termed fronds, are generally more or less divided in a wing-like 

 manner, rarely simple or entire : when the divisions extend to the 

 rachis or continuation of the leaf-stalk or its branches, the fronds 

 are described as pinnate, bipinnate, or tripinnate (once, twice, or 

 thrice winged), the first or primary divisions being called pinna, 

 the subsequent ones pinnules; when they are only partial, the 

 fronds are said to be pinnatifid or wing-cleft, and the divisions are 

 denominated lobes or segments. The disposition of the leaves of 

 plants in the bud, generally regarded by botanists as an important 

 feature, is called their vernation, and in the ferns is circinate (except, 

 in one small group), the divisions as well as the entire frond being 

 coiled inwards previous to expansion like the spring of a watch, a 

 disposition beautifully exhibited by those of some of the larger 

 species. 



The reproductive germs of the flowerless plants are very minute, 

 indeed generally microscopic, and, notwithstanding the gigantic 

 size of some members of the Fern tribe, no exception occurs in 

 this respect ; their production apparently taking place under dif- 

 ferent laws to those which regulate the fructifying function in 

 flowering plants : they are not called seeds, but spores or sporules, 

 and are enclosed in little cases denominated thecce; which, in the 

 ferns, are mostly aggregated in small clusters of different size and 

 shape, termed sort, and arise from the veins on the under surface 

 of the frond, or from their extremities upon its margins : in some 

 instances the thecse, instead of forming sori, are associated in spikes 

 or clusters called panicles, formed by the depauperation of the 

 fructifying frond or of its lobes. The primary development of the 

 thecae takes place in immediate contact with the vein, and beneath 

 the epidermis or outer covering of the leaf, which is forced up by 

 their enlargement in the form of a whitish membrane, constituting 

 the indusium or protecting cover of the sori. During the advance 

 of the fructification towards maturity, the indusium separates partly 

 or wholly from the surrounding epidermis, and subsequently either 



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