250 



CRYPTOGAMS 



212. A FERN 



Object. To learn the characteristics of the spore-bear- 

 ing stage of a fern. 



Apparatus. Any common fern (one of the shield ferns (aspid- 

 ium) is preferable), and a magnifier. 



Method. Study the plant as a whole, making out its 



roots, its under- 

 ground stem (rhi- 

 zoma), its leaves 

 (fronds) , and their 

 peculiar manner of 

 folding or rolling in 

 the bud (circinate). 



Examine the frond 

 and make out its 

 venation. How does 

 the veining differ 

 from that of leaves 

 hitherto observed ? 

 Note the parts into 

 which the frond is 

 divided (primse, etc.). 

 Is the frond alike on 

 a both sides? If so, 



FIG. 110. A fern plant, a, fronds and root- u j g a s er ile frond, 

 stock ; b, fertile pinna ; s, s, sori ; c, cross sec- 

 tion of a stipe, showing ends of the fibro vascular rind a irond wnicn 

 bundles ; d, a cluster of sporangia, magnified ; has dots On the Under 

 e, a single sporangium still more magnified, . . _, ,, , 



shedding its spores. side. These are called 



son'. Describe the 



sori, their size, color, and arrangement on the frond. Make 

 a sketch of a portion of the frond, indicating as many 



