366 ANNUAL REPORT SMITHSONIAN" INSTITUTION, 1918. 



smaller genera show apparent anomalies of distribution coupled 

 with an extended history. 



There are a number of Mesozoic genera, of which Brachyphyllum 

 (Echinostrobus) is the most prominent and including Earitania, 

 Thuites, Androvettia, and presumably Moriconia and Inolepis, 

 which have been investigated anatomically and which show various 

 combinations of the following features : Sclerotic pith, lateral pits 

 of ray cells, branched leaf traces, mucilaginous resin canals, uni- 

 serial spaced bordered pits of the tracheids passing into alternating 

 and sometimes mutually flattened series, transfusion tissue not lat- 

 eral to the foliage strands, but showing a tendency to surround the 

 phloem. These and other features are regarded in some quarters as 

 indicating that these genera are descended from the Abietineacoae 

 and should be included in the order Araucariales — a view that has 

 received but slight acceptance and one that is dissented from in the 

 present article;. 



The family history goes back to Widdringtonites of the Triassic, 

 and to Palaeocyparis and Brachyphyllum of the Jurassic. These 

 are not altogether conclusive in their testimony, but the family 

 springs into unquestionable prominence during the Upper Cretace- 

 ous at which time in addition to Brachyphyllum, Thuja, Tlmites, 

 Juniperus, and disputed genera like Androvettia, Moriconia, and 

 Inolepis, there were well marked species of Widdringtonites and 

 Frenelopsis in which the foliar features are substantiated by fructi- 

 fication characters, which in the case of the valvular cones of the 

 Actinostrobinae are unmistakable. The genera Callitris, Cupressus, 

 Chamaecyparis, and Libocedrus appeared in the Eocene, while many 

 of the Cretaceous genera survived into that time and attained an 

 extended range. 



The family Abietineaceae is characterized by almost completely 

 distinct bract and scale, by winged pollen, short shoots, needle leaves, 

 and various recondite anatomical features of unproved phylogenetic 

 import. They are admittedly the most complex morphologically, and 

 are usually regarded as the most modern family of Coniferophytes, 

 although some students consider them to represent the ancestral stock 

 from which the Araucarialea, Taxales, and the Taxodiaceae and Cu- 

 pressaceae have been derived by reduction. Whichever view finally 

 prevails, there can be no question but that in the light of present 

 knowledge they have much the shortest geological history. There 

 are 9 genera and about 125 existing species, of which more than half 

 belong to the genus Pinus, and they form extensive forested areas in 

 the North Temperate Zone, to which they are practically confined. 

 Extinct genera are rare and include the Upper Cretaceous Prepinus, 

 Entomolepis, and Plutonia. Among the still existing genera, Pinus 



