THE AMERICAN BOTANIST, 
33 
here of carpet plants, 3'et, since the terms mat and carpet 
are often used synon_vmously, it might be stated that 
typical carpets are perennials with numerous trailing 
branches or runners which take root at the nodes and 
develop low tufts of leaves or rosettes, finally forming a 
close low covering of the ground. Among this type of 
carpet plants maybe mentioned the buffalo-grass {Bulbilis 
dactyloides) and the various species of Antennaria, 
Mat plants are at home in open and exposed places 
where there is little or no individual crowding. They are 
abundant on prairies and appear extensively on newly 
plowed land. On newly broken prairie they are usually 
the most characteristic vegetation. They are also promi- 
nent on dr3^ or moist sandbars, on salt marshes and in 
cultivated fields. 
Nearly all t^^pical mats, when growing in shaded 
places, assume the upright habit. But it is especially 
interesting to note that normally erect plants may 
assume the mat habit in a suitable environment. One of 
the most striking cases is the slender pig-w^eed (Amaran- 
thus hjbridus), w^hich is usually erect and often attains 
the height of eleven feet. This plant when growing on 
exposed dr^^ or moist sandbars frequently developes as a 
mat without a central stem but with a number of pros- 
trate radiating branches. Sometimes there is a central 
erect stem a few inches high with long prostrate branches 
radiating in all directions from the base. The same form 
has been seen by the wn-iter on sandhills in central Kansas. 
So peculiar is the appearance that one hardly recognizes 
the plant in its new form. Eragrostis purshii and Dip- 
lachne acuminata also form mat-like bodies when grow- 
ing on sandbars. On exposed broken ground various 
normally erect, ascending, or decumbent plants also form 
mats. Noteworthy among these are Echinochloa crus- 
galli, Eragrostis major and Cenchrus tribuloides. In salt 
marshes of the interior one meets with fleshy mat plants 
like Sesuvium sessile. Sesuvium martimum is common 
on the sands of the Atlantic coast. Dondia depressa is 
