LESSONS IN BOTANY. 203 



the mid vein, in a divided frond it is called the rachis. When a 

 frond is cut into lobes extending halfway or more toward the 

 mid vein, it ia pinnatified ; when the divisions extend to the mid- 

 vein the frond is simply pinnate, and the divisions are called pinnae. 

 When the pinnae are lobed the frond is bipinnatified and the lobes 

 are called segments. When these divisions extend to the mid vein 

 of the pinnae the frond is bipinnate and the divisions are called 

 pinnules, and the midvein of the pinnae becomes a secondary 

 rachis. The delicacy and extent to which this division is carried 

 is the chief beauty of many ferns. 



Besides the leaves, the stem gives rise to roots, so that the 

 ferns and their allies are the first plants to show distinct stems, 

 roots and leaves; and in them the three tissue systems first make 

 their appearance. If the stipe of almost any fern be crushed or 

 broken, the vascular bundles, as yellowish bands, are easily found 

 and with a little care may be traced into the stem or rhizoma, 

 and also into the divisions and subdivisions of the frond. The 

 epidermal and'fundamental tissues can easily be made out at the 

 same time. 



The reproductive process in the ferns is interesting and some- 

 what peculiar. On the under surface of the frond bodies called 

 sporangia are developed, in which spores are formed. The 

 spores, when mature, develop into a flat roundish body, deeply 

 notched on one side, so that it is sometimes heart-shaped, which 

 is called the prothalium. The prothalium develops the sexual 

 organs, archegonia and antheridia. After fertilization an ovum 

 is developed in each archegonium which produces a young fern. 

 The prothalia in most cases are small, and they escaped the eye 

 and investigation of the botanist until about 1848, when they 

 were discovered and the mystery of the reproduction of ferns 

 was cleared up. 



Some variety of the maiden-hair fern may be found in almost 

 any locality. It may be recognized by its black polished stem, 

 which divides into two equal recurved branches, from these arise 

 secondary branches which support oblong leaflets. On the under 

 side of the leaflets, along their margins are the crescent-shaped 



