THE " TR UMPE T- LIL V " FA MIL Y, 275 



between Monocotyledons and aquatic Dicotyledons. 

 I have already called attention to the structure of the 

 rhizome of the water-lily, which closely resembles a 

 stem of any monocotyledon. Again, when the seeds 

 germinate, the first, primary, or axial root is soon 

 arrested, as it always is in Monocotyledons. 



Many points in the microscopical structure within 

 the roots and stems also agree ; so that the number of 

 features in common is so great, that it is thought that 

 the whole class Monocotyledons has been derived from 

 some aquatic forms of Dicotyledons many thousands of 

 years ago. 



Many Monocotyledons are, of course, now terrestrial 

 plants, but they still retain features which are really 

 characteristic of water-plants. 



Another fact may be mentioned, that the percentage 

 of aquatic Monocotyledonous orders is about eighteen ; 

 whereas that of Dicotyledons is only four. Again, so 

 long ago as 1835, a German botanist, who studied South 

 African plants, came to the conclusion that the dis- 

 tribution of Monocotyledons over the world was 

 regulated more by moisture than by temperature, as 

 Dicotyledons are. 



Again, a large number of the beautiful flowers, for 

 which South Africa is famous, possess large bulbs. 

 Now, we know that these are special storehouses, not 

 only of reserve food materials, but also of water ; and 

 it seems probable that when they ceased to be true 



