572 FILICALES 
of Gleichenia, it is plain that the sporangia are of the same type, as regards 
the position of the annulus, though differing in the details ; or the comparison 
might be extended to the Schizaeaceae on the one hand, or the Hymeno- 
phyllaceae on the other, as regards the position of the annulus. 
The longitudinal slit of dehiscence traverses the distal part of the 
annulus, following the median plane of the sporangium, and may extend 
some distance down its peri- 
A B pheral side, so that it faces 
outwards from the receptacle. 
The orientation of the spor- 
angia being strictly upon the 
Gleicheniaceous type, it ap- 
pears that the main difference 
is that, while maintaining the 
same position of the annulus, 
the slit gapes towards the 
peripheral face of the spor- 
angium rather than on the 
central side of it. There is no 
differentiation of a stomium, 
but the rupture occurs regu- 
larly at the distal end (a, 
Fig. 320). The portions of 
\ }} the annulus on either side of 
= we the slit straighten as they dry 
wy rang and curve outwards in the 
usual way; they may even 
become reflexed, tearing away 
irregularly from the rest of 
c D E the wall, or carrying frag- 
ments of it outwards; in this 
tat ay appear 
Loxsoma Cunninghami, Br. £=young sorus with sporangia 3 € the two flaps may appe 
still protected by indusium (¢, 2), A=sorus rather older, with like the covers of an open 
sporangia (s, s) carried up on the elongated receptacle (Js). : : 
#=vertical section of the base of the young receptacle (ry) book. As the induration 
showing sporangia (s) in basipetal sequence. C, D=mature 
sporangia showing the incompletely indurated annulus, and stops short about half-way 
distal point of dehiscence (x). A and Zxabout 20. Bx250. “3 
C and Dx 50. down the side, the general 
form of the sporangium is 
not altered by the dehiscence, so as to press upon or displace neighbouring 
sporangia ; in fact, no elbow-room is required, as in Gleschenta, and this 
is a distinct advantage in a sorus where sporangia are numerous; in this 
we may perhaps see the vatona/e of the incomplete annulus. No sudden 
jerks of the annulus have been observed, nor would such jerks be very 
efficient, since the majority of the spores lie below the flaps of the annulus ; 
the shedding of the spores seems to be mainly on the principle of the 
pepper-box. 
Ch} Dis 
Fic. 320. 
