THE STRUCTURE OF FLOWERS. 225 



Imperfect as the geological record is, the direction of progress 

 is always from the lower types to the higher, though the steps may 

 be often obliterated. And, in some mysterious manner, the 

 evolution of the higher types seems coincident with the fading 

 away of types immediately lower. It is in the Aflanfosaurus beds, 

 so called from that hugest of deinosaurs, that these earliest 

 American mammals are found. The largest of these mammals 

 was no larger than a weasel, yet the great reptiles gradually faded 

 out of the world before these small, warm-blooded creatures. 



On the threshold of the Tertiary period I will bring this paper 

 to a close. The puzzles of Palaeontology are equally insoluble in 

 Kainozoic times, and more nearly affect ourselves. Their mere 

 statement would require another paper, and I have already 

 tresi)assed too fiir on the space of this journal. 



Authorities consulted : — 



Professor Marsh, " American Jurassic Mammals," Geological 

 Magazifie, June and July. 



Heilprinn's " Geological and Geographical Distribution of 

 Animals." 



Nicholson's " Palaeontology." 



" Eozoon Canadense," Science Gossip, April and May, 1887. 



^be Structure of jflowere witb reference to 

 3n0ect ai^ in tbeir fertilisation. 



By Wx G. Wheatcroft. 



Plate 24. 



IN the year 1793 Christian Conrad Sprengel published his 

 interesting treatise on the structure of flowers with special 

 reference to insect aid in their fertilisation. This book was almost 

 wholly neglected for more than half a century. Nevertheless, it 

 contains, with some fanciful ideas, the germs of the doctrine now 

 generally held, together with many excellent illustrations of it. 

 Vol. VI. Q 



