574 MR. G. BENTHAM ON COMPOSITA. 
The ripening the seed at the same time as the corn or other 
cultivated seed-crop with which the plant has become mixed is a 
great assistance tothe transport of cornfield-weeds, their seed being 
usually gathered, mixed, and carried with that of the cultivated 
plant. Cornfield-weeds, however, are not so numerous in Com- 
posites as in Papilionacez, Caryophyllee, &c.: Anthemis cotula 
and arvensis, Matricaria chamomilla, Chrysanthemum segetum, and 
Centaurea cyanus, amongst the European ones, and the American 
Galinsoga are the principal ones ; and perhaps some of the tropical 
weeds similarly deprived of any serviceable pappus, such as Eclipta, 
may owe their wide dissemination partly to their ripening their 
seeds with those of the cultivated crops. 
The stations affected by certain species may be such as to place 
them specially within reach of means of transport, as, for instance, 
maritime plants, which are often carried out across seas to great 
distances, probably in some measure connected with navigation 
and commerce. In Composite Solidago mexicana, Soliva, Cotula 
coronopifolia, Centaurea melitensis and calcitrapa may owe their 
disjointed areas to this amongst other causes. 
Great fertility, the very abundant production of small seeds, is 
most serviceable in multiplying the chances of some of them being 
seized upon by extraneous means of transport, as well as in esta- 
blishing a plant when transported. This may be specially 
exemplified in the dispersion of annuals to short distances, as in 
the case of the annuals escaped from cultivation in table 18, and 
of the rapid establishment of Ageratum, Erigeron canadense, Suc. 
when carried to great distances, as well as of the sudden appear- 
ance from nearer homes of such extraordinary numbers of Blumeas, 
Conyzas, Erigerons, Senecios, &c. in newly cleared ground or 
drained lakes. 
Of the various other means of transport and facilities offered to 
plants fitted for availing themselves of them, commented upon by 
Alphonse De Candolle, Darwin, and others, no special instances 
ealling for remark have occurred to me in Composite. It is not, 
however, enough for the seed to be carried to a new spot; when 
there, the seed and the plant to proceed from it must present 
qualifications and properties enabling them to germinate, grow, 
and multiply. 
Ready germination is often highly servieeable. Small seeds 
arriving in great numbers have usually great obstacles to overcome, 
many enemies to contend with. Ifthe physical and meteorological 
conditions of the soil they are deposited upon are not favourable 
