The Aravallis intersect the State of Rajasthan in a southwest-northeast direction. Mt. Abu on the Aravallis is the highest point in the wide gap between the Himalayas and the Nilgiris, and thus has phytogeographlc significance. The flora of Mt. Abu has been compared with that of other hilly regions of India, and also with the flora of adjacent regions of the dry zones. It is observed that : i. the flora of Mt. Abu has some representation of mountain element belonging to subtropical and temperate regions of India. This element comprises three groups of plants, namely, (a) those occurring in all or most hilly regions of India, such as in Himalayas, Parasnath, Pachmarhi, Western Ghats, Nilgiris, etc. (26 species); (b) plants found in the Himalayas or moist places of northern India, whose southern limit is the Mt. Abu (19 species); and (c) plants found in the Ghats and hills of Deccan Peninsula and whose northern limit of distribution is Mt. Abu 38 species).
ii. there are only a few plants of alpine regions in this flora;
iii. large number of plants are of wide general distribution;
iv. biotic factors are resulting in increase of xerophytic species on this hill.
A study ofthe world distribution of the plants of Mt. Abu shows that:
i. out of 469 species, 267 are tropical;
ii. 80 species are eastern, southeastern, Asian and Australian;
iii, 46 species are African-Arabian; and
iv. 22 species are American. The American plants are mostly weeds of cultivation.