70 THE BOOK OF NATURE STUDY 



for instance ; and the filo-plumes. These last are the long hair- 

 like feathers seen in the common fowl after being plucked for 



FlG. 1 8. Diagram of a contour-feather, 

 showing its several parts. C, calamus 

 or quill ; R, rhachis or shaft ; V, vane 

 formed by B, rami or barbs ; Bs, radii 

 or barbules, which are shown slightly 

 magnified in the area enclosed by semi- 

 circles, and highly magnified in Fig. 19. 



FlG. 19. Barbules or radii removed from 

 the ramus or barb, slightly magnified. 

 A, shows one of the anterior series 

 that pointing towards the top of the 

 feather ; B, shows two of the posterior, or 

 hinder series. These may be seen in 

 their natural relations in Fig. 20. 



Bs. 



Bs, 



FlG. 20. A highly magnified section through two rami or barbs, showing the radii 

 or barbules in their natural position. The section has been taken parallel with the 

 barbules of the anterior series, and hence of necessity the posterior barbules are 

 shown in cross section. A reference to the area enclosed by semicircle in Fig. 18 

 should make this clear. Note the way in which the booklets are thrust down into 

 the trough formed by the in-curved blades of the posterior series. 



