I 12 



PERN STRUCTURE (continued). 



The fern frond grows, however, in a different way to 

 leaves proper, all its parts are developed by growth of the 

 tips and circinately, that is coiled or rolled up upon them- 

 selves. In the bud of a tree, shrub, or flower we find as a 

 rule a spiky growth consisting of a bunch of embryo leaves 

 whose points are plainly visible, but in the bud or embryo 

 fern frond we see a rounded, smooth, or scaly mass, con- 

 sisting of the base of the frond stalk, which curves over 

 and covers a spiral coil of embryo subdivisions. When the 

 frond rises, this stalk lengthens, carrying with it the still 

 coiled portion for some distance, and presently we shall 

 see this loosen and the side divisions will each present the 

 original appearance of a stalk rolled up and covering a 

 coil. This repeated lengthening of stalks or midribs, and 

 uncoiling goes on until it may be a very large and much 

 divided frond develops. Careful observation of this 

 process shows it to be a very wonderful one, the lengthen- 

 ing of the stalks and expansion of the parts being so 

 admirably adjusted to catch the maximum of light. 



If we study the internal structure of a large frond as it 

 proceeds from the incipient rounded bud to the full-fledged 

 stage, and consider that all this has been evolved in course 

 of time from the simple cellular form of the prothallus, we 

 cannot fail to be struck with admiration. First, within the 

 originally soft and succulent stem, a complex and beautiful 

 arrangement of woody fibre, pith, and cortex is built up to 

 stand the evergrowing strain brought to bear upon it by 

 the growth of the secondary parts, and the increasing 

 leverage these exercise as they spread far and wide in the 

 process ; subtly arranged vessels are interspersed with 

 these strengthening girders to convey the sap from root to 

 frond, and vice versa, each minor stalk is doing the same 

 work in nicest possible relation to the needs, so that every 



