596 



WEED FLORA OF IOWA 



Serrate, when the teeth point forward, as in the common sun- 

 flower {Helicmthus awnuus). 



Serrulate, when the margin is finely serrate as in milk purslane 

 (Euphorbia maoulata). 



Crenate, when the teeth are broad and rounded as in the common, 

 mallow {Malva rotundifoUa) . 



<^^^ 



Fig. 



Fig. 451 1 

 451. Compound leaves. 



Pig. 451 II Fig. 451 III 



I. Leaf of Clover with three leaflets. IL. 



Pedately divided leaf of Dragon Root. III. Pinnate leaf of Locust withi 

 19 leaflets. 



(After Thomd.) 



Lohed, when the leaf is deeply cut, as in the great ragweed. The- 

 projecting portions are then called lobes. When the incisions are- 

 sharp the term cleft is often used; the leaf is pinnatifid when the 

 incision extends almost to the midrib, as in the prickly lettuce 

 {Lactuca scariola) ; it is pinnate when the incisions have extended?, 

 to the midrib and each separated portion takes the character of a 

 leaf. Bach of the smaller portions is a leaflet, and the kaf is now 

 considered compound. The spotted eowbane (Cicuta macuUda), 

 spring vetch {Vicia sativa) and cinquefoil (Potentilla monspelien- 

 sis) are good examples. 



