K 



458 FLOWERS OF FIELD, HILL, AND SWAMP 



35 



Variety repens is lower and more prostrate, with flower white 

 or light pink, and leaves with narrower, arrow-shaped basal 

 lobes. Stem somewhat softly downy. Common. 



36. Common Dodder 



Cuscuia Gronovii. — Farnily, Convolvulus. Color, yellowish 

 white. Leaves, none. Time, summer. 



Our commonest parasite, and very troublesome in clover and 

 alfalfa fields, or wherever it obtains a hold. The seed — a coiled 

 thread, a worm-like embryo — germinates in the ground. When 

 the yellow stem which springs from this seed is 2 inches high, it 

 reaches for any neighboring herb or shrub. Once in touch, it 

 develops haustoria, or suckers, which penetrate the bark of the 

 host, and thence draw the plant's juices, already assimilated, 

 appropriating them for its own. The part in the ground now 

 dies and falls away, leaving the plant wholly parasitic. It quickly 

 entwines itself around the whole shrub, reaching out for others 

 near by, and thus we often see tangled mats and masses of yellow 

 threads in the woods, by the roads, everywhere. Under the mag- 

 nifying-glass the small, cabbage-like flowers show 5 divisions of 

 calyx and corolla, with a 2-celled ovary, and thus they are brought 

 within the family which includes the apparently most dissimilar 

 morning-glory and sweet-potato. 



Being parasitic, the plants possess no green leaves, but yellow- 

 ish scales instead. By twining too tightly around the bark they 

 inflict additional injury. Dr. Gray gives 10 species of dodder, 

 besides the flax and clover dodders. The most common, C. Grono- 

 vii, VAv\es considerably in size of blossom and coarseness of stem. 

 It is a curious, but repulsive, plant. 



From Canada southward to Florida and Texas. 



37 

 C. injlexa bears small flowers, few scales, and is parasitic 

 on hazel and other shrubs or coarse herbs. 

 Soutiiern New England to Nebraska. 



