JEFFRP^Y. — AR.VUCARIOXYLOX TYPE. 571 



tribe among the Cycadophyta. It is finally cK^ar that tnorphologists 

 will find it necessary in the fnture more and more to adopt certain 

 general working principles, as in the case for example in the sister 

 sciences of chemistry and physics. If there prove on trial to be no 

 generally applicable fnndamental principles in morphology, that branch 

 of biological science cannot be too soon cast into the outer darkness, 

 which prevails outside the scientifir view of nature. 



Genteral Conclusions. 



1. The Araucariineae cannot have l)een derived from the Cordai- 

 tales since they possessed primitively a numl)er of features which 

 so far as our knowledge goes, never existed in the Cordaitean stock. 



2. The Araucarioxylon type is derived from ancestral forms, 

 which possessed opposite pitting, bars of Sanio, strongly pitted rays 

 and horizontal and vertical resin canals. 



3. The primitive existence of these features in the ancestral type 

 from which Araucarioxylon has been derived, show clearly that it ha3 

 taken its origin from the Abietineous Pityoxylon type. 



4. This conclusion is entirely confirmed by a consideration of the 

 reproductive structures both sporophytic and gametophytic. 



5. Any hypothesis as to the origin of the Coniferales in general 

 must start with the Abietineae as the most primitive tribe. 



6. It is absolutely essential to the progress of plant morphology, 

 that investigation be carried on in connection with the elucidation of 

 the general working principles of the biological sciences. 



7. The comparative, developmental, paleobotanical and experi- 

 mental investigation of the Coniferales is likely to throw more light 

 on the stable and sound general principles of biology, than that of 

 any other large group of animals or plants, on account of their great 

 geological age and remarkably continuous and complete display, both 

 as regards external form and internal structure in the strata of the 

 earth. 



Botanical Laboratories of Harvard University, 

 17th, June, 1912. 



