LATER LIFE ON THE EARTH 55 



(1) The Apetalse, in which the perianth consists 



of the calyx only. 



(2) The Polypetalse, which has a corolla formed 



by four or five separate petals, in addition 

 to the calyx. 



(3) The Gamopetalse , in which the lower por- 



tions of the petals are united together to 

 form a tube, which protects the honey 

 secreted at its base. 



In the Cretaceous period nearly half of the 

 Dicotyledons belonged to the Apetate, such as 

 willows, poplars, oaks, walnuts, figs, &c. About half 

 belonged to the Polypetalae ; while the Gamopetalai 

 formed but five per cent, of the whole. The heaths, 

 clovers, rhododendrons, myrtles, olives, and Com- 

 positse appear in the Oligocene ; the azaleas and con- 

 volvulus in the Miocene ; but the Gamopetalse were 

 still in a minority, and did not attain their present 

 position until recent times. A table will show this 

 better than any description. 



Apetalae. Polypetalse. Gamopetalse. 



Cretaceous 45 p. c. 50 p. c. 5 p. c. of the flora. 



Miocene 37 p. c. 48 p. c. 15 p. c. ,, 



Recent 14 p. c. 50 p. c. 46 p. c. ,, 



The introduction of herbaceous grasses must have 

 materially affected mammalian life. According to 

 Mr. J. Starkie Gardner, 13 grasses are first known in 

 the upper Cretaceous of Europe, North America, and 



^Proceedings of the Geologists' Association of London, 

 1886, p. 433. 



