114 Dr. W. C. Williamson on 



Middle Transverse. 

 C.N. 405. 



Middle Longitudinal. 



C.N. 416. 

 Outer Transverse. 



Q.— Fig. 7, C.N. 408. 

 Outer Longitudinal, 



C.N. 414 and 415. 



Tracheids. 

 Lons^itudinal. 



Q. — p. 197, Figs. 14A, and 14B, C.N. 414 and 415. 



Dichotomy. 

 T7-ansverse. 



Q. — p. 198, Fig.14, C.N. 412. See also 416a. 



Exogenous Secondary Xylem Strand. 

 Q.— p. 198, Fig. 15, C.N. 416b. 



Type of Lepidodendron Spenceri, Williamson. 



A small and rare Lepidodendroid form, which exhibits so 

 many peculiarities in its fructification that it may possibly 

 be necessary sometime to make it the type of a new genus. 

 I have only obtained a few specimens at a time, with long 

 intervening intervals ; hence the notices of the type 

 scattered through several Memoirs have been imperfect and 

 unsatisfactory. These notices will be found in Memoirs IX., 

 X., XVI., and XIX. But the plant is most distinct, and 

 though our knowledge of it is yet far from complete, 

 what we do know being probably only its young state, 

 it is now very coherent as far as it goes ; hence I propose 

 to extend this description of it to a greater length than has 

 seemed needful in the case of the other types. 



Its vegetative features are largely those of a young 

 Lepidodendron. My specimens don't exceed a mean of 

 10 mm. in diameter, and the only one which has attained 

 that size is a strobilus, including its sporangiophores 

 and sporangia. None of my vegetative twigs exceed 

 4 millimetres ; but they may have had a more external 

 cortex than I have yet discovered, and their well-defined 



