LLO 
Spikes dense, seldom over 1. inch, not leafy. 
Flower-stalks and buds dotted with minute raised 
glands ; leaf-stipules not (or scarcely) fringed. 
lapithifo'lium. 
Stalks and buds smooth, not glandular; stipules fringed 
with long hairs. 
SE PEY een SER 
Persica'ria. Persicaria. 
Spikes slender, interrupted and leafy below. 
Buds rough with minute glands; leaves biting the 
tongue when chewed ; spikes usually drooping at | 
the tip. Hydrop'iper. Water Pepper. 
Buds smooth; leaves not biting the tongue; a 
erect, rarely 3 inches long. 5 
minus 
POP’ULUS. 
Shoots, and the under side of the leaves, covered with a. — 
whitish felt. } 
al'ba. White Poplar, Abele. 
Leaves not white-felted beneath. 
Leaves more or less triangular and long-pointed, with 
f numerous small teeth. ) 
L nigra. Black Poplar? 
Leaves roundish, very shortly pointed, with few rather 
large teeth or lobes. 
trem’ula. Aspen. 
POTAMOGE'TON. 
Leaves all long and narrow, strap-shaped or thread-like, 
+ inch wide or less, not toothed. 
Leaves thread-like, with a dilated, sheathing base, which 
(usually) ends in 2 little points. : 
pectina'tus. 
Leaves without any dilated, sheathing base. 
Stem much flattened ; leaves narrow-pointed, with 3 
f strong nerves and several intermediate ones. } 
i acutifo'lius 
Stem scarcely flattened; leaves 1- to 5-nerved. 
Leaves rarely ~, inch wide, scarcely narrowed 
f towards their base ; fruits ;'; inch long. ) 
L pusillus./ 
Leaves $ inch wide or more, narrowed towards 
their base, bluntish; fruits } inch long. } 
obtusifo'lius. 
Leaves (or some) over } inch wide, or toothed. 
