HOW TO KNOW FERNS 



247 



occur in large patches. The fertile fronds look very different 

 being much contracted with the pinnules rolled up into spore cases 

 which are green at first and later 

 brown. There sometimes occur 

 intermediate forms with narrower 

 fronds which are sterile. This is 

 called the Sensitive Fern because it 

 is killed by the first frost. 



The Sensitive Fern 



The Ostrich Fern grows in moist 

 woods or other shady, damp places 

 and often grows luxuriantly on the 

 north side of houses where it joins 

 the army of ornamental plants. 

 It is a magnificent fern with dark- 

 green fronds from two to ten feet in height which have some 

 resemblance to ostrich plumes. The sterile 

 fronds grow in a circle and the fertile fronds 

 which are shorter grow at the center. The 

 fertile fronds have pinnae which are very stiff 

 with the lobes rolled inward to cover the spores 

 which gives the fruiting pinnae a beaded effect. 



The Woodsias. Woodsia 



These are rock-loving ferns, all of them small 

 and growing in tufts or climips. They may be 

 known by their manner of fruiting — the indu- 

 sium is fastened to the frond beneath the fruit 

 dot and splits open above spreading out in star 

 shape around the spore cases (Fig. lb). There are 

 six species of Woodsias but the only common one 

 is that figured here. 



The Obtuse Woodsia. This species has fronds 

 that may grow to fifteen or twenty inches in length 

 but are commonly shorter. This is found in but one 

 place (in Nova Scotia) outside of the United States. 

 It grows on rocky banks and cliffs from New Eng- 

 land to Georgia and westward. In the South it is 

 evergreen. 



Th* Ortrich Fern 



