116 TREE ANCESTORS 



all of somewhat questionable identity. The alders, like the hazels, 

 make a prominent display in the moist temperate floras of the 

 Eocene, no less than a score of species haxang been described from 

 the rocks of this age, in which they are represented by leaves, cat- 

 kins, cones, and wood. True alders appear in the earliest Eocene 

 of France, Wyoming, Montana, Dakota, and Colorado; and they 

 are especially common in the Eocene rocks of Alaska, Sachalin, 

 Greenland, Iceland and Spitzbergen. Tertiary species of alder 

 have been described from both Austraha and Tasmania, but these 

 .are not certainly iden tilled. 



Undoubtedly the earliest flowering plants reached Australia 

 over a land bridge from Asia, but until the plant fossils of that 

 region receive a thorough revision at the hands of a competent 

 botanist, too great rehance cannot be placed on the identifications 

 of the early students of these floras. If authentic these Australian 

 occurrences mark the greatest penetration of the Southern Hemi- 

 sphere by any members of this family, and almost rival the 

 remarkable southward migration of the beech family. 



Ohgocene alders number 6 or 7, and are confined to Europe, 

 one being present in the Baltic amber deposits. As I will have 

 occasion to remark in connection with so many of our trees, this 

 paucity of Ohgocene records is due to the absence or lack of dis- 

 covery of Ohgocene plant beds in many regions, and especially in 

 North America. However, there is not the sHghtest doubt but 

 that there were Ohgocene alders at that time in both North America 

 and Asia. 



During the succeeding Miocene tune the geological record be- 

 comes profuse again and we find over 20 different species of alders 



Fig. 25. Some Fossil Leaves and Nuts of the Hazel (Slightly Reduced) 



1. Corylus MacQuarrii Heer, from the Oligocene of France. 



2. Corylus americanu fossilis Newb., from the early Eocene of Montana. 



3. Corylus Fosteri Ward, from the early Eocene of JMontana. 



4. Corylus rostratajossilis Newb., from the early Eocene of Montana. 



5. Hazel nut from the Oligocene of Saxony. 



6. Hazel nut from the Oligocene of Baltic Prussia. 



