196 Plants and their Ways in South Africa 



together which are naturally related. A study of plant groups 

 shows a gradually increasing complexity from the simpler 

 water plants, the algae, to those which live in damp places but 

 bear their spores in the air, on to the seed-bearing plants. 

 That there has been a continuous line of ascent is far from 

 probable. But the laws of growth and development which are 

 observed in common by different plant families leads to an 

 interesting study of plant relationships. 



The most highly developed plants are the Spermaphvtes 

 or seed-bearing plants. They were formerly known as Pha- 

 nerogams (this term means sexual organs exposed), and 

 were distinguished from all the lower groups or Cryptogams 

 or plants with " sexual organs concealed ". At the time these 

 words were coined, it was thought that stamens and pistils were 

 sexual organs and these are found only among seed-bearing 

 plants. When microscopes and methods were improved it was 

 found that the sexual organs were much more in evidence in 

 the Cryptogams than in the seed-bearing plants. 



Two groups of seed-bearing plants are recognized : the 

 Gymnosperms and Angiosperms. While these divisions are 

 based on many distinct characters, the groups may be readily 

 distinguished by the fact that in Gymnosperms the seeds are 

 exposed on a scale as in the pines and yellow woods, while in 

 Angiosperms they are enclosed within the ovary. In the former 

 group the pollen grains (microspores) are lodged directly 

 within the micropyle, while in the angiosperms they are carried 

 to the stigma and the pollen tube has farther to travel before 

 they convey the sperm cells to their destination within the 

 ovule. Of the Spermaphytes the Gymnosperms are a very 

 ancient group as their imprints in the older rocks show. To 

 go into details of their subdivisions would be perplexing to 

 those for whom this book is written. The classes represented 

 in South Africa will be mentioned later. 



The Angiosperms are subdivided into two main groups, 

 Dicotyledons and Monocotyledons, which have been men- 

 tioned in previous chapters. It will be well here to review 

 some of the more prominent characters by which they are 

 distinguished. 



