148 American Midland Naturalist Monograph No. 7 



17. Lateral veins 4-8 pairs; fruit on peduncles 2-6 cm 

 long; alluvial soil nearly throughout 111. 

 Swamp White Oak. [Q. platanoides (Lam.) 



Sudw.] Q. bicolor Willd. 



The following known or supposed hybrids have been reported growing 

 spontaneously in Illinois: Q. alba X bicolor [ X Q,. jackiana Schneid.], Cook, 

 Randolph. — Q. alba X macrocarpa [ X Q- bebbiana Schneid.], Winnebago. 

 — Q. alba X muhlenbergii [ X Q. deamii Trelease], White. — Q. alba X 

 stellata [ X Q. fernowl Trelease], Winnebago. — Q. bicolor X lyrata [X Q. 

 hurnidicola E. J. Palmer], Clay. Pulaski, Richland. — Q. imbricaria X falcata 

 [ X Q. anceps E. J. Palmer], Gallatin, Hardin. — Q. imbricaria X marilandica 

 [X Q. tridentata (A. DC.) Engelm.], Richland. — Q. imbricaria X palus- 

 tris [ X Q. exacta Trelease], Richland, St. Clair, Vermilion, Wabash. — Q. 

 imbricaria X rubra [ X Q. runcinata (A. DC.) Engelm.], Champaign, Johnson, 

 Richland, St. Clair, Wayne. — Q. imbricaria X velutina [ X Q- leana Nutt.], 

 Cook, Fulton, Hancock, Hardin, Johnson, Peoria, Richland, Sangamon, 

 Wabash, Will, — Q. macrocarpa X muhlenbergii [ X Q. hillii Trelease], Cook, 

 Richland. — Q. marilandica X velutina [ X Q. bushii Sarg.], Hancock, Hen- 

 derson, Randolph, Richland, Union, Wabash, Woodford. — Q. palustris X 

 phellos [ X (2- schochiana Dieck], Alexander, Massac, Pulaski. — Q. phellos 

 X velutina [ X Q. filialis Little], "s. 111." 



66. Betulaceae Agardh — Birch Family 



1. Nuts small, compressed and often winged, without an involucre, borne in 



catkins; staminate flowers consisting of 2-4 stamens and a 2- to 4-parted 



calyx. 



2. Scales of the pistillate catkins 3-lobed, deciduous (sometimes only 



tardily so); stamens 2, bifid; leaf-buds sessile, with 3 or more scales; 



bark often peeling horizontally 1. Betula 



2. Scales of the pistillate catkins 5-lobed, woody, persistent; stamens 4; 



buds usually stalked and with 2 valvate scales 2. Alnus 



l.Nuts with a foliaceous involucre or subtended by or enclosed in a large 

 bractlet, borne in clusters or catkins; stamens 3-10; calyx none; buds 

 with several scales. 



3. Shrubs; leaves broadly cordate-ovate, doubly serrate, usually with 5-8 



pairs of veins; leaf-buds obtuse; nuts in clusters, each enclosed in a 



foliaceous involucre 3. Corylus 



3. Small trees; leaves oval or ov-ate, with 9 or more pairs of veins; leaf- 

 buds acute; fruits in pendent catkins, the nut subtended by or enclosed 

 in a large bractlet. 

 4. Fruiting bracts foliaceous, 3-lobed; bark of the trunk and branches 

 smooth; lower surface of leaves glossy green with small tufts of 

 whitish hairs in the axils of the principal veins; lateral veins un- 



branched; anthers glabrous 4. Carpinus 



4. Fruiting bracts becoming sac-like, inflated, enclosing the nut; bark 

 rough, scaly; lower surface of leaves pale dull green, thinly short- 

 pilose; lateral veins usually forked near the margin; anthers pilose 

 at apex 5. Ostrya 



1. Betula L. — Birch 

 1 . Trees up to 30 m tall, with acute or acuminate, serrate or double- 



