Ragweed

Common ragweed is one of the most important herbs.

Source: tatoeba (11823947)

More than 50 million people in the United States suffer from allergies, and their numbers are growing. New studies suggest that climate change may be at least partly to blame. Scientists say rising average temperatures and elevated levels of carbon dioxide are spurring the growth of many weedy, allergenic plants — such as ragweed — and extending the season of suffering for pollen-sensitive people across the country.

Source: tatoeba (12247946)

Fig. 1.—Spiculated pollens of ragweeds (ambrosias) low in protein. […] In the cocklebur (Xanthium americanum) and the rough wild elder (Iva ciliata), the spicules are shorter, being 0.7 and 0.5 microns, and the reaction is proportionately less active than with the ragweeds (ambrosias). […] While the grass pollens have so light a coat that they are frequently crushed in the ordinary process of mounting, the ragweed (ambrosias) pollen grains resist pressure between two glass slides carried to the point of crushing the glass.

Source: wiktionary

RAGWEED (Jeffogia Fingerolia) : The hayfever king, ragweed, brings tears to the eyes of grown men.

Source: wiktionary