Elkins and Wieland — On Devonian Wood. 77 



species, Callixylon Trifilievi, plainly differs, having smaller 

 medullary rays with less biseriation and, so far as the figures 

 show, fewer bordered pits in the groups.* As to whether or 

 not the American species have, like C. Trifilievi, a fine develop- 

 ment of primary xylem is of course more or less conjectural, so 

 that in accepting classification under Callixylon a sharp doubt 

 remains. However, no other course appears consistent, and 

 our species is therefore named in honor of the early Indiana 

 geologist, David Dale Owen, and the illustrious family to 

 which he belonged, — 



Callixylon Oweni sp. nov. 



Inasmuch as the characters of this new form have been 

 clearly brought out in the preceding descriptions, while Cal- 

 lixylon (Cordaites) Newberryi is not very well known (efforts 

 to locate the types having so far failed), and C. Trifilievi 

 awaits further description, it is not necessary to here append a 

 searching recapitulation of the specific characters separating 

 the three members of Callixylon, C. Newberryi, C. Oweni and 

 C. Trifilievi. It is sufficient to state in resume that all three 

 plainly differ in various minor features and that while the 

 small medullary rays and low number of bordered pits to the 

 group clearly separate Callixylon (Cordaites) Newberryi 

 Dawson from C. Trifilievi Zalessky, both are further isolated 

 from Callixylon Oweni by obscurity or absence of the growth 

 rings, which, while not a strongly fixed character, are in the 

 latter species distinct. Moreover it could at most only pro- 

 duce confusion to assign this perfectly conserved material to 

 so imperfectly known a species as C. Neioberryi in reality is. 



I have in other connections urged the necessity for basing 

 types on the best known material. 



In conclusion it may be added that the main value of this 

 contribution must consist in Miss Elkins' excellently drawn 



* The lateral tracheidal bordered pits of the Callixylon species are small 

 of diameter, not large as in many modern conifers and cycads, the actual 

 dimensions having some interest as follows : — In Callixylon Newberryi the 

 pits have a diameter of 9 microns, in C. Oweni 10 to 11 microns, in C. Trifi- 

 lievi 12 to 13 microns ; in Araucaria Bidwilli 11, in Agathis bornensis 10 to 

 12, and in Araucaria Cookei roots only 3 microns ; while these measure- 

 ments rise in Pityoxylon (sp.) to 15, in Larix americana to 16, in Dion spi- 

 nulosum to 19, and in Pinus strobus to from 25 to 35 microns. Lest any 

 doubt as to the bordered pit features of C. Oweni should remain, I may 

 emphasize the fact that the cellulose bands or "bars of Sanio " often so 

 characteristic in various recent Abietineae, are not present in even a rudi- 

 mentary condition. The testimony of the sections is conclusive on this 

 point. Indeed the pits can be studied to even better advantage than in 

 some artificially stained woods. Nor are the bars absent because there is 

 crowding. Normally the pits barely touch and no more, although the outer 

 border does appear very distinct and it is easy to see how cellulose thicken- 

 ing on a contact line could arise. 



