LOXSOMACEAE 573 
The receptacle performs an important part in connection with dispersal. 
At first it is short, so that the sporangia are all included within the indusium 
(Fig. 320), and this is so till the oldest sporangia are mature ; an inter- 
calary growth then takes place at the base of the receptacle, the thin- 
walled cells above the terminal mass of tracheids (¢r.) become greatly 
elongated (Fig. 320 4), forming a sort of pseudopodium (fs.), upon which 
the sporangia are raised so as to project beyond the lip of the protective 
indusium, and are thus free to scatter their spores. The arrangement is 
similar to that seen in the Hymenophyllaceae, but in Zoxsoma the pseudo- 
podium is formed independently of the long-continued formation of a 
series of sporangia. 
The sporangium makes its first appearance as a massive deeply sunk 
cell, near the base of the groove between the receptacle (7) and the 
indusium (zz@.) (Fig. 3208): the first segmentation in it passes down to 
the base of the cell, as in the Schizaeaceae and some other Simplices ; the 
later ones cut the previous wall obliquely, and thus a three-angled conical 
cell is surrounded by three lateral segments. The cap-division, and 
segmentations forming the tapetum take place in the usual way; the inner 
series of tapetal cells enlarge considerably, and become polynucleate, thus 
resembling other large sporangial types. The definite sporogenous group is 
composed of 16 spore-mother-cells, which undergo a tetrad division to give 
typically 64 large spores. ji 
ANaTomy.! 
The chief point of anatomical interest is the structure of the stele of 
the stem: a transverse section of an internode shows a typical solenostele, 
with phloem, pericycle, and 
endodermis, both outside 
and inside of the continu- 
ous ring of xylem. The 
protoxylem elements are all 
scalariform, and are not 
localised into groups, but 
are distributed around the 
periphery of the solenostele. 
Where a leaf-trace is given 
off the tube of the stele : . 
‘opens, forming a foliar gap 
s H Loxsoma Cunninghami. Diagram showing the form of the 
‘on the acroscoplic side. vascular system at the node of the rhizome. ss=solenostele ; 2¢= 
eS j ; departing leaf-trace: /e=leaf-gap. ‘lhe arrow points toward the 
The leaf-trace itself consists apex of the rhizome. (After Gwynne-Vaughan.) 
Fic. 321. 
of a single vascular strand, 
showing the horse-shoe outline in transverse section (Fig. 321). An unusual 
feature is the occurrence of islets of parenchyma in the sclerenchymatous 
masses of the stem, a peculiarity shared with certain species of Dicksonia. 
‘ 1Gwynne-Vaughan, Ann. of Bot., vol. xv., p. 71. 
