DICKSONIEAE 593 
series of actively dividing cells. In sections perpendicular to the leaf- 
surface the young sorus appears as in Fig. 330 a, the cell marked (m) 
being one of the marginal series. A section of a similar sorus in a 
plane (x, x) appears as shown in Fig. 330 p (the chain of 10 cells 
superposed on the lip of the indusium), while at the lower level 7) 
jt is as shown between the indusial lips. It is thus seen that the receptacle 
is structurally like a normal leaf-margin, a conclusion again supported by 
Fig. 330 8, which shows a similar sorus traversed in a plane (z, 2) 
“i 
a 
ae 
CSS 
U7 
Oe 
oe 
sea 
tt 
= 
——— ai 
D 
DvD 
Fic. 330. 
Dicksonia Schiedei, Baker. A=section through a young sorus perpendic ular to the 
leaf-surface ; 7, 2=indusium ; #=cell of marginal series. B=section of sorus parallel to 
the leaf-surface as along a line z, z, in Fig. A, showing receptacle bearing sporangia s, s. 
C=a similar section bearing older sporangia. =transveise section of a young sorus 
showing the two lips of the indusium (zmd@), and receptacle between them, as along a 
plane y, ¥, in Fig. A. A section of the receptacle as in plane x,x, in A, is superposed on 
the lower indusial lip. The central figure shows sporangial stalks cut transversely. A-D 
X200. E, F, G, H sporangia of Dicksonia Menziesiz from four different points of view. 
X50. : 
indicated in Fig. 330 a. It is important to note the inequality in size 
of the two lips of the indusium. Here it is only slight, but in forms to 
be subsequently described an increasing inequality, both in area and in 
substance, makes its appearance. The formation of the sporangia has 
begun in the marginal cells, and it is seen that their appearance is 
almost simultaneous, a point better shown in Fig. 330 c, which repre- 
sents a slightly more advanced stage. These marginal sporangia are 
succeeded by others produced in a basipetal sequence, but the succession 
is not long continued, and in D. Cudzta, L’Herit, it is not clearly marked ; 
there is, however, no evidence of intercalation of younger sporangia 
‘between those already present. 
2P 
