N. E. Stevens — Petrified Palms. 



433 



fibrovascular bundles, are usually about 50 /x to 75 /x in 

 diameter, and show from 15 to 30 cells in cross section. 



Fibrovascular himdles. — The fibrovascular bundles are 

 rather close together, in the sections examined, and vary 

 from about 20 per sq. cm. to about 35 per sq. cm. (cf. figs. 

 1 and 2).- The bundles themselves are rather large, 

 usually measuring at least 1 mm in shortest diameter, by 

 1 to 1.5 mm in longest diameter, as compared, for example, 

 with .6 to .75 mm. by 1 mm. in P. anchorus Stevens of the 

 New Jersev Cretaceous, and .5 mm. by 1 mm. in P. Cliff- 





.Q 



Fig. 1. — P. cheyennense, outline showing relative size and arrangement 

 of the fibrovascular bimdles in the interior portion of the stem. X 5. 



Fig. 2. — P. cheyennense, outline showing relative size and arrangement 

 of the bundles in the outer portion of the stem. X 5. 



u'oodensis Berry. In the material studied the bundles 

 were chiefly of the "longitudinal" type, that is, typical 

 upright stem bundles with two, or sometimes three large 

 vessels, .133 mm. to .055 mm. in diameter {fig. 3). In the 

 phloem, which is preserved in a few of the bundles, twelve 

 to twenty sieve tubes may be distinguished. The scleren- 

 chyma portions, which are composed of typical bast fibres 

 closely appressed, vary in shape but are predominantly 

 ovoid and rather regular in outline. As is best shown in 

 longitudinal section (fig. 5) a band of sclerenchyma fibers 

 occurs on the side of the vessels opposite the phloem. 

 This is the so called posterior sclerenchymous arch of 

 Stenzel.^ 



On one slide, that from which figure 2 was made, there 

 occur nine or ten bundles of the type shown in figs. 4, 6, 

 and 7. These are obviously either the ''Ubergangs- 



^ Stenzel, K. G., Fossile Palmenholzer, Beitrage zur Palaontologie und 

 Geologie Osterreieh — Ungarns und des Orients, Band XVI, Heft IV, p. 1-182, 

 1904. 



