466 URTICACE.E. (nettle FAMILY.) 



1. P. piimila, Gray. (RicHWEED. Clearweed.) Low (3- 18' high); 

 stems smooth and shining, pellucid ; leaves ovate, coarsely toothed, pointed, 

 3-ribbed and veiny ; flower-clusters much shorter than the petioles ; sepals of 

 the fertile flowers lanceolate, scarcely unequal. — Cool and moist shaded 

 places. July - Sept. 



11. BCEHMERIA, Jacq. False Nettle. 



Flowers monoecious or dioecious, clustered ; the sterile much as in Urtica 

 the fertile with a tui)ular or urn-shaped entire or 2 - 4-toothed calyx enclosini 

 the ovary. Style elongated awl-shaped, stigmatic and papillose down out 

 side. Achene elliptical, closely invested by the dry and persistent compressed 

 calyx. — No stings. (Named after G. R. Boehmer, Professor at Wittenberp 

 in the last century.) 



1. B. cylindriea, Willd. Perennial, smoothish or pubescent and more 

 or less scabrous ; stem (1 - 3° high) simple ; leaves chiefly opposite (rarely all 

 alternate), ovate to ovate- or oblong-lanceolate, pointed, serrate, 3-nerved ; stip- 

 ules distinct; petioles short or elongated; flowers dioecious, or the two kinds 

 intermixed, the small clusters densely aggregated in simple and elongated 

 axillary spikes, the sterile interrupted, the fertile often continuous, frequently 

 leaf-bearing at the apex. — ]\Ioist or shady ground, common. Very variable. 



12. PARTE TAR I A, Tourn. Pellitorf. 



Flowers monoeciously polygamous; the staminate, pistillate, and perfect in- 

 termixed in the same involucrate-bracted cymose axillary clusters ; the sterile 

 much as in the last ; the fertile with a tubular or bell-shaped 4-lobed and 

 nerved calyx, enclosing the ovary and the ovoid achene. Style slender or 

 none; stigma pencil-tufted. — Homely, diffuse or tufted herbs, not stinging, 

 with alternate entire 3-ribbed leaves, and no stipules. (The ancient Latin 

 name, because growing on old walls.) 



1. P. Pennsylvanica, Muhl. Low, annual, simple or sparingly 

 branched, minutely downy ; leaves oblong-lanceolate, thin, veiny, roughish 

 with opaque dots ; flowers shorter than the involucre ; stigma sessile. — Shaded 

 rockv banks, E. Mass. and Vt. to Minn., and southward. June -Aug. 



Order 100. PLATAXACE^, (Plane-tree Family.) 



Trees, icith ivatert/ Juice, alternate palmately-lohed leaves, sheathing stip^ 

 ules, and moncecious flowers in separate and naked spherical heads, des- 

 titute of calyx or corolla ; the fruit merely club-shaped 1 -seeded nutlets, 

 furnished luith a rincj of bristly hairs about the base ; consists only of the 

 following genus (of uncertain relationship). 



1. PLAT ANUS, L. Sycamore. BrTToxwooD. 



Sterile flowers of numerous stamens, with club-shaped little scales inter- 

 mixed ; filaments very short. Fertile flowers in separate catkins, consisting 

 of inversely pyramidal ovaries mixed with little scales. Style rather lateral, 

 awl-shaped or thread-like, simple. Nutlets coriaceous, small, tawny-hairy be- 

 low, containing a single orthotropous pendulous seed. Embryo in the axis of 



