6e KOYAL SoriKTY OF t'ANADA 



characteristic features of form and distrilnitiun belonging to the genus. 

 In a radial distance of 15 nun., tliere is no evidence of growth 

 rings beyond tlie occurrence of tlirce vaguely ilotlned zones in which the 

 tntc'lu'ids appear to have a somewhat shorter radial diameter. There 

 is uo such distinction as commonly rehites t.(j the dilferentiation of 

 growth rings. A nuicr()scoi)ic examination of a hand specimen shows 

 that in a radial distance of 22 mm. eight api>arent growth rings appear. 

 These vary from 2-4 mm. in width, but their limits are poorly defined 

 and they do not have the sharp termimitions commonly met with in 

 properly developed growth r'ngs. A transparent section examined 

 under a low power hand lens, slu>ws no evidence of growth rin^s, from 

 which we nuiy infer that the appearances presented macroscopically, de- 

 pend upon features which simulate rings only when taken collectively. 

 This conforms exactly to what niiiy be observed in modern Araucarias. 

 The si>ecies thus agrees with the characters of the genus in the well de- 

 fined absence of growth rings. 



In a radial section the elements of the proti>xylem are seen to be 

 narrow, spiral and scal'ariform structures which pass into tracheids with 

 bordered pits by a series of gradations. 'J'ho bordered pits on the radial 

 walls of the tracheids are in 2-4 rows throughout. The medullary rays 

 present the s:i)eciial ditl'erential feature of the species. The elements 

 are of two kinds, i)arenchyma cells aud tracheids. The parenchJ^na 

 cells are usually equal to about three tracheids in length, and their 

 latertd walls are too much decomposed to determine the number and 

 character of the pits. The tracheids are usually long and narrow, in- 

 terspei'sod; and on their lateral, upjier and lower walls boar numerous 

 crowdiMl and small ])or(lered pits. Tliis feature occurs in no other 

 species brought under my notice, and it servos to differentiate C. 

 Clarkii beyond aJl question. The further question arises as to whether 

 this cliaracter is sutficient to separate the plant from the genus Cor- 

 daites. All the other essential characters are tho.-e which belong to 

 Oordaites, and the deviation indicated by the occurrence of ray tracheids 

 is still such as may well come within the limits of the genus. This 

 N-iew finds its justification in the parallel case afforded by Abies, in 

 which A. balsamea stands as a ])arallel exception to the rule that only 

 parenchyma elements are present. 



In a tangential section (fig. 16), the rays are seen to be very variable 

 in height as well as in their detailed structure. In some cases the rays 

 are relatively broad celled %nA low, and more or less 2-seriate in part. 

 In the higher rays the tracheids are at once distinguishable by their 

 contracted form, and often greater heiirht of the individual element. 



