FAMILIES OF FLOWERING 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 structure may be seen in Fig. 113. A fruit of this type : 
is known to botanists as a pome (from pomum, fruit). 
Generic differences in this family are more apparent than real, and 
indeed the apple (Malus), 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, Malus 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. 115. The cockspur thorn (Crataegus Crus-gallt). 
accompanying plat e (FE ig. After Britton & Brown, Ill. Fl, Northeast. U. S. 
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, 
