n] GEOGRAPHICAL DISTRIBUTION 17 



supplanting all rivals, may be better understood 

 when we remember that it forms 85 7o ^f the flora 

 of the Dakota group ' ; that is a series of sedimentary 

 rocks in Dakota referred by geologists to the middle 

 of the Cretaceous period (is). In the Wealden rocks 

 of England, which are rich in the remains of Lower 

 Cretaceous plants, no undoubted Flowering Plant 

 has so far been found. 



The more efficient protection of the ovules, the 

 germs which, after fertilisation, become the seeds, 

 the extraordinary variety in the floral mechanisms 

 for assisting cross-pollination, the arrangements for 

 nursing the embryo, and the structural features of 

 the wood in relation both to rapid transport of water 

 and to the storage of food, are factors which have 

 pi'obably contributed to the success of the Angio- 

 sperms. The degree of weight to assign to each 

 contributing cause cannot as yet be satisfactorily 

 determined, but the general question raised by the 

 recent origin of these latest products of evolution 

 offers a promising field for work. While admitting 

 our inability at present to do more than suggest 

 possibilities, we may encourage research by specula- 

 tion. 



The members of the Vegetable Kingdom placed 

 next to the Flowering Plants are the Gymnos perms 

 or naked-seeded {yv/iv6<;, naked) plants, including 

 (i) the Conifers, e.g. pines, firs, larches, the yew, etc., 



s. 2 



