FAMILIES OF FLOWEKING PLANTS 



129 



proper. The apples and their allies may be easily distinguished by 

 the fruit, which consists of the enlarged fleshy calyx-tube, enclosing 

 from one to five thin-walled or papery carpels, each usually single- 

 seeded. This stnicture may be seen in Fig. 113. A fruit of this type 

 is known to botanists as a pome {horn pomum, fruit). 



Generic differences in this family are more apparent than real, and 

 indeed the apple {3falus), the pear (Pyrus), and the mountain ash {Sor- 

 bus), were until recently generally placed together in the single genus 

 Pyrus. But all three belong to very distinct natural types, and one 

 who is absolutely ignorant of botany can distinguish any pear from any 

 apple, and any quince from either. 



The family contains 

 about 20 genera and 225 

 species of wide distribution; 

 all are trees or shrubs. In 

 this country we have very 

 few indigenous species of 

 Pyrus, 3Ialiis or Sorbus, but 

 Amelanchier, the shad-bush 

 or service-berry, is repre- 

 sented by about 12 species 

 in the United States, while 

 Crataegus, the hawthorn, 

 now contains over 100, and 

 the number is rapidly on 

 the increase. Two hand- 

 some photographs of the 

 shad-bush {Amelanchier Can- 

 adensis) may be seen in the Fig- "S- The cockspur thom (Crataegus Crtis-galli). 

 1 L t-cy- After Britton & Brown, 111. Fl. Northeast. U. S. 



accompanying plate (rig. 



114). The cockspur thorn {Crataegus Crus-galli) is shown in Fig. 115. 

 Hawthorns are extremely ornamental trees in cultivation, with their 

 white or pink flowers and often brightly colored fruits. Most of the 

 trees are armed with spines; their wood is very hard. 



Family Drupaceae. Plum family. Contains about 6 genera and 

 over 100 species of wide distribution, most abundant in the north tem- 

 perate zone. They are trees or shrubs with resiniferous bark, nearly 

 all parts of the plant containing prussic acid. The flowers have five 

 petals, borne on the calyx, which is free from the ovary; stamens nu- 

 merous; ovary consisting of a single carpel, becoming what is known as 

 a drupe in fruit, the outer coating being fleshy or pulpy, the inner hard 

 and crustaceous, enclosing a solitary seed. The great majority of the 

 species are comprised in Prunus, the plum, and Cerasus, the cherry, 



