CHAPTER IX 



TYPES OF VARIATION 



In the foliage of flowering plants there is immense diversity of form, 

 both specific and varietal, but in Ferns it would almost appear that, 

 prevented by their absence of obvious flowers from displaying 

 their powers of variation in that direction, they have made up for it 

 by doing so in a very wonderful and surprising fashion in their 

 foliage. Between the forms of fronds of diverse genera we naturally 

 find great differences, but it is in the case of our native Ferns 

 especially that one and the same species has proved itself capable 

 of assuming hundreds of different types of fronds, and this not due 

 to any human selection at all, but solely to some natural impulse 

 to which we have absolutely no clue. Naturally the study of these 

 types, despite their multiformity, shows them to permit of some 

 classification, and they may be broadly divided into two sections, 

 viz. those in which the terminal points of the fronds and sub- 

 divisions branch in such a way as to form tassels or crests (cristate) , 

 and those in which the normal extent of subdivision is increased 

 or diminished. Thus a once divided or pinnate form may possibly 

 yield a quadri- or quinque-pinnate one, i.e. four or five times divided, 

 in this way, practically losing all similarity to the specific and 

 simpler type, while in rarer cases a normally divided frond may 

 not be divided at all, but become simply strap-shaped. The for- 

 mation of terminal tassels is the most prevalent type of abnormality, 

 and has been found to occur in a very large number of species 

 both native and exotic. No cresting proper has been remarked in 

 the foliage of any flowering plant. In the Celosias, or Cockscombs, 

 and many other cases of fasciation, there is a similarity, but also 

 a fundamental difference. In fasciation we find a multiplication of 

 growing points, which develop so closely together as to coalesce, 

 a normally round stem thus becoming a flat, or almost ribbonlike 

 one, or, as in the Cockscomb, a dense Cactus-like mass built up 

 of innumerable conjoined branches and flower stalks massed solidly 

 together. The typical Fern crest, on the other hand, commences to 

 develop on what may be considered a normal stalk or midrib, the 

 growing point of which, at a certain stage in this development, and 



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