THE VASCULAR CRYPTOGAMS 41 



a midrib, springing from the rachis, and giving rise 

 to lateral veins, which fork, and end near the edge of 

 the leaf. This type of venation is a common one in 

 Ferns (see Fig. 18, B). 



The petiole and rachis, and sometimes also the larger 

 veins of the leaflets, are clothed with brown chaffy hairs, 

 the palece or ramenta, which are characteristic of the 

 order (see Fig. 18). 



The leaves develop very slowly, arising in the bud 

 two years before they unfold. The growth of the leaf 

 goes on at the apex like that of the stem. Thus the 

 leaf -stalk is the first part to be formed, and is generally 

 the only part developed in the first year of growth. The 

 blade is formed later, and this also grows from the base 

 upwards. The blade of the young leaf is rolled up in 

 such a way that the rachis or midrib forms a spiral 

 like a watch-spring, the apex of the leaf being at the 

 centre of the spiral (see Fig. 17, c). Everyone who has 

 ever watched a Fern coming up in spring must have 

 noticed the form of the young leaves. The curvature 

 is due to the greater growth of the under-side of the 

 leaf, which is external in the bud. Each leaflet is 

 coiled up in a similar way. This mode of folding of 

 the young leaf is called circinate or crosier-like vernation, 

 vernation being a general word for the folding of a 

 leaf in the bud. When the leaf finally expands, the 

 inner side grows more rapidly than the outer, so that 

 the curves become straightened out. Circinate vernation 

 in characteristic of the Ferns generally. 



The branching of the stem in this Fern is peculiar ; 

 no branches at all are formed at the growing point, 

 but buds arise on the petioles of some of the leaves, 

 springing from their outer sides a little above the 



