THE DICOTYLEDOXES 



1651 



The corolla is polypetalous, consisting of five petals which are often 

 brightly coloured and of large size; white, red or yellow being the pre- 

 dominant colours. These petals are imbricated in the bud. Petals may be 

 absent in certain genera, e.g., Alchemilla. 



Fig. 1 5 12. — Pyrus mains. Longitudinal section of flower. 



The androecium is made up of stamens which are in number either 

 a simple multiple of the perianth parts or indefinite. They are free, the 

 anthers being small and bilocular. They split longitudinally. 



The gynoecium may consist of from one to many carpels which may 

 be free or adnate to the receptacle. The ovary is usually apocarpous and 

 each carpel contains either one or two anatropous ovules. 



The fruit may be either dry or succulent; in the latter case usually a 

 drupe, or occasionally a pseudocarp. xA.lternatively it may be a cluster or 

 etaerio of small akenes, follicles or drupes. 



The seeds are almost always non-endospermic and the embryo pos- 

 sesses planoconvex, fleshy cotyledons which on germination are epigeal. 



The family is world-wide in distribution, though its main centre appears 

 to be in the north temperate regions. There are some 2,000 species which 

 are grouped in 100 genera. 



Anatomically there are certain features which are more or less charac- 

 teristic of the family or at least of the woody members. The cork cambium 

 in one sub-family is epidermal while in another it is hypodermal. The 

 primary cortex normally has a collenchymatous hypodermis and crystal 

 sacs occur in the cortical parenchyma. Stone cells are usually absent from 

 the primary and secondary cortex. The medullary rays are broad in the 

 sub-families Rosoideae and Prunoideae but narrow in the Pomoideae. Pear 

 wood is one of the smoothest and finest-grained woods known. It is 



