CONTRIBUTIONS TO THE FLORA OF ISRAEL .6. STIPAGROSTIS-DRARII AND AMBROSIA-CONFERTIFLORA AND TENUIFOLIA, NEW RECORDS FROM ISRAEL

Stipagrostis drarii, found recently in sandy soils of the Arava Valley , is a typical component of sandy soils in extreme desert areas. It is adapted to sand mobility by having the ability to overcome up to 50 c m of sand-cover by producing new shoots from the axillary buds of the leafy culm and adventive roots from nodes close to the new soil surfac e. Two species of Ambrosia which seem to be relatively new introductio ns to the flora of Israel are recorded here for the first time. It is not clear if these colonizing species will become established. However ,judging from their way of dispersal by many small diaspores and effic ient vegetative propagation they are potentially noxious weeds.