320 TRIANDRIA DIGYNIA. Ischtcmvm. 



its anterior margins and apex enlarged with a broad, mem- 

 branaceous, bifid border ; inner valve boat-shaped, keeled, ci- 

 liate, and sub-aristate, one floret male, the other hermaphro- 

 dite. Carol, (jinnies of each floret two valved ; the exterior 

 one of the hermaphrodite floret bifid, with a long arista in the 

 fork. Calyx of the pedicelled flower two-valved, two -flow- 

 ered ; valvelets equal, boat-shaped, keeled, ciliate, and sub- 

 aristate; one floret male, the other hermaphrodite. Coronas 

 in the sessile flowers, and also awned in the same manner. 



Obs. I am not certain that this is the original I. aristatam 

 of Linnaeus and Retzius. 



2. I. rugosum. Linn. sp. pi. ed. Willd. iv. 940. 



Erect, ramous. Leaves lanceolate; spikes paired, both 

 flowers awned ; calyces oblique, obtuse, hard, and transverse- 

 ly rugose. 



Is generally found growing among rice, and is so much 

 like it, the inflorescence excepted, that they are not, till in 

 flower, to be distinguished. Leaves large, smooth ; mouths of 

 the sheaths crowned with a long, two-parted ligula. Spikes 

 terminal, and from the exterior axills paired, erect, from two to 

 three inches long. Racftis jointed. Flowers in pairs ; one ses- 

 sile, the other on a short, thick, angular, clubbed pedicel. 



Sessile Flower. Calyx two-valved ; valvelets in size 

 nearly equal, the exterior one rugose, and very hard ; one of 

 the florets hermaphrodite, the other male, each with two 

 membranaceous valves; the inner valve of the hermaphrodite 

 flower has a long twisted awn issuing from the middle of its 

 back. 



Pedicelled Flower smaller. Calyx as in the other, but 

 containing two male flowers, one of which is al&o awned. 



3. I. semisagittatum. R. 



Annual. Leaves ovate-lanceolate, semisagittate. Spikes 

 paired, secund, all the calyces two-flowered, exterior valvelets 



