THE DICOTYLEDONES 



1763 



The fruit is a dry, indehiscent, one-seeded nut. The bracts during 

 development undergo modification, forming a wing in Carpimis (Fig. 

 1646) or a cupule in Cory his. 



Fig. 1646. — Carpimis ovatus. Shoot with female catkin furnished with large bracts 



which form the wings of the ripe fruits. 



The seed is non-endospermic. The embryo possesses two large 

 cotyledons which contain a reserve of oil. 



The family is not a large one, but contains some six genera and about 

 105 species. At the present time the family is restricted chiefiy to north 

 temperate regions. A few American species extend southwards in the Andes 

 as far as the Argentine. 



The family is classified quite simply into two sub-famihes: 



I. Coryloideae 



The male flowers are in three-flowered cymes borne in the axil of a 

 bract. \ perianth is present. Betiila, Alniis. 



II. Betuloideae 



The male flowers are in three-flowered cymes borne in the axil of a bract 

 A perianth is present. Betula, Alniis. 



The Coryloideae contain chiefly temperate genera. Carpinus betiiliis 

 (Hornbeam) is common in Britain. The other twenty-one species of the 

 genus occur chiefly in eastern Asia. The female catkins are terminal on long 

 shoots while the males are themselves short shoots. In the axils of the latter 

 are from four to twelve stamens but no bracteoles are present. In the 

 female catkin there are two lateral flowers in each axil with six bracteoles 



