STUDIES IN FERN LIFE 39 



It may, perhaps, be well to mention that all 

 these spleenworts vary very much in size 

 according to the situation in which they are 

 growing. On damp walls or rocky hedgerows, 

 where there is an abundance of moisture, the 

 size of the frond is much greater than when 

 the plants are in dry places. 



Many species of ferns show a very distinctive 

 manner of producing their spore cases. Every- 

 body is familiar with the common Hart's-tongue 

 {Scolopendrium vnlgare) . The plant is, of course, 

 exceedingly variable (several hundred different 

 kinds have been identified), but its main points 

 are fairly stable. The chief characteristic of 

 the leaf is its undivided form, in outline generally 

 tongue-shaped and tapering to a fine point. 

 The spore cases are usually confined to the 

 upper two-thirds of the back of the leaf, and 

 have been likened to a number of long brown 

 caterpillars. The clusters are placed on the 

 veins of the leaf, and are usually at a distance 

 of about one-eighth of an inch from each other. 

 Each actually consists of two clusters of spores, 

 and is covered when young with a thin white 

 scale. This is, of course, thrown aside when 

 the spore cases ripen. 



