BETULACEAE 61 



monoecious. The staminate catkins, about ^ inch long, clus- 

 tered together on the ends of branches, fall about the middle 

 of May. The globular pistillate catkins stand at the end of 

 short, lateral branches. They become burlike at maturity and 

 as a rule are 4-seeded. In the pistillate flower the ovary is 

 surrounded by 8 long, narrow, awllike, persistent, pubescent 

 scales or bracts that eventually surround and nearly conceal 

 the light brown nut, which is only about ]/s inch long. 



Distribution. — More widely distributed than the other 

 species of the family, the Sweetfern ranges from Nova Scotia 

 westward to Saskatchewan, southward in the east to North 

 Carolina and in the west into northern Indiana, northeastern 

 Illinois, and Minnesota. In Illinois, it is known to occur only 

 in the extreme northeastern corner of the state, growing in 

 sandy open woods and swamps. 



BETULACEAE 

 The Birch Family 



The birch family consists of monoecious or occasionally dio- 

 ecious trees and shrubs with flowers generally in catkins. 

 Staminate flowers always are in catkins, but pistillate flowers 

 may be clustered or arranged in spikes. The leaves, subtended 

 by early deciduous stipules, are alternate, simple, and straight 

 veined. The fruit is typically a 1-celled or 1-seeded nut, which 

 is borne free or inclosed in a foliaceous, sometimes woody, 

 involucre. 



This is a small family of about 5 genera, some trees and 

 some shrubs, all of which occur in Illinois. Ostrya, the Hop 

 Hornbeam, Carpinus, the Hornbeam, and the tree birches have 

 been described among the trees of the state. The shrubby 

 forms include hazelnuts, alders and small birches. 



Key to Shrubby Genera 



Staminate flowers in catkins, pistillate flowers in clusters; nuts 

 large, inclosed in a leafy, somewhat lignified involucre. . . . 

 Corylus, p. 62 



Both staminate and pistillate flowers in catkins; the seedlike 

 nutlets free and winged. 



Fruiting catkins membranous; winter buds sessile . Betula, p. 64 



Fruiting catkins woody, miniature cones; winter buds stalked 



Alnus, p. 66 



