FLORA OF THE DISTRICT OF COLUMBIA. 173 



2. LIQUID AMBAR L. 



1. Liquidambar styraciflua L. Sweet gum. 



Moist wtx)cls; frequent. May. Southern states, north to Conn. 



78. PIATANACEAE. Sycamore Family. 



1. PLATANUS L. 



1. Platanus occidentalis L. Sycamouk. 



Rich or moist woods; frequent. May. Eastern U. S. 



79. ROSACEAE. Rose Family. 



Plants shrubby. 

 Leaves simple; fruit a follicle or pod with several seeds; plants not prickly. 



Follicles iuQated ; leaves palmately nerved and lobed 1 . OPTJLASTER . 



Follicles not inflated ; leaves pinnately veined, not lobed 2. SPIRAEA. 



Leaves compound; fruit of achenes (several within a fleshy receptacle) or a cluster 

 of drupelets; plants armed with prickles. 

 Leaves piunatelycompound; fruit of several bouyachene^ or nutlet.'? inclosed in a 

 globular or pear-shaped, somewhat fleshy receptacle; flowers pink, some- 

 times fading to nearly white 3. ROSA. 



Leaves palmately compound; fruit a globular or oblong cluster of drupelct>!; 

 flowers white, sometimes becoming pinkish with age, rarely purplish red. 



4. RTJBUS. 

 Plants herbaceous. 



Pistil containing more than 1 ovule; fruit a follicle. 



Leaves 2-3- pinnate; flowers small, in a large spicate panicle 5, ARUNCUS. 



Leaves 3-foliolate; flowers few, long-peduncled 6. PORTERANTHUS. 



Pistil 1-ovuled; fruit an achene, the receptacle sometimes fleshy. 



Receptacle enlarged in fruit, juicy or spongy. Plants with I'unners; leaves 



3-foliolate. 



Petals white; fruiting receptacle juicy 7. FRAGARIA. 



Petals yellow; fruiting receptacle spongy 8. DUCHESNEA. 



Receptacle not enlarged m fruit, d'y. 



Achenes numerous, upon a convex receptacle. 



Styles elongating in fruit, jointed and bent near the middle, the upper part 



deciduous, the lower persistent as a hook 9. GEUM. 



Styles not elongating in fruit and not forming hooks... 10. POTENTILLA. 



Achenes few, inclosed in an um-shaped calyx tube. 



Petals present, yellow; flowers in long racemes. Margin of the top-shaped 



fruiting calyx with hooked prickles 11. AGRIMONIA. 



Petals absent; flowers clustered or spicate. 



Flowers in small, nearly sessile clusters; plant a low annual.. 12. APHANES. 



Flowers in long-peduncled dense heads or spikes; plants perennial. 



Inflorescence cylindric, white; leaflets 2-5 cm. long. 



13. SANGUISORBA. 



Inflorescence globular, green; leaflets 8-1") mm. long.. 14. POTERIUM. 



1. OPULASTER Medic 



1. Opulaster opulifolius (L.) Kuntze. Nlne-bahk. 



Rocky woods; fi-equent. May. Eastern U. S. (Phi/somrjuix npulifolius Maxim.; 

 Neillia opuUfolia Benth. & Hook.) 



