2/2 PLANT LIFE. 



the main stalk. Many minor details in the shape 

 and attachments of these leaflets can be understood, 

 if a half unfolded leaf is carefully examined. A 

 dense mass of overlapping golden-brown scales covers 

 its entire surface. These scales keep off rain, prevent 

 injury from cold, and are sometimes very necessary 

 to keep out small insects which occasionally destroy 

 whole fronds by colonising the bud (see p. 275). 



Wherever the plant grows under different conditions, 

 the leaves vary accordingly. Thus, in Ophioglossum 

 the leaf is very like that of the grasses amongst which 

 it grows. Hart's Tongue (^Scolopendrimn), often found 

 on sloping banks, in Devonshire lanes, and elsewhere, 

 has a broad simple leaf which hangs out over that of 

 other plants. Both the Common Polypody and the Hard 

 Fern {Bleckniim spicant) have very slightly divided leaves; 

 the latter is a hardy species often found in the open, 

 and the former prefers dry stone dykes. On the other 

 hand, the British Filmy Ferns show an extraordinary 

 resemblance to some hypnoid mosses, and they grow 

 amongst such mosses under almost identical conditions. 



In the course of its development, the leaf gradually 

 unrolls itself, and its stalk is at first almost vertical. 

 If it is growing in the ordinary damp atmosphere of a 

 wood, the leaves then droop over into their natural 

 position ; but if the place is dry and exposed, they 

 remain more or less erect, so that the light falls 

 chiefly on their edges, and not upon the whole 

 upper surface. 



Fern stems vary greatly in size and appearance. 

 The erect, unbranched, pillar-like trunks of the tree- 

 ferns are sometimes 80 feet in height. The stem of 

 the common bracken is buried from 6 to 1 8 inches 

 deep below the surface of the soil, so that its leaf 



