THE MALE FERN 149 



germinate. The prothallus of the Male Fern at maturity 

 may be nearly half an inch in diameter ; it is green, fiat, 

 and heart-shaped, and is attached to the soil by means 

 of rhizoids growing from its under-surface. An enlarged 

 drawing of a prothallus is seen in Fig. 45, which shows 

 that the sexual organs occur on the under surface, the 

 archegonia towards the apex, and the antheridia towards 

 the base, the former being confined to a thickened 

 central part called the cushion. These organs are small, 

 and we must use the microscope if we would observe 

 their structure; the antheridia are little hemispherical 

 outgrowths; each one produces about twenty coiled 

 spermatozoids, with numerous fine cilia at one end (see 

 Fig 46). In the presence of water these active male 

 elements are liberated; they work their ways through 

 the water ciliated ends foremost, and wriggle by a 

 devious course towards the attractive archegonia. 

 Fig. 47 shows an archegonium greatly enlarged and 

 ready for fertilization; note the neck, n, and the ovum, 

 o; the contents of the canal cells become mucilaginous, 

 they swell and force the neck open, and a drop of muci- 

 lage, m, is extruded at the mouth. It seems that the 

 archegonia produce malic acid, which diffuses in the 

 water, and constitutes an attraction to the spermato- 

 zoids. One of the latter works its way into the drop of 

 mucilage, m, and swims slowly through the mucilage in 

 the canal until it reaches the ovum, with which it fuses. 

 So fertilization is effected. More than one male element 

 may get into the canal, but it is questionable if more 

 than one is permitted to fuse with the ovum. The 

 embryo arising from the fertilized ovum is dependent 

 upon the prothallus for a time, but the nutrient sub- 



