IS^ Prof. Scliouw on the Geographic Distribution of Grasses, 
rid zone, and are there found in perfection, are monoecious, or 
polygamous. Holcus is perhaps the only extratropical genus 
with separate sexes. 
4. The flowers are softer, more downy, and elegant. 
5. The extra- tropical grasses, on the contrary, far surpass the 
tropical in respect of the number of individuals. The compact 
grassy turf, which, especially in the colder parts of the tempe- 
rate zones, in spring and summer, composes the green meadows 
and pastures, is almost entirely awanting in the torrid zone. 
The grasses there do not grow crowded together, but, hke other 
plants, more dispersed. Already in the southern parts of Eu- 
rope, the assimilation to the warmer regions, in this respect, is 
by no means inconsiderable. Arundo donax, by its height, re- 
minds us of the bamboo ; Saccharum RavemiXy S, Teneriffxy 
i mperata arundinacea^ Lagurus ovatus^ Lygeum spartum, and 
the species of Stipa, by their soft, downy,,' elegant flowers, and 
the species of Andropogon^ jDgilops, &c., by separate sexes, 
exhibit tropical qualities. The grasses are also less gregarious, 
and meadows seldomer occur, in the south than in the north of 
Europe. 
As to what relates to the distribution of individuals, the ge- 
nerality of species are social plants. 
Lastly, Do we wish to know how this family is distributed in 
respect of the number of species, and where they reach their 
maxima and minima, the following materials may supply, not 
indeed either a complete or faithful representation, because the 
grasses are not treated of by botanists or travellers in general, 
with the same care as the other families ; but they will at least 
give some hints towards effecting that object. In Persoon’s Sy- 
nopsis, the grasses of the torrid zone form 1-S5th, and those 
of the northern temperate zone l-22d of the whole vegetation; 
but when it is considered that the grasses of the former have 
been less investigated than the European, the quotient would b© 
nearly alike in both zones. In the systems of Earner and 
Schultes, the tropical are to the European grasses as 2 to S ; 
but this is, from a probable conjecture, also the proportion of 
all the tropical and extra-tropical plants. In Persoon’s Synopsis 
it is as 1 to 2 ; and since the publication of that work, the know- 
ledge of the tropical has been enlarged in a greater proportion 
