14] VEGETATIONAL TYPES OF TROPICAL LANDS 445 



tinguished by the fact that in them the trees appear to be dominant, 

 although such types grade into savannas, even as these last grade 

 into treeless grasslands. 



The savanna presents mostly a park- or orchard-like appearance 

 — a landscape typically of plains of tall Grasses with scattered trees 

 and shrubs. In hollows or swales the trees frequently grow close 

 enough together to form woods, whereas on ridges they are sparse 

 or wholly absent, the vegetation thus constituting a steppe. The 

 Grasses commonly exceed the height of a Man, but range, in different 

 instances, from less than i to more than 4 metres high, and form 



Fig. 152. — Palm-savanna in southern F"lorida. 



a yellowish straw frequently topped by silvery ' spikes '. They 

 typically grow clustered in dense tufts which exhibit, in the intervals, 

 patches of bare soil often of a reddish or yellowish hue. Low 

 bushes with small and hard evergreen leaves and often prickles or 

 thorns may occur among the Grasses. 



The trees which appear at greater or lesser intervals in the savanna 

 are usually stunted and gnarled but sometimes lofty. While many 

 are deciduous, others are evergreen ; common heights are 3-6 

 metres. They belong to characteristic species not usually occurring 

 in the forest, and commonly include Palms (Fig. 152) or other 

 plants of peculiar habit (Fig. 153). Often the fast-growing, coarse 

 and stiff Grasses interpenetrate the lower branches of the trees and 

 remind the ecologist of their tendency to dominate. Elephant Grass 

 {Pennisetum purpureum) may exceed 5 metres in height and form 

 an almost impenetrable ' thicket '. The trees typically include some 



