4 OUR NATIVE FERNS AND THEIR ALLIES. 



sterile frond totally unlike the fertile, sterile fronds will some- 

 times be found which are fertile at the apex the normal method 

 of fruiting in the royal flowering-fern (Osmunda regalis) ; and in 

 turn the royal flowering-fern is sometimes fertile in the middle, 

 in imitation of Osmunda Claytoniana. 



9. Time of Fruiting. The time of maturing fruit is dif- 

 ferent among different species, and also varies with geographi- 

 cal location and proximity to tropical climates. In the Northern 

 States some species produce their fruit as early as May (Osmunda 

 cinnamomed), and others as late as September (Lygodiuui), 

 but the greater number are best studied in July and August. 

 In the Northeastern States, where the two species of Cystopteris 

 abound on limestone rocks, C. fragilis matures its spores and 

 withers in June or July, while C. bulbtfera reaches its maturity 

 only in August or September. In semi-tropical climates, like 

 Southern California and the Gulf States, the time of fruiting is 

 often earlier, sometimes occurring in February or March. Some 

 fronds are killed by the early frosts, while others, like the Christ- 

 mas-fern, are evergreen, and may be gathered in midwinter. 



10. Local Distribution. Ferns are largely dependent for 

 successful growth on the amount of warmth, moisture, and 

 shade to which they are subjected, and we would naturally ex- 

 pect to find them reaching a maximum in size and abundance in 

 warm swamps or shady marshes. While this is in general true, 

 we nevertheless find many species thriving only in rocky places, 

 thrusting their roots into the crevices of the rocks with little 

 earth for their nourishment, and many times exposed to the 

 scorching rays of the sun. Of necessity, such species are of 

 comparatively small size, and likely to be protected in some 

 way against the heat of the sun, and provided with means to 

 retain their moisture in times of drought. Others still are 

 found in wet, rocky ravines, often where moistened by the spray 

 of cascades or waterfalls, and consequently have no such pro- 

 vision against the heat of an extended summer. Certain others 

 thrive in open fields that are comparatively dry and unshaded. 

 One species of Southern Florida is aquatic, having the sterile 

 fronds floating in shallow water. A few species are epiphytic, 

 or grow on other plants, some being found on tree-trunks to 

 the height of 150 or 200 feet ! 



