1648 



A TEXTBOOK OF THEORETICAL BOTANY 



In Cretaceous and Tertiary times the genus appears to have been wide- 

 spread in Europe, northern Asia and North America. 



>,« 



Fig. 1508. — Platanus orientolis. Above, clusters of female 

 flowers and, below, of male flowers. 



Rosaceae 



The Rosaceae are one of the most important famihes of the Archichla- 

 mydeae, for not only does the family embrace a very large number of genera 

 and species, but so many of them are of economic importance that a very 

 considerable proportion of the fruit trade depends upon species belonging 

 to the family. Many are so well known by their popular names, such as the 

 apple, the pear or the plum, that they need no description. Others are 

 less well known and we may begin by listing some of the most important. 



In the genus Primus (Fig. 1509): P. spinosa (Sloe or Blackthorn), P. 

 avium (Wild Cherry), P. cerasus (Cherry), P. padus (Bird Cherry), P. persica 

 (Peach), P. armenaka (Apricot), P. amygdahis (Almond), and P. domestica 

 (Plum) may be mentioned, the first four and the last occurring wild in 

 Britain. 



