534 FILICALES 



to be noted that the cells marked (x) do not compose the whole outgrowth, 

 but that adjoining cells also contribute in a certain degree, so that 

 strictly speaking the whole sporangium is not referable in origin to the 

 single cell. The massive stalk is partly formed from surrounding cells : 

 this is a further feature for comparison with Eusporangiate types. How 

 various the subsequent segmentations may be will be seen from the 

 Figs. 296 A, E ; these show that the large cell in the centre of the growing 

 sporangium may be of prismatic or of conical form, while they also prove 



Todea barbara, Moore. .4=small part of section of pinnule showing two young 

 sporangia (-r, x). B, C, D = examples of variety of segmentation, as seen in vertical 

 sections. E = older sporangia in transverse section, showing differences in sporangia in 

 juxtaposition. F= vertical section of sporangium of like age, with square-based sporo- 

 genous cell. = similar sporangium with triangular sporogenous cell. //, /vertical 

 and transverse sections of older sporangia. The central figures show two unequal 

 sporangial stalks, in transverse section. All X 200. 



that adjoining cells take part in the formation of the sporangial outgrowth ; a 

 comparison of Figs. 296 c, D, also brings out clearly the very great difference 

 of bulk occasionally seen in sporangia of the same age. The large cell 

 in the centre divides usually by three anticlinal walls corresponding to 

 those seen in the usual Leptosporangiate type, though the cell which 

 remains in the middle may still be either truncate or pointed at the 

 base. But sometimes it appears that four lateral cells may be cut off by 

 anticlinal walls, as in the largest sporangium in Fig. 296E; thus the central 

 cell after periclinal divisions in Todea, may sometimes have the form 

 which is characteristic rather of the Eusporangiate sporangia, though this 

 is exceptional. Then follows the periclinal division to separate the cap-cell 

 from the archesporium : the cell which thus undergoes periclinal division 



