160 THE BOOK OF NATURE STUDY 



be recognised by its black buds and stout twigs, for, as the leaves 

 are compound, consisting of several pairs of leaflets, their weight 

 is considerable, and could not be supported by slender twigs. 

 The leaves come out after the flowers, and are among the earliest 

 to fall in autumn. The flowers blossom in April or May. Both 

 staminate and pistillate may be found on the same tree, or only 

 one kind on a tree. This accounts for the fact that many ash 

 trees have no fruit. The stamens are dark purple, and the 

 pistillate flowers a greenish-yellow. The ovary is two-celled, 

 with one or two ovules in each cell, but as a rule only one seed 

 develops. The fruit is winged. The Mountain Ash, or Rowan, 

 has leaves similar to those of the ash, but it is a rosaceous tree, 

 and is easily distinguished from the other by its flowers and its 

 red berries. Its flowers are not unlike the hawthorn blossoms, 

 and have very much the same structure as those of the apple 

 or pear. As far as has been observed, the following plants are 

 characteristic of ash woods growing on limestone, but are absent 

 from oak and oak-hazel woods : Hellebore Viridis, Mountain 

 St. John's-wort, Blood Geranium, Solomon's seal, Lily-of-the- 

 Valley. This may be due to the fact of lime in the soil, as these 

 plants are characteristic of the oolitic limestone of the Cotswolds, 

 where the beech is more abundant than the ash. 



EFFECT OF MOISTURE 



The effect of moisture on the vegetation of woods is very 

 evident in a county like Northumberland, where there are many 



ravines and mountain torrents, 

 with woods sloping down to the 

 water's edge. One of the con- 

 spicuous trees in such a situation 

 is the Alder. It may be recognised 

 by its rough, black bark, by its 



FIG. 46. A, Staminate flower of Alder ; J . ' J 



p, perianth. B } Pistillate flower of horizontal branching and slightly 

 Aider ; c, scale covering two flowers ; upward bend of the terminal twigs, 



6, scale belonging to single flower. an( j fey the dark re ddish-brown 



woody scales of the catkins, which remain on the tree long after 

 the seeds have fallen out. 



The staminate catkins are two or three together and hang 



