EEPKODrCTIOX OF ACROGEXS. 771 



and 797, «) and pistillidia sporangia or ovules {figs. 795 and 

 797, b). These two structures are either contained in separate 

 sacs, as in Sahnnia (fig. 797), or in the same, as in MarsUea 

 {fig. 793). The antheridia contain a number of small cells 

 called generally pollen-spores or small spores {fig. 794), which 

 ultimately produce spermatozoids remarkable for their length 

 and delicacy {fig. 1114), The pistillidia sporangia {fig. 797, h) 



Fig. IIU. Fig. 1115. 



Fig. 1114. Pollen-spore, small spore, or microspore, of Pil'.-wort (PHidaria 

 globidifera^, bursting and discharging small cells enclosing sperma- 

 tozoids. Some of the latter may be ol)served to hare escaped by the 



rupture of the small cells in which they were contained. Fig. ills. 



Vertical section of the prothallium of the above, whicb is formed, as in 

 the LycopodiaceoB, in the interior of the large spore or megaspore. Oiilr 

 onearchegonium.rt, is here produced in the centre. The archegoniura 

 consists of an intercellular canal, leading into a sac below, in which 

 may be seen a solitary germ or embryonal cell. 



contain commonly but one spore {fig. 795), called an ovidary 

 spore, large spore, or megaspore. In their organs of fructification 

 the plants of this order closely resemble the Lycopodiacese (see 

 p. 365). Like the Lycopodiacese also, the large spores produce 

 a small prothallium confluent with them {fig. 1115), in which 

 subsequently only a single archegonium generally, as in Pilularia 

 and Marsilea, appears {fig. 1115, a), although in Salvinia there 

 are several archegonia formed. Impregnation takes place by the 

 contact of the spermatozoids with the germ-cell of the arche- 

 gonium, which immediately developes, and forms a pseudo-embryo 

 bearing a great apparent similarity to the embryo of a mono- 

 cotyledonous plant, from which a leafy stem bearing fructifica- 

 tion is ultimately produced. 



6. Equisetacea or Horse-tails, and 



7. Filices or Ferns. — The mode of reproduction of the plants 

 of these two orders is essentially the same, and we shall ac- 

 cordingly allude to them together. As already fully noticed 

 (see pp. 359—363), their leafy structures bear sporangia or 

 capsules in which the spores are enclosed {figs. 786 and 790- 

 792). There is, however, but one kind of spore. 



The germination of these spores has already been noticed 

 (p. 360), but it will be better to refer to it again in this place. The 

 spores ultimately form a thin, flat, green parenchymatous expan- 

 sion {figs. 787 and 1116, h), which somewhat resembles the pernia- 

 3d 2 



