THE DICOTYLEDOXES i 



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Blackberries, Hedge Parsley, Nettles and many other plants may be dis- 

 covered living epiphytically in this way in pollarded Willows. 



The genus Populus is considerably smaller than Salix. It contains some 

 twenty species, which are distributed in north temperate regions. Three 

 species, P. alba, P. canescens and P. tretniila, occur wild in Britain, but 

 P. nigra and P. serotina are common as planted trees. 



Unlike the genus Salix, the species of Populus are pollinated entirely by 

 wind, though there is some evidence that the male flowers are often visited by 

 pollen-collecting bees (Fig. 1634). The male and female catkins are long 

 and pendulous and the bracts are toothed. There is a cup-shaped disc 

 surrounding the essential organs, which secretes no nectar and is con- 

 sidered to represent the remains of a perianth. 



Fig. 1634. — Populus nii>ra. Male catkins. 



Closely allied to the Salicales are the Garryales, a small order contain- 

 ing a single family, the Garryaceae. They are trees or shrubs but differ 

 from the Salicales in that the leaves are opposite, with the petioles connate 

 at their bases. The flowers are less reduced and possess four sepals and four 

 alternate stamens in the male flowers, which are arranged in long pendulous 

 catkins. In the female flowers there are no sepals but only a unilocular 

 ovary with two styles and containing two ovules which are pendulous from 

 its apex. The fruit is a berry and the seed contains copious endosperm. 



The family contains the single genus Garrya which has some eighteen 

 species, distributed in North America and the West Indies. Several are 

 cultivated, of which G. elliptica is the most common. It is an evergreen 



