200 



BOTANY. 



419. The leaves are in nearly all cases supplied with 

 fibro-vascular bundles, which run as veins through the soft 

 tissue; there is usually a prominent midrib, upon each side 

 of which are small veins, which w&free (i.e., running more 

 or less parallel from the midrib to the margin) or reticu- 

 lated. Some or all of the leaves at maturity bear spore- 

 cases containing spores. 



420. The ferns are all richly supplied with chlorophyll, 

 and none are in any degree parasitic. Nearly all the species 



Fio. 111.—^, the first stage of a Fern, under side ; 6, root-hairs; an, antherids; 

 ar. archegones. B, the same after fertilization, showing the growth of the fern- 

 let; b, its leaf; w', its first root. Magnified a few times. 



are perennial; in some cases, however, dying down to the 

 ground at the end of the summer, the underground por- 

 tions alone surviving the winter. 



421. The first stage in the ferns is frequently somewhat 

 heart-shaped, and is generally provided with root-hairs on 

 its under surface, by means of which it secures nourishment 

 for its independent growth (Fig. Ill, A). In the Pepper- 

 worts the first stage is so reduced as to be only a small 

 outgrowth of the germinating spore. 



