IIOLDEX. — CRETACEOUS PITVOXYLA. 611 



tlian is usually the case in the latter. Aside from our specimen, there 

 are but two instances whore ray tracheides have been described in a 

 fossil, — Pi7ius scituafcnslformis, Bailey (5) and P. succinifera (Goepp.) 

 Conw. (4). In the former, the walls seem to be smooth like those of 

 living soft pines, while in the latter, Conwentz figures just such a 

 sculptured appearance as is presented by the lignite under considera- 

 tion. 



The pitting of the tracheides is entirely confined to the radial wall. 

 Owing to the small size of the elements, the pores are usually uniseriate. 

 They are normally circular in outline and scattered; rarely toward 

 the end of a tracheide, they become closely approximated and flat- 

 tened by nuitual contact. Figure d, Plate 1, represents a typical 

 condition. In the larger tracheides of the spring wood, the pores are 

 often diseriate. In such instances they are always opposite and sep- 

 arated by well marked "bars of Sanio." In the living condition 

 these bars are formed by the thickening of the cellulose middle lamella, 

 which in the process of fossilization, rots away, leaving an empty 

 space. Consequently the bar appears as a white line. A particularly 

 favorable region is shown in Figure /, Plate 2. Were anything more 

 needed to demonstrate the Abietineous affinities of our lignite, these 

 would suffice, since as shown by Miss Gerry (6) these bars of Sanio 

 are invariably absent in woods of Araucarian affinities. 



The short shoots in this fossil are much larger than those in most 

 living pines, though never showing annual rings as in Ginkgo, Figure c, 

 Plate 4, represents one of these organs. On careful examination it may 

 be seen that there is a single row of resin ducts in the wood, and that 

 the medulla contains sclerotic nests similar to those of the main axis. 

 This section was cut at some distance from the pith. Figure d, Plate 4, 

 shows, at a lower magnification, a section cut considerably nearer the 

 centre. In the upper part of the photograph the short shoot may be 

 seen; toward the lower limit, there is a dark spot. Figure/, Plate 1, 

 represents this spot at a much higher magnification, and demonstrates 

 its foliar nature. Examination of serial sections has shown that at its 

 departure from the medulla, each brachyblast is subtended by an 

 axillating leaf trace, which dies out after a few years, leaving an appar- 

 ently unaxillated short shoot. A similar condition has been described 

 by Dr. Jeffrey in the case of Woodworthia, an Araucarian from the 

 Triassic (7) : in Woodworthia, however, these short shoots often branch, 

 which is never the case in this Pityoxylon. The short shoot of Ginkgo 

 is always axillated, in this case by a double leaf trace; in Larix also the 

 short shoots are axillary structures. In the majority of living pines, 



