IX] EQUISETITES BURCHARDTI. 279 



of the examples figured by Schenk^ show clearly marked im- 

 pressions of displaced nodal diaphragms exactly as in E. lateralis. 

 Another form, Equisetum rotiferum described by Tenison-Woods'^ 

 from Australia, is closely allied to, or possibly identical with 

 E. lateralis. 



8. Equisetites Burchardti Dunker'. Fig. 65. 



This species of Equisetites is fairly common in the Wealden 

 beds of the Sussex coast near Hastings, and also in Westphalia. 



Fig. 65. Equisetites Burchardti Dunk. Showing a node with two tubers and 

 a root. From a specimen in the British Museum. Nat. size. 



It is characterised by having long and slender internodes, 

 bearing at the nodes leaf-sheaths with five or six pointed seg- 

 ments, and by the frequent formation of branch-tubers. These 

 tuberous branches closely resemble those which are formed on 

 the underground shoots of Equisetum arvense L., E. sylva- 

 ticum L. and others; they occur either singly or in chains*. 

 In the specimen shown in the figure the left-hand tuber is 

 remarkably well preserved, its surface is somewhat sunk and 

 shrivelled, and the apex is surrounded by a nodal leaf-sheath. 

 A thin branched root is given off just below the point of 

 insertion of the oval tuber. 



No other species of Equisetites affords such numerous 



1 Schenk (67). 



2 Tenison-Woods (83), PI. vi. tigs. 5 and 6. Specimen no. V. 8858 in the 

 British Museum. 



* Dunker (46) p. 2, PL v. fig. 7. * Seward (94») p. 80. 



