KEY. 



259 



III. Ovary 4 celled, inferior. Leaves pinnately dis- 

 sected into linear divisions, commonly whorled. Floating 

 aquatics. Myriophylluin (838). 



829. Style or stigma simple. Leaves stipulate, on (mostly 

 long) petioles 830 



Styles or stigmas 2 or 3. Leaves alternate, exstipu- 

 late 834 



830. Leaves opposite 832 



Leaves alternate 831 



831. Herb beset with stinging bristles. Sterile flowers 

 with 5 sepals, 5 stamens, and a rudimentary ovary ; the fer- 

 tile with 4 (apparently only 2) sepals and an ovary with a 

 long subulate stigma. Achenium very oblique, and at length 

 reflexed on the winged pedicel. Flowers in axillary, loosely 

 and divaricately branched panicles, with the sterile flowers 

 below. Leaves long-petioled, serrate, large. 



Laportea Canadensis, Gaud. (899). 

 Herbs destitute of stinging hairs. Calyx of the 

 sterile, 4-androus flowers 4-sepalled, that of the fertile tubu- 

 lar-bell-shaped, 4-lobed ; stigma tufted. Achenium polished. 

 Involucrate-bracted clusters of green flowers axillary. Peti- 

 oled leaves entire. 



{Q^l) Parietaria Pennsylvanica, Muhl. 



832. Herbs without stinging bristles 833 



Herbs beset with stinging bristles. Sepals 4 in 

 both sterile and fertile flowers. Stigma capitate-tufted. 

 Achenium straight, enclosed by the 2 inner and larger sepals. 

 Flowers in branching, panicled spikes, or in peduncled capi- 

 tate clusters. * Urtica (898). 



833. Sepals 3 or 4, those of the fertile flowers all, or all 

 but one small. Stigma pencil-tufted. 



(825) Pilea pumila, Gray (898). 

 (Hichweed ) 

 Calyx of the fertile flowers 4- (or 2-) toothed, or 

 nearly entire, tubular or urn-shaped. Style long and thread- 

 form. Calyx of the sterile flowers 4-parted. Flowers glome- 

 rate, the clusters spiked. 



Boehmeria cylindrica, Willd. (897). 



(False Nettle.) 



