Fig. 146. Series of transverse sections arranged in ascending sequence, showing the relations of the 

 polycyclic axial system to the leaf-traces in Saccoloma elegatis, Klf. The numbers relate to the 

 actual sections cut. Natural size. 



complete cylinders a fourth is initiated (Fig. 147). Polycycly has also 



been observed in a lateral shoot of Thyrsopteris elegans (Fig. 149, 5), 



in which Fern the sappy stems are said to be 



sometimes as thick as the thigh. It would be 



interesting to know whether still more numerous 



cycles of vascular tissue are present in the largest 



of them. 



The familiar structure of the rhizome of the 

 Bracken {Pteridiimi) is an example of polycycly 

 in the Pterideae (Fig. 3), complicated by profuse 

 perforation both of the outer and inner cylinders, 

 and by the fact that the inner as well as the outer 

 contributes to .the supply of the leaf-trace (see 

 Tansley and Lulham, New Phyt. Vol. iii, 1904, 

 and compare their Fig. 6"]^. 



Such observations relate to Ferns belonging to the Marginales, and the 

 comparisons are based upon adult material. A similar structure is seen in 



Fig 147. Stem and leaf- baseof/'/c'm 

 (Litobrochia) podophylla, Sw., 

 represented the natural size. It 

 shows polycycly in the axis, to 

 the fourth degree. Note the com- 

 pleted ring of the leaf-trace {l.t.)\ 

 on the right a further leaf-trace 

 is preparing for departure, with 

 an island of unconnected vascular 

 tissue at its centre. This is sur- 

 rounded by endodermis. 



