ASTERACEAE Fortnight Part 2-Discoid heads: Ageratum conyzoides from Uttarakhand_DSR_2

[D.S Rawat]

Ageratum L. genus is represented in India by two species- A. conyzoides and A.houstonianum. Both of these species are not native in India but are invasive alien species originating in Tropical America. In Uttarakhand these reach up to 2000m altitude in the Himalaya. These closely related pantropica weed species can be differentiated as follows:

Involucral bracts linear, sharply acute-acuminate, sparsely hairy; Corolla of the florets 1.5mm long, shorter than awned pappus scale.... A.conyzoides L.

Involucral bracts linear setaceous, densely hairy; Corolla of the florets 2.5mm long, as long as or longer than awned pappus .... A.haustonianum Mill.

DSRawat Pantnagar

[Gurcharan Singh]

Very good photographs Rawat ji

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Dr. Gurcharan Singh

Retired  Associate Professor
SGTB Khalsa College, University of Delhi, Delhi-110007
Res: 932 Anand Kunj, Vikas Puri, New Delhi-110018.
Phone: 011-25518297  Mob: 9810359089

http://www.gurcharanfamily.com/ 
http://people.du.ac.in/~singhg45/ 

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[radha...@gmail.com]

Thank you for explaining the differences between the 2 species.

regards
Radha