THE VEGETABLE KINGDOM 341 



no such restriction in latitude, being common in England 

 for instance, and some of them attained a far higher grade 

 of floral structure, which makes it probable that from 

 them sprang the Angiosperms (typical flowering plants 

 with seeds enclosed in a fruit). They are doubtfully 

 represented in the Coal Measures, but undoubtedly from 

 the Rhaetic, Jurassic, and Lower Cretaceous. The 

 Jurassic period has been termed the "age of cycads." 

 Their remains are abundant in the Jurassic estuarine 

 beds of the North of England, in some of the Purbeck 

 beds, where they occur in the position of growth in the 

 " fossil forest " of Dorset cliffs, and in the Wealden beds. 

 But the most famous locality for them is the Black Hills 

 of Dakota, where wonderfully preserved specimens of 

 Upper Jurassic age have enabled Dr. Wieland to deter- 

 mine the full details of the floral organs. Leaf-genera : 

 Pterophyllum ( Trias. ),Cycadeoidea, Williamsoma(Fig. 100,7), 

 Ptilophyllnm (all Jur.), Otozamites (Trias.-L. Cret), Nils- 

 sonia (Jur.-L. Cret.), Zamites (L. Cret.) 



3. Cordaitales. The genus Cordaites (Dev.- Rhaetic) 

 was a forest tree resembling in habit the Australian 

 Kauri pine, to which it may have been not very distantly 

 related. Its leaves were long, narrow, thick and parallel 

 veined ; its seeds (Cardiocarpus) were borne on a cone. 



4. Ginkgoales. The maiden-hair tree, Ginkgo, with 

 its bifid wedge-shaped leaves (Fig. 100, k), is now confined 

 to parts of China and Japan ; but closely allied forms had 

 a world-wide distribution in Jurassic times, ranging from 

 Greenland to Tasmania. Its time-range in Europe is 

 Rhaetic to Eocene. 



