602 The Outline of Science 



on the wall to the cedar of Lebanon, from the annuals in our 

 garden to the Big Trees of California which have sometimes lived 

 for over two thousand years. The first plants were probably free- 

 swimming open-sea single-celled Alga?, and there are many of 

 them to-day. As shallow waters were established around up- 

 bulging continental masses, fixed seaweeds began to flourish- 

 fixed to the floor of the sea and yet not out of the reach of the 

 light. At a very low tide it is worth while wading out cautiously 

 among the great seaweeds, some of them many yards long. This 

 is the forest primeval, and it is possible, as Church maintains, that 

 some of them were slowly transformed into terrestrial plants as 

 the shore continued to rise. 



On a path of their own are the Fungi moulds and toad- 

 stools of many kinds living on rottenness, or as parasites on 

 green plants. Among them, but rather by themselves, most 

 botanists include bacteria. Lichens are strange double plants, 

 consisting of Alga? and Fungi living together in intimate mutually 

 beneficial partnership. On a higher level are the sprawling liver- 

 worts, and above them come the mossses, the ferns, the horsetails, 

 and the club-mosses. The beginning of Seed Plants may be 

 traced very far back, probably to the Devonian period, but it 

 was not till the geological "middle ages" that they began to come 

 to their own. It was a great step in evolution when seeds were 

 established, for that meant as in mammals among animals that 

 what was liberated from the parent was a young plant which had 

 lived for a considerable time in the seed-box, as it were in partner- 

 ship with its parent. Conifers and Cycads represent a lower level 

 than the ordinary flowering plants like grasses and lilies, daffodils 

 and orchids, buttercups and poppies, roses and lupins, bluebells 

 and daisies. The variety suggested by these names seems endless, 

 but the flowering plants fall into well-defined groups, and it is pos- 

 sible to work out a pedigree tracing them back to a few common 

 ancestors. Just as all the important varieties of cultivated wheat 

 can be traced back to the Wild Wheat, which still grows on Mount 



