FLORA OF ADEN. 
73 
some awned seeds and fruits are the various types of modification for 
wind-distribution. 
(a) Winged. This group includes all winged, margined or flattened 
fruits and seeds. 
(a) Flat, broad fruits : Species of Cassia, several Acacias v. g. 
A. hamulosa , mellifera. 
(/?} Winged fruits or seeds : Atriplex fariuosa , Bipterygium 
glaucum , Farsetia longisiliqua , Compylanihus junceus . 
(3) Fruits with persistent wing-like calyx : Helioir opium ptero - 
curpum , Kissenia spathulata. In the latter the sepals develop 
into long wings. 
(S) Fruits with spreading glumes: Fragrostis ciliaris , Fleusine 
cegyptica. 
[h] Sack-like. The species belonging to this group possess various 
fruits all of which agree in having a sack-like envelop. If it is membra- 
nous it serves for wind-distributrion : most species of Crotalaria , 
Tephrosia pogonostigma. 
(<?) Comate. Fruits and seeds with long silky hairs and bristles, 
often plumose, belong to this group : most species of Aristida, Trichol&na , 
Andropogon Iwarancusa , Saltia pappsosa , Folygala Thurmanniana , P. 
erioptera , Heliotr opium lignosum , the seeds of the various species 
of Asclepiadacecs Apocynace cc i and Composite (pappus). 
(d) Small spherical or discoid seeds which are often less than 1 mm 
in diameter may be carried away by the wind : species of Cadaba and 
Cleome, some Indigoferas and Acacias, Biplotaxis pendula , Reseda 
amblyocarpa , Oldenlandia Schimperi , Anticharis arabica , several Eu- 
phorbias. 
(b) Water . 
To this group beloug all plants distributed by water, whether in the 
form of ocean currents, tides, streams, or surface run-off. It is evi- 
dent that, with regard to Aden, the sea alone can play an active part in 
the immigration of species from neighbouring countries. 
The plants of this group possess various fruits, but all have an 
envelop impervious to sea- water and containing large or smaller air- 
cavities. Species of Sueeda , Halopeplis perfoliata ) Traganum nudatum , 
Thespesia populnea. 
