300 MESOZOIC FLORAS OF UNITED STATES. 



The teeth average in length about 6 mm. They show the narrow 

 lancet to linear form which belongs mostly to the Equiseta of late Jurassic 

 and early Cretaceous times. The size of the stem surpasses that of the 

 characteristic Equiseta of the Lower Cretaceous, and in this feature the 

 plant has rather Jurassic than Cretaceous affinities. A Jurassic and 

 Older Mesozoic character is seen also in the sheaths, which are closely 

 consolidated with the stem, unlike the loose, baggy sheaths seen in the 

 small Lower Cretaceous Equiseta, such as Equisetum BurcharcUi Dunk., 

 etc. Dunker, in his Monogr. d. Norddeutsch. Wealdenbildung, estab- 

 lished the species from a single imperfect specimen, calling it Equi- 

 setites Phillipsii. No other specimen of the plant seems to have JDeen 

 found, for all writers who notice the species base their remarks on Bun- 

 ker's specimen. Schenk carefully examined Dunker's specimen and 

 gives the fullest description of it." He says that the internodes are 

 2 cm. in diameter and 15 mm. long; the sheaths are short, 2-2.5 mm. 

 long, and toothed, and the bases of the teeth are persistent and truncate 

 in form, while the stems are obscurely striate. He remarks that it is 

 larger than any of the Wealden species. 



There is nothing in Schenk' s figures to show the true length of the 

 sheaths. What he appears to regard as the entire sheath is its upper 

 portion, where the bases of the teeth are united to the stem. 



PI. LXXII, Fig. 1, gives, natural size, a portion of a node of one of 

 the larger-sized stems, which has been compressed in the direction of the 

 axis of the stem so as to squeeze out the diaphragm. The upper part 

 of a portion of the sheath is preserved and the lower portions of some of 

 the teeth are shown. Fig. 2 shows a node compressed in a manner 

 similar to Fig. L This is a smaller stem. It shows the diaphragm in 

 place, the sheath spUt down along the bases of the teeth so that these 

 appear too long. Fig. 3 shows a much compressed portion of one of the 

 larger sized stems, which at its upper end carries the greater part of a 

 sheath with its strise. This is the most common form in which the 

 remains of this plant are found. Fig. 4 represents one of the smallest 

 sized detached diaphragms, and Fig. 5 one of the largest size. Fig. 6 

 shows a portion of a flattened stem with some of the processes that are 

 left at the node when the teeth are torn off. Fig. 7 shows a portion of a 



« Die Foss. Flor. der Nordwestdeutsch. Wealdenformation, p. 4, pi. i, figs. 6-9 (Palaeontographica, Vol. 

 XIX, p. 206, pi. x.xii, figs. 6-9). 



