52 PERNS I BRITISH AND FOREIGN. 



Synangium* 



The synangia are formed by the union of a greater or lesser 

 number of exannulate sporangia, arranged side by side, forming a 

 series of cells, disposed in a circle, or in two rows side by side, 

 united in one mass, which either remain united (plate I. fig. 5), 

 or separate longitudinally in two valve-like lobes (plate I. fig. 6). 

 The cells open for the escape of the spores by a slit on their inner 

 side or by a pore at their apex. 



In Lycopodiaceae and Marsileacese there are two kinds of sporangia, 

 the one containing numerous small spores, the other only a few 

 considerably larger. Some authors consider them to represent 

 different sexes, and therefore named the first Antheridangia, the 

 other Oophoridangia. The large spores are known to vegetate, and 

 some say the small ones also ; the large ones are called Corpuscules. 

 In the genus Marsilea the sporangia are called conceptacles, because 

 they contain free vesicles of two kinds, one containing small 

 spores, Antheridangia, the other large ones, Oophoridangia. 



3. Sorus. 



The sori are the masses of sporangia borne upon the recep- 

 tacles, and are either naked or furnished with variously shaped 

 hairs and scales, or with membranous or rarely coriaceous covers 

 of various forms (indusia) ; their form and position correspond 

 with and are dependent upon those of the receptacles, which are 

 their foundations. Thus, when the receptacles are punctiform, the 

 sori are always round (5) or globose, while elongated receptacles bear 

 sori of many forms, oblnng ovate, oval, elliptical, arcuate, linear (50), 

 reticulated (54), &c. When situated on the margin of the frond or 

 segment (marginal), a little wiihin the margin (antemarginal), 

 somewhere between the margin and the midrib (intramarginal), close 

 to the midrib (costal or basal), or sometimes on a pedicel, and pro- 

 jecting slightly beyond the margin (exserted or extrorse} (73). In some 

 cases they are irregularly scattered, but in others they are arranged 

 either in rows (serial) (7) or in continuous lines, and when these 

 diverge at an angle from the midrib they are said to be oblique (110) ; 

 und when parallel with either the margin or the costa, transverse 

 (96 and 100). As a general rule, each sorus is distinct and well- 



