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Chloiis, are every where nearly equal, those that are peculiar being generally 

 not at all numerous. The generic difference between North America and the 

 temperate regions of the European continent is very small. In North America, 

 however, a greater number of tropical forms appears. Between the two tem- 

 perate zones also the distinction seems to be by no means considerable. Of 36 

 genera from the Cape, 30 occur in the temperate zone of the northern hemi- 

 sphere, while, in other families, southern Africa has many peculiar to itself. In 

 the extra-tropical part of New Holland the greater number of genera is found 

 also in the north (about 2-3ds) ; and this appears to be still more the case 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. 



" 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 Bambusa are from 50 to 60 

 feet high. 



"2. The leaves of the tropical Grasses are broader, and approach more in 

 form to those of the other families of plants. Of this the genus Paspalus af- 

 fords many examples. 



" 3. Separate stamens and pistils are more frequent in the tropical Grasses. 

 Zea, Sorghum Andropogon, Olyra, Anthistiria, Ischsemum, iEgilops, and 

 many other genera, which only occur in the torrid zone, and are there found in 

 perfection, are monoecious, or polygamous. Holcus is perhaps the only extra- 

 tropical genus with separate stamens and pistils. 



" 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. That compact grassy turf, which, espe- 

 cially in the colder parts of the temperate zones, in spring and summer, composes 

 the green meadows and pastures, is almost entirely wanting in the torrid zone. 

 The Grasses there do not grow crowded together, but, like other plants, more 

 dispersed. Even in the southern parts of Europe, the assimilation to the 

 warmer regions, in this respect, is by no means inconsiderable. Arundo donax, 

 by its height, reminds us of the Bamboo ; Saccharum Ravenna^, S. Teneriffse, 

 Imperata arundinacea, Lagurus ovatus, Lygeum spartum, and the species of 

 Stipa, by their soft, downy, elegant flowers ; and the species of Andropogon, 

 jiEgilops, &c, by separate stamens and pistils, 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 generality of spe- 

 cies 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 1 The 

 following materials may supply, not indeed either a complete or faithful repre- 

 sentation, 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 Synopsis, the Grasses 

 of the torrid zone form l-25th, and those of the 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 be nearly alike in 

 both zones. In the systems of Romer and Schultes, tropical are to the Eu- 

 ropean Grasses as 2 to 3 ; but this, from a probable conjecture, is also the pro- 



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