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THE AMERICAN NATURALIST [Vol. XL VI 



strobili, and had made notable changes in the vegetative 

 body, changes which characterize the second great gym- 

 nosperm phylum, fittingly called the Coniferophytes. 



The connections of the paleozoic Cordaitales with the 

 Mesozoic ginkgos and conifers are very obvious, and 

 these two groups, associated with Bennettitales and some 

 Cycadales, made up the mesozoic gymnosperm flora. 

 The Ginkgoales are really a mesozoic type, for their rep- 

 resentation to-day by a single species is probably due to 

 preservation by culture. It is an interesting fact that 

 the ginkgos, directly connected with the paleozoic Cor- 

 daitales, have retained the primitive reproductive struc- 

 tures of that group and of the Cycadophytes, but ad- 

 vanced in vegetative structures as did the conifers. The 

 group is very old in its reproductive methods, and modern 

 in its vegetative body. 



The great gymnosperm group of the Mesozoic, as of 

 the present time, is the Coniferales, and their deployment 

 during the Mesozoic is a subject of fascinating interest. 

 The so-called tribes of conifers are found distinctly dif- 

 ferentiated during the Mesozoic, and the determination 

 of their relative ages is one of the triumphs of vascular 

 anatomy. My colleague in this symposium, Professor 

 Jeffrey, has lived in the storm center of this work, and 

 it would not be fitting for me to invade his own special 

 field. It may be said, however, that to discover that the 

 Abietineae (the pine tribe) are the oldest conifers is up- 

 setting the older phylogeny fully as much as paleobotany 

 has done for other gymnosperm groups. 



The conifers are distinguished among the other gym- 

 nosperms that have been discussed, in being modern both 

 in reproductive methods and vegetative structure. In 

 contrast with cycads, therefore, they present the same 

 paradox conversely, that is, they are structurally younger 

 than cycads, but historically older. 



This hasty outline of gymnosperm history, which pa- 

 leobotany has interpreted for us, proves convincingly 

 that no plant phylogeny is adequate until it has included 



