% FLORA OF PHILADELPHIA. 



Chester (W. Tr.)'. Chester— (P.). Lancaster— (P. j. Lehigh— Sals- 

 burg, Jordan (Kr.). Northampton — (P.). 

 New Jersey and New Castle— Frequent. 



5. ACORUS L. 

 h AoofcuS Calamus L! Sweet Flag. Oalainus. M. p. 231. Swamps' and 

 along streams. Summer. 



Family 2. LEMNAOEAE Dumorfc. Duckweed Family. 



Thallus with one root' or several. 



Roots' several! L Spirodela. 



Hoot solitary. 2: Lemna. 



Thallus rootless. 3. Wolflia. 



1. SPIRODELA Schleid. 



1*. Spirodela polyrhiza (L.) Schleid. M. p. 232. Ponds and pools. Summer. 



2. LEMNA L. Duck-weed. 

 Ttoa'lli lon'g^stipitate. 1. L. trisUlca. 



Thalii short-stipitate or sessile. 



Spathe open, 2. L. perpusilla. 



Spathe sac-like. 3. L. minor. 



X. Lemna tkisulca L. M. p. 232. Ponds and springy places. Summer. 

 Philadelphia— Frankford, Jesse Burk (B. C). Bucks— In shalloW 

 pond in Trap Rock Region (Pr.). Chester— (P.).. Lancaster— (P.). 

 Northampton— (P.): 

 21 Lemna perpusilla Torr. M. p. 232. Ponds and springs. Summer. 

 Northampton— (P.) . 



New Castle — Ditches near Edgemoor, New Castle, Commons (now 

 extinct there). 

 3. Lemna minor L. M. p. 233. Stagnant water. Summer. 



3. WOLFFIA Horkel. 

 l'. Wolffia Columbiana Karst. M. p. 234. Floating beneath the surface 

 of stagnant water. Summer. 

 Philadelphia— Neck (Cr.). Bucks— Tullytown , (Cr.). 

 Camden— Kaighn 's Point (C). Salem— Jumbo Station (He.), W. of 

 Pedricktown (Li.). 

 New Castle— Ditches and Canal Coves. 



Order 5. XYRIDALES. 

 Ovary 1-celled. 



Erect-scapose rush-like herbs; flowers in terminal scaly heads or spikes! 



Fam. 1. Xyridaceae. 

 Mud or aquatic herbs, the flowers subtended by spathes (Heteranthera 

 in Pontederiaceae). , 



Ovary 2-3-celled. 



Flowers very small, densely capitate, monoscious or dioecious. 



Fam. 2. Eriocaulaceae. 

 Flowers perfect. 



Perianth of 2 series of parts, the outer (sepals) green, the inner 



(petals) colored. Fam. 3. Cqmmelinaceae. 



Perianth 6-parted. Fam. 4. Pontederiaceae. 



