266 



DICKSONIACEAE 



[CH. 



same age demonstrates its relation to the indusium, and that the receptacle 

 is structurally like a normal leaf-margin {D). Already the indusial lips are 

 of unequal size, the upper being the larger. Sporangia appear first in a 

 simultaneous row along the margin {B, C): these are succeeded later by 

 others in basipetal sequence, but the succession is not long continued, and 

 in B. Culcita it is not clearly marked. There is, however, no intercalation 

 of younger sporangia between those first formed. The sporangial mother- 

 cells are deeply sunk, and the first segmental wall may sometimes be 

 inserted upon the basal wall (3, Fig. 535, Q, in others upon the lateral 

 wall (4). Speaking generally the segmentation is characteristic of bulky 

 sporangia. 



A B 



E F G H D 



Fig. 535. Cibotiiiin Scheidei Baker. A =section through a young sorus perpendicular to the leaf- 

 surface: /,/ = indusium; /;/= cell of marginal series. i>= section ofsorus parallel to the leaf-surface 

 as along a line i, i in Fig. A : it shows the receptacle bearing sporangia s,s. C = a similar section 

 bearing older sporangia. Z* = transverse section of a young sorus showing the two lips of the 

 indusium {ind.) and the receptacle between them, as along a plane jr, y in Fig. A. A section of 

 the receptacle in the plane jr, x, in Fig. A is superposed on the lower indusial lip. The central 

 figure shows sporangial stalks cut transversely. {A-D x 200.) E^ F, G, i^ adult sporangia of 

 Cibotiiiin Menziesii from four different aspects. ( x 50.) 



The sporangia themselves are large and relatively long-stalked : they vary 

 in form, those of B. Ctilcita being pear-shaped with very oblique ring, while 

 in those of C. Menziesii it is almost vertical. The stalks are elongated, and 

 show in transverse section six or seven cells (Fig. 535). The sporangia of 

 C. Menziesii are represented in four aspects in Fig. 535, E, F, G, H, from 

 which it appears that except for the long stalk, and the almost vertical 

 annulus, they are substantially like those of Thyrsopteris or of Hyinenophyl- 

 liiin. There is, however, a more definite stomium, associated on both sides 



