No. 544] BOTANICAL SOCIETY OF AMERICA 231 



astronomy. The three most important laws or general 

 principles of morphology are those which have to do with 

 recapitulation, reversion and retention. The first is 

 common to both plants and animals, while the other two 

 are infinitely better illustrated by botanical than zoolog- 

 ical facts. The validity of these laws has long been ad- 

 mitted in a somewhat hazy and unpractical fashion. It 

 has remained for morphology based on paleobotany to 

 bring them into prominence as the fundamental working 

 principles of the investigator of plant evolution. They 

 are in fact the rudiments, the three R's of biological sci- 

 ence, with which even the tyro should become well 

 acquainted. 



We can not do better than take a particular illustra- 

 tion of these laws as applied to botanical facts. The 

 conifers show themselves particularly favorable for the 

 elucidation of general evolutionary principles, because 

 they not only constitute a large, varied and widely dis- 

 tributed element of our existing flora, but can be traced, 

 with trifling interruptions, continuously far into the past. 

 Of the conifers there is one tribe at the present time 

 entirely confined to the southern hemisphere. I refer 

 to the Araucariineae, of which the New Zealand Kauri and 

 the Norfolk Island pine may appropriately stand as 

 examples. In the Mesozoic period, the middle ages of 

 our earth, they flourished throughout the entire world. 

 It is often considered that the Araucariineae represent 

 the most ancient group of conifers. This belief appears 

 to be based on a too common fallacy, that groups nearly 

 extinct in the existing flora necessarily represent ancient 

 forms. A further basis for the hypothesis of the extreme 

 antiquity of the Araucarian conifers is derived from 

 their habit and the general features of organization of 

 their wood, in both of which respects they present points 

 of resemblance, by no means complete, however, with 

 those Paleozoic gymnosperms to which the origin of the 

 general coniferous class is by common consent of morphol- 

 ogists and paleobotanists referred, namely, the Cordai- 



