662 FOURTH RKPORT 1834. 



observed, except in the above specimen, the true coniferous 

 structure. The coniferous origin of jet will, in all probability, 

 be generally admitted ; and the analogy of the naphtha of coal to 

 the turpentine of the Coniferce, as lately indicated by Dr. Reichen- 

 bach, gives room to surmise that coal in general has resulted 

 from the bituminization of coniferous plants. 



The transverse section, though alvraj'S sufficient to distinguish 

 the Cotiiferce from the monocotyledons and dicotyledons, does 

 not furnish any criterion by which to distinguish with certainty 

 one species from another. The longitudinal section, however, 

 parallel to the partitions extending from the centre to the sur- 

 face, enables us to divide the whole family oiConifercB, whether 

 recent or fossil, into two distinct divisions. The discs or areolas 

 to be seen in that section are so different in form and arrange- 

 ment in the two divi^ionsjthat there is no risk of mistaking any 

 species in the one for any species in the other. 



The first divison, which may be called the Pine division, in- 

 cludes the true pines, the cypresses, the junipers, the thujas, 

 the callitrises, and Salisburia adiantifolia ; the second divison, 

 which may be called the Araucariayi, includes the araucarias 

 and dammaras. The author first took notice of the discs in the 

 recent pine division, and then pointed out examples of similar 

 discs occurring in fossils of the same division. 



The discs or areolfe to be seen in all the species do not occur 

 in every part of a section. They are generally distributed in 

 groups more or less extensive. Their form is for the most part 

 cii'cular ; but they are sometimes slightly elliptical, and when 

 that is the case the transverse diameters are perpendicular to 

 the longitudinal partitions. They are arranged in a vertical di- 

 rection, most frequently in single rows. Doiible rows, however, 

 are often to be seen ; but more than that number the author has 

 never observed, although he has cut and examined many hun- 

 dreds of sections. The discs in a row are sometimes in contact 

 with one another, but often detached at very different distances ; 

 and wherever they occur in double rows, they are always placed 

 side by side in a liorizontal direction. In many of the true pines 

 the discs have the largest dimensions towards the inner side of 

 each annual layer, and they are larger and better defined than 

 those in most of the other tribes of this division. When a section 

 of any of the larger true pines is properly cut, the discs often pre- 

 sent an apparently flat surface, consisting of a number of distinct 

 concentric rings, especially when illumined with artificial light, 

 as that of a candle, and viewed with a garnet lens of the fortieth 

 or fiftieth of an inch radius. It does not always happen tliat 

 the discs are wholy composed of concentric circles. In many 



