570 PROCEEDINGS OF THE AMERICAN ACADEMY. 



dition of the Araucariineae. Here the two prothallial cells common 

 to the Abietineae and the equally ancient Ginkgoales become prolifer- 

 ated into a large number, doubtless in correlation with the extreme 

 length and meandering course of the fertilizing tube. Moreover 

 the absence of a stalk cell in connection with the setting off of the body- 

 cell, which gives rise to the two sperm cells, is a clear and outstanding 

 feature of aberrancy. Mr. Eames in the memoir, already cited, has 

 shown moreover, that in the organization of the female gametophyte, 

 the structure of the archegonium, the nature and functions of the 

 archegonium neck, as well as in the method of penetration of the pollen 

 tube and the development of the embryo, the Araucarian conifers 

 manifest not a primitive but an extremely aberrant condition. They 

 are in fact comparable to a large degree in their systematic position 

 with the edentate fauna, likewise characteristic of the antarctic region, 

 Developmental investigations on the zoological side have recently 

 shown that the edentulous features which have been until the present 

 time regarded as a primitive feature of this group are in reality marks 

 of al)errancy, since a more abundant dentition, at first makes its 

 appearance in the embryo. 



Reviewing all the evidence in the light of many recent investigations 

 both in general morphology and in the morphology of the conifers in 

 particular, it is clear that it is the anatomical features of the repro- 

 ductive and vegetative organs, which give us the most reliable criteria 

 as to the evolution of the coniferous stock and above all in the present 

 connection, as to the evolution of the Araucarian tribe. The ana- 

 tomical conditions in the living forms cannot be understood without 

 careful comparison with the organization of those which are now 

 extinct. Basing our conclusions on these criteria, the result is reached 

 that the Araucarioxylon type has been derived from the Pityoxylon 

 type and as a consequence formerly possessed the opposite pitting, 

 the bars of Sanio, the strongly pitted rays and the resin canals of the 

 ancient Abietineous woods. Some of these characters are still to be 

 observed in primitive regions of the existing Araucariineae, while 

 others are to be inferred from a consideration of the organization of 

 Araucarian forms now extinct. It is further clear that the external 

 form of the reproductive structures and the organization of the 

 gametophytes supplies as little light, regarded independently from the 

 anatomical organization of the reproductive and vegetative parts, 

 for the interpretation of the true course of evolution and affinities 

 of the ancient but highly aberrant coniferous tribe, the Araucariineae 

 .as is the case with the corresponding structures in the Bennettitean 



