OAK FAMILY. 393 



angled or winged nut, coming from an ovary with 2 or more 

 cells having 1 or 2 ovules hanging from the summit of each; 

 but all except one cell and one ovule are abortive. There is 

 a calyx adhering to the ovary, as is shown by the minute 

 teeth crowning its summit. Seed filled by the embryo, which 

 has thick and fleshy cotyledons. 



* Sterile and fertile flowers in separate scaly catkins ; fertile flowers with no calyx or 



involucre ; fruit flat or winged, small ; stigmas 2, thread-like. 



1. BETULA. Sterile catkins long and hanging, with 3 flowers under each shield-shaped 



scaly bract, each with a scale bearing 4 short stamens with 1-celled anthers. (Lessons, 

 Fig. 207.) Fertile catkins stout ; 2 or 8 flowers under each 3-lobed bract, each of a 

 naked ovary ripening into a rounded broadly winged scale-like little key-fruit, tipped 

 with the 2 stigmas. 



2. ALNUS. Flowers much as in Betula, but usually a distinct 3-5-parted calyx ; anthers 



2-celled ; oval fertile catkins composed of thick and at length woody persistent scales ; 

 and the little nutlets less winged or wingless. 



* * Sterile flowers in pendulous catkins, the fertile in a short cluster or head ; the 



sterile consisting of a few short stamens partly adhering to the bract, and des- 

 titute of any proper calyx ; the anthers l-celled ; fertile flowers in pairs under 

 each bract of a head, spike, or short catkin, each with one or two bractlets, form- 

 ing afoliaceous or sac-like involucre to the nut. Sterile catkins rather dense. 

 8. CORYLUS. Scales of the sterile catkin consisting of a bract to the inside of which 2 

 bractlets and several stamens adhere. Fertile flowers in a little head, like a scaly 

 bud ; stigmas 2, long and red. Nut rather large, bony, wholly or partly inclosed in 

 a leaf-like or tubular and cut-lobed or toothed involucre. 



4. OSTRYA. Scales of the sterile catkin simple. Fertile flowers in a sort of slender cat- 



kin, its bracts deciduous, each flower an ovary tipped with 2 long slender stigmas 

 and inclosed in a tubular bractlet, which becomes a bladdery greenish-white oblong 

 bag, in the bottom of which is the little nut ; these together form a sort of hop-like 

 fruit. 



5. CARPINUS. Sterile catkin as in Ostrya. Fertile flowers in a sort of slender loose cat- 



kin ; each with a pair of separate 3-lobed bractlets, which become leaf-like, one each 

 side of the small nerved nut. 



* * * Sterile flowers in hanging catkins or a pendulous head, with a distinct 4-1-lobed 



calyx and 3-20 slender stamens ; fertile flowers 1-4 in a cup or bur-like invo- 

 lucre. 



-*- Sterile flowers clustered in slender catMns ; their bracts inconspicuous or decid- 

 uous. 



6. QUERCUS. Stamens 3-12. Fertile flower only one in the bud-like involucre, which 



becomes a scaly cup. Stigma 3-lobed. Nut (acorn) terete, with a firm shell, from 

 which the thick cotyledons do not emerge in germination. (Lessons, Figs. 36, 37, 388.) 



7. CASTANEA. Stamens 8-20. Fertile flowers few (commonly 3) in each involucre, one 



or more ripening ; stigmas mostly 6 or 7, bristle-shaped. Nuts coriaceous, ovoid, 

 when more than one flattened on one or both sides, inclosed in the hard and thick 

 very prickly bur-like at length 4-valved involucre. Cotyledons somewhat folded 

 together and cohering, remaining underground in germination. 



+- +- Sterile flowers in small heads on drooping peduncles. 



8. FAGUS. Calyx of sterile flowers bell-shaped, 5-7-cleft, containing 8--16 long stamens. 



Fertile flowers 2 together on the summit of a scaly-bracted peduncle ; the innermost 

 scales uniting form the 4-lobed involucre ; ovary 3 celled when young, crowned by 6 

 awl-shaped calyx teeth and a 3-cleft or 3 thread-like styles ; in fruit a pair of sharply 

 3-sided nuts in the 4-cleft soft-prickly rigid involucre. Cotyledons thick, somewhat 

 crumpled together, but rising and expanding in germination. (Lessons, Figs. 31-33.) 



