58 Dr. W. C. Williamson on 



Lyginodendron was a plant with a magnificent zone of 

 secondary exogenous wood, developed from a true cambium. 

 But Dr. Scott and I have recently united with it a second 

 form viz., the Kaloxylon Hookeri, which proves to be its root. 

 No true fern previously discovered had exhibited such a 

 cambium ; but the Lyginodendron Oldhamium described 

 now took its place, along with the Catamites and the Lycopods, 

 in both of which important groups of Cryptogams the 

 possession of an active cambium was the normal condition. 

 This family of the Lyginodendra is the first that I propose 

 to deal with in this part of the Index. 



FILICES. 



TYPE OF LYGINODENDRON OLDHAMIUM. 



Primary Branch prior to emergence throtigh Cortex. 

 Earliest State. Transverse. 



No Medullary Cavity occupied by primary Wood. 

 R.— p. 92, Fig. 10, C.N. 1 885 A. 



a. Tracheids of Primary Xylem. 



b. Secondary Fascicular Xylem. 



Seco7idary State. 



R. — p. 92, Fig. 11, C,N. 1885H. Primary Xylem broken up into about 

 five separate bundles, a', a'. See also C.N. 1 138. 



Medullary Rays. 



R.— p. 92, Fig. 10, C.N. 1885A. 

 p. 92, Fig. 11, C.N. 1885H. 



Branch extended beyond the Cortex of the parent stem, and 

 invested by its own cortex. 



R. — p. 93, Fig. 12, C.N. 1 141. Medullary cavity further enlarged, 

 and filled with medullary cells. 



Secondary Xylem. 



R. — p. 92, Fig. 12, C.N. 1 141. New Tracheae to the periphery of each 

 of the secondary Laminae. 



Cortex — Young. 



R. 1 141. Irregular Cambium at the innermost border of the Cortex. 



Cortex more matured. 



Cambium not previously figured or described. 

 Innermost Cortex of O.N. 1141, 1193, 1194, and 1195. 



