262 



DICKSONIACEAE 



[CH. 



Fig. 528. Series of transverse sections. 1 — 8, arranged in ascending sequence, from the rhizome of 

 Thyrsoptcris elegans, showing the relatively primitive, but polycyclic vascular system. The leaf 

 traces a, b depart without opening the solenostele, owing to the action of compensation strands that 

 fill up the gaps. 



Fig. 529. Thyrsopteris elegans Kze. A =longitudinal section 

 through the young sorus, showing the two-lipped indusium z, i, 

 and sporangia s, s, seated on the receptacle, the oldest being at 

 the distal limit of it. C = two young sporangia. ^ = one rather 

 more advanced. Z'^a sporangium with the tapetum and 

 sporogenous groups shaded. .£, 7^= mature sporangia. {A — D 

 X 200; E, Fx 50.) 



