The Present Position of Palaeozoic Botany. 



193 



been axillaiy. Tlie adventitious roots, commonly found in connection 

 with the stem, had when young- a somewhat Marattiaceous cliaracter, 

 but on undergoing* secondaiy growth assumed the structure of the 

 roots of Gymnosperms. 



Fig. 21. Lyginodendron oldhammtn. Transverse section of leaf-stalk, x. V-shaped 

 xylem of bnndle v.b.; ph. phloem, surronnding- xylem; hy. hypoderma. X about 35. 



Thus the vegetative organs of the plant, present a manifest com- 

 bination of Filicean and Gymnospermous characters indicating affini- 

 ties in both directions.^) The convenient name Cycadofilices. intro- 

 duced by Potonié in 1897 for plants in this intermediate position, 

 has been generally adopted. 



Our knowledge of the vegetative structure of Lyginodendron was 

 completed by the year 1902. (See the restoration of the plant in 

 Fig. 22.) In the following year we obtained, for the first time, de- 

 finite evidence as to the nature of its reproductive organs. 



As Williamson first observed, both the stem and leaves of Lygino- 

 dendron Oldhamium are studded with multicellular outgrowths, like 

 blunt spines. These outgrowths played an important part, years 

 ago, in enabling Williamson to identify his '•Rachiopteris aspera'' as 

 the petiole of Lyginodendron. In certain cases the outgrowths assume 

 the character of capitate glands, which in some forms of the plant are 

 very abundant on stem and foliage. Both the head and stalk of the 

 gland are multicellular, but sometimes the glandular tissue has broken 

 down, leaving the cavity of the head empty (Fig. 26). It was by means 



1) Williamson, 1887, p. 299, Williamson and Scott, 1895, p. 769 



Progressus rei botanicae I. 



13 



