548 PROCEEDINGS OF THE AMERICAN ACADEMY. 



tion with the obvious presence of bars of Sanio, might possibly be 

 common to all secondary woods in the region of the primary xylem. 

 Sections of the cone axis, the leaf -strands and roots of Cycas and Zamia 

 were accordingly made and subjected to the same treatment. In no 

 case was there any indication of the presence of horizontal bands of 

 cellulose in the tracheids, between the radial bordered pits. Similar 

 observations were made on the vegetative stem, the leaf strands and 

 the reproductive axes of Ginkgo. Here as in the case of Cycas and 

 Zamia, no bars of Sanio were seen in proximity to the primary wood. 

 In fact in the reproductive axes and in the leaf strands no bars of Sanio 

 were seen at all. In the vegetative stem, however, they appear late 

 in the first annual ring, not in close proximity to the primary xylem. 

 As is well known, Ginkgo resembles the mass of Conifers, in showing 

 bars of Sanio clearly in its mature wood. Pinus, as probably the most 

 primitive living representative of the Coniferales was likewise exam- 

 ined in this connection. Here the conditions closely resemble those 

 found in Gingko, so far as the vegetative shoots are concerned, for the 

 bars of Sanio make their appearance late and not in proximity to the 

 primary wood. In the cone of Pinus strobus, bars of Sanio were not 

 found at all. It is to be noted in connection wdth these results, as con- 

 trasted with those found in the case of the Araucarian Conifers that, 

 there is clear evidence, so far as may be judged from the structure of 

 the first annual ring, that Ginkgo and the genus Pinus are directly 

 connected with the Cordaitean stock, in which bars of Sanio are 

 absent and the pitting is alternating, while Agathis and Araucaria 

 have obviously come from ancestors which, in accordance with 

 accepted principles of comparative anatomy, had opposite pitting and 

 bars of Sanio in their tracheids. 



It seems to be quite clear so far as the particular features of wood 

 structure, considered in the present article, are concerned, that far 

 from the absence of bars of Sanio and the presence of alternating 

 pitting in the woods of the Araucariineae, being an argument for their 

 direct filiation with the Cordaitales, these features have clearly been 

 secondarily acquired and the Araucarian stock primitively was 

 characterized by the bars of Sanio and opposite pitting, Avhich have 

 been retained in the ligneous structure of all the other li\ing tribes 

 of the Coniferales. It is also quite clear from the fossil evidence that 

 the loss of bars of Sanio, in the case of the Araucariineae, as well as 

 the disappearance of the ancestral opposite pitting, took place at a 

 period relatively remote. That this general inference is justified 

 by a number of other equally important facts will be shown in the 

 later articles. 



