PARTS OF FERNS. 



next larger division of the frond by stalks ; but in other cases by bases of greater or 

 less width, when they are said to be " sessile," that is, seated. This term is also used 

 to express any other part which is connected with the body or next larger division of 

 a frond by a base instead of a stalk ; and any which is more or less enclosed in the 

 body of a frond, particularly in its edge, is called " inserted" ; while such as project 

 are " exserted." Anything growing in a hollow in the surface of a frond is said to be 

 " depressed," and anything standing above it " elevated." The upper angle formed 

 by the junction of any two parts of a frond is called an " axil," and anything growing 

 in it is termed " axillary." 



On looking at a frond, one sees lines of woody fibre traversing it, and forming a 

 sort of ribbed framework, to stiffen the thinner portions. The lines are " veins," and 

 the total of them the " venation." When veins run direct from the midrib of any part 

 of a frond to its edge, they are " simple" or " free" ; but they often divide, in which 

 case they are " forked." Small secondary veins are " veinlets," or " venules" (ve-nu- 

 les), and when these, after dividing, join again, or unite with another vein so as to 

 form a sort of network, they are called " anastomosing" (anna-sto-mo-sing), and the 

 spaces enclosed by them " areoles" (a-re-o-les). The veins are sometimes very dis- 

 tinct, but in other ferns scarcely traceable by the eye. They exist, however, and are 

 connected with the fructification, the manner of the connection being one of the points 

 to be noticed in classing ferns. Mr. Smith, of Kew Gardens, first pointed out this 

 connection ; and by it fossil ferns, which showed no trace of fructification, have been 

 classed. 



The portion of a frond which contains the spore-capsules is called a " sorus" 

 (plural, sori), and is variously placed in the different sub-orders and genera of ferns. 

 Sometimes it consists of single capsules, at others of groups or lines of them, each 

 capsule standing alone ; and either bare or protected in some way. In other classes 

 it consists of capsules closely packed together round a central stalk called a recep- 

 tacle ; and this cluster of capsules may be either naked or enclosed in or protected by 

 a covering of some kind. In others again the capsules are piled in little heaps, which 

 may be round, oval, curved, or in straight lines, and in the several classes are, or are 

 not, protected while young and tender by a covering ; the manner in which the 

 covering opens to allow of the growth of the capsules being one of the means of 

 identifying ferns. The covering which protects a sorus is called an "involucre" 

 (in-vol-u-cre) or " indusium" (in-du-si-um). Properly speaking, the former term 

 applies where the covering is wrapped over or round the sorus, and the latter to the 

 other kinds, but the words are used interchangeably by different writers, and sometimes 

 even by the same person. In fact, the manner in which a sorus is protected varies 

 in so many ways that it would be hard to say in some cases which term is the more 

 -applicable. As " involucre" is the term used in the Synopsis, I shall generally use it 



