Prof^- Scholl w on the Geo^m^hic Distribution ofGrmses. ISl 
in the southern parts of South America^ as well as-New Zealand. 
One of the most extensively distributed genera is Poa. It is 
found almost over the whole earth ; and, although it reaches its 
maximum in the temperate, has also many species in the torrid 
zone. 
A tendency to a wider distribution in the family of the 
grasses, is- found, not only in the groups and genera, but also in 
the species. Among many examples, we particularize only 
pago racemosa^ which occurs in the south of Europe, in^ Ara- 
bia, in both Indies, and in South America ; Cenchrus echinatus, 
Festuca mpurus, Poa megastachyaj Andropogo^ Allionii^ Holciis 
Imlepensis^ in the high lands of South America, and in Europe ; 
Panicum Crus gallic P, glaucum, Cynodon Dactyhn, Holcus 
gryllus, Arundo Ph?'agmites^ and Festuca JluUans, in Europe 
and New Holland; Paspalus vaginatus^ in Tranquebar, Ja- 
maica, and the Isle of France ; P. fil^ormis in India, Jamaica, 
North America ; Rotthollia dimidiata^ in Guinea, at the Cape, 
and in Jamaica ; and Imperata arundinacea on the Mediterra- 
nean, in India and New Holland. 
This family, then, is every where nearly the same, or it has a 
tendency to distribution in whole groups, genera, and species (dis- 
tributio formis subordinatis conjunctis), to which, however, cer- 
tain genera and species form exceptions. The individuals, also, 
of several species occur, not unfrequenty mixed (distributio spe- 
ciebus mixtis) ; for meadows usually contain many species of the 
grasses. 
What has been said of the decided influence of the degrees 
of latitude on groups and genera, holds also of the habitus of 
vegetation in general. The greatest differences between tropical 
and extra-tropical grasses appear to be the following : 
1 . The tropical grasses acquire a much greater height and 
occasionally assume the appearance of trees. Some species of 
Bamhusa are from .50 to 60 feet high. 
2. The leaves of the tropical grasses are broader, and ap- 
proach more in form to those of the other families of plants. Of 
this the species Paspalus affords many examples, 
3. Separate sexes are more frequent in the tropical grasses. 
Zea^ Sorghum^ Andropogon^ Olyra^ AntMstiria^ Ischmmum^ 
AEgilops, and many other genera, which only occur in the tor- 
