11 
tromit. The apices of veins or veinlets are 
said to be clavate when thickened like a club. 
Reproductive Organs. 
1. Receptacle. The sporangia or spore cases 
are arranged on a projection of tissue termed 
the receptacle or placenta. Its position on the 
frond varies. It may terminate a vein or its 
branches ; it may be on the point where the 
veins fork, or on the point of union of two 
or more veinlets, or on the back of a vein 
or veinlet. It presents various forms, being 
a rounded elevation, or more elongated or 
conical, or very long and filiform or ridge-like. 
2. Sporangium. (Fig. 1). The sporangia or 
spore-cases or capsules are the organs which con- 
tain the reproductive 
spores (sp.). They are 
minute roundish oval 
bodies containing a 
single cavity and are 
usually stalked, but 
sometimes sessile. They 
are encircled by acom- 
plete jointed elastic ring 
Fic. 1.—A sporangium 
termed an annulus (an.) (magnified); Az. = Annulus ; 
ox destitute of such 5? Stl; Sp.'— Spores. 
