[Chap. LI SOME FAMILIES OF FLOWERING PLANTS 713 



food. Hemlock, poison parsnip, conium, and a few others are v^ery 

 poisonous to livestock and sometimes fatal to man. 



Fig. 350. Stages in the growth of the flower clusters (umbels) of the wild carrot 

 (Daiiciis) from buds to mature fruits. 



The heath family {Ericaceae). The plants of this family are world- 

 wide in distribution, except in deserts and the moist tropics. They most 

 frequently grow on acid soils and are often found in bogs. The heath 

 family proper is represented by erica (Fig. 351), laurel, rhododendron, 

 sourwood, azalea, bearberry, and trailing arbutus. The plants are usually 

 shrubby; but herbs, trailing vines, and a few trees are included. The 

 leaves are often evergreen, and the flowers of some species are scarcely 

 exceeded in the plant kingdom for fragrance, luster, and general beauty. 

 The sourwood is an important source of honev in the southeastern 

 United States, but except for the esthetic value of some species the 

 group is commerciallv rather unimportant. 



Closely related to and sometimes included in the heaths are the In- 

 dian pipe familv (Monotropaceae), the wintergreen family {Pyrola- 

 ceae ) , and the cranberry-blueberry-huckleberry family ( Vacciniaceae ) . 

 The Indian pipe, the pinesap, and pine drops are herbaceous annuals 

 without chlorophvll, and thus represent the relatively few non-green 



