174 



MORPHOLOG Y, 



leaf appears as if it was rolled up as in fig. 204 of the Christmas fern. As the 

 leaf elongates this portion unrolls. 



359. Longevity of ferns. — Most ferns live from year to year, by growth 

 adding to the advance of the stem, while by decay of the older parts the stem 

 shortens up behind. The leaves are short-lived, usually dying down each 

 year, and a new set arising from the growing end of the stem. Often one can 

 see just back or below the new leaves the old dead ones of the past season, 

 and farther back the remains of the petioles of still older leaves. 



360. Budding of ferns. — A few 

 ferns produce what are called bulbils 

 or bulblets on the leaves. One of 

 these, which is found throughout the 

 greater part of the eastern United 

 States, is the bladder fern (Cystop- 

 teris bulbifera), which grows in shady 

 rocky places. The long graceful 

 delicate leaves form in the axils of 

 the pinnae, especially near the end of 

 the leaf, small oval bulbs as shown 

 in fig. 212. If we examine one of 

 these bladder-like bulbs ,we see that 

 the bulk of it is made up of short 

 thick fleshy leaves, smaller ones ap- 

 pearing between the outer ones at the 

 smaller end of the bulb. This bulb 

 contains a stem, young root, and 

 several pairs of these fleshy leaves. 

 They easily fall to the ground or 

 rocks, where, with the abundant 

 moisture usually present in localities 



where the fern is found, the bulb 

 fig. 212. ' 



Cystopteris bulbifera, young plant growing grows until the roots attach the plant 



from bulb. At right is young bulb in axil of tf) the soi i or in thf , crevices of the 



pinna ot leal. 



rocks. A young plant growing from 



one of these bulbils is shown in fig. 212. 



361. Greenhouse ferns. — Some of the ferns grown in conservatories have 

 similar bulblets. Fig. 213 represents one of these which is found abundantly 

 on the leaves of Asplenium bulbiferum. These bulbils have leaves which are 

 very similar to the ordinary leaf except that they are smaller. The 

 bulbs are also much more firmly attached to the leaf, so that they do not 

 readily fall away. 



362. Plant conservatories usually furnish a number of very interesting 

 ferns, and one should attempt to make the acquaintance of some of them, for 



