XI] LEAVES. 399 



b. Roots. 



Our knowledge of the anatomy of Sphenophyllum roots is 

 very limited. Renault has described a somewhat imperfect 

 example of a silicified root from St. Etienne and Autun. The 

 drawing in fig. 107, B, which is copied from one of Renault's 

 figures, shows a cylindrical mass of xylem with a small band of 

 narrower elements occupying the centre, and surrounded by 

 rows of larger secondary tracheae. The central bipolar band 

 is described as the diarch primary xylem, around which the 

 secondary pitted elements have been developed. 



It is probable that the specimen described by Renault is 

 a root of Sphenophyllum, but my impression gained from an 

 examination of the section was that the diarch primary strand 

 is not quite so clear as in the published figures. Until we 

 possess better material we cannot attempt any very satisfactory 

 description of the anatomical features of the roots of this 

 genus. 



A section of a Sphenophyllum stem has been figured by 

 Felix', in which a lateral meinber is being given off; this may 

 possibly represent the origin of an adventitious root, but the 

 preservation is not sufficiently distinct to render this certain. 



c. Leaves. 



Renault 2 has described some silicified leaves of Sphenophyl- 

 lum from Autun in which the laminae consist of thin-walled 

 loose parenchyma, traversed by small groups of tracheids con- 

 stituting the simple or forked veins. The epidermis is made up 

 of a single layer of cells, with here and there indistinct indi- , 

 cations of stomata. A more perfect stoma has, however, been 

 described by Solms-Laubach from the epidermis of a bract in a 

 strobilus (fig. 107, A). 



1 Felix (86), PI. vi. fig. 2. 



- For figures vide Eenault (82), PI. xvi. fig. 1, (762) pig. yii. and ix. 



