ORGANS OF REPRODUCTION. 



363 



791 and 792). These spiral elastic filaments, which are called 

 elaters, are at first wound round the spore {fig. 791), but when 

 dry they ultimately uncoil {fig. 792), and thus appear to assist 

 in the dehiscence of the capsule, and in the dispersion of the 

 spore to which they are attached. 



When these spores germinate, a little pouch-like process pro- 

 trudes from their surface by an elongation of their membrane ; 

 this ultimately forms a green lobed flattened expansion, re- 

 sembling in all its essential characters the frotlialUum of a Fern. 

 Like Ferns also, this prothallium is furnished with anthe- 

 ridia containing anther ozoids, and archegonia. From the embry- 

 onal corpuscle of the germ-cell of the archegonium also, after im- 

 pregnation by the antherozoids, as in Ferns, a new plant is ulti- 

 mately produced resembling in every respect that of the parent 

 plant from which the spores were derived. As is the case in 

 Ferns therefore, we have in the Equisetacese also, an instance of 

 alternation of generations. 



3. MA.RSLLEACEJE OR Pepper WORTS. — In the plants of this 

 order the fructification is placed at the base of the leaf- stalks. 

 It consists usually of a two-valved stalked involucre or sporo- 

 carp {fig. 793, s), which is generally many-celled, or sometimes 

 one-celled, and appears to be a modified leaf. The contents 

 of the sporocarps, and the mode in which they are arranged, 

 differ somewhat in the different genera of this order, and 

 hence it will be necessary for us to allude to them separately. 



Fig. 793. 



Fig.l^Z. Fructification of a species of JWar- 

 silea. s. Two-vnlved sporocarp. p. Pe- 

 duncle. /. Fructification. Fig. 794. 



Antheridium of the above. Fig. 795. 



Ovule or sporangium of tbe above. After 

 Maout. 



In MarsiUa, the fructification consists of a stalked two-valved 

 hardened sporocarp {fig. 793, s). The valves are held together 

 by a mucilaginous ring, which is at first connected with the 

 stalk of the sporocarp, but when the latter organ bursts, the 



