152 MOUNTAIN AND MOORLAND 



largest as well as the most graceful of European 

 Ferns, that it shows an almost diagrammatic contrast 

 between the foliage part, which keeps the plant agoing 

 from day to day, and the multiplying part, which 

 produces the spores the spores that in a roundabout 

 way secure the continuance of the race of Royal 

 Ferns. For the tiny spores that are scattered about 

 by wind and by runlets of water give rise to a genera- 

 tion of small green leaf like plants, called "prothalli," 

 which bear minute male and female organs. From 

 the fertilised egg-cell of the prothallus, which lies 

 more or less flat on the moist soil, there grows the 

 stately fern plant, the spore-making generation. This 

 is a very remarkable complication of the life-history 

 of the Fern, and is known as " alternation of genera- 

 tions" the alternate occurrence in one life-history of 

 two different forms, differently produced. It is well 

 illustrated by Mosses and Horsetails; it is much dis- 

 guised in flowering plants. It is interesting to know 

 that the same alternation occurs in the life-history of 

 many zoophytes, in the common Jellyfish, in some 

 Worms like the Liver Fluke, and in a number of other 

 animals. 



Before our stream joins the river it lingers in a 

 meadow, where Cuckoo Flowers (Cardamine pratensis) 

 are common in spring, and it is extraordinary the way 

 it wriggles about, now to one side and now to 

 another, in the soft alluvial soil. Longfellow has 

 recorded his impressions of a river in the well-known 

 lines : 



And silver white the river gleams 

 As though Diana in her dreams 

 Had dropped her bow 

 Upon the meadows low. 



