MODERN SCIENCE 



readiness for fertilisation, might be compared with 

 the eggs of birds and some reptiles, the calcareous 

 shell of which protects the embryo in all but the 

 latest stages of development. Furthermore, it is 

 by no means fanciful to see a parallel as regards 

 protection between the Gymnosperms and Angio- 

 sperms among plants on the one hand, and 

 the Marsupials and higher Mammals on the other. 

 Just as the Gymnosperms are characterised by open 

 carpels, usually in a cone, while the Angiosperms 

 have closed carpels affording an additional protec- 

 tion to the young embryo, so the Marsupials, the 

 later development of whose young takes place in 

 an open pouch, were supplanted by the higher 

 Mammals, in which the complete protection of 

 the mother's body is afforded until all the critical 

 stages of development are passed through. 



Returning now to the palaeozoic seeds, whose 

 investigation has been of so much importance in 

 recent pakeobotany, Williamson as early as 1875 

 described fossil seeds from the Lower Carboni- 

 ferous of Lancashire. But only since the begin- 

 ning of the present century has it been shown that 

 these seeds belonged to plants having the habit, 

 foliage, and essentially the male reproductive 

 organs of ferns. In 1903 Oliver and Scott showed 

 that the seed known as Lagenostoma Lomaxi 

 belonged to the fern-like plant Lyginodendron 

 Oldhamtum^ and founded the group of Pterido- 



