FILICES 



75 



The Aphlebia of Hemitelia cape n sis. 



Hemitelia capensis (Plate 11) is one of the few living ferns, the fronds of 

 which are provided with two peculiar basal pinnae (Fig. 55 a, 2), called 

 aphlebia. Such structures were frequent on ferns of former geological 

 periods, but are rare now. Their function has been a cause of much 

 speculation among botanists. 



Some authors look upon them as " hydrofoliola," which absorb dew or other 

 moisture, thus assisting in the supply of water to the plant. That, however, 

 cannot be so in our case, for the following reasons : 



1 . Hemitelia capensis grows only in permanently wet and shaded spots of 

 the forests or mountain ravines, where, owing to the canopy of the trees, no 

 dew occurs, and where the plant has always an unlimited supply of water at its 

 disposal in the soil. 



2. The aphlebia are not capable of absorbing water placed upon them in 

 the form of spray, for water does not adhere to their surface, in fact one cannot 

 moisten them in this way. 



We think that their function is simply that of the stipules of various 

 other leaves, which, while assimilating themselves, protect the young foliage 

 against the effect of drying winds or other injuries. 



They are always fully developed before the frond to which they belong 

 makes its appearance (beginning of winter, viz. May or June), and they become 

 dry before the next season's aphlebia begin to show, while their fronds are still 

 fresh and vigorous. 



Fig. 56. Hymenophyllum. 1, 2. H. Marlothii Brause 1. Frond, without the stalk, 2/1. 

 2. Segment, 4/1. 3-6. H. tunbridgcnse (L.) Smith 3-5. Different views of 

 sporangia. 6. Pinnule with two sori enclosed in the cup-shaped indusia. (From 

 ■ nature) 



