404 



ABIETINEAE 



[CH. XLVIII 



this condition.' The fossil shoots from the Potomac series de- 

 scribed as Leptostrobus longifolius differ in the larger number of the 

 needles from modern Pines and resemble abnormal short shoots 

 of Pinus excelsa 1 produced by wounding. The short foliage-shoot 

 of Prepinus furnishes a more completely known example of a 

 branch bearing spirally disposed leaves. In view of the palaeonto- 

 logical evidence and of the facts obtained from a study of recent 

 Pines it would seem that, as Thomson holds, the present form of 

 the Pine spur is the result of specialisation and not a primitive 

 feature. 



1 Thomson (14), PI. xxn. fig. 10. 



