i8 



A FIELD GUIDE IN NATURE-STUDY 



Spurges 



Milk Spurge 



Flowering Spurge 



Dogbane 



Indian Hemp 



The Milkweeds 



Swamp Silkweed 



Swamp Milkweed 



Dandelion 

 Wild Lettuce 



Prickly Lettuce 

 Sow Thistle 



c Leaves not awl-pointed (Fig. 3 a) 



d Low 

 dd Tall, much branched 



There are several other species, not 

 usually occurring as weeds (see Gray, 

 P- 545) 

 cc Leaves awl-pointed 



d Leaves all with stem (petioled) 

 dd Upper leaves at least without stem 



(sessile) 

 bb Leaves large 



c Fields and roadsides 

 cc Swamps 



aa Leaves with lobed or cut margins 

 b Leaves in a rosette 

 bb Leaves not resetted, but prickly 

 c Midrib prickly 

 cc Midrib not prickly, but margins prickly 



d Stem of plant prickly 

 dd Stem of plant not prickly 



Several other species of Lettuce occur in 

 the Chicago region, not commonly as 

 weeds (see Gray, p. 866) 



II. Weeds with compound leaf (Figs. 3 b and 3c) 

 a Leaves of three leaflets 



b A woody vine often appearing shrubby; berries 

 white. "Leaflets three, quickly flee. Berries 

 white, take to flight" Poison Ivy 



bb Herbs of low, prostrate habit 



c Flowers in dense clusters (head or spike) 



d Blossoms white (several species) White Clover (see Gray] 

 dd Blossoms red Red Clover 



ddd Blossoms pink Alsike Clover 



dddd Blossoms yellow 



e Blossom cluster as large as thumb nail Hop Clover 



ee Blossom cluster (spike) only as large 



as little-finger nail Black Medick 



cc Flowers single, leaves of acid flavor Wood Sorrel 



bbb A tall, much-branched plant; flowers in long 

 slender clusters 



c Blossoms white White Sweet Clover 



cc Blossoms yellow Yellow Sweet Clover 



aa Leaves of more than three leaflets 

 b Once pinnately compound 



c Flowers purple or rose, in clusters 



Vetch (several species; see Gray, p. 525) 

 cc Flowers yellow like buttercup Cinque foil (Gray, p. 481) 



