10 ON GENERA AND SPECIES. 



FRONDS. 



THE fronds before expansion are involutely coiled, in the 

 manner of a watch spring-, and gradually uncoil during 

 the period of growth, and with a few exceptions have all 

 their parts formed before they begin to unfold (definite), 

 all of which increase in size with the progress of the frond. 

 Fronds present extreme variation in size and form, vary- 

 ing from less than an inch to 15 or 20 feet in length, and 

 in form, from entire, like a blade of grass or ribbon to 

 being compoundly divided. In describing them, the same 

 terms are used as are applied to the leaves of flowering 

 plants, that is, they are simple, entire, linear lanceolate, 

 ovate, elliptical or sub-rotund, or they are pedate or pal- 

 mately lobed, pinnatifid, or they are pinnate, ~bi-tripinnate, or 

 more highly divided, and then termed compound multifid. 

 They also vary considerably in texture, some being thin, 

 pellucid, membranous, and flaccid ; while others are thick, 

 fleshy, or hard and rigid. 



In pinnate, bi-and-tripinnate fronds, the divisions (seg- 

 ments) of the first are called pinnae and the second pin- 

 nules, each of which individually represents a simple 

 frond. The margins of simple fronds, and of pinnae and 

 pinnules, are either entire or variously dentate or sinuose 

 repand, regularly pinnatifid or otherwise divided, the divi- 

 sions being called lobes or lacince. The general form of 

 fronds, whether simple or in any way divided, is linear 

 lanceolate, or oblong elliptical, or deltoid ; in deltoid com- 

 pound fronds, the primary pinnae assume the character of 

 branches, the ultimate divisions of which are often divided 

 into small lacinae or dents, such being termed multifid. 

 The axis of attachment of the pinnas and pinnules is 



