No. 448.] NORTH AMERICAN CONIFERA LES. 



the 2-5-seriate pits stand much nearer to the primitive lor 

 the tracheid than do the i -seriate. From this point of vie 

 is then evident that in C. Vccentium, the name of whii- 

 thereby seen to be fully justified, the i -seriate pits plac e 

 the upper end of a series which has its inferior terminati( 

 the 2-5-seriate C. acadianum, while between the two. intc 

 diate forms appear as members of a series of nine variants, 

 it is possible to arrange these in such a manner as to ex 

 the probable sequence in development as follows: — 













A. 





hamiltonense 















The wide range of variations here shown, especial])' ^ 

 pared with other genera, at once serves to suggest that 

 was in this respect somewhat of the nature of a tran>ii 

 from which others were given off, or else that it cpito 

 collective changes through which a number oi goncM 1 

 passed. And inasmuch as this genus exhibits a m< 

 developed, multiseriate arrangement than any other \ 

 general i)hylum, we must concede that it is, with rcsj). 

 character, the most primitive of all. 



The genus Araucaria shows a much more re^tru 

 of variations, there being only four ^ 

 distributed among fourteen species, 

 While the most highly developed meml 

 represented by i -seriate pits, the most 



both 



