IOWA ACADEMY OF SCIENCES. 169" 



pecan and //. uiinitna. [C. olircefonnis and C. amara.} 

 Barnes, Reppert, and Miller in their Flora of Scott and 

 Muscatine counties mention two hybrids as occurring in 

 the big timber near Muscatine, namely, Carija olivceformis 

 X C. tonientosa and Canja oUvfeformis X C. amara. 



BETULACEAE OF IOWA. 



BY T. J. AND M. F. L. FITZPATRICK. 



BETULACE^ Agardh, Aphor. 208, 1825. 



THE BIRCH FAMILY. 



The Birch family as now understood, comprises six 

 genera and about seventy-five species, mostly natives of 

 the northern hemisphere. Some authors include this 

 family with the Oak or Beech family under the name of 

 CupuLiFERAE. The chief distinction is the arrangement of 

 the pistillate flowers. The Birch family has the pistillate 

 flowers in aments while the Oak family has the pistillate 

 flowers subtended by an involucre which becomes a bur op 

 cup in fruit. 



The family may be briefly characterized as trees or 

 shrubs, with alternate petioled simple leaves, deciduous 

 stipules, and monoecious flowers. The sterile flowers are 

 in oblong or subglobose pendulous aments; stamens 2-10, 

 inserted at the base of the regular or scale-like calyx; 

 anthers 2-celled. the cells adnate or distinct. Pistillate 

 aments erect, spreading or drooping, spicate or capitate; 

 calyx adnate to the ovary, sometimes wanting. Ovary 

 1-2-celled, with 1-2 ovules in each cell; style 2-cleft or 

 2-parted. Fruit a one-celled, one-seeded nut, solitary or 

 clustered, and usually involucrate. In most cases the fruits 

 should be collected for certain identification. 



Iowa has within its borders only seven species distrib- 

 uted through five genera. Only one species, the hazel-nut, 

 is distributed throughout the state. All the others have a 



