Natural Orders .] 
APPENDIX. 
583 
structure of these genera may be proved by a series of species connecting 
them with each other, and Panicum with Paspalum. 
Panicece have their maximum within the tropics, and they cease to 
exist in the most northern parts of Europe and the higher southern latitudes. 
Of this tribe, 99 species have been observed in Terra Australis, 79 of which 
were found within the tropic, and of these, 66 only within it. There is no 
Australian genus of this tribe ; Neurachne and Hemarthria excepted, 
which is not chiefly intratropical. 
The second tribe, which may be called Poace.®, is more numerous 
than Paniceae, and comprehends the greater part of the European genera, 
as well as certain less extensive genera peculiar to the sequinoctial coun- 
tries ; it extends also to the highest latitudes in which Phtenogamous plants 
have been found, but its maximum appears to be in the temperate climates 
considerably beyond the tropics. The Locusta in this tribe mayconsist of 
one, of two, or of many flowers, and the two flowered genera are distin- 
guished from Paniceae by the outer or lower flower being always perfect ; 
the tendency to imperfection in the locusta existing in opposite directions in 
the two tribes. In conformity with this tendency in Poaceae, the outer valve 
of the perianthium in the single flowered genera is placed within that of the 
gluma, and in the many flowered locusta the upper flowers are frequently 
imperfect. There are, however, some exceptions to this order of suppres- 
sion, especially in Arundo Phragmitis, Campulosus, and some other genera, 
in which the outer flower is also imperfect, but as all of these have more 
than two flowers in their locusta, they are still readily distinguished from 
Paniceae. 
In Terra Australis the Poacece amount to 115 species, of which 69 
were observed beyond the tropic and of these 63 only beyond it ; but of the 
52 species that occur within the tropics 49 belong to genera which are 
either entirely or chiefly intratropical, and of the remaining three species, 
two, namely, Arundo Phragmitis, and Agrostis virginica, are very general 
and also aquatic plants. The distribution of this tribe, therefore, in Terra 
Australis agrees with that which obtains in other parts of the world. 
FILICES.* Of this order nearly 1000 species are described in the 
* Prodr. Jl- nov. holt. 145. 
